Genetic Basis of Grain Yield and Quality under Heat Stress in Rice

Anil Chandran, Postdoctoral Researcher Department of Agronomy and Horticulture University of Nebraska-Lincoln Author

10/08/2024 Added

11 Plays

Description

Heat stress during the grain-filling period has a detrimental effect on rice yield and quality. The development of heat-resilient cultivars could help address this issue if tolerant alleles can be identified and incorporated into the germplasm. This presentation will focus on the research conducted to understand the genetic basis of grain yield and quality under heat stress in rice.

Searchable Transcript

Search:

[00:00:00.140]The following presentation is part of the Agronomy and Horticulture Seminar Series at the University of Nebraska-Lincoln.
[00:00:07.720]So on behalf of the seminar committee, my pleasure to introduce Anil Chandran.
[00:00:15.180]Anil comes to us from the Walia Lab, where he's been a postdoc and research tech since 2020.
[00:00:23.540]Anil, before that, got his PhD at Kanghee University in South Korea, and before that,
[00:00:30.600]a master's at Amright University in India. And his work in the Walia Lab and the work he's going
[00:00:37.080]to present to us today is really focused on the genetic basis and the physiology of
[00:00:42.340]drought and heat tolerance in rice. So with that, join me in welcoming Anil.
[00:00:47.740]Thanks for the nice introduction, Brian. And good morning, everyone.
[00:00:58.240]Today, I'll be giving an idea about the impact of heat stress during the early grain development
[00:01:07.840]stages. And I'm particularly interested in the early grain development stages because the
[00:01:14.280]heat stress during that stage significantly lower than the early grain development stage.
[00:01:17.720]The grain yield and quality. And I'll be covering two aspects of the research. The first one is the
[00:01:23.380]physiological and transcriptome analysis of a set of rice extractions from the germplasm pool,
[00:01:29.120]and which is more targeted towards the understanding of how yield is impacted.
[00:01:33.740]And then we'll move on to the natural variation for the grain quality aspect.
[00:01:38.720]We all know that earth's mean surface temperature is increasing
[00:01:46.240]over the period of time. And we know that the earth's mean surface temperature is increasing
[00:01:47.700]and it can be seen that the rate of increment is more for the recent years compared to the
[00:01:54.340]long-term trend. And several climatic models have predicted a 1 to 4 degree Celsius increment
[00:02:00.160]by the end of the century. On the other hand, even a small degree Celsius in temperature
[00:02:08.760]increment substantially reduce the yield for major crops. Here is an estimate that shows
[00:02:17.680]a yield reduction for rice by 3.2%, wheat by 6%, and so on. And this is more concerning
[00:02:25.620]for rice because rice is a major nutrient source for more than half of the world population.
[00:02:32.820]And as you can see here, the major rice-growing countries such as China, India, Bangladesh,
[00:02:40.740]and other Southeast Asian countries experience frequent heat waves and extreme temperature
[00:02:47.660]growing seasons.
[00:02:52.380]And this yield reduction occurs due to an impact on both the vegetative phase as well
[00:02:56.440]as the reproductive developmental phase.
[00:02:58.860]However, the magnitude of heat stress is more when the impact occurs during the early grain
[00:03:04.360]development phases.
[00:03:11.320]And early grain development in rice has four distinct stages: after the double fertilization,
[00:03:17.640]endosperm enters the stage called syncytium stage, which is the formation of free nuclei
[00:03:22.580]that takes place around 24 hours after the fertilization.
[00:03:26.260]Then the formation of radial microtubules that takes place around 48 hours after the
[00:03:31.020]fertilization.
[00:03:32.600]Then endosperm enters the stage called cell wall initiation stage, that is basically the
[00:03:37.560]formation of cell walls around this free nuclei that takes place around 72 hours after the
[00:03:43.000]fertilization and the cellularization is completed by 96 hours.
[00:03:47.620]The duration and the rate of the synthesization stages are very important because these cellularized
[00:03:55.060]cells are later on filled with the storage and starch product.
[00:03:59.300]So if you look at the overall endosperm development cycle after the synthesization and cellularization
[00:04:04.700]stage, next is the formation of alluron layer in the developing endosperm and the grains
[00:04:11.060]enter the stage called storage product accumulation.
[00:04:14.340]So in this stage, starch, proteins and other
[00:04:17.600]nutrients are being filled to the cellularized endosperm and later on water content is released
[00:04:24.020]from the cells and grain get matured by 30 days after pollination.
[00:04:30.880]As you can see here, these are the stages marked by the rapid expansion of the seeds
[00:04:37.100]and the timely transition of these stages are very important for the proper grain development.
