Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement & Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement & Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
Plant Sci. 2024 Nov;348:112234. doi: 10.1016/j.plantsci.2024.112234. Epub 2024 Aug 30.
Plant architecture is an important agronomic trait to determine the biomass and sward structure of forage grass. The IGT family plays a pivotal role in plant gravitropism, encompassing both the gravitropic response and the modulation of plant architecture. We have previously shown that LjLAZY3, one of the IGT genes, plays a distinct role in root gravitropism in L. japonicus. However, the function of LAZY proteins on shoot gravitropism in this species is poorly understood. In this study, we identified nine IGT genes in the L. japonicus genome, which have been categorized into four clades based on the phylogenetic relationships of IGT proteins from 18 legumes: LAZY1, NGR (NEGATIVE GRAVITROPIC RESPONSE OF ROOTS), IGT-LIKE, and TAC1. We found that LAZY genes in the first three clades have demonstrated distinct role for modulating plant gravitropism in L. japonicus with specific impacts as follows. Mutation of the LAZY1 gene, LjLAZY1, defected the gravitropic response of hypocotyl without impacting the main stem's branch angle. In contrast, the overexpression of the NGR gene, LjLAZY3, substantially modulated the shoot's gravitropism, leading to narrower lateral branch angles. Additionally, it enhanced the shoots' gravitropic response. The overexpression of another NGR gene, LjLAZY4, specifically reduced the main stem's branch angle and decreased plant stature without affecting the shoot gravitropic response. The phenotype of IGT-LIKE gene LjLAZY2 overexpression is identical to that of LjLAZY4. While overexpression of the IGT-LIKE gene LjLAZY5 did not induce any observable changes in branch angle, plant height, or gravitropic response. Furthermore, the LjLAZYs were selectively interacted with different BRXL and RLD proteins, which should the important factor to determine their different functions in controlling organ architecture in L. japonicus. Our results deepen understanding of the LjLAZY family and its potential for plant architecture improvement in L. japonicus.
植物形态结构是决定牧草生物量和草丛结构的重要农艺性状。IGT 家族在植物向重力性中起着关键作用，包括向重力性反应和植物形态结构的调节。我们之前已经表明，IGT 基因中的 LjLAZY3 在 L. japonicus 的根向重力性中发挥了独特的作用。然而，在该物种中，LAZY 蛋白在茎向重力性中的功能知之甚少。在这项研究中，我们在 L. japonicus 基因组中鉴定了 9 个 IGT 基因，根据来自 18 种豆科植物的 IGT 蛋白的系统发育关系，将这些基因分为四个分支：LAZY1、NGR（根负向重力反应）、IGT-LIKE 和 TAC1。我们发现，前三个分支中的 LAZY 基因在调节 L. japonicus 的植物向重力性方面表现出不同的作用，具体影响如下。LAZY1 基因（LjLAZY1）的突变使下胚轴的向重力性反应缺失，而不影响主茎的分枝角度。相比之下，NGR 基因（LjLAZY3）的过表达显著调节了茎的向重力性，导致侧枝角度变窄。此外，它增强了茎的向重力性反应。另一个 NGR 基因（LjLAZY4）的过表达特异性地降低了主茎的分枝角度和植物的高度，而不影响茎的向重力性反应。IGT-LIKE 基因 LjLAZY2 过表达的表型与 LjLAZY4 相同。而过表达 IGT-LIKE 基因 LjLAZY5 并没有引起分枝角、植物高度或向重力性反应的任何可观察到的变化。此外，LjLAZYs 与不同的 BRXL 和 RLD 蛋白选择性地相互作用，这可能是决定它们在控制 L. japonicus 器官形态结构中不同功能的重要因素。我们的研究结果加深了对 LjLAZY 家族及其在 L. japonicus 中改良植物形态结构的潜力的理解。
