The Cucumber WRKY Transcription Factor WRKY50 Positively Regulates Shoot Branching

As sessile organisms, plants adapt to their environments through shoot branching, a key determinant of plant architecture. However, the regulatory mechanisms governing this trait in cucumber remain incompletely understood. Although certain WRKY transcription factors have been implicated in branching regulation in other species, whether they are involved in cucumber branching has not yet been reported. In this study, we identified a transcription factor, CsWRKY50, whose expression positively correlates with branching in cucumber. The transcript level of CsWRKY50 was markedly elevated in the multi-branching mutant nwd and in high-branching cucumber varieties. Notably, CsWRKY50 showed the highest expression in axillary meristems compared to other tissues. Heterologous overexpression of CsWRKY50 in Arabidopsis significantly increased branch number and altered the transcriptional levels of several branching-related genes. Yeast two-hybrid assays confirmed that CsWRKY50 interacts with CsRAX5 and a truncated form of CsMYB84. The additive branching phenotype observed in the CsWRKY50-overexpressing Atbrc1 mutant indicates that CsWRKY50 may function independently of BRC1. Notably, RAX genes were up-regulated under these conditions. This work provides novel genetic resources and a theoretical foundation for improving plant architecture in cucumber cultivation.