Instituto de Biología Molecular y Celular de Plantas, CSIC-UPV, 46022 Valencia, Spain.
Instituto de Biología Molecular y Celular de Plantas, CSIC-UPV, 46022 Valencia, Spain.
Curr Biol. 2022 Feb 28;32(4):749-762.e3. doi: 10.1016/j.cub.2021.11.069. Epub 2021 Dec 27.
In monocarpic plants, all reproductive meristem activity arrests and flower production ceases after the production of a certain number of fruits. This proliferative arrest (PA) is an evolutionary adaptation that ensures nutrient availability for seed production. Moreover, PA is a process of agronomic interest because it affects the duration of the flowering period and therefore fruit production. While our knowledge of the inputs and genetic factors controlling the initiation of the flowering period is extensive, little is known about the regulatory pathways and cellular events that participate in the end of flowering and trigger PA. Here, we characterize with high spatiotemporal resolution the cellular and molecular changes related to cell proliferation and meristem activity in the shoot apical meristem throughout the flowering period and PA. Our results suggest that cytokinin (CK) signaling repression precedes PA and that this hormone is sufficient to prevent and revert the process. We have also observed that repression of known CK downstream factors, such as type B cyclins and WUSCHEL (WUS), correlates with PA. These molecular changes are accompanied by changes in cell size and number likely caused by the cessation of cell division and WUS activity during PA. Parallel assays in fruitfull (ful) mutants, which do not undergo PA, have revealed that FUL may promote PA via repression of these CK-dependent pathways. Moreover, our data allow to define two phases, based on the relative contribution of FUL, that lead to PA: an early reduction of CK-related events and a late blocking of these events.
在单性结实植物中，所有生殖分生组织活动在产生一定数量的果实后停止，花的产生也随之停止。这种增殖停滞（PA）是一种进化适应，确保了种子生产所需的养分供应。此外，PA 是一个具有农业意义的过程，因为它影响开花期的持续时间，从而影响果实的产量。虽然我们对控制开花期起始的输入和遗传因素有广泛的了解，但对参与开花结束和触发 PA 的调控途径和细胞事件知之甚少。在这里，我们以高时空分辨率表征了与整个开花期和 PA 期间茎尖分生组织中细胞增殖和分生组织活动相关的细胞和分子变化。我们的结果表明，细胞分裂素（CK）信号转导的抑制先于 PA，并且这种激素足以防止和逆转这个过程。我们还观察到，已知的 CK 下游因子，如 B 型细胞周期蛋白和 WUSCHEL（WUS）的抑制与 PA 相关。这些分子变化伴随着细胞大小和数量的变化，这可能是由于 PA 期间细胞分裂和 WUS 活性的停止造成的。在不经历 PA 的 fruittulll（ful）突变体中的平行实验表明，FUL 可能通过抑制这些 CK 依赖的途径来促进 PA。此外，我们的数据允许根据 FUL 的相对贡献定义两个导致 PA 的阶段：早期减少与 CK 相关的事件和晚期阻断这些事件。
