Department of Biology,Institute of Plant and Food Science, Southern University of Science and Technology (SUSTech), Shenzhen 518055, China.
Key Laboratory of Molecular Design for Plant Cell Factory of Guangdong Higher Education Institutes, Southern University of Science and Technology (SUSTech), Shenzhen 518055, China.
Plant Cell. 2022 Aug 25;34(9):3280-3300. doi: 10.1093/plcell/koac146.
Although the role of ethylene in tomato (Solanum lycopersicum) fruit ripening has been intensively studied, its role in tomato fruit growth remains poorly understood. In addition, the relationship between ethylene and the developmental factors NON-RIPENING (NOR) and RIPENING INHIBITOR (RIN) during ripening is under debate. Here, we carried out comprehensive genetic analyses of genome-edited mutants of tomato ETHYLENE INSENSITIVE 2 (SlEIN2), four EIN3-like genes (SlEIL1-4), and three EIN3 BINDING F-box protein genes (SlEBF1-3). Both slein2-1 and the high-order sleil mutant (sleil1 sleil2 sleil3/SlEIL3 sleil4) showed reduced fruit size, mainly due to decreased auxin biosynthesis. During fruit maturation, slein2 mutants displayed the complete cessation of ripening, which was partially rescued by slebf1 but not slebf2 or slebf3. We also discovered that ethylene directly activates the expression of the developmental genes NOR, RIN, and FRUITFULL1 (FUL1) via SlEIL proteins. Indeed, overexpressing these genes partially rescued the ripening defects of slein2-1. Finally, the signal intensity of the ethylene burst during fruit maturation was intimately connected with the progression of full ripeness. Collectively, our work uncovers a critical role of ethylene in fruit growth and supports a molecular framework of ripening control in which the developmental factors NOR, RIN, and FUL1 act downstream of ethylene signaling.
尽管乙烯在番茄（Solanum lycopersicum）果实成熟中的作用已得到深入研究，但它在番茄果实生长中的作用仍知之甚少。此外，乙烯与发育因子 NON-RIPENING（NOR）和 RIPENING INHIBITOR（RIN）在成熟过程中的关系仍存在争议。在这里，我们对番茄 ETHYLENE INSENSITIVE 2（SlEIN2）、四个 EIN3 样基因（SlEIL1-4）和三个 EIN3 BINDING F-box 蛋白基因（SlEBF1-3）的基因编辑突变体进行了全面的遗传分析。slein2-1 和高次 sleil 突变体（sleil1 sleil2 sleil3/SlEIL3 sleil4）的果实均变小，主要是由于生长素生物合成减少所致。在果实成熟过程中，slein2 突变体表现出完全停止成熟，这部分被 slebf1 拯救，但 slebf2 或 slebf3 则不能。我们还发现，乙烯通过 SlEIL 蛋白直接激活发育基因 NOR、RIN 和 FRUITFULL1（FUL1）的表达。事实上，过表达这些基因部分挽救了 slein2-1 的成熟缺陷。最后，果实成熟过程中乙烯爆发的信号强度与完全成熟的进展密切相关。总之，我们的工作揭示了乙烯在果实生长中的关键作用，并支持了一个成熟控制的分子框架，其中发育因子 NOR、RIN 和 FUL1 作为乙烯信号的下游因子发挥作用。
