Wang Jiao, Luo Qian, Deng Jingjing, Liang Xiao, Li Yimei, Wang Anran, Lin Teng, Liu Hua, Zhang Xuanbo, Liu Zhaoyu, Hu Zhangjian, Ding Shuting, Pan Changtian, Yu Jingquan, Gao Qifei, Foyer Christine H, Shi Kai
Department of Horticulture, Zhejiang University, Hangzhou 310058, China.
Hainan Institute, Zhejiang University, Sanya 572025, China.
Plant Cell. 2025 Apr 2;37(4). doi: 10.1093/plcell/koaf070.
The shoot apex is a critical determinant of plant growth, development, morphology, and yield. The G-protein β subunit (Gβ) is an essential regulator of apical meristem dynamics, yet its precise mechanism of action remains unclear, with notable interspecific variation. This study reveals that in the dicot tomato (Solanum lycopersicum), Gβ subunit mutants (Slgb1) display abnormal shoot morphogenesis and, in severe cases, shoot apex death. Such a phenotype has also been observed in monocot species, like maize (Zea mays) and rice (Oryza sativa), but not in the model dicot Arabidopsis (Arabidopsis thaliana). Using integrated multiomics and liquid chromatography-mass spectrometry, we identified a significant upregulation in tyramine-derived phenolamides in Slgb1 mutants, particularly N-p-trans-coumaroyltyramine (N-P-CT) and N-trans-feruloyltyramine (N-FT). Biochemical and genetic assays pinpointed tyramine hydroxycinnamoyl transferases (THTs) as the enzymes catalyzing N-P-CT and N-FT biosynthesis, with THT8 overexpression inducing shoot apex death. Comparative genomic analysis revealed the presence of a THT-mediated tyramine-derived phenolamide metabolic pathway in species exhibiting gb1 mutant-associated apex death, which is notably absent in Arabidopsis. Protein interaction assays showed that SlGB1 interacts with bHLH79 at the cell membrane and cytoplasm, thereby attenuating the bHLH79-MYB10 interaction within the nucleus, leading to altered THT expression and phenolamide biosynthesis. This study unravels the molecular mechanisms by which SlGB1 governs tomato shoot apex growth and development, highlighting interspecific differences critical for developing breeding strategies aimed at optimizing shoot apex architecture.
茎尖是植物生长、发育、形态和产量的关键决定因素。G蛋白β亚基（Gβ）是顶端分生组织动态的重要调节因子，但其确切作用机制仍不清楚，存在显著的种间差异。本研究表明，在双子叶植物番茄（Solanum lycopersicum）中，Gβ亚基突变体（Slgb1）表现出异常的茎形态发生，严重时茎尖死亡。在单子叶植物如玉米（Zea mays）和水稻（Oryza sativa）中也观察到了这种表型，但在模式双子叶植物拟南芥（Arabidopsis thaliana）中未观察到。通过综合多组学和液相色谱-质谱分析，我们发现Slgb1突变体中酪胺衍生的酚酰胺显著上调，特别是N-p-反式香豆酰酪胺（N-P-CT）和N-反式阿魏酰酪胺（N-FT）。生化和遗传分析确定酪胺羟基肉桂酰转移酶（THTs）是催化N-P-CT和N-FT生物合成的酶，THT8过表达会诱导茎尖死亡。比较基因组分析表明，在表现出与gb1突变相关的茎尖死亡的物种中存在THT介导的酪胺衍生的酚酰胺代谢途径，而拟南芥中明显不存在。蛋白质相互作用分析表明，SlGB1在细胞膜和细胞质中与bHLH79相互作用，从而减弱细胞核内bHLH79-MYB10的相互作用，导致THT表达和酚酰胺生物合成改变。本研究揭示了SlGB1调控番茄茎尖生长发育的分子机制，强调了种间差异对制定旨在优化茎尖结构的育种策略至关重要。
