Uncoupling of nutrient metabolism and cellular redox by cytosolic routing of the mitochondrial G-3-P dehydrogenase Gpd2 causes loss of conidiation and pathogenicity in Pyricularia oryzae

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 gpd2Δmts 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 gpd2Δmts 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:gpd2Δmts. Thus, our studies indicate the essential role of cytosolic redox control in nutrient metabolism fueling the asexual and infection-related development in P. oryzae.