[00:04:47.580]However, occurrence of evenness transient heat stress significantly impacts the endosperm
[00:04:52.600]cellularization.
[00:04:55.660]Here for example, for the Kitake accession, Kitake is an accession which is widely used
[00:05:00.080]for the genetic experiments and when the seeds are grown in control condition, that means
[00:05:05.160]when the seeds are grown in 28 degree Celsius the daytime and 24 at night, endosperm get
[00:05:11.780]half-celerated by 72 hours and the cellularization is completed by 96 hours.
[00:05:17.560]And the seeds formed during this stage are of perfect translation structure and with
[00:05:24.100]optimal grain size.
[00:05:26.180]However, moderate heat stress is imposed.
[00:05:29.400]That means when the temperature is increased as high as 35 degree Celsius, endosperm get
[00:05:34.560]cellularized as early as 72 hours.
[00:05:38.300]And the seeds produced at this condition are of poor quality with a reduction in the seed
[00:05:44.540]size.
[00:05:45.540]So, which indicates that the moderate heat
[00:05:47.540]stress accelerated the cellularization process.
[00:05:50.480]However, this phenotypic response is very diverse for the different genotypes.
[00:05:59.360]And this also indicates that even a transient heat stress at the early grain development
[00:06:03.920]stage also determines the mature grain size and quality.
[00:06:17.520]So, we can see that when we impose heat stress to a set of axons, some of the axons had relatively
[00:06:30.180]high grain abortion, while other axons had, such as Tropical Japonica 3, this had medium
[00:06:37.000]level of sensitivity with the reduction in the seed size, while axons such as Tropical
[00:06:42.280]Japonica 1, which had a relatively tolerant phenotype in response to the heat stress.
[00:06:47.500]So, which indicates that if you take some axons from the diversity pool, the phenotypic
[00:06:56.120]response is very diverse.
[00:07:00.560]And if you look at the cellularization pattern, for most of these axons, cellularization is
[00:07:05.560]completed by 96 hours, but the heat stress delayed the cellularization.
[00:07:13.100]So which indicates that the severe heat stress, so we impose 39 degrees Celsius at the day
[00:07:17.480]time, 35 degrees Celsius at night.
[00:07:20.280]So this is the severe heat stress.
[00:07:21.860]So which indicates that the severe heat stress delayed the cellularization, whereas the moderate
[00:07:26.300]heat stress accelerated the cellularization process.
[00:07:36.420]Similar to the magnitude of the heat stress, the time of heat stress imposition also make
[00:07:41.420]a significant difference in the gradient development stage, for instance, we have two regimes here
[00:07:47.460]the first set of plants were grown in controlled condition that means 28 day and 25 at night
[00:07:54.460]throughout the development phase and other batch was given heat stress with a non-overlapping
[00:08:00.460]window such as HS1 correspond to first two days of cellularization after the fertilization
[00:08:08.460]then HS2 between two and four days after the fertilization all the way up to HS4 which is
[00:08:14.460]between six day to eight days after the fertilization.
[00:08:17.440]And if you look at the panicle for this histose treatment the HS1 you can see that the most
[00:08:26.440]of the spikelets are of greenish color which means that the seeds were not completely formed
[00:08:33.440]and this was true for both HS1 and HS2 but if you compare this HS1 and HS2 panicles with
[00:08:41.440]HS3 and HS4, these were mostly filled grains because HS1 and HS2 grains were not completely
[00:08:47.420]formed. These were imposed heat stress during the syncytium to cellularization phase. So this observation also corroborates with the panicle weight measurement. For instance, HS1 had a lower panicle weight compared to HS2, HS3 and HS4.
[00:09:17.400]We also identified some of the genes which also plays an important role in the regulation of seed size during these heat stress conditions. One of them is fertilization independent endosperm 1. And the gene expression is misregulated in response to the heat stress. As you can see that the moderate heat stress induced the expression of the gene and the severe heat stress, that means the 42 degrees Celsius, reduced the expression of the gene at 48 hours. So to get a more clear window of this
[00:09:47.380]heat stress response, we induce heat stress in every two degree increment manner from 28 degree
[00:09:54.640]all the way up to 40 degrees Celsius. And for the 48 days, 48 hours after fertilized samples. And
[00:10:01.440]what we found was that the sample of the fever had higher expression in the 34 degrees Celsius
[00:10:09.240]temperature treatment. And then the expression goes down all the way to 40 degrees Celsius.
[00:10:14.700]So the gene expression is reduced.
[00:10:17.360]The genetic analysis shows that the fever regulates the syncytion stage window. And
[00:10:23.820]that's the reason why overexpression of the gene reduces the seed size, because the syncytion
[00:10:29.120]window is reduced.
[00:10:30.300]And MADS-78 and MADS-78 and MADS-79, these are the two transcription factors, type 1
[00:10:47.340]early seed development.
