Poster: Molecular & Cellular Plant-Microbe Interactions: MPMI
Macrophomina phaseolina promotes charcoal rot susceptibility in sorghum through induced host nitric oxide (NO) production
A. BANDARA (1), D. Weerasooriya (1), S. Liu (1), C. Little (1) (1) Kansas State University, U.S.A.
Macrophomina phaseolina (MP) is an important necrotrophic pathogen causing charcoal rot disease in sorghum (Sorghum bicolor (L.) Moench). Exploring the host-pathogen interaction is a key to understanding the molecular basis of resistance. An RNA-Seq experiment was conducted to discover differentially expressed genes (DEG) in response to MP infection. SC599 (resistant) and Tx7000 (susceptible) sorghum lines were grown in the greenhouse and inoculated with MP and phosphate-buffered saline (mock-inoculated control). RNA was extracted from three biological replicates at 2, 7, and 30 d post-inoculation (d.p.i.) from stem tissues adjacent to the inoculation point and subjected to RNA-Seq. Among the DEG, three genes (Sb08g011530, Sb05g000680, and Sb04g027860) involved in NO biosynthesis were significantly upregulated in Tx7000 at 7 d.p.i., while those of SC599 were not differentially expressed. To further confirm the findings, confocal microscopy was used. At 7 d.p.i, in situ NO production in MP- and mock-inoculated stem cross sections of two resistant (SC599, SC35) and two susceptible (Tx7000, BTx3042) lines was analyzed using 4-amino-5-methylamino-2?,7?-difluorofluorescein diacetate (DAF-FM DA). Strong green fluorescence was observed in both MP-inoculated susceptible lines confirming the presence of NO while no signal was detected in the resistant lines. We believe that NO-mediated cell death contributes to the rapid proliferation of MP within susceptible hosts.