Caño-Delgado Ana, Yin Yanhai, Yu Cong, Vafeados Dionne, Mora-García Santiago, Cheng Jin-Chen, Nam Kyoung Hee, Li Jianming, Chory Joanne
Howard Hughes Medical Institute and Plant Biology Laboratory, The Salk Institute for Biological Studies, 10010 N. Torrey Pines Rd, La Jolla, CA 92037, USA.
Development. 2004 Nov;131(21):5341-51. doi: 10.1242/dev.01403.
Plant steroid hormones, brassinosteroids (BRs), are perceived by the plasma membrane-localized leucine-rich-repeat-receptor kinase BRI1. Based on sequence similarity, we have identified three members of the BRI1 family, named BRL1, BRL2 and BRL3. BRL1 and BRL3, but not BRL2, encode functional BR receptors that bind brassinolide, the most active BR, with high affinity. In agreement, only BRL1 and BRL3 can rescue bri1 mutants when expressed under the control of the BRI1 promoter. While BRI1 is ubiquitously expressed in growing cells, the expression of BRL1 and BRL3 is restricted to non-overlapping subsets of vascular cells. Loss-of-function of brl1 causes abnormal phloem:xylem differentiation ratios and enhances the vascular defects of a weak bri1 mutant. bri1 brl1 brl3 triple mutants enhance bri1 dwarfism and also exhibit abnormal vascular differentiation. Thus, Arabidopsis contains a small number of BR receptors that have specific functions in cell growth and vascular differentiation.
植物类固醇激素油菜素内酯（BRs）由定位于质膜的富含亮氨酸重复序列的受体激酶BRI1感知。基于序列相似性，我们鉴定出了BRI1家族的三个成员，分别命名为BRL1、BRL2和BRL3。BRL1和BRL3而非BRL2编码功能性BR受体，它们能以高亲和力结合活性最强的BR——油菜素内酯。相应地，当在BRI1启动子的控制下表达时，只有BRL1和BRL3能够挽救bri1突变体。虽然BRI1在生长中的细胞中普遍表达，但BRL1和BRL3的表达仅限于维管细胞的不重叠亚群。brl1功能缺失会导致韧皮部与木质部分化比例异常，并加剧弱bri1突变体的维管缺陷。bri1 brl1 brl3三突变体加剧了bri1的矮化现象，并且还表现出异常的维管分化。因此，拟南芥含有少量在细胞生长和维管分化中具有特定功能的BR受体。
