Clouse S D, Langford M, McMorris T C
Department of Horticultural Science, North Carolina State University, Raleigh 27695, USA.
Plant Physiol. 1996 Jul;111(3):671-8. doi: 10.1104/pp.111.3.671.
Brassinosteroids are widely distributed plant compounds that modulate cell elongation and division, but little is known about the mechanism of action of these plant growth regulators. To investigate brassinosteroids as signals influencing plant growth and development, we identified a brassinosteroid-insensitive mutant in Arabidopsis thaliana (L.) Henyh. ecotype Columbia. The mutant, termed bri1, did not respond to brassinosteroids in hypocotyl elongation and primary root inhibition assays, but it did retain sensitivity to auxins, cytokinins, ethylene, abscisic acid, and gibberellins. The bri1 mutant showed multiple deficiencies in developmental pathways that could not be rescued by brassinosteroid treatment including a severely dwarfed stature; dark green, thickened leaves; males sterility; reduced apical dominance; and de-etiolation of dark-grown seedlings. Genetic analysis suggests that the Bri1 phenotype is caused by a recessive mutation in a single gene with pleiotropic effects that maps 1.6 centimorgans from the cleaved, amplified, polymorphic sequence marker DHS1 on the bottom of chromosome IV. The multiple and dramatic effects of mutation of the BRI1 locus on development suggests that the BRI1 gene may play a critical role in brassinosteroid perception or signal transduction.
油菜素甾醇是广泛分布的植物化合物，可调节细胞伸长和分裂，但对于这些植物生长调节剂的作用机制知之甚少。为了研究油菜素甾醇作为影响植物生长发育的信号，我们在拟南芥（L.）Hen yh.生态型哥伦比亚中鉴定出一个对油菜素甾醇不敏感的突变体。该突变体称为bri1，在下胚轴伸长和主根抑制试验中对油菜素甾醇无反应，但对生长素、细胞分裂素、乙烯、脱落酸和赤霉素仍保持敏感性。bri1突变体在发育途径中表现出多种缺陷，油菜素甾醇处理无法挽救这些缺陷，包括严重矮化的株高、深绿色增厚的叶片、雄性不育、顶端优势降低以及黑暗中生长的幼苗去黄化。遗传分析表明，Bri1表型是由单个基因中的隐性突变引起的，该基因具有多效性，位于第四条染色体底部的切割扩增多态序列标记DHS1的1.6厘摩处。BRI1基因座突变对发育产生的多重显著影响表明，BRI1基因可能在油菜素甾醇感知或信号转导中起关键作用。
