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Poster: Molecular & Cellular Plant-Microbe Interactions: MPMI


Induced rhamnose biosynthesis in sorghum by Macrophomina phaseolina contributes to charcoal rot susceptibility
A. BANDARA (1), D. Weerasooriya (1), S. Liu (1), C. Little (1) (1) Kansas State University, U.S.A.

Macrophomina phaseolina (MP) is a necrotrophic pathogen that causes charcoal rot disease in sorghum (Sorghum bicolor (L.) Moench). To detect differentially expressed genes (DEG) in response to MP infection, an RNA-Seq experiment was conducted. SC599 (resistant) and Tx7000 (susceptible) sorghum lines were stalk-inoculated with MP hyphal fragments and phosphate-buffered saline (control). Stalk RNA extracted at 2, 7, and 30 d post-inoculation (d.p.i.) was subjected to RNA-Seq. Among the DEG, 7 genes involved in the rhamnose biosynthetic pathway (Sb01g038050, Sb01g039220, Sb01g043370, Sb02g029130, Sb08g022850, Sb09g018070, and Sb10g024490) were significantly upregulated in Tx7000 at 7 d.p.i., while those of SC599 showed no differential expression. To confirm the results, stem juice extracted from two MP- and mock-inoculated resistant (SC599, SC35) and susceptible (Tx7000, Btx3042) sorghum lines were subjected to HPLC. Compared to control, the MP-inoculated charcoal rot susceptible lines had significantly higher (P < 0.005) stalk rhamnose concentrations (mg/mL) (Tx7000, 7.2; BTx3042, 5.8), while no such effect was evident in the resistant lines (SC599, 1.6; SC35, 1.4). To test the effect of rhamnose on MP growth, two isolates were grown on minimal medium supplemented with rhamnose at 0, 25, 50, 75, 100, and 125 mM concentrations. MP grew on rhamnose in a concentration-independent manner. Results suggested the potential role of host rhamnose as a virulence factor for MP.