The homeobox transcription factor CoHox1 is required for the morphogenesis of infection hyphae in host plants and pathogenicity in Colletotrichum orbiculare

Genome-Wide Identification and Characterization of Homeobox Transcription Factors in Phoma sorghina var. saccharum Causing Sugarcane Twisted Leaf Disease

A homeobox transcription factor is a conserved transcription factor, ubiquitous in eukaryotes, that regulates the tissue formation of structure, cell differentiation, proliferation, and cancer. This study identified the homeobox transcription factor family and its distribution in Phoma sorghina var. saccharum at the whole genome level. It elucidated the gene structures and evolutionary characteristics of this family. Additionally, knockout experiments were carried out and the preliminary function of these transcription factors was studied. Through bioinformatics approaches, nine homeobox transcription factors (PsHOX1-PsHOX9) were identified in P. sorghina var. saccharum, and these contained HOX-conserved domains and helix-turn-helix secondary structures. Nine homeobox gene deletion mutants were obtained using the homologous recombinant gene knockout technique. Protoplast transformation was mediated by polyethylene glycol (PEG) and the transformants were identified using PCR. The knockouts of PsHOX1, PsHOX2, PsHOX3, PsHOX4, PsHOX6, PsHOX8, and PsHOX9 genes resulted in a smaller growth diameter in P. sorghina var. saccharum. In contrast, the knockouts of the PsHOX3, PsHOX6, and PsHOX9 genes inhibited the formation of conidia and led to a significant decrease in the pathogenicity. This study's results will provide insights for understanding the growth and development of P. sorghina var. saccharum. The pathogenic mechanism of the affected sugarcane will provide an essential theoretical basis for preventing and controlling sugarcane twisted leaf disease.

Homeobox Transcription Factors Are Required for Fungal Development and the Suppression of Host Defense Mechanisms in the Colletotrichum scovillei-Pepper Pathosystem

Colletotrichum scovillei, an ascomycete phytopathogenic fungus, is the main causal agent of serious yield losses of economic crops worldwide. The fungus causes anthracnose disease on several fruits, including peppers. However, little is known regarding the underlying molecular mechanisms involved in the development of anthracnose caused by this fungus. In an initial step toward understanding the development of anthracnose on pepper fruits, we retrieved 624 transcription factors (TFs) from the whole genome of C. scovillei and comparatively analyzed the entire repertoire of TFs among phytopathogenic fungi. Evolution and proliferation of members of the homeobox-like superfamily, including homeobox (HOX) TFs that regulate the development of eukaryotic organisms, were demonstrated in the genus Colletotrichum. C. scovillei was found to contain 10 HOX TF genes (CsHOX1 to CsHOX10), which were functionally characterized using deletion mutants of each CsHOX gene. Notably, CsHOX1 was identified as a pathogenicity factor required for the suppression of host defense mechanisms, which represents a new role for HOX TFs in pathogenic fungi. CsHOX2 and CsHOX7 were found to play essential roles in conidiation and appressorium development, respectively, in a stage-specific manner in C. scovillei. Our study provides a molecular basis for understanding the mechanisms associated with the development of anthracnose on fruits caused by C. scovillei, which will aid in the development of novel approaches for disease management. IMPORTANCE The ascomycete phytopathogenic fungus, Colletotrichum scovillei, causes serious yield loss on peppers. However, little is known about molecular mechanisms involved in the development of anthracnose caused by this fungus. We analyzed whole-genome sequences of C. scovillei and isolated 624 putative TFs, revealing the existence of 10 homeobox (HOX) transcription factor (TF) genes. We found that CsHOX1 is a pathogenicity factor required for the suppression of host defense mechanism, which represents a new role for HOX TFs in pathogenic fungi. We also found that CsHOX2 and CsHOX7 play essential roles in conidiation and appressorium development, respectively, in a stage-specific manner in C. scovillei. Our study contributes to understanding the mechanisms associated with the development of anthracnose on fruits caused by C. scovillei, which will aid for initiating novel approaches for disease management.