The GATA Transcription Factor NsdD Regulates Vegetative Growth, Asexual Sporulation, and Melanin Biosynthesis in Colletotrichum siamense and C. graminicola

The genus Colletotrichum infects over 3,000 monocot and dicot plant species, inflicting substantial economic losses globally. GATA zinc finger proteins play a pivotal role as transcription factors governing fungal growth and development. In this study, we characterized the GATA transcription factor NsdD in C. siamense (CsNsdD) and C. graminicola (CgrNsdD), respectively. Disruption of CsnsdD or CgrnsdD resulted in a reduced mycelial growth rate and sparse hyphal morphology. Functional characterization revealed that NsdD acted as a typical negative regulator of conidiation and melanin biosynthesis in both pathogens. Notably, the CsnsdD knockout mutant demonstrated precocious conidiation and increased conidial yield. Similarly, deletion of CgrnsdD led to enhanced production of both oval and falcate conidia while additionally promoting the formation of falcate conidia in a liquid culture. Furthermore, genetic disruption of CsnsdD/ CgrnsdD substantially elevated melanin accumulation in mycelia. Pathogenicity assessment demonstrated that deletion of CsnsdD/CgrnsdD led to a marked attenuation of fungal virulence. Transcriptomic analysis revealed that both CsNsdD and CgrNsdD contribute to the regulation of multiple functional genes, including those associated with conidiation, the DHN (1,8-dihydroxynaphthalene) melanin biosynthesis pathway, and the production of cell wall-degrading enzymes. In summary, NsdD functions as a global transcriptional regulator in orchestrating vegetative growth, conidiation, and melanin biosynthesis in C. siamense and C. graminicola.