The basic helix–loop–helix transcription factor Crf1 is required for development and pathogenicity of the rice blast fungus by regulating carbohydrate and lipid metabolism

Abstract

Pyricularia oryzae is a plant pathogen causing rice blast, a serious disease spreading in cultivated rice globally. Transcription factors play important regulatory roles in fungal development and pathogenicity. Here, we characterized the biological functions of Crf1, a basic helix-loop-helix (bHLH) transcription factor, in the development and pathogenicity of P. oryzae with functional genetics, molecular and biochemical approaches. We found that CRF1 is necessary for virulence and plays an indispensable role in the regulation of carbohydrate and lipid metabolism in P. oryzae. Deletion of CRF1 led to defects in utilization of lipids, ethanol, glycerol and L-arabinose, and down-regulation of many important genes in lipolysis, β-oxidation, gluconeogenesis, as well as glycerol and arabinose metabolism. CRF1 is also essential for peroxisome and vacuole function, and conidial cell death during appressorium formation. The appressorium turgor, penetration ability and virulence in Δcrf1 were restored by supplementation of exogenous glucose. The virulence of Crf1 mutant was also recovered by adding exogenous D-xylose, but not by addition of ethanol, pyruvate, leucine or L-arabinose. These data showed that Crf1 plays an important role in the complex regulatory network of carbohydrate and lipid metabolism that governs fungal development and pathogenicity.

Endoplasmic reticulum‐associated degradation mediated by MoHrd1 and MoDer1 is pivotal for appressorium development and pathogenicity of Magnaporthe oryzae

“…Conidial nuclear degeneration is also the consequence of autophagy following mitosis and nuclear migration (He et al ., 2012). And the effective transfer of lipid droplets from the conidia to the nascent appressoria is required for appressorial maturation and appressorium‐mediated host penetration (Thines et al ., 2000; Cao et al ., 2018). Because the result of delayed conidial nuclear degeneration suggested reduced conidial death in Δ Mohrd1 Δ Moder1 , we therefore monitored the lipid droplets and conidial cell death during conidial germination and appressorium morphogenesis via Bodipy and live‐cell fluorescent dye fluorescein diacetate (FDA) staining.…”

The zinc finger protein StMR1 affects the pathogenicity and melanin synthesis of Setosphaeria turcica and directly regulates the expression of DHN melanin synthesis pathway genes

“…Deletion of the basic helix-loop-helix TF CRF1 in P. oryzae leads to the down-regulation of many important genes in carbohydrate and lipid metabolism, which affects fungal development and pathogenicity (Cao et al, 2018). Therefore, the effects of growth and pathogenicity caused by the knockout of StMR1 may be explained by the differential expression of genes related to these metabolic pathways described above.…”

“…In Metarhizium robertsii , the differential expression of proteins in the biosynthesis of secondary metabolites and glyoxylate and dicarboxylate metabolism was detected by iTRAQ between conidia and mycelia (Wang, Zhou, et al., 2018). Deletion of the basic helix‐loop‐helix TF CRF1 in P. oryzae leads to the down‐regulation of many important genes in carbohydrate and lipid metabolism, which affects fungal development and pathogenicity (Cao et al., 2018). Therefore, the effects of growth and pathogenicity caused by the knockout of StMR1 may be explained by the differential expression of genes related to these metabolic pathways described above.…”

Regulation of Autophagy Machinery in Magnaporthe oryzae

“…Autophagy pathways can be found in yeast, plants, and metazoans [ 15 ]. A collection of more than 30 autophagy-related genes (ATGs) is at the center of the autophagic process, each integral to a distinct, yet ongoing stage [ 16 ]. There was increased phosphorylation of five autophagy proteins (ATG1, ATG2, ATG3, ATG17, and ATG18) during appressorium formation in M. oryzae , but only one site on ATG13 was decreased, suggesting that post-translational ATG alterations are involved in host penetration [ 17 , 18 ].…”