Cloning and Functional Analysis of the Aldehyde Dehydrogenase Gene VvALDH in the IAA Synthesis Pathway of Volvariella volvacea

<i>Volvariella volvacea</i>, the Chinese mushroom, is a high-temperature grass-rot fungus with great production potential, yet its low yield limits industrial development. Exogenous sodium acetate (NaAc) has been shown to increase yield by promoting indole-3-acetic acid (IAA) synthesis during the primordium stage, but the underlying mechanism remains unclear. In this study, the aldehyde dehydrogenase gene <i>VvALDH</i>, highly expressed at the primordium stage, was cloned and functionally characterized. <i>VvALDH</i> encodes a 1509 bp cDNA with a conserved aldehyde dehydrogenase domain. Using Agrobacterium-mediated transformation, overexpression lines showed a 4.76-fold increase in <i>VvALDH</i> expression, accompanied by higher biomass (38%), yield (83%), and IAA content (34%), while RNAi lines showed opposite trends. These results demonstrate that <i>VvALDH</i> promotes IAA biosynthesis, enhances primordium differentiation, and increases yield. Further analysis revealed its involvement in multiple IAA biosynthetic pathways, including indolepyruvate, tryptamine, and tryptophan side-chain oxidase pathways. This work clarifies the molecular basis of NaAc-mediated yield improvement and provides a theoretical foundation for genetic and cultivation strategies in <i>V. volvacea</i>.