拟南芥光敏色素调控GAI蛋白积累促进植物耐盐性的分子机理

GAI is one of the most important members of DELLA gene family in Arabidopsis, which is involved in several signaling pathways of plant hormones and stress responses. In plants, DELLA proteins enhance plant resistance to biotic and abiotic stresses by suppressing GA signaling transduction. Light is one of the most important environmental factors. Plants have evolved a series of photoreceptors to monitor light quality, quantity and duration to optimize their growth and reproduction through a variety of positive and negative factors. Previous studies indicate that PIFs and DELLAs can be regulated each other at both transcriptional and protein levels. However, the roles of photoactivated photoreceptors in regulation of DELLA protein accumulation still remain unknown. Recently, we found that light can regulate GAI accumulation in two different ways at seed germination or seedling stages. Our results showed that light promotes seed germination frequencies through suppressing the accumulation of GAI protein in response to salt stress. Moreover, we demonstrated that light improves seedling salt tolerance by enhancing the accumulation of GAI protein. We also determined that both phytochrome A and phytochrome B, red and far-red light receptors, can interact with GAI in yeast two hybrid assays. These results may suggest that photoactivated phytochromes may forms a protein complex with GAI via a direct interaction to modulate GAI stability. In this study, we will provide strong genetic, molecular and biochemical evidences to reveal how photoactivated phytochromes enhance plant salt tolerance via modulation of GAI protein accumulation.

GAI是拟南芥DELLA基因家族的重要组分，其蛋白参与多种激素和逆境胁迫。DELLA蛋白通过抑制赤霉素信号转导，增强植物对各种胁迫的抗性。光是影响植物生长的重要因素之一，植物利用光受体来感知光强、光质和光周期变化，通过一系列调节因子控制生长和发育进程。前人的研究发现光敏色素互作因子 (PIFs) 与DELLA在转录和蛋白水平相互调节，但是光激活的光受体如何调节DELLA蛋白积累，进而增强植物的抗逆性未见报道。本研究发现：光通过两种不同的机制调节DELLA蛋白积累；在种子萌发阶段，光抑制GAI的蛋白丰度来提高盐胁迫下种子的萌发率；而在幼苗生长阶段，光通过促进GAI的蛋白积累增强植物抗盐性。我们进一步证实了红光/远红光受体光敏色素A和B能够与GAI互作。本研究将从遗传、分子和生化水平逐步揭示光激活的光敏色素通过与GAI形成蛋白复合体来调节其丰度，从而增强植物的耐盐性。