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

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)