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In the rice blast fungus M agnaporthe oryzae, the high-affinity cyclic adenosine monophosphate (c AMP) phosphodiesterase MoPdeH is important not only for c AMP signalling and pathogenicity, but also for cell wall integrity ( CWI) maintenance through an unknown mechanism. By utilizing affinity purification, we found that MoPdeH interacts with MoMck1, one of the components of the mitogen-activated protein ( MAP) kinase cascade that regulates CWI. Overexpression of MoMCK 1 suppressed defects in autolysis and pathogenicity of the Δ MopdeH mutant, although partially, suggesting that MoPdeH plays a critical role in CWI maintenance mediated by the MAP kinase pathway. We found that MoMck1 and two other MAP kinase cascade components, MoMkk1 and MoMps1, modulate intracellular c AMP levels by regulating the expression of MoPDEH through a feedback loop. In addition, disruption of MoMKK 1 resulted in less aerial hyphal formation, defective asexual development and attenuated pathogenicity. Moreover, MoMkk1 plays a role in the response to osmotic stress via regulation of MoOsm1 phosphorylation levels, whereas endoplasmic reticulum ( ER) stress enhances MoMps1 phosphorylation and loss of the MAP kinase cascade component affects the unfolded protein response ( UPR) pathway. Taken together, our findings demonstrate that MoPdeH functions upstream of the MoMck1- MoMkk1- MoMps1 MAP kinase pathway to regulate CWI, and that MoPdeH also mediates crosstalk between the c AMP signalling pathway, the osmotic sensing high osmolarity glycerol ( HOG) pathway and the dithiothreitol ( DTT)-induced UPR pathway in M. oryzae. [ABSTRACT FROM AUTHOR]

Rice blast caused by the fungal pathogen M agnaporthe oryzae is one of the most destructive diseases worldwide. Although the rice- M . oryzae interaction has been studied extensively, the early molecular events that occur in rice before full maturation of the appressorium during M . oryzae invasion are unknown. Here, we report a comparative transcriptomics analysis of the durably resistant rice variety Digu and the susceptible rice variety Lijiangxintuanheigu ( LTH) in response to infection by M . oryzae (5, 10 and 20 h post-inoculation, prior to full development of the appressorium). We found that the transcriptional responses differed significantly between these two rice varieties. Gene ontology and pathway analyses revealed that many biological processes, including extracellular recognition and biosynthesis of antioxidants, terpenes and hormones, were specifically activated in Digu shortly after infection. Forty-eight genes encoding receptor kinases ( RKs) were significantly differentially regulated by M . oryzae infection in Digu. One of these genes, LOC _Os08g10300, encoding a leucine-rich repeat RK from the LRR VIII-2 subfamily, conferred enhanced resistance to M . oryzae when overexpressed in rice. Our study reveals that a multitude of molecular events occur in the durably resistant rice Digu before the full maturation of the appressorium after M . oryzae infection and that membrane-associated RKs play important roles in the early response. [ABSTRACT FROM AUTHOR]