From phenotype to mechanism: background-dependent function of CtDnaJ.16 in thermotolerance-divergent Coriolopsis trogii haploids

Abstract

The two haploids, Ct001_29 and Ct001_31, derived from the thermotolerant strain Coriolopsis trogii Ct001, differ in mating type and exhibit distinct thermotolerance capacities. To investigate the underlying molecular mechanisms, their phenotypic responses to different temperatures were characterized, and comparative RNA-sequencing (RNA-Seq) analyses were performed using an upgraded, manually curated genome annotation. Phenotypic observations revealed that Ct001_31 displayed more robust hyphal growth at 35 °C than Ct001_29, including denser mycelia, larger hyphal diameter, smoother hyphal surfaces, and the ability to sustain growth at 40 °C. Through manual correction, a high-quality genome annotation for Ct001_31 was generated, comprising 12,953 high-confidence genes. Comparative RNA-Seq analysis identified 108 up-regulated and 121 down-regulated genes commonly shared between the two haploids at 35 °C. The up-regulated genes in Ct001_29 were significantly enriched in functions related to protein folding and heat response, whereas no significant functional enrichment was observed among the differentially expressed genes (DEGs) in Ct001_31 at 35 °C. Notably, CtDnaJ.16 showed increased expression in Ct001_31 at 35 °C, while no significant change was observed in Ct001_29. Functional investigation revealed that Ct31DnaJ.16 was specifically involved in thermotolerance in Ct001_31, with transformants overexpressing this gene capable of germinating at 43 °C. In contrast, neither overexpression nor RNA interference of Ct29DnaJ.16 in Ct001_29 led to detectable phenotypic alterations. These findings demonstrate that CtDnaJ.16 plays a strikingly haploid-specific role in thermotolerance, deepening our understanding of functional differentiation between allelic genes.