基于GbWRKY1与GhPHO2研究磷稳态调控棉花生长发育与多抗的分子机制

Generally, the application of phosphate fertilizer during cotton production could improve the broad spectrum resistance of cotton, which infers that there be a kind connections between phosphate homeostasis and disease resistance in gene regulation network. The mechanism remains unknown. In our previous study, a WRKY transcription factor, GbWRKY1, which was up-regulated in cotton upon inoculation with Verticillium dahliae, was isolated and identified with functions in improving the phosphate usage efficiency and regulating root development and early flowering. The GbWRKY1-overexpressing cotton plants were obtained through Agrobacterium mediated transformation and characterized. To our surprise, GbWRKY1-overexpressing cotton and Arabidopsis showed more susceptibility to V. dahliae and Botrytis cinerea, while knockdown of GbWRKY1 by RNA interfering in cotton improved the resistance to the fungi. Our preliminary results also indicated that GbWRKY1-overexpression in cotton and Arabidopsis attenuated the sensitive to abscisic acid (ABA) compared with the wild type. Moreover, GhPHO2, which shares 55% in identity with PHO2 and may be involved in the regulation of phosphate homeostasis as well, was significantly down-regulated when the biosynthesis of jasmonic acid (JA) in cotton roots was constitutively activated. All these results suggested that GbWRKY1 and GhPHO2 might be the important regulators in phosphate homeostasis and multiple resistance signaling networks. Thus, illuminating the function, interaction and signaling network of these two genes in plants would provide more information in theory and guide for cultivating new cotton varieties with phosphate-efficient, early-maturing and broad spectrum resistance.

棉花生产中增施磷肥能提高广谱抗性，表明棉花磷稳态和抗病性在基因调控网络上可能存在某种联系，但其机制仍不清楚。在前期研究中我们鉴定到一个受黄萎病菌接种诱导的WRKY转录因子，GbWRKY1，并证明其能提高植物对磷的高效利用和调控根发育与花期发育。利用农杆菌介导的遗传转化获得了GbWRKY1转基因棉花,但接种黄萎病菌和灰霉病菌后却发现GbWRKY1超量表达转基因植株更感病，而抑制GbWRKY1表达的转基因棉花抗病性增强。初步鉴定表明GbWRKY1超量表达转基因棉花和拟南芥还对ABA敏感性降低。同时我们还发现组成型激活棉花根中茉莉酸合成时，与PHO2同源的GhPHO2的表达受到明显抑制。以上结果表明GbWRKY1和PHO2可能是参与植物磷稳态与多种抗性信号网络的重要调控因子。阐明这两个基因在植物体中的功能、互作及其所调控的信号网络将为培育磷高效、早熟、多抗协调的棉花新材料提供理论基础。

棉花生产中增施磷肥能提高广谱抗性，表明棉花磷稳态和抗病性在基因调控网络上可能存在某种联系，但其机制仍不清楚。我们以两个可能参考磷稳态调控的基因GbWRKY1和PHO2为例，研究这两个基因在植物体中的功能、磷稳态调控植物多抗的信号网络为培育磷高效、早熟、多抗协调的棉花新材料提供理论基础。我们的研究发现GbWRKY1能直接调控茉莉酸信号路径负调控因子JAZ1的表达从而使得超量表达GbWRKY1的植株表现出对茉莉酸敏感性降低；同时抗病水平降低。而JAZ1蛋白通过互作赤霉素信号路径的负调控因子Della蛋白，从而实现赤霉素信号路径的激活。这证明GbWRKY1在平衡植物生长发育和免疫中具有重要作用。研究还发现GbWRKY1超量表达转基因棉花和拟南芥还表现出对ABA不敏感，同时转基因植株对干旱等非生物逆境更敏感，这同样可能由于JAZ蛋白能同时也ABA的调控因子互作而实现。获得了GhPHO2的超量表达和RNAi抑制表达转基因材料，但没有发现其表达水平变化对磷稳态和棉花抗性的影响。研究发现低磷胁迫处理后，棉花的抗病性增强。转录组分析发现低磷胁迫下，棉花中次生代谢和茉莉酸合成增强。通过研究茉莉酸信号路径负调控因子JAZ2和HDTF1证明JA信号路径在棉花抗黄萎病反应中具有重要作用。此外还通过转录组学数据分析鉴定到茉莉酸合成的一个新的负调控因子GhCPK33。该蛋白能磷酸化茉莉酸合成的关键基因OPR3，并导致其更容易被降解而对茉莉酸合成形成负调控。以上研究结果对于阐述棉花对黄萎病的抗性以及磷稳态对于植物的多抗机制提供了理论基础，同时对于利用棉花抗病机制创新抗病新种质提供了新思路。