Genome-Wide Identification, Expression Analysis, and Potential Roles under Abiotic Stress of the YUCCA Gene Family in Mungbean (Vigna radiata L.)

YUCCA, belonging to the class B flavin-dependent monooxygenases, catalyzes the rate-limiting step for endogenous auxin synthesis and is implicated in plant-growth regulation and stress response. Systematic analysis of the YUCCA gene family and its stress response benefits the dissection of regulation mechanisms and breeding applications. In this study, 12 YUCCA genes were identified from the mungbean (Vigna radiata L.) genome and were named based on their similarity to AtYUCCAs. Phylogenetic analysis revealed that the 12 VrYUCCAs could be divided into 4 subfamilies. The evidence from enzymatic assays in vitro and transgenetic Arabidopsis in vivo indicated that all the isolated VrYUCCAs had biological activity in response to IAA synthesis. Expression pattern analysis showed that functional redundancy and divergence existed in the VrYUCCA gene family. Four VrYUCCAs were expressed in most tissues, and five VrYUCCAs were specifically highly expressed in the floral organs. The response toward five stresses, namely, auxin (indole-3-acetic acid, IAA), salinity, drought, high temperatures, and cold, was also investigated here. Five VrYUCCAs responded to IAA in the root, while only VrYUCCA8a was induced in the leaf. VrYUCCA2a, VrYUCCA6a, VrYUCCA8a, VrYUCCA8b, and VrYUCCA10 seemed to dominate under abiotic stresses, due to their sensitivity to the other four treatments. However, the response modes of the VrYUCCAs varied, indicating that they may regulate different stresses in distinct ways to finely adjust IAA content. The comprehensive analysis of the VrYUCCAs in this study lays a solid foundation for further investigation of VrYUCCA genes’ mechanisms and applications in breeding.