Li Wenzhen, Chen Lulu, Zhao Weihua, Li Yuhang, Chen Ying, Wen Tengjian, Liu Zhengjun, Huang Chao, Zhang Lida, Zhao Lingxia
Department of Plant Science, School of Agriculture and Biology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China.
Joint Tomato Research Institute, School of Agriculture and Biology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China.
Hortic Res. 2024 Jul 24;11(9):uhae202. doi: 10.1093/hr/uhae202. eCollection 2024 Sep.
Tomato fruit colors are directly associated with their appearance quality and nutritional value. However, tomato fruit color formation is an intricate biological process that remains elusive. In this work we characterized a tomato (, , ) mutant with yellow fruits. By the map-based cloning approach, we identified a transversion mutation (A2117C) in the gene encoding a putative isopentenyl diphosphate isomerase (SlIDI1) enzyme, which may function in the isoprenoid biosynthetic pathway by catalyzing conversion between isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP). The mutated (A2117C) (designated ) and the genes did not show expression difference at protein level, and their encoded YFT3 allelic (S126R) and YFT3 proteins were both localized in plastids. However, the transcript levels of eight genes (, , , , , , and ) associated with carotenoid synthesis were upregulated in fruits of both and knockout () lines at 35 and 47 days post-anthesis compared with the red-fruit tomato cultivar (M82). and biochemical analyses indicated that YFT3 (S126R) possessed much lower enzymatic activities than the YFT3 protein, indicating that the S126R mutation can impair YFT3 activity. Molecular docking analysis showed that the YFT3 allele has higher ability to recruit isopentenyl pyrophosphate (IPP), but abolishes attachment of the Mg cofactor to IPP, suggesting that Ser126 is a critical residue for YTF3 biochemical and physiological functions. As a result, the mutant tomato line has low carotenoid accumulation and abnormal chromoplast development, which results in yellow ripe fruits. This study provides new insights into molecular mechanisms of tomato fruit color formation and development.
番茄果实颜色与其外观品质和营养价值直接相关。然而，番茄果实颜色形成是一个复杂的生物学过程，目前仍不清楚。在这项研究中，我们鉴定了一个具有黄色果实的番茄（，，）突变体。通过图位克隆方法，我们在编码假定的异戊烯基二磷酸异构酶（SlIDI1）的基因中鉴定到一个颠换突变（A2117C），该酶可能通过催化异戊烯基焦磷酸（IPP）和二甲基烯丙基焦磷酸（DMAPP）之间的转化在类异戊二烯生物合成途径中发挥作用。突变的（A2117C）（命名为）和基因在蛋白质水平上没有表达差异，它们编码的YFT3等位基因（S126R）和YFT3蛋白都定位于质体中。然而，与类胡萝卜素合成相关的八个基因（，，，，，，和）的转录水平在开花后35天和47天的和敲除（）品系的果实中相对于红色果实番茄品种（M82）上调。和生化分析表明，YFT3（S126R）的酶活性远低于YFT3蛋白，表明S126R突变会损害YFT3活性。分子对接分析表明，YFT3等位基因具有更高的募集异戊烯基焦磷酸（IPP）的能力，但消除了Mg辅因子与IPP的结合，表明Ser126是YTF3生化和生理功能的关键残基。因此，突变番茄品系类胡萝卜素积累低且有色体发育异常，导致成熟果实为黄色。本研究为番茄果实颜色形成和发育的分子机制提供了新的见解。
