Molecular studies of NAD- and NADP- glutamate dehydrogenases decipher the conundrum of yeast-hypha dimorphism in zygomycete Benjaminiella poitrasii

Abstract

Abstract Benjaminiella poitrasii, a zygomycete shows glucose and temperature dependent yeast (Y)-hypha (H) dimorphic transition. Earlier we reported the biochemical correlation of relative proportion of NAD- and NADP- glutamate dehydrogenases (GDH) with Y-H transition. Further, we observed the presence of one NAD-GDH and two form–specific NADP-GDH isoenzymes in B. poitrasii. However, molecular studies are necessary to elucidate the explicit role of GDHs in regulating Y-H reversible transition. Here, we report the isolation and characterization of one NAD- (BpNADGDH, 2.643 kb) and two separate genes, BpNADPGDH I (Y form specific, 1.365 kb) and BpNADPGDH II (H form specific, 1.368 kb) coding for NADP-GDH isoenzymes in B. poitrasii. The transcriptional profiling during Y-H transition showed higher BpNADPGDH I expression in Y cells while expression of BpNADPGDH II was higher in H cells. Moreover, the yeast form monomorphic mutant (Y-5) did not show BpNADPGDH II expression under normal dimorphism triggering conditions. Transformation with H form specific BpNADPGDH II induced the germ tube formation in Y-5, which confirmed the cause-effect relationship between BpNADPGDH genes and morphological outcome in B. poitrasii. Interestingly, expression of H-form specific BpNADPGDH II also induced germ tube formation in human pathogenic, non-dimorphic yeast Candida glabrata, which further corroborated our findings.