Jeong Dong-Hoon, Lee Shinyoung, Kim Song Lim, Hwang Ildoo, An Gynheung
Department of Life Science and Functional Genomic Center, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Republic of Korea.
Plant Cell Environ. 2007 May;30(5):590-9. doi: 10.1111/j.1365-3040.2007.01644.x.
Plant growth and development are coordinately controlled by environmental signals and internal factors. Light signals, mediated by phytochromes, regulate photomorphogenesis by interacting with endogenous programmes that involve multiple phytohormones. Brassinosteroids (BRs) are a group of growth-promoting phytohormones with a crucial role in the light-dependent development of plants. However, the interaction between light-signalling pathways and BR signalling is not well understood. Here, we examined the responses of lamina joint inclination and coleoptile elongation to exogenous brassinolide (BL) under light or dark conditions. Both responses were more pronounced under darkness, implying that BR signalling is inhibited by light. To elucidate which phytochrome is involved in this interaction, we isolated rice phytochrome-deficient mutants (osphyA, osphyB and osphyC) from a T-DNA insertional population. Whereas the osphyA and osphyC knockout mutants did not differ from the wild-type plants in their BL responses, osphyB mutants were more sensitive. In addition, RT-PCR analysis revealed enhanced expression of BR-inducible genes and decreased transcript levels of BR-biosynthetic genes in osphyB plants. These results suggest that Phytochrome B acts as a negative regulator of BL-regulated growth and development processes in rice.
植物的生长和发育受环境信号和内部因素的协同控制。由光敏色素介导的光信号，通过与涉及多种植物激素的内源程序相互作用来调节光形态建成。油菜素甾醇（BRs）是一类促进生长的植物激素，在植物的光依赖发育中起关键作用。然而，光信号通路与BR信号之间的相互作用尚不清楚。在此，我们研究了在光照或黑暗条件下，叶片关节倾斜度和胚芽鞘伸长对外源油菜素内酯（BL）的反应。两种反应在黑暗条件下都更明显，这意味着BR信号受到光的抑制。为了阐明哪种光敏色素参与了这种相互作用，我们从一个T-DNA插入群体中分离出水稻光敏色素缺陷突变体（osphyA、osphyB和osphyC）。虽然osphyA和osphyC敲除突变体在对BL的反应上与野生型植物没有差异，但osphyB突变体更敏感。此外，RT-PCR分析显示，osphyB植株中BR诱导基因的表达增强，而BR生物合成基因的转录水平降低。这些结果表明，光敏色素B在水稻中作为BL调节的生长和发育过程的负调节因子发挥作用。