[00:10:48.400]And you can see that the FEE1 negatively regulates the expression of these two MADS genes.
[00:10:54.080]When the FEE1 goes up at 72 hours, the expression of these two genes are suppressed.
[00:11:00.440]And the overexpression of these two, MADS-78 and MADS-79, significantly delayed the cellularization
[00:11:09.140]process, and the seeds produced in overexpression lines were also having very small quality.
[00:11:17.320]Then, we conducted a transmittance analysis of these two mutants, MADS-78 and MADS-79
[00:11:27.100]mutants, and found that many of the genes involved in auxin response, such as auxin
[00:11:33.920]biosynthesis gene, UCA7, and the auxin transporter genes, such as ABC11, ABC22, and auxin signaling
[00:11:42.340]genes, these were having a differential expression compared to the wild type.
[00:11:47.300]So which indicates that the role of MAT78 and MAT79 are like in the auxin homeostasis.
[00:11:55.040]And these auxins are very important for the cell division and early-grain development.
[00:12:06.700]So far we have seen the impact of he stress at the early-grain development stage and some
[00:12:12.580]of the morphological and phenotypic changes and the genes associated with the
[00:12:17.280]seed size determination for some specific accessions.
[00:12:21.660]But it's also important to know that how this gene expression changed for the different
[00:12:27.560]genotypes in the geoplasm accession because they exhibited diverse phenotypic response
[00:12:33.100]to the transient he stress.
[00:12:39.320]To understand that, we designed a greenhouse-based experiment in which we selected 10 rice diversity
[00:12:47.260]accessions, a compressing of three indica, four temperate japonica, and three tropical
[00:12:51.800]japonica accessions.
[00:12:53.740]Then at the time of spikelet flowering, spikelet is a single unit of the panicle, we mark the
[00:13:00.440]spikelet and we remain the plants in the control condition, and 24 hours after fertilization,
[00:13:06.480]we split the plants in two groups.
[00:13:08.600]The first batch was given he stress that covers the syncytium to cellularization stage.
[00:13:14.960]You can see that's 48, 72, and 90.
[00:13:17.240]So it's all the way up to five days.
[00:13:21.080]And we also collect the transcriptome samples from these three time points.
[00:13:26.180]And we move back the plants to the control condition and grown until maturity.
[00:13:32.520]So the matured dehusk plants were used for the grain size estimation.
[00:13:47.220]Here is the seed size estimation that we obtained from the previous experiment.
[00:13:52.220]And shows that the selected indica accession had a lower grain width, grain length along with the temperate japonica accession Tj1, Tj2, Tj2 and Tj4.
[00:14:08.220]And shown that the indica 3 had a significant reduction in the grain length while none of the other accession had any reduction in the grain length.
[00:14:17.200]In contrast to the grain length, grain width was more sensitive to heat stress because we can see that nearly half of the selected accession had significant reduction in the grain width.
[00:14:28.180]Which indicates that the grain length and grain width are regulated in a different genetic pathways and that grain width is more sensitive to heat stress compared to the grain length.
[00:14:47.180]So we can see how the transient heat stress impact the grain quality and we analyze the grain chalkiness.
[00:14:52.180]Grain chalkiness is nothing but a grain quality index.
[00:14:57.180]And here you can see that the INDICA3 accession had significantly high grain chalkiness.
[00:15:02.180]So the grain chalkiness is an opaque white discoloration at the endosperm that occurred due to the distortion, the starch and storage packaging.
[00:15:12.180]Some of the accessions such as TEJ2 had relatively low chalkiness.
[00:15:17.160]Which indicates that the transient heath stress also reduced the grain quality.
[00:15:24.160]So now we move on to the transcriptome from the phenotypic analysis.
[00:15:35.160]And the principal component analysis shows that the samples are clustered based on the subpopulation of origin.
[00:15:47.140]The temperature and tropical Japanese accessions were clustered separately based on the subpopulation.
[00:15:52.140]And the control one is the circle one and the heath stress is the triangle one.
[00:15:59.140]And from 48 to 72, up to 96, when the temperature progress, when the temperature stress progress, the samples started getting separated.
[00:16:08.140]As you can see here, the samples were clustered together at 48 hours, but they were slightly going separated at 90 hours.
[00:16:17.120]So which indicates that both subpopulation of origin and the heat stress drive the sample separation.
[00:16:31.120]Then we estimated the differential expressed genes by comparing all the stress samples along with their control for all the three time points for all the ten accessions.
[00:16:42.120]And this showed the union of all the differential expressed genes.
[00:16:47.100]And the x-axis indicates the genes and y-axis indicates the accessions.
[00:16:52.100]The first panel indicates the indica accessions.
