Abstract: As an important environmental factor, light affects many aspects of plant growth and development. Plants use several classes of photoreceptors to perceive the light signals in the ambient environment. Among the photoreceptors, phytochromes, which sense red and far-red light signals, are best studied so far. Previous studies have shown that changing the tyrosine (Y) at position 104 and 361 of Arabidopsis phyB to phenylalanine (F) can enhance its activity. To investigate the function of maize phytochrome B1, we constructed three binary vectors: Wild type pZmPHYB1∷ZmPHYB1WT, pZmPHYB1∷ZmPHYB1Y98F (mimicking Y104F of Arabidopsis phyB) and pZmPHYB1∷ZmPHYB1Y359F (mimicking Y361F of Arabidopsis phyB), and transformed them into the Arabidopsis phyB-9 loss-of-function mutant. Phenotypic analyses of the transgenic lines showed that the maize PHYB1 gene can largely complement the Arabidopsis phyB-9 mutant phenotypes, including hypocotyl elongation and petiole elongation. Furthermore, ZmPHYB1 can physically interact with the Arabidopsis PIF5 protein and induce the expression of downstream shade avoidance responsive and auxin biosynthesis related genes. The Y98F and Y359F amino acid substitutions can enhance the activity of ZmPHYB1. In summary, our results indicated that ZmPHYB1 plays an important role in mediating shade avoidance response in Arabidopsis, and provided useful clues for genetic improvement maize plant architecture for adapting to high-density planting.

Key words: ZmPHYB1, hypocotyl, shade avoidance response, phytochrome interacting factors (PIFs)

摘要： 光是一个重要的环境因子，影响植物生长发育的诸多方面。植物通过多种光受体感受环境中的光信号，其中以红光与远红光受体——光敏色素的研究最为透彻。研究表明，将拟南芥phyB的104位点与361位点的酪氨酸（Y）残基改造为苯丙氨酸（F）残基可增强其活性。为了研究玉米光敏色素B1（PHYB1）的功能，构建了玉米光敏色素B1基因的3种重组质粒:pZmPHYB1∷ZmPHYB1WT、pZmPHYB1∷ZmPHYB1Y98F（对应拟南芥Y104F突变）和pZmPHYB1∷ZmPHYB1Y359F（对应拟南芥Y361F突变），并将其转入拟南芥phyB-9突变体中，然后对转基因株系进行表型分析。结果表明,ZmPHYB1可抑制phyB-9突变体下胚轴及叶柄的伸长；ZmPHYB1可与拟南芥AtPIF5互作并诱导下游避荫反应响应基因和生长素合成基因的表达；Y98F和Y359F氨基酸的替换可增强ZmPHYB1的活性。研究结果表明ZmPHYB1在拟南芥中具有介导避荫反应的作用,同时也将为玉米耐密株型改良提供参考。

关键词: ZmPHYB1, 下胚轴, 避荫反应, 光敏色素互作因子（PIFs）