Prabu Gnanasekran and Madan Panday

Dr. Prabu Gnanasekran is a post-doctorial researcher in Dr. Hanu Pappu’s Laboratory and Pandey Madan is a graduate student with Dr. Achour Amiri.

“Phenotypic and molecular Characterization of fungicide sensitivity in various Penicillium species causing blue mold of pome fruit in Pacific Northwest”
Madan Pandey, Masters student, Department of Plant Pathology
Abstract:
Blue mold disease poses a significant threat to apples and pears in storage, causing economic losses estimated to make up to 50% of total decays. Penicillium expansum is believed to be the primary causal species of blue mold, however several other Penicillium species have been identified and reported to make up to 25% of PNW Penicillium population. Postharvest fungicides, i.e., thiabendazole (TBZ), pyrimethanil (PYR), and fludioxonil (FDL) have been used to manage blue mold and other postharvest diseases for decades, whereas difenoconazole (DIF) has been registered in 2017. Frequent applications of these fungicides have selected for strains of P. expansum . that are resistant to TBZ, FDL and PYR. .However, Penicillium species that were phenotypically different from P. exapansum showed unusual higher levels of tolerance when tested in vitro on a single discriminatory dose of each of the 3 fungicides. The reasons behind the elevated in vitro tolerance of these “non-expansum” isolates are unknown. The ability of the label rates of the four postharvest fungicides to control these Penicillium spp. populations on fruits is also unknown. Therefore, a research study that combines both in vitro and in vivo fungicide sensitivity assays among various Penicillium isolates, along with molecular characterization of the Penicillium populations will help understand the resistance mechanisms and the development of effective control measures. Our preliminary findings indicate a high level of tolerance to FDL among various Penicillium species, whereas the test for sensitivity to PYR, TBZ and DIF is currently being done. The research goal is to determine if the level of in vitro tolerance translates into in vivo resistance, hence control failure. Furthermore, the research is also aimed towards identifying the possible molecular mechanism(s) that may be causing this high level of resistance in comparison with known mechanisms in P. expansum.

References:
Amiri A., and Pandit LK. 2019. Fungicide resistance in Penicillium expansum from pome fruit in the U.S. Pacific Northwest. Phytopathology 109-10: S2.75.

For more information about Madan’s seminar, please see the seminar announcement .

“Potato virus Y modulates the auxin-signaling pathway to promote disease development”
Dr. Prabu Gnanasebaran, post-doctorial researcher in Pappu Laboratory,  Department of Plant Pathology
Abstract:
Potato virus Y (PVY) is one of the most economically important plant pathogens that affects staples such as potato and several other solanaceous plants and is considered as top five economically important viruses in the world. The PVY genome encodes a single polyprotein which is then post-translationally cleaved into P1-pro, HC-pro, P3, CI, VPg, NIa-pro, NIb, and coat protein (CP). In this study, we performed a yeast two-hybrid (Y2H) screen of Nicotiana benthamiana cDNA library using PVY-encoded NIa-pro as the bait. The N. benthamiana Indole-3-acetic acid-amido synthetase (IAAS) was identified as an interactor of NIa-pro protein. The interaction was confirmed via targeted Y2H and bimolecular fluorescence complementation (BiFC) assays. We have shown the subcellular localization of both NIa-pro and IAAS protein in the nucleus and cytosol. IAAS converts free (active) IAA to the inactive, conjugated form, which plays a crucial regulatory role in auxin signaling. Transient silencing of IAAS in N. benthamiana plants interfered with the PVY-mediated symptom induction and virus accumulation. Conversely, overexpression of IAAS enhanced the symptoms induction and virus accumulation in the infected plants. In addition, the expression of several auxin-responsive genes was found to be downregulated during PVY infection. Our findings demonstrate that PVY NIa-pro protein potentially promotes disease development via modulating auxin homeostasis.
References:
Gadhave, K. R., Gautam, S., Rasmussen, D. A. & Srinivasan, R. 2020. Aphid Transmission of Potyvirus: The Largest Plant-Infecting RNA Virus Genus. Viruses, 12, 773.
González-Lamothe, R., El Oirdi, M., Brisson, N. & Bouarab, K. 2012. The conjugated auxin indole-3-acetic acid-aspartic acid promotes plant disease development. The Plant cell, 24, 762-777.

For more information about Dr. Gnanasebaran seminar, please see the seminar announcement.