The role of spermine in host penetration between fungus Magnaporthe oryzae and rice plants.

Ngoc Pham Author

04/04/2021 Added

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Rice is one of the important crops in the world, but it is threatened by pathogenic fungi called Margnaporthe oryzae. Spermine has been found to correspond to mucilage production which enhances the penetration to the host.

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[00:00:01.020]Hello, my name is Ngoc Pham and I'm from Dr. Richard Wilson's lab.
[00:00:06.000]Our lab is focusing on host-pathogen
[00:00:08.190]relationship between Margnaporthe oryzae and rice plants. In this
[00:00:12.990]presentation,
[00:00:14.040]I would like to share about the role of spermine in host penetration. For
[00:00:18.960]the background, rice is one of important crops.
[00:00:22.740]This is the third-highest grain production in the world. However,
[00:00:27.360]is threatened by a pathogenic fungi called Margnaporthe oryzae that
[00:00:31.740]causes the rice blast disease. From the previous lab work,
[00:00:35.850]we have known that not all fungi synthesize polyamine,
[00:00:39.660]but spermine is detected in Margnaporthe oryzae, and SPS1
[00:00:44.220]is the enzyme that synthesizes spermine.
[00:00:48.140]This led us to the first question
[00:00:50.310]if SPS1 important in rice infections.
[00:00:54.300]We came up with the null hypothesis that there is no difference in rice
[00:00:59.040]infection between the wild type and SPS1 mutant strain.
[00:01:03.480]Here were three strains that we used in this study that the G11,
[00:01:07.650]which was the wild-type, the SPS1 mutant strain which the gene encoding
[00:01:12.550]the SPS1 was disrupted, and the complementation strain.
[00:01:18.240]This is the infection process. After this spore contacts the plant cell,
[00:01:23.280]the appressorium will form on the surface of the plant cells.
[00:01:26.970]After that, the penetration peg will form underneath the appressorium
[00:01:31.680]into the cells.
[00:01:33.180]This will initiate the development of the infected hyphae inside a plant
[00:01:38.160]cell and spread out to the neighbor cells.
[00:01:41.010]This will cause lesion on the leaves,
[00:01:44.910]And this is the result was obtained at 120 hours post
[00:01:49.410]inoculations. As you can see in the wild-type, the leaf
[00:01:53.160]was severely damaged by the fungi with a lot of lesions, and
[00:01:58.110]and the leaf also discolored to yellow. However,
[00:02:01.590]in the mutant strain, the leaf
[00:02:03.180]was still healthy, and very less lesions were observed.
[00:02:08.010]In a complementation strain,
[00:02:09.900]The phenotype is somehow similar to the wild-type with more lesions,
[00:02:14.940]and some of the parts also discolored on the leaf.
[00:02:19.290]On the other hand, we also detected at different inoculation time points. It was interesting for
[00:02:24.270]us to see that in the mutant strain, the appressoria
[00:02:28.380]could still be formed, which is more than 60%. However,
[00:02:32.760]they could not penetrate the leaf cuticles
[00:02:35.880]and spread out to the neighbor cells. Thus,
[00:02:40.200]we rejected our null hypothesis,
[00:02:42.630]and we know that SPS1 has a role in rice infections.
[00:02:47.880]Then we want to find out why the deletion In this genes reduce the penetrations.
[00:02:55.110]These are the S E M images of the wild-type and the mutant strain done by Dr.
[00:02:59.920]Rocha. She found that in the mutant strain,
[00:03:03.340]the appressorium shape was different from the wild-type. Also,
[00:03:08.110]less mucilage was produced in the mutant strain comparing to the wild-type.
[00:03:12.670]Thus,
[00:03:13.300]we know that mucilage is necessary for the appressorium adhesions and penetration.
[00:03:17.650]Additionally,
[00:03:20.320]SPS1 also participates in mucilage productions.
[00:03:25.060]Furthermore,
[00:03:26.590]we wonder if spermine corresponds to mucilage productions. Thus,
[00:03:31.240]we came up with another hypothesis.
[00:03:33.640]Sperming supplemented to a mutant strain will restore mucilage production and
[00:03:37.930]penetration. As the results,
[00:03:41.530]We found that the mutant strain with spermine supplement can somehow restore
[00:03:46.270]the shape of the appressorium and produce more mucilage around it
[00:03:50.530]comparing to the mutant without spermine supplement. To the right,
[00:03:55.180]We also compared the adhesions.
[00:03:58.300]They showed that there was no significant difference between the wild-type
[00:04:03.130]and mutant with spermine
[00:04:04.690]supplement. This means that the hypothesis
[00:04:09.700]is supported, and we concluded that spermine might correspond to mucilage
[00:04:14.650]production
[00:04:15.610]and enhances the appressorium adhesion. About the
[00:04:20.170]method,
[00:04:21.190]Here are the two main methods that I did the most in the study. In the infection
[00:04:25.960]essay. After obtaining the two-week-old fungi,
[00:04:29.920]I harvest the spores and diluted it and sprayed 10 ml of the diluted
[00:04:34.790]solution containing spores to the rice plants.
[00:04:38.110]The infected plants were kept in the dark overnight. Then,
[00:04:43.270]they were transferred to the growth chamber. In the leaf sheath assay
[00:04:47.950]the first two steps were similar to the infection essay.
[00:04:52.810]Instead of spraying, I pipetted
[00:04:55.000]the solution into the leaf sheath, incubated at the 26
[00:04:59.650]degree. After a certain hour of inoculations,
[00:05:05.050]we, um,
[00:05:06.130]I cut the leaf sheath to prepare the slides for the microscopy.
[00:05:12.430]Personally,
[00:05:13.570]I found this study is very significant because understanding the
[00:05:18.100]infection process and the row of spermine in penetration can help
[00:05:23.020]reduce the rice blast disease. For the future,
[00:05:26.470]we can apply to study on different crops like wheat or barley, because
[00:05:31.240]these crops were found to be infected by this fungi.
[00:05:36.640]Thus, we can study if this fungi using the same penetration
[00:05:40.990]mechanism in causing wheat blast or
[00:05:45.760]barley blast disease. On the other hand,
[00:05:49.300]some fungi have have been found to contain spermine, so we can study
[00:05:54.130]if their spermine has the same role comparing to the Margnaporthe oryzae.
[00:05:59.960]Lastly, I would like to express my special thanks to Dr.
[00:06:03.800]Wilson and UCARE program for an opportunity to join in the lab.
[00:06:08.150]I also appreciate Dr.
[00:06:09.560]Rocha and Michael Richter for letting me be their side during
[00:06:14.420]the Graduate program. I have learned a lot, not only the techniques,
[00:06:19.160]but also developing my
[00:06:23.480]logical thinking as a scientist. Secondly,
[00:06:27.410]I would like to thank my parents and friends who support and encourage me during
[00:06:31.790]the project. Lastly,
[00:06:34.190]I would like to extend my appreciation to those who I have not mentioned here.
[00:06:39.200]Thank you, you all, for your help. And here were some
[00:06:44.000]brief references that I used in this presentation. Thank you so much for listening.

The role of spermine in host penetration between fungus Magnaporthe oryzae and rice plants.

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The role of spermine in host penetration between fungus Magnaporthe oryzae and rice plants.

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