Cellular moonlighting function of Hsp20 directs morphological and pathogenic development in Ustilago maydis

Abstract

Ustilago maydis Hsp20 is involved in the pathogenicity of the fungus. In this study we have investigated the molecular basis of contribution of Hsp20 to U. maydis pathogenicity. Through biochemical studies we have demonstrated environment-dependent oligomeric plasticity associated with Hsp20. Hsp20 was also found to form higher order oligomers that undergo phase separation in vitro. Within cells Hsp20 was found to form distinct punctate structures that we believe play a pivotal role in its function. These punctate structures were demonstrated to sequester proteins such as actin and septin within it. Absence of Hsp20 was found to significantly affect key cellular processes like endocytosis, budding, cell polarity determination and mating in U. maydis cells. The deletion mutant failed to sporulate and complete pathogenic life cycle. This study presents a comprehensive understanding of the pathogenic development of U. maydis in reference to the moonlighting function of Hsp20 within the cell.