SPA1通过抑制DELLA-HFR1蛋白复合体的稳定性来负向调节拟南芥抗盐性

Plants have evolved a high degree of developmental plasticity to optimize their growth and reproduction in response to various environmental stresses. SPA1 is one of the most important negative factors in seedling photomorphogenesis. The results of lower germination frequency caused by overexpression of SUPPRESSOR OF PHYA-105 (SPA1) and up-regulated expression levels of SPAs in response to high salt treatment suggested that SPA1 may be involved in repressing salt resistance in Arabidopsis. The results of yeast two hybrids showed that both SPA1 and CONSTITUTIVE PHOTOMORPHOGENESIS 1 (COP1) physically interacted with all five DELLA proteins and that the seedlings of both spa1 and cop1 mutants accumulated much more DELLA proteins than these of the wild type. All those results implied that SPA1-COP1 E3 complex might mediate degradation of DELLA proteins in vivo. Plants of overexpression of LONG HYPOCOTYL IN FAR-RED 1 (HFR1) and DELLA were much shorter but thicker and stronger, leading to high resistance to various stresses. We demonstrated that HFR1 physically interacted with DELLA proteins. Thus, it is necessary to prove that DELLA proteins may form a protein complex with HFR1 to enhance salt resistance in Arabidopsis. Crosstalk between light signaling, GA pathway and plant salt resistance may help us not only to switch a new way exploring plant salt resistance but also to enhance our understanding on interactions among various signaling pathways in Arabidopsis.

植物生活在变化的环境中，受到多种胁迫的干扰，作为完善进化的产物，植物能动地应对各种胁迫来优化自己的生长和繁衍。SPA1是光形态建成中的最关键负向调节因子之一；在高盐胁迫下，SPA1过量表达导致萌发率急剧降低，并且SPAs的转录水平受盐胁迫上调表达，表明SPA1很可能参与负向调节拟南芥的抗盐性反应。酵母双杂交证实了SPA1和COP1均与5个DELLA蛋白存在物理互作；spa1和cop1突变体比野生型积累更多的内源DELLA蛋白；暗示着SPA1-COP1 E3复合体可能介导DELLA蛋白的降解。HFR1与DELLA的过量表达均表现为株型矮壮、叶色深绿和抗逆性增强，并且二者蛋白间存在物理互作，因此HFR1与DELLA是否通过形成复合体增强抗盐性值得深入探讨。解析光信号、GA信号和植物抗盐途径之间的交互作用，不但能为植物抗盐的机理研究提供新思路，也将增强我们对这些信号途径交互作用的认识。

植物生活在变化的环境中，受到多种胁迫的干扰，作为完善进化的产物，植物能动地应对各种胁迫来优化自己的生长和繁衍。拟南芥SPAs基因家族有四个成员，它们与光形态建成的重要抑制因子COP1形成E3泛素化连接酶复合体，共同促进光形态建成正向调控因子的降解，从而促进植物的黄化反应。SPA1是SPAs基因家族最重要的成员。在高盐胁迫下，SPA1过量表达导致萌发率急剧降低，并且SPAs的转录水平受盐胁迫上调表达，表明SPA1参与负向调节拟南芥的抗盐性反应。酵母双杂交证实了SPA1和COP1均与5个DELLA蛋白存在物理互作；spa1和cop1突变体比野生型积累更多的内源DELLA蛋白；表明SPA1-COP1 E3复合体介导DELLA蛋白的降解。HFR1与DELLA的过量表达均表现为株型矮壮、叶色深绿和抗逆性增强，并且二者蛋白间存在物理互作，因此HFR1与DELLA可以通过形成复合体增强抗盐性。解析光信号、GA信号和植物抗盐途径之间的交互作用，不但能为植物抗盐的机理研究提供新思路，也将增强我们对这些信号途径互作的认识。拟南芥HFR1转化小麦导致小麦植株降低、分蘖和叶绿素含量增加，并且抗盐萌发和耐光饥饿能力显著增加。可见，拟南芥的HFR1基因无论是在拟南芥，还是在小麦中均导致抗盐能力的增加。一方面表明HFR1基因不仅是光信号途径的关键基因，而且在植物的抗盐中起重要作用；另一方面，植物的通过光信号途径提高植物的抗盐能力是可行的。我们也将拟南芥的HFR1基因转化的水稻和玉米，我们也将克隆小麦和玉米中HFR1的同源基因，进行其抗盐能力的研究。