AUTHOR=Shi Yongkai , Wang Huan , Yan Yuxin , Cao Huijuan , Liu Xiaohong , Lin Fucheng , Lu Jianping 

TITLE=Glycerol-3-Phosphate Shuttle Is Involved in Development and Virulence in the Rice Blast Fungus Pyricularia oryzae

JOURNAL=Frontiers in Plant Science

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.00687

DOI=10.3389/fpls.2018.00687

ISSN=1664-462X

ABSTRACT=<p>The glycerol-3-phosphate (G-3-P) shuttle is an important pathway for delivery of cytosolic reducing equivalents into mitochondrial oxidative phosphorylation, and plays essential physiological roles in yeast, plants, and animals. However, its role has been unclear in filamentous and pathogenic fungi. Here, we characterize the function of the G-3-P shuttle in <italic>Pyricularia oryzae</italic> by genetic and molecular analyses. In <italic>P. oryzae</italic>, a glycerol-3-phosphate dehydrogenase 1 (PoGpd1) is involved in NO production, conidiation, and utilization of several carbon sources (pyruvate, sodium acetate, glutamate, and glutamine). A glycerol-3-phosphate dehydrogenase 2 (PoGpd2) is essential for glycerol utilization and fungal development. Deletion of <italic>PoGPD2</italic> led to delayed aerial hyphal formation, accelerated aerial hyphal collapse, and reduced conidiation on complete medium (CM) under a light–dark cycle. Aerial mycelial surface hydrophobicity to water and Tween 20 was decreased in Δ<italic>Pogpd2</italic>. Melanin synthesis genes required for cell wall construction and two transcription factor genes (<italic>COS1</italic> and <italic>CONx2</italic>) required for conidiation and/or aerial hyphal differentiation were down-regulated in the aerial mycelia of Δ<italic>Pogpd2</italic> and Δ<italic>Pogpd1</italic>. Culturing under continuous dark could complement the defects of aerial hyphal differentiation of Δ<italic>Pogpd2</italic> observed in a light–dark cycle. Two light-sensitive protein genes (<italic>PoSIR2</italic> encoding an NAD<sup>+</sup>-dependent deacetylase and <italic>TRX2</italic> encoding a thioredoxin 2) were up-regulated in Δ<italic>Pogpd2</italic> cultured on CM medium in a light–dark cycle. Δ<italic>Pogpd2</italic> showed an increased intracellular NAD<sup>+</sup>/NADH ratio and total NAD content, and alteration of intracellular ATP production. Culturing on minimal medium also could restore aerial hyphal differentiation of Δ<italic>Pogpd2</italic>, which is deficient on CM medium in a light–dark cycle. Two glutamate synthesis genes, <italic>GDH1</italic> and <italic>PoGLT1</italic>, which synthesize glutamate coupled with oxidation of NADH to NAD<sup>+</sup>, were significantly up-regulated in Δ<italic>Pogpd2</italic> in a light–dark cycle. Moreover, deletion of PoGpd1 or PoGpd2 led to reduced virulence of conidia or hyphae on rice. The glycerol-3-phosphate shuttle is involved in cellular redox, fungal development, and virulence in <italic>P. oryzae</italic>.</p>