[00:16:55.100]Then second panel is tropical japonica one, tropical japonica accession.
[00:16:59.100]And the third one is the temperature japonica accession.
[00:17:01.100]So we did the clustering analysis of all these genes and found some interesting clusters.
[00:17:06.100]For instance, if you look at the cluster five, six and seven, these genes are having similar expression across all the genotypes, irrespective of the
[00:17:17.080]genetic difference, subpopulation level difference, which indicates that these genes are the common pool of genes involved in the grain development.
[00:17:26.080]At the same time, some other accessions, such as cluster three, the genes in this cluster three are having high expression in the indica accessions,
[00:17:36.080]but they were turned off in temperature and tropical japonica accessions.
[00:17:41.080]Cluster three and cluster 15 show the opposite expression, where cluster 15 genes are having
[00:17:47.060]high expression in indica accessions, where high expression in the tropical and temperature
[00:17:51.060]japonica accessions.
[00:17:53.060]And the same goes for cluster eight and cluster one.
[00:17:58.060]These two are having opposite expression, and the genes in this cluster might be involved
[00:18:03.060]in the subpopulation level adaptation of this adaptation of this accession based on the
[00:18:09.060]temperature regimes across the world.
[00:18:14.060]And we also found some cluster where the genes
[00:18:17.040]are only expressed in response to the heat stress, and these are the stress related clusters.
[00:18:30.040]I'll give a snapshot of some of the analysis.
[00:18:35.040]The first one is the heat shock proteins and heat shock factor.
[00:18:38.040]So basically, we did the network analysis of all the grain expression genes and found that the group of heat shock proteins and heat shock factors
[00:18:47.020]along with some other genes such as MAD57, MBF1, and EAL1, ethylene responsive factor genes,
[00:18:56.020]these are highly expressed in three tolerant accessions, the TGA1, TGA4, and TGA5.
[00:19:03.020]And this heat shock proteins and heat shock factors, which are not to be associated with the stress tolerance.
[00:19:10.020]So which indicates that the transient heat stress constitute a heat shock proteins and heat shock factor
[00:19:17.000]network that is activated in temperature japonica accessions in response to alleviate the stress effect.
[00:19:32.000]In our analysis, there is one accession, INDICA2, that was showing moderate heat stress sensitivity.
[00:19:40.000]And we found that many of the grain filling transcription factors was uniquely induced in INDICA2.
[00:19:46.980]Especially at 96 hours.
[00:19:49.980]And when we analyzed the downstream genes of this grain filling transcription factor,
[00:19:54.980]we found that all these genes are highly expressed in INDICA2 compared to the other accessions.
[00:19:59.980]These are the grain filling transcription factors, the grain filling downstream genes of this BC50 transcription factors.
[00:20:07.980]So which indicates that the grain filling in INDICA2 is coordinated by BC50 transcription factor.
[00:20:16.960]Similar to the HSP and HSF network, the network analysts also identify a group of genes in which the function of the many genes are related to protein folding and protein folding chaplonins and response to heast stress.
[00:20:37.960]And many of the genes are highly expressed in a tolerant accession TGFI.
[00:20:46.940]And many of the genes are highly expressed in a tolerant accession TGFI.
[00:21:16.920]And many of the genes are highly expressed in a tolerant accession TGFI.
[00:21:46.900]And many of the genes are highly expressed in a tolerant accession TGFI.
[00:22:16.880]And many of the genes are highly expressed in a tolerant accession TGFI.
[00:22:46.860]And many of the genes are highly expressed in a tolerant accession TGFI.
[00:23:16.840]And many of the genes are highly expressed in a tolerant accession TGFI.
[00:23:46.820]And many of the genes are highly expressed in a tolerant accession TGFI.
[00:24:16.800]And many of the genes are highly expressed in a tolerant accession TGFI.
[00:24:46.780]And many of the genes are highly expressed in a tolerant accession TGFI.
[00:25:12.660]the regression grain quality under his stress condition
[00:25:15.460]we have seen that even the transient history impairs the impaired grain chalkiness in rice
[00:25:25.460]and if you ask what why this chalkiness is very important there are few factors to consider the
[00:25:31.140]first one is the yield reduction you can see that the scanning electron microscopy structure of
[00:25:37.220]normal grains and chalky grains the normal grains have perfect polygonal shape whereas
[00:25:42.500]the chucky grains have a loosely bounded starch starch formation and which had many
[00:25:47.860]air space between these starch granules and because of the air space the chalky grains had
[00:25:56.260]have lower grain size and weight lower grain weight
[00:26:00.900]also the chalky grains also have a reduction in the
[00:26:07.220]protein content and overall nutrition values and the air space between the starch granules
