Diévart Anne, Hymes Matthew J, Li Jianming, Clark Steven E
Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA.
Funct Plant Biol. 2006 Aug;33(8):723-730. doi: 10.1071/FP06080.
CLAVATA1 (CLV1) and BRASSINOSTEROID INSENSITIVE 1 (BRI1) belong to the leucine-rich repeat receptor-like kinase (LRR-RLK) family, comprising more than 200 members in Arabidopsis thaliana (L.) Heynh. and playing important roles in development and defence responses in many plant species (Diévart and Clark 2003, 2004; Shiu and Bleecker 2001a, b). To dissect the mechanisms of receptor function, we assessed the ability of chimeric proteins containing regions from two different receptors to function in vivo. Using domains from the receptor-kinases CLAVATA1 and BRASSINOSTEROID INSENSITIVE1, we tested the ability of the resulting chimeric receptors to replace CLV1 function. Receptors with the BRI1 extracellular domain and CLV1 kinase domain were able to partially replace CLV1 function. Both loss-of-function and gain-of-function mutations within the BRI1 leucine-rich repeats (LRRs) altered the extent of rescue. Chimeric receptor function was unaffected by addition of either exogenous brassinosteroids (BR) or BR biosynthesis inhibitors, suggesting that the chimeric receptors function in a ligand-independent fashion. We propose that the BRI1 LRR domain drives chimeric receptor homodimerisation, and that the BRI1 LRR domain mutations influence homodimerisation efficiency independent of ligand binding.
CLAVATA1（CLV1）和油菜素内酯不敏感1（BRI1）属于富含亮氨酸重复序列的受体样激酶（LRR-RLK）家族，在拟南芥中该家族包含200多个成员，并在许多植物物种的发育和防御反应中发挥重要作用（迪瓦特和克拉克，2003年、2004年；修和布利克，2001年a、b）。为了剖析受体功能的机制，我们评估了含有来自两种不同受体区域的嵌合蛋白在体内发挥功能的能力。利用受体激酶CLAVATA1和油菜素内酯不敏感1的结构域，我们测试了所得嵌合受体替代CLV1功能的能力。具有BRI1细胞外结构域和CLV1激酶结构域的受体能够部分替代CLV1功能。BRI1富含亮氨酸重复序列（LRR）内的功能丧失和功能获得突变均改变了拯救的程度。添加外源油菜素内酯（BR）或BR生物合成抑制剂均不影响嵌合受体的功能，这表明嵌合受体以不依赖配体的方式发挥作用。我们提出，BRI1 LRR结构域驱动嵌合受体同源二聚化，并且BRI1 LRR结构域突变独立于配体结合影响同源二聚化效率。
