背景回顾：Lateral organ boundaries domain (LBD) proteins are plant-specific transcription factors. Class-I LBD members have been widely demonstrated to play pivotal roles in organ development; however, knowledge on class-II members remains limited. 

主要发现：Here, we report that ZmLBD5, a class-II LBD member, is involved in the regulation of maize growth and drought response by affecting gibberellin (GA) and abscisic acid (ABA) synthesis. 

结果1-ZmLBD5作用机制：ZmLBD5 is mainly involved in regulation of the TPS-KS-GA2ox gene module, which comprises key enzymatic genes upstream of GA and ABA biosynthesis. 

结果2-ZmLBD5过表达和敲除表型：The insufficiency of ABA increases stomatal density and aperture in overexpressed plants, and causes the drought sensitive phenotype by promoting water transpiration. The increase of GA1 promoted seedling growth in overexpressed plants. Accordingly, the CRISPR/Cas9 knockout lbd5 seedlings were dwarf but drought tolerant. 

结果3-籽粒产量：Moreover, lbd5 has larger grain yield under drought stress and no penalty in well watered conditions than the wild type.

结论：On the whole, ZmLBD5 is a negative regulator in maize drought tolerance, and it is a potentially useful target for drought resistance breeding.

 摘 要 

侧生器官边界结构域（LBD）蛋白是植物特异性转录因子。I类LBD基因被广泛证明在器官发育中发挥重要作用，但是有关II类LBD基因的作用还不清楚。本文中，作者发现玉米中一个II类LBD基因ZmLBD5通过影响赤霉素（GA）和脱落酸（ABA）合成来参与玉米的生长和干旱响应调控。ZmLBD5主要参与TPS-KS-GA2ox基因模块的调控，而后者是GA和ABA生物合成上游的关键酶编码基因。ZmLBD5过表达植株中ABA的不足导致气孔密度和开度的增强，从而通过促进水分蒸腾而增强了干旱敏感性。另外，ZmLBD5过表达植株中GA1水平的增加促进幼苗的生长。与此同时，利用CRISPR/Cas9敲除ZmLBD5基因获得的lbd5突变体存在矮化表型，但是其干旱耐受性增强。此外，与野生型相比，lbd5突变体在干旱条件下的籽粒产量更高，而且在水分充足条件下与野生型产量相当。综上，ZmLBD5基因是玉米干旱耐受性的负调控因子，并且其是玉米干旱抗性育种的潜在靶标。

** 卢艳丽 **