[00:26:14.580]also make the chalky grain more breakable during the milling process and which also
[00:26:20.340]pitches a low market price and there were several methods that quantified the chalky
[00:26:29.940]chalky phenotype and some of them are based on the commercial scanners based approach and others are
[00:26:36.100]based on the image based approach and previously we developed a software called seed extractor
[00:26:42.020]that helps to that previously helped us to identify the grain size
[00:26:47.140]but the chalky grain is kind of uh intrinsic property grain intrinsic property
[00:26:53.940]also has a kind of surface texture changes so we ask whether these changes in the surface
[00:27:00.740]texture of the chalky grain can be detected using the seed extractor so
[00:27:05.860]we extracted the grain rg pixel values of this chalky grains using the seed extractor so that
[00:27:13.860]we first marked the chalky grains also the background then we subtracted the background
[00:27:20.420]from the foreground and segmented the images then we extracted the grain pixel values rgb pixel values
[00:27:28.980]then we analyzed the pixel values for the chalky and non-chalky grains and found that the
[00:27:41.540]rg values are significantly correlated with the grain chalkiness here you can see that the
[00:27:46.420]chalky grains have higher rg value compared to the non-chalky grains
[00:27:51.460]and this is for the kitak kitaki accessions we also
[00:27:57.460]tested the
[00:27:58.820]this for other accession in the gemplasm collection and found that
[00:28:01.940]many accidents have which have lower rg value had better grain quality under his stress condition
[00:28:09.140]while that accident with high rg values had higher grain chalkiness under his stress condition
[00:28:16.180]this is the point where we decided to conduct a genome-wide experiment
[00:28:25.220]genome-wide analysis and we used the rice diverter
[00:28:28.740]city panel one accession for the genome-wide association analysis and
[00:28:32.260]we used 230 accession and the rdb1 accession has five different subpopulation aromatic oz indica
[00:28:43.060]temperate japonica and tropical japonica and which are from the different geographical regions
[00:28:48.660]and we impose a history for all the 230 accessions in both control and history we collect the samples
[00:28:57.220]and extracted the
[00:28:58.500]rg values
[00:28:59.220]this is a manhattan plot shows the significant snips the x-axis contains the chromosome rises
[00:29:11.940]12 chromosomes and we identify 30 significant snips in control condition and 76 snips in stress
[00:29:20.500]conditions and the topmost tip in control condition harbor a penta trichopectoid domain protein
[00:29:28.180]and this domain previously known to be associated with the chalky grade phenotype for instance a
[00:29:35.300]small kernel one this this gene contains a penta trichopeptid domain and the mutant of the gene
[00:29:41.940]has a chalky phenotype and in ortholog of the gene in maize also had a reduction the seed size
[00:29:47.940]over in he stress we found a significant peak
[00:29:57.940]on the penta trichopeptid domain protein and this domain previously known to be associated with the chalky grade phenotype for instance a small kernel one this this gene contains a penta trichopeptid domain and the mutant of the gene has a chalky phenotype and in ortholog of the gene in maize also had a reduction the seed size
[00:29:57.940]over in he stress we found a significant peak
[00:29:57.940]on the penta trichopeptid domain and this domain previously known to be associated with the chalky grade phenotype
[00:29:57.940]on chromosome five and all these marked genes are having somewhat related to
[00:30:02.740]chalky grain phenotype and we found a gene which is not characterized earlier that is cg5
[00:30:10.340]and if you look at the anatomical expression pattern of the cg5 the expression peaks at s1
[00:30:22.420]stage and it's two stage these two stages are marked by the syncytion to cellular research phase
[00:30:27.700]while the other stages had least expression for this gene also the expression was induced
[00:30:34.260]in response to he stress so this makes the gene perfect candidate for the quality green quality
[00:30:42.100]analysis we also did the promoter gas analysis for this gene and found that the expression is
[00:30:54.420]peak in three and four days after fertilization you can
[00:30:57.460]see that the blue color corresponds to the expression of the gene and which is in the
[00:31:04.420]endosperm transfer layer in maize the endosperm transfer layer is called basal endosperm transfer
[00:31:11.380]layer and that channels the nutrients to the developing endosperm so the function of the
[00:31:15.940]gene is supposed to be transferring the nutrients to the developing endosperm coming back to the
[00:31:27.220]generation so the in the population 90 percentage of the accession had g allele for the snip
[00:31:33.380]while 10 percent of the accession had t allele and we call it as minor allele because only 10
[00:31:39.540]percentage of oxygen had t allele and if you look at the distribution for rg between the
