植物幼年向成年阶段转变是一个重要的发育过程，该过程受保守的miR156-SPLs-miR172途径所调控，但该途径上游调控网络研究较少。本项目以EMS诱变筛选获得的拟南芥del2（Delayed juvenile to adult transition mutant 2, del2）突变体为材料，del2突变体表现为幼年叶数目增多、叶片变圆、幼年期延长，为典型幼年向成年阶段转变延迟突变体。前期工作确定del2为油菜素内酯 （Brassinosteroid, BR）合成缺陷突变体，为dwf5等位突变。基因检测发现del2中miR172前体MIR172B显著下调，确定BR参与调控miR156-SPLs-miR172途径。本项目将利用遗传学和分子生物学来研究BR信号调控miR156-SPLs-miR172途径的作用节点和作用机制，揭示BR调控植物营养期发育的新功能，并拓展该途径的上游调控网络。

The juvenile-to-adult phase transition (J-to-A transition) is a critical process in plant development, and it is regulated by a highly conserved miR156-SPLs-miR172 pathway. However, how upstream factors regulate this conserved pathway remains little known. We will carry out this study using a del2 (Delayed juvenile to adult transition mutant 2, del2) mutant isolated from an EMS-mutagenized mutant screen. The del2 mutant exhibited some typical characteristics of juvenile traits including more juvenile and rounder leaves. Preliminary study revealed that del2 is allelic to dwf5 defective in Brassinosteroid (BR) biosynthesis. Gene expression analysis showed that the primary transcript of miR172, MIR172B, was significantly downregulated in del2, suggesting that BR is involved in the miR156-SPLs-miR172 pathway. In this study, we will employ genetics and molecular biology to study the function of BR in the regulation of the miR156-SPLs-miR172 pathway. We try to elucidate how BR converge to the miR156-SPLs-miR172 pathway to regulate plant vegetative development in order for us to explore more regulatory factors upstream of this conserved pathway.