Lateral branching is a crucial agronomic trait that impacts crop yield. In tomato (Solanum lycopersicum), excessive lateral branching is unfavorable and results in substantial labor and management costs. Therefore, optimizing lateral branching is a primary objective in tomato breeding. Although many genes related to lateral branching have been reported in tomato, the molecular mechanism underlying their network remains elusive. In this study, we found that the expression profile of a WRKY gene, WRKY-B (for WRKY-BRANCING), was associated with the auxin-dependent axillary bud development process. Wrky-b mutants generated by the CRISPR/Cas9 editing system presented fewer lateral branches, while WRKY-B overexpression lines presented more lateral branches than did wild-type plants. Furthermore, WRKY-B can directly target the well-known branching gene BLIND (BL) and the auxin efflux carrier gene PIN4 to activate their expression. Both the bl and pin4 mutants exhibited reduced lateral branching, similar to the wrky-b mutant. The IAA contents in the axillary buds of the wrky-b, bl, and pin4 mutant plants were significantly higher than those in the wild-type plants. In addition, WRKY-B can also directly target the AUX/IAA gene IAA15 and repress its expression. In summary, WRKY-B works upstream of BL, PIN4, and IAA15 to regulate the development of lateral branches in tomato.

中文翻译：

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番茄 WRKY-B 转录因子通过靶向 BLIND、PIN4 和 IAA15 调节侧支


侧向分枝是影响作物产量的重要农艺性状。在番茄 （Solanum lycopersicum） 中，过度的横向分枝是不利的，并导致大量的劳动力和管理成本。因此，优化横向分枝是番茄育种的主要目标。尽管番茄中已经报道了许多与侧支相关的基因，但其网络背后的分子机制仍然难以捉摸。在这项研究中，我们发现 WRKY 基因 WRKY-B （用于 WRKY-BRANCING） 的表达谱与生长素依赖性腋芽发育过程相关。CRISPR/Cas9 编辑系统产生的 WRKY-b 突变体呈现较少的侧枝，而 WRKY-B 过表达系呈现比野生型植物更多的侧枝。此外，WRKY-B 可以直接靶向已知的分支基因 BLIND （BL） 和生长素外排载体基因 PIN4 以激活它们的表达。bl 和 pin4 突变体都表现出减少的横向分支，类似于 wrky-b 突变体。wrky-b 、 bl 和 pin4 突变株腋芽中 IAA 含量显著高于野生型植株。此外，WRKY-B 还可以直接靶向 AUX/IAA 基因 IAA15 并抑制其表达。总之，WRKY-B 在 BL、PIN4 和 IAA15 的上游工作，以调节番茄侧枝的发育。