[00:31:45.300]major and minor allele and the minor allele had higher rg values compared to the major allele
[00:31:52.180]and we also found some other accession in the
[00:31:56.980]major allele which also had higher rg values
[00:32:00.020]then we analyzed the expression of cg5 in major and minor allele accessions and found that the
[00:32:13.540]major allele accession had higher value expression for the cg5
[00:32:19.140]and compared to the minor allele accessions and also had the major allele accessions this expression
[00:32:26.740]of cg5 is even induced in response to the heast stress and if you look at the grain quality
[00:32:33.140]all the major allele accession had better grain quality in response to heast stress while the
[00:32:39.300]minor allele accessions had more grain chalkiness so which indicates that the transcript abundance
[00:32:45.380]of cg5 could be positively associated with the grain quality then to test
[00:32:56.500]that we generated the transit explains we got obtained two crisper cast mutant lines
[00:33:03.380]one with one neutron base period deletion other with a single base period deletion we descend that
[00:33:09.860]gate from the first exon and we also got over expression lines with more than two fold expression
[00:33:16.500]then using the transient channel transient
[00:33:26.260]excellence we conducted a phenotype analysis and found that the wild type and that over
[00:33:33.460]expression lines were really comparable while the no coats had more chalky phenotype in the
[00:33:40.180]under the hysteresis conditions you can see that many of the grains are had more chalky phenotype
[00:33:48.340]and if you look at the distribution of rg the chalky grains under his stress had more rg
[00:33:56.020]values which corroborates the phenotypic response which indicates that the oscg5 no
[00:34:03.220]coats are more sensitive to his stress and the overexposing in the oscg5 could improve the his
[00:34:09.780]stress sensitivity the low quality of this no coat lines also had a reduction the single grain weight
[00:34:25.780]you can see that the no coats had reduction single grain weight and grain width in response to his
[00:34:31.540]stress and over expression and kitake wild type kitake had comparable grain size parameters
[00:34:39.540]which indicates that the oscg5 expression is positively correlated with the
[00:34:46.180]grain quality and this could be used for the breeding program for developing the tolerant accessions
[00:34:55.540]in summary grain rgp values are associated with the grain chalkiness and jivas revealed several
[00:35:06.340]significant snip that are related to grain rgp which are also probably involved in the
[00:35:11.300]controlling the grain chalkiness level also
[00:35:14.740]we found that cg5 positively regulate the grain quality under his stress
[00:35:19.860]and the knockouts of this cg5 reduce the grain quality and yield due to the production of more
[00:35:25.300]chalky grades under histories so herewith i am thanking you uh my pa dr malvaria and all lab
[00:35:38.020]members involved in this project dr punith paul dr jaspreet kaur and dr burpreet thanks sir
[00:35:44.500]thanks no uh we'll open up for questions
[00:35:55.060]questions i'm happy to start uh so um with the subgroups of rice subpopulations of rice are any
[00:36:02.420]of them known to be more heat tolerant and do you see any of these the alleles of these genes um
[00:36:09.300]like uh in those subpopulations and rich in those subpopulations
[00:36:14.420]yeah in the subpopulation some of them are tolerant accessions
[00:36:18.420]some of them are very sensitive accessions and this chalkiness is a polygenic trait
[00:36:25.780]and are any of the but are any of the subgroups like known to be more
[00:36:32.020]tolerant than the other ones subgroup means you mean the subpopulation level yeah
[00:36:37.220]no we didn't find any specific subpopulation which are tolerant accessions
[00:36:42.580]but uh from our 10 accessions we found that the temperate jeopardy cancers are more of tolerant
[00:36:48.900]because of they induce the his hsphs of network the temperate ones yes
[00:36:54.580]okay nice talk um two unrelated questions so with the chalky phenotype um do you know what happens
[00:37:11.380]to the so you showed smaller starch grains and more space down what happens to the total
[00:37:18.180]starch content but perhaps more interest importantly interestingly do you know
[00:37:24.340]anything about the amylose to amylopectin ratio which could impact um you know lysemic index yes
[00:37:33.780]so the chalky grains have a different uh starch branching because uh we are conducting an
[00:37:41.140]experiment on that so what we found was that branching is different so amylose content and
[00:37:45.380]amylose pectin content is different for the chalky grains as well as the total protein
[00:37:49.460]also content is different for chalky grains do you know which way i mean is it
[00:37:54.100]like increased in amylose in the chalky no we didn't we are conducting an experiment on that
[00:37:59.380]that would be interesting to know and then unrelated to that um the fertilization independent
