UvVelC is important for conidiation and pathogenicity in the rice false smut pathogen Ustilaginoidea virens

Rice false smut disease is one of the most significant rice diseases worldwide. Ustilaginoidea virens is the causative agent of this disease. Although several developmental and pathogenic genes have been identified and functionally analyzed, the pathogenic molecular mechanisms of U. virens remain elusive. The velvet family regulatory proteins are involved in fungal development, conidiation, and pathogenicity. In this study, we demonstrated the function of the VelC homolog UvVELC in U. virens. We identified the velvet family protein UvVELC and characterized its functions using a target gene deletion-strategy. Deletion of UvVELC resulted in conidiation failure and pathogenicity. The UvVELC expression levels during infection suggested that this gene might be involved in the early infection process. UvVELC is also important in resistance to abiotic stresses, the utilization efficiency of glucose, stachyose, raffinose, and other sugars, and the expression of transport-related genes. Moreover, UvVELC could physically interact with UvVEA in yeast, and UvVELC/UvVEA double-knockout mutants also failed in conidiation and pathogenicity. These results indicate that UvVELC play a critical role in the conidiation and pathogenicity in U. virens. Functional analysis indicated that UvVELC-mediated conidiation and nutrient acquisition from rice regulates the pathogenicity of U. virens. Understanding the function of the UvVELC homolog could provide a potential molecular target for controlling rice false smut disease.

One Juliet and four Romeos: VeA and its methyltransferases

Fungal secondary metabolism has become an important research topic with great biomedical and biotechnological value. In the postgenomic era, understanding the diversity and the molecular control of secondary metabolites (SMs) are two challenging tasks addressed by the research community. Discovery of the LaeA methyltransferase 10 years ago opened up a new horizon on the control of SM research when it was found that expression of many SM gene clusters is controlled by LaeA. While the molecular function of LaeA remains an enigma, discovery of the velvet family proteins as interaction partners further extended the role of the LaeA beyond secondary metabolism. The heterotrimeric VelB–VeA–LaeA complex plays important roles in development, sporulation, secondary metabolism, and pathogenicity. Recently, three other methyltransferases have been found to associate with the velvet complex, the LaeA-like methyltransferase F and the methyltransferase heterodimers VipC–VapB. Interaction of VeA with at least four methyltransferase proteins indicates a molecular hub function for VeA that questions: Is there a VeA supercomplex or is VeA part of a highly dynamic cellular control network with many different partners?