利用修饰光敏色素信号途径改良作物产量和品质的探讨

In recent years, the breakthrough varieties occur much more difficult than before due to the limitation of crop breeding materials. Thus, it is necessary to explore new strategies for crop breeding. Phytochromes are the primary photoreceptors that mediates de-etiolation and shade avoidance in response to red, far-red or low red/far-red light conditions. In the grasses, three subfamilies are present: PHYA, PHYB and PHYC. In maize, an ancient genome duplication has increased the family size to six (PHYA1, PHYA2, PHYB1, PHYB2, PHYC1 and PHYC2). As an allohexaploid, there are 9 phytochrome genes in the common wheat. As sessile organisms, plants use phytochromes and other photoreceptors to monitor the changes of the light quality, intensity and duration in the environment to optimize their growth and developmental processes, including plant height, flowering time, shade avoidance and yield. PHYA overexpression or phyB mutant significantly leads to early flowering. Both PHYA and PHYB transgenic plants cause shortened internodes and plant height, reduced shade avoidance, resulting in compact plant, high photosynthetic efficiency, and yield increase. Regulatory network of phytochrome signaling pathway in maize and wheat will be interpreted via gene expression profiling. Moreover, the modification of phytochrome signaling pathway can be used on crop improvement, including of compact plant type, early maturity, high photosynthetic efficiency and high yield, by means of transgenic or gene silence technology. Our long term goal is to develop a new strategy for crop improvement on yield and quality through modification of phytochrome signaling pathway.

近年来作物育种材料和理论的创新乏力，突破性新品种的选育举步维艰，开展作物新育种策略的探讨是当务之急。光敏色素是植物最重要的一类红光和远红光受体，在禾本科中光敏色素三个亚家族PHYA、PHYB和PHYC，因此玉米(古四倍体)和小麦(异源六倍体)的光敏色素基因分别有6个和9个成员。植物利用光敏色素等监控环境中光质、强弱和节律的变化，进而调控自身生长和发育进程, 包括株高、开花期、避荫性和产量等。PHYA过量表达或phyB突变体能引起提早开花；PHYA和PHYB转基因导致植株节间缩短而株高降低、耐密性加强而株型紧凑、光合效率高而增产。借助于转录表达分析来解析光敏色素的分子调控网络；通过转基因和基因沉默来修饰光敏色素途径，能显著地改变其生长和发育进程，最终育成株型紧凑、高光效、早熟丰产的优良品种。因此，通过对光敏色素途径分子机制的研究，利用修饰玉米的光敏色素途径，来探讨改良作物产量和品质新策略。

近年来作物育种材料和理论的创新乏力，突破性新品种的选育举步维艰，开展作物新育种策略的探讨是当务之急。植物利用光受体等监控环境中光质、强弱和节律的变化，进而调控自身生长和发育进程, 包括株高、开花期、避荫性和产量等。通过转基因和基因沉默来修饰作物的光信号途径，能显著地改变其生长和发育进程，最终育成株型紧凑、高光效、早熟丰产的优良品种。（1）在蓝光和白光下，ZmCRY1b在玉米中的过表达通过增加bZIP转录因子ZmHY5和ZmHY5L的丰度，来直接上调GA2氧化酶基因的表达，导致活性GA下降，抑制植株高度，进而抑制幼苗黄化和避荫反应。另外，ZmCRY1b通过降低植株和穗高，促进自交系和杂交种的根系生长，增强抗倒伏能力。（2）在玉米自交系中表达ZmCRY1a导致中胚轴和第一叶鞘长度的缩短，引起玉米株高、穗位和节间显著降低或缩短，并抑制低蓝光诱导的避荫综合症。（3）拟南芥AtHFR1是一种光形态发生促进因子，参与多种光相关信号通路，并抑制幼苗黄化和避荫。AtHFR1在小麦中的过表达抑制了黄化表型，导致在田间植株高度降低和穗数增加，并且显著增产。相比与非转基因小麦，AtHFR1小麦转基因幼苗中表现出显著对种子萌发过程中渗透胁迫的耐受性。在田间，三个AtHFR1转基因系的籽粒产量比非转基因小麦高18.2–48.1%。AtHFR1转基因对小麦株型的改变，可见利用光形态发生促进因子对光信号通路的遗传修饰对粮食产量具有积极影响，并增强了对渗透胁迫和避荫反应的耐受性。（4）利用玉米自交系B73和Mo17及其杂交种B73×Mo17（BM）和Mo17×B73（MB），在黑暗或远红光、红光或蓝光下生长，进行了转录组和代谢组联合分析。大多数差异表达的基因（73.72–92.50%）和不同积累的代谢产物（84.74–94.32%）在BM和MB杂种中表现出非加性效应。不同的基因和代谢产物参与谷胱甘肽转移、碳水化合物转运、萜类生物合成和光合作用。总之，我们对小麦、黑麦和玉米开展了光信号转导及其在作物改良中应用的相关研究。