[00:38:05.080]endosperm mutant fie so we know what that looks like in the rabidopsis the phenotype the mutant
[00:38:11.740]phenotype yes i mean you've showed that that gene's involved in regular in orchestrating the
[00:38:17.300]heat shock response yes um firstly what does that that mutant look like
[00:38:23.860]in rice and and secondly um can you predict how what how that mutant might respond to
[00:38:33.580]heat stress given its role as an overarching factor in regulating the response so the free
[00:38:42.360]one basically involves in the determining the duration of the syncytium stage and which also
[00:38:47.920]we have as i shown it's going up under the moderate heat stress condition the expression goes up and
[00:38:53.620]and it improves the grain quality under the history conditions although the overall grain
[00:39:01.780]size reduces under the history it perform better
[00:39:04.780]fear one first so fewer knockouts make seeds bigger but when you wear them they're actually
[00:39:23.380]lighter so because they're puffed up uh whereas Anil mentioned that over expression lines make
[00:39:30.280]the seeds smaller but when you heat stress them they maintain better quality uh as for the first
[00:39:36.580]question um so we're still doing some work but uh our initial analysis tells that the total starch
[00:39:45.220]and protein content decrease under heat stress even this transient heat stress and that the um
[00:39:53.140]the readily digestible starch percentage increases and the resistant starch percentage decreases
[00:40:00.520]uh when you have this so essentially uh affecting the packaging uh we're
[00:40:07.000]kind of looking well we are looking at the amylose uh uh and amylopectin it's just the
[00:40:16.420]there's variation in the panicle itself so you can't assign so we have to be very very careful
[00:40:22.900]in marking which means that you need like 50 60 plants for them to the biochemist directly
[00:40:28.600]do the analysis in a reliable way because we grind them uh and so so yeah so we're doing that
[00:40:34.700]it's just the amount of materials that they require and the amount of material plants we
[00:40:39.960]have to grow to precisely match it makes it like very labor intensive and very low throughput so
[00:40:47.120]but we are doing that which should sign up to increase that's the expectation and
[00:40:52.660]they've done some they run some of the samples uh but they basically came back and said that well
[00:41:00.060]we had to combine several of your replicates to make one so we're kind of in the process of doing
[00:41:06.020]that it's the contrary to how your mind works when you increase amylose you make it for less
[00:41:15.820]digestible starch because you have less uh you know branch branch ends to chew on for the end
[00:41:22.420]of that would actually be a positive that came out of these slides yeah i mean if we if that
[00:41:29.080]comports but we do know that the digestibility of cooked rice so we cook them uh and uh and in
[00:41:37.360]that case the uh the the resistant starch decreases essentially even a transient heat stress
[00:41:46.360]uh with the with the material that we were of course we haven't looked at 50 lines yet
[00:41:52.180]uh the digestible the glycemic index would increase so rice actually would become
[00:41:56.740]unhealthier from that perspective with with temperature uh you know these spikes or heat
[00:42:03.540]waves or whatever you want from your um major little manual effect size slides you show that
[00:42:17.620]um the effect size is pretty much the same or very similar
[00:42:21.940]but why you your GWAS results only show up the signal uh under stress condition
[00:42:28.260]so how do we explain that yeah this first thought appeared in the control conditions
[00:42:38.100]but we also didn't find any big difference in the
[00:42:43.860]you know uh under control and heat stress because the major and minor little
[00:42:51.780]they were different but not in response to the heat stress conditions
[00:42:59.380]so it responds to stress differently
[00:43:07.220]you mean this measure and manually accessions
[00:43:13.380]yeah just how to explain that so you know in the figure
[00:43:21.460]and this results so you need to explain this and clarify why you detect
[00:43:29.220]only under stress condition and what's the indication there
[00:43:33.780]yeah we do not see that hip appeared on the
[00:43:42.020]yeah this slip was supposed in control condition right only appeared in
[00:43:51.220]the stress condition
[00:43:52.180]we're seeing that several other games too that are validated like when you
[00:44:01.460]look at the jurors it seems to miss it like in one condition versus the other
[00:44:05.780]but when you kind of box plot it so clearly something's happening
[00:44:10.500]with the analysis when it's run independently
[00:44:15.140]so yeah so we we've had that it's probably the third time
[00:44:21.300]that the three g's that we're going to show and validate phenotype
[00:44:24.980]you only show in one condition not the other but when you plot it you see the difference
[00:44:30.980]does that mean the the phenotype would be more severe under certain conditions or it could mean
