Identification and Characterization of a Novel Basic Helix-Loop-Helix Transcription Factor of Phospholipid Synthesis Regulation in .

The synthesis of phospholipids relies on a sort of genes, whose promoter regions contain inositol-sensitive upstream activation sequence (UAS) and are regulated by the basic helix-loop-helix (bHLH)-type transcription factor (TF) pair. Ten putative bHLH TFs have been found through whole genome sequencing of , but none of these TFs have been characterized. In this study, we identified and characterized the bHLH-type TF in Electrophoretic mobility shift assay (EMSA) and yeast two-hybrid assay demonstrated that functions as a homodimer in UAS genes (e.g., and ) and binds to . Real-time quantitative PCR of and quantification of total phospholipid indicated that the disruptant downregulated the transcription of and the amount of total cellular phosphatidylinositol. In addition, phenotype analyses showed that a loss of led to resistance to cell wall interference and DNA damage. Comparative transcriptome analyses showed that more than 1000 genes and GO terms associated with UAS, endoplasmic reticulum-associated protein degradation, phosphatidylinositol synthesis, chitin synthesis, and fatty acid synthesis were differentially expressed in Δino2 compared to the wild type (WT). Taken together, these observations indicate that the bHLH TF functions as a homodimer that regulates the synthesis of phosphatidylinositol, fatty acid, and chitin and influences the homeostasis of the endoplasmic reticulum membrane.