Sherif Sherif, El-Sharkawy Islam, Mathur Jaideep, Ravindran Pratibha, Kumar Prakash, Paliyath Gopinadhan, Jayasankar Subramanian
BMC Biol. 2015 Feb 13;13:11. doi: 10.1186/s12915-015-0124-6.
Variations in floral display represent one of the core features associated with the transition from allogamy to autogamy in angiosperms. The promotion of autogamy under stress conditions suggests the potential involvement of a signaling pathway with a dual role in both flower development and stress response. The jasmonic acid (JA) pathway is a plausible candidate to play such a role because of its involvement in many plant responses to environmental and developmental cues. In the present study, we used peach (Prunus persica L.) varieties with showy and non-showy flowers to investigate the role of JA (and JA signaling suppressors) in floral display.
Our results show that PpJAZ1, a component of the JA signaling pathway in peach, regulates petal expansion during anthesis and promotes self-pollination. PpJAZ1 transcript levels were higher in petals of the non-showy flowers than those of showy flowers at anthesis. Moreover, the ectopic expression of PpJAZ1 in tobacco (Nicotiana tabacum L.) converted the showy, chasmogamous tobacco flowers into non-showy, cleistogamous flowers. Stability of PpJAZ1 was confirmed in vivo using PpJAZ1-GFP chimeric protein. PpJAZ1 inhibited JA-dependent processes in roots and leaves of transgenic plants, including induction of JA-response genes to mechanical wounding. However, the inhibitory effect of PpJAZ1 on JA-dependent fertility functions was weaker, indicating that PpJAZ1 regulates the spatial localization of JA signaling in different plant organs. Indeed, JA-related genes showed differential expression patterns in leaves and flowers of transgenic plants.
Our results reveal that under stress conditions – for example, herbivore attacks – stable JAZ proteins such as PpJAZ1 may alter JA signaling in different plant organs, resulting in autogamy as a reproductive assurance mechanism. This represents an additional mechanism by which plant hormone signaling can modulate a vital developmental process in response to stress.
花展示的变化是被子植物从异花授粉向自花授粉转变的核心特征之一。在胁迫条件下自花授粉的促进表明，存在一条在花发育和胁迫反应中具有双重作用的信号通路。茉莉酸（JA）途径是发挥这种作用的一个合理候选途径，因为它参与了许多植物对环境和发育信号的反应。在本研究中，我们使用了具有艳丽花朵和不艳丽花朵的桃（Prunus persica L.）品种，来研究JA（和JA信号抑制因子）在花展示中的作用。
我们的结果表明，桃中JA信号通路的一个组成部分PpJAZ1，在花期调节花瓣扩展并促进自花授粉。在花期，不艳丽花朵花瓣中的PpJAZ1转录水平高于艳丽花朵。此外，PpJAZ1在烟草（Nicotiana tabacum L.）中的异位表达，将艳丽的、开花的烟草花转变为不艳丽的、闭花受精的花。使用PpJAZ1-GFP嵌合蛋白在体内证实了PpJAZ1的稳定性。PpJAZ1抑制转基因植物根和叶中依赖JA的过程，包括对机械损伤诱导JA反应基因。然而，PpJAZ1对依赖JA的育性功能的抑制作用较弱，表明PpJAZ1调节JA信号在不同植物器官中的空间定位。事实上，JA相关基因在转基因植物的叶和花中表现出不同的表达模式。
我们的结果表明，在胁迫条件下——例如，食草动物攻击——稳定的JAZ蛋白如PpJAZ1可能会改变不同植物器官中的JA信号，导致自花授粉作为一种繁殖保障机制。这代表了植物激素信号传导可以调节一个重要发育过程以响应胁迫的另一种机制。
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