[00:44:41.540]that the it's there's something about the data sensors maybe the gs analysis is not picking it up
[00:44:50.740]it could be that there's still more variability like um right because us is just on mean
[00:45:01.140]differences so your mean differences might not be different but it's causing more variability
[00:45:05.780]i got a question about the first part of the presentation
[00:45:14.340]you propose a molecular model that says the heat stress induces er stress and then
[00:45:20.500]also iron starvation right yes so i'm kind of curious just from a management perspective
[00:45:26.740]if you deliberately give your rice a iron stress like iron deficiency does that also
[00:45:34.740]increase heat tolerance in that sense or is the interpretation it's most likely going to
[00:45:40.020]decrease the history of tolerance because you know the irons are very and accumulation is
[00:45:44.740]very important for the optimal upr activation so that's what we are seeing that most of the
[00:45:50.340]most of the these genes are activated in response to the
[00:45:54.180]and starvation conditions oh so in this case if you give your plants more iron they'll be more
[00:46:00.660]tolerant yes oh okay have you guys tried to see that no we are working on that okay sounds good
[00:46:06.020]thank you i have a question from lamar maybe global perspective
[00:46:20.020]as a commercial rice breeding program trying to develop commercial rice varieties
[00:46:26.660]how would you advise them to use the information that you've generated in this research
[00:46:32.740]to successfully improve rice varieties that will be more heat tolerant
[00:46:37.300]this first of all this chalky grain is a kind of a polygenic trait
[00:46:43.380]so this gene alone cannot improve the history's resilience but when this gene expression
[00:46:49.780]in combination with other genes might improve the history's tolerance under yeah
[00:46:55.060]when they're dealing with literally thousands of different plants in their breeding program
[00:47:08.420]are they going to be able to do the analyses
[00:47:13.380]that you are proposing there very economically or successfully
[00:47:19.540]yeah that's a good question well the snip is associated with that allele that will give you
[00:47:25.860]either more or less chocolate so that's just you know knowing that dna status there so you could
[00:47:31.460]find uh so that information for rice right now is already available for more than 5 000 accessions
[00:47:38.580]in the world so so yeah so from a breeding perspective you're going to need to be able to
[00:47:45.940]get that information and then you're going to have to go through that process again
[00:47:49.300]and then you're going to have to go through that process again
[00:47:50.740]select for that the only challenge is that
[00:47:54.020]several programs have in the u.s and other places have kind of found the same locations
[00:48:01.860]if you look at it to show the math there's uh the manager
[00:48:06.340]yeah so there's you there's papers on that bha yeah they've also they also think that that's
[00:48:19.060]the gene uh you know that's involved in brain quality under the stress so there's at least
[00:48:26.500]another we learned about it in the department there's another gene sitting there so clearly
[00:48:32.180]that locus is strong even under control conditions but we found this maybe they didn't find this gene
[00:48:40.900]because they did not pose a heat stress they were just mapping for brain quality so we find that this
[00:48:48.820]is showing up under uh under high temperature obviously we still cannot explain why it's not
[00:48:57.300]showing up under control conditions that's generally mentioned but that's to me seems like a
[00:49:03.780]work of whatever is happening under the gbus analysis uh but i i i don't have a better
[00:49:12.420]explanation at this point right i can talk to you for that but that's the third gene that we've seen
[00:49:18.900]that when we it's only seen in one condition whether it's controlled or de-stressed or
[00:49:23.540]when you separate when you parse it out and you look at the phenotypic value you see the
[00:49:30.180]difference even under uh non-stressed conditions so i don't know why it's not showing up uh in
[00:49:37.220]one condition and not the other the difference between like dry land rice types and uh
[00:49:43.620]what you call the other ones that are flooded
[00:49:48.340]we the germ product that we used i don't think that has the information or does it
[00:49:58.500]think yeah i don't think it has that information but no but it could be
[00:50:03.060]dug in like by going in an individual location
[00:50:05.700]well thanks for the discussion thanks for the talk anil uh one more time let's uh thank the
[00:50:18.100]audience
[00:50:21.460]Thank you.
[00:50:21.560]Thank you.
[00:50:21.600]Thank you.

The screen size you are trying to search captions on is too small!

You can always jump over to MediaHub and check it out there.

Comments

0 Comments

Genetic Basis of Grain Yield and Quality under Heat Stress in Rice

Description

Searchable Transcript

Comments icon comment

Related Channels

Comments