Abstract

背景回顾：Root lodging poses a major threat to maize production, resulting in reduced grain yield and quality, and increased harvest costs.  

主要发现：Here, we combined expressional, genetic and cytological studies to demonstrate a role of ZmYUC2 and ZmYUC4 in regulating gravitropic response of the brace root and lodging resistance in maize. 

结果1-ZmYUC2/4表达模式和蛋白定位：We show that both ZmYUC2 and ZmYUC4 are preferentially expressed in root tips with partially overlapping expression patterns, and the protein products of ZmYUC2 and ZmYUC4 are localized in the cytoplasm and endoplasmic reticulum (ER), respectively. 

结果2-ZmYUC2/4基因功能：The Zmyuc4 single mutant and Zmyuc2/4 double mutant exhibit enlarged brace root angle compared to the wild type plants, with larger brace root angle being observed in the Zmyuc2/4 double mutant. Consistently, the brace root tips of the Zmyuc4 single mutant and Zmyuc2/4 double mutant accumulate less auxin and are defective in proper reallocation of auxin in response to gravi-stimuli. Further, we show that the Zmyuc4 single mutant and the Zmyuc2/4 double mutant display obviously enhanced root lodging resistance.

结论：Our combined results demonstrate that ZmYUC2- and ZmYUC4-mediated local auxin biosynthesis is required for normal gravity response of the brace roots and provide effective targets for breeding root lodging resistant maize cultivars.

根倒伏严重威胁着玉米生产，导致玉米籽粒产量减少和质量降低，并且会增加收割成本。本文中，作者综合表达、遗传和细胞水平的研究，揭示了ZmYUC2和ZmYUC4基因作用于玉米气生根的重力响应以及抗根倒伏的机制。作者发现ZmYUC2和ZmYUC4基因优先在根尖中表达，并且存在部分的表达模式重叠，而ZmYUC2和ZmYUC4蛋白则分别定位于细胞质和内质网。相比于野生型，Zmyuc4单突和Zmyuc2/4双突植株气生根的角度增大，并且Zmyuc2/4双突的气生根角度更大。与此一致的是，Zmyuc4单突和Zmyuc2/4双突植株根尖积累了更少的生长素，并且在响应重力刺激时对于生长素的正确再分配存在缺陷。此外，作者发现Zmyuc4单突和Zmyuc2/4双突表现出增强的抗根倒伏能力。综上，作者提出ZmYUC2和ZmYUC4基因通过介导局域的生长素合成，从而作用于气生根对重力的正确响应。本文的研究为将来进行玉米抗根倒伏育种提供了有效靶标。

** 王海洋 **