MoSfl1 Is Important for Virulence and Heat Tolerance in Magnaporthe oryzae

Abstract

The formation of appressoria, specialized plant penetration structures of Magnaporthe oryzae, is regulated by the MST11-MST7-PMK1 MAP kinase cascade. One of its downstream transcription factor, MST12, is important for penetration and invasive growth but dispensable for appressorium formation. To identify additional downstream targets that are regulated by Pmk1, in this study we performed phosphorylation assays with a protein microarray composed of 573 M. oryzae transcription factor (TF) genes. Three of the TF genes phosphorylated by Pmk1 in vitro were further analyzed by coimmunoprecipitation assays. One of them, MoSFL1, was found to interact with Pmk1 in vivo. Like other Sfl1 orthologs, the MoSfl1 protein has the HSF-like domain. When expressed in yeast, MoSFL1 functionally complemented the flocculation defects of the sfl1 mutant. In M. oryzae, deletion of MoSFl1 resulted in a significant reduction in virulence on rice and barley seedlings. Consistent with this observation, the Mosfl1 mutant was defective in invasive growth in penetration assays with rice leaf sheaths. In comparison with that of vegetative hyphae, the expression level of MoSFL1 was increased in appressoria and infected rice leaves. The Mosfl1 mutant also had increased sensitivity to elevated temperatures. In CM cultures of the Mosfl1 and pmk1 mutants grown at 30°C, the production of aerial hyphae and melanization were reduced but their growth rate was not altered. When assayed by qRT-PCR, the transcription levels of the MoHSP30 and MoHSP98 genes were reduced 10- and 3-fold, respectively, in the Mosfl1 mutant. SFL1 orthologs are conserved in filamentous ascomycetes but none of them have been functionally characterized in non-Saccharomycetales fungi. MoSfl1 has one putative MAPK docking site and three putative MAPK phosphorylation sites. Therefore, it may be functionally related to Pmk1 in the regulation of invasive growth and stress responses in M. oryzae.

NTPDase Specific Inhibitors Suppress Rice Infection by Magnaporthe oryzae

“…Pathogenicity assay with dilution‐drop conidia suspension (3×5 μ l/leaf) was performed as previously described (Li et al. ). The lesion areas were measured with the imagej (http://imagej.nih.gov/ij/)software package as previously described (Qin et al.…”

The Magnaporthe grisea species complex and plant pathogenesis

“…Furthermore, many downstream transcription factor targets of these pathways have been shown to play pleiotropic roles in M . oryzae , including MoAp1, MoAtf1, MoMsn2, MoSwi6, MoMig1, MoMcm1, MoSfl1, MoMst12, MoMstu1, MoPth12, MoCtdf1 and MoSom1 (Guo et al ., , ; Li et al ., ; Mehrabi et al ., ; Nishimura et al ., ; Park et al ., ; Qi et al ., ; Yan et al ., ; Zhang et al ., ; Zhou et al ., ) (Fig. ).…”

“…Sln1, Ssk1, Ssk2 and Osm1, which are major components of the HOG1 pathway, have critical roles in osmoregulation and stress responses (Dixon et al, 1999;Motoyama et al, 2005;Zhang et al, 2010). Furthermore, many downstream transcription factor targets of these pathways have been shown to play pleiotropic roles in M. oryzae, including MoAp1, MoAtf1, MoMsn2, MoSwi6, MoMig1, MoMcm1, MoSfl1, MoMst12, MoMstu1, MoPth12, MoCtdf1 and MoSom1 Li et al, 2011;Mehrabi et al, 2008;Nishimura et al, 2009;Park et al, 2002;Qi et al, 2012;Yan et al, 2011;Zhou et al, 2011) (Fig. 2).…”

Genetic control of infection-related development in Magnaporthe oryzae

“…Sfl1 was identified in in vitro phosphorylation assays with a protein microarray of over 500 M. oryzae transcription factors [18 ]. It has putative MAPK docking and MAPK phosphorylation sites.…”