背景回顾：Vegetative phase change in plants is regulated by a gradual decline in the level of miR156 and a corresponding increase in the expression of its targets, SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) genes. Gibberellin (GA), jasmonic acid (JA), and cytokinin (CK) regulate vegetative phase change by affecting genes in the miR156-SPL pathway. 

提出问题：However, whether other phytohormones play a role in vegetative phase change remains unknown. 

主要发现：Here, we show that a loss-of-function mutation in the brassinosteroid (BR) biosynthetic gene, DWARF5 (DWF5), delays vegetative phase change, and the defective phenotype is primarily attributable to reduced levels of SPL9 and miR172, and a corresponding increase in TARGET OF EAT1 (TOE1). 

结果1-突变体库筛选：We further show that GLYCOGEN SYNTHASE KINASE3 (GSK3)-like kinase BRASSINOSTEROID INSENSITIVE2 (BIN2) directly interacts with and phosphorylates SPL9and TOE1 to cause subsequent proteolytic degradation. 

结论：Therefore, BRs function to stabilize SPL9 and TOE1 simultaneously to regulate vegetative phase change in plants.

植物营养生长期转变（进入生殖生长）受到miR156水平逐渐衰减以及其靶标基因SPL逐渐上调表达的调控。赤霉素、茉莉酸以及细胞分裂素能够通过影响miR156-SPL途径的基因，调控植物营养生长期转变。但是，是否还有其他植物激素参与营养生长期转变仍不清楚。本文中，作者发现油菜素内酯生物合成基因DWF5的功能缺失会导致营养生长期转变的延迟，而这一缺陷表型主要是由于SPL9和miR172的水平降低、而TOE1的水平增加所导致的。作者进一步发现糖原合酶激酶GSK3类激酶BIN2能够直接与SPL9和TOE1发生互作，并磷酸化SPL9和TOE1，导致随后的蛋白水解降解。因此，BRs作用于SPL9和TOE1蛋白的稳定，从而调控植物中营养生长期转变。

** 吴 刚 **