Oxidation of self-stored carbohydrates and lipids provides the energy for the rapid morphogenetic transformation during asexual and infection-related development in Pyricularia oryzae, which results in intracellular accumulation of reducing equivalents NADH and FADH₂, requiring a cytosolic shuttling machinery towards mitochondria. Our previous studies identified the mitochondrial D-lactate dehydrogenase MoDld1 as a regulator to channel the metabolite flow in conjunction with redox homeostasis. However, the regulator(s) facilitating the cytosolic redox balance and the importance in propelling nutrient metabolite flow remain unknown. The G-3-P shuttle is a conserved machinery transporting the cytosolic reducing power to mitochondria. In P. oryzae, the mitochondrial G-3-P dehydrogenase Gpd2 was required for cellular NAD⁺/NADH balance and fungal virulence. In this study, we re-locate the mitochondrial G-3-P dehydrogenase Gpd2 to the cytosol for disturbing cytosolic redox status. Our results showed overexpression of cytosolic gpd2^Δmts without the mitochondrial targeted signal (MTS) driven by Ribosomal protein 27 promoter (PR27) exerted conflicting regulation of cellular oxidoreductase activities compared to the ΔModld1 deletion mutant by RNA-seq and prevented the conidiation and pathogenicity of P. oryzae. Moreover, overexpression of gpd2^Δmts caused defects in glycogen and lipid mobilization underlying asexual and infectious structural development associated with decreased cellular NADH production and weakened anti-oxidation activities. RNA-seq and non-targeted metabolic profiling revealed down-regulated transcriptional activities of carbohydrate metabolism and lower abundance of fatty acids and secondary metabolites in RP27:gpd2^Δmts. Thus, our studies indicate the essential role of cytosolic redox control in nutrient metabolism fueling the asexual and infection-related development in P. oryzae.

Avirulence effectors (Avrs), encoded by plant pathogens, can be recognized by plants harboring the corresponding resistance proteins, thereby initiating effector-triggered immunity (ETI). In susceptible plants, however, Avrs can function as effectors, facilitating infection via effector-triggered susceptibility (ETS). Mechanisms of Avr-mediated ETS remain largely unexplored. Here we report that the Magnaporthe oryzae effector Avr-PikD enters rice cells via the canonical cytoplasmic secretion pathway and suppresses rice basal defense. Avr-PikD interacts with an LSD1-like transcriptional activator AKIP30 of rice, and AKIP30 is also a positive regulator of rice immunity, whereas Avr-PikD impedes its nuclear localization and suppresses its transcriptional activity. In summary, M. oryzae delivers Avr-PikD into rice cells to facilitate ETS by inhibiting AKIP30-mediated transcriptional regulation of immune response against M. oryzae.

DNA methylation participates in regulating the expression of coding and non-coding regions in plants. To investigate the association between DNA methylation and pathogen infection, we used whole-genome bisulfite sequencing to survey temporal DNA methylation changes in rice after infection with the rice blast fungus Magnaporthe oryzae. In contrast to previous findings in Arabidopsis, global DNA methylation levels in rice increased slightly after rice blast infection. We identified over 38,000 differentially methylated regions (DMRs), and hypermethylated DMRs far outnumbered hypomethylated DMRs. Most DMRs were located in transposable element regions. Using transcriptome analysis, we identified 8830 differentially expressed genes (DEGs) after 1, 3, and 5 days of infection. Over one-third of DEGs, most of which were CHH-type DMRs, were associated with DMRs. Functional analysis of the CHH DMR-DEGs indicated their involvement in many important biological processes, including cell communication and response to external stimulus. The transcription of many NBS-LRR family genes was affected by changes in DNA methylation, suggesting that DNA methylation plays essential roles in the response of rice to M. oryzae infection. More broadly, the DNA methylation analysis presented here sheds light on epigenomic involvement in plant defense against fungal pathogens.