主要发现：In this study, we identify Arabidopsis SAUR17 as a downstream effector of etiolation, which serves to bring about etiolated apical structures, i.e. apical hook and closed cotyledons.

结果1-SAUR17表达模式：SAUR17 is highly expressed in apical hooks and cotyledons and is repressed by light.

结果2-拮抗因子SAUR50：The apical organs also express a group of light-inducing SAURs as represented by SAUR50, which work to promote opening of the hook and cotyledons.

结果3-下游因子PP2C-D1：Development of etiolated or de-etiolated apical structures requires asymmetric differential cell growth. We present evidence that the opposing action of SAUR17 and SAUR50 on apical development largely results from their antagonistic regulation of PP2C-D1, the phosphatase that suppresses cell expansion and promotes apical hook development in the dark.

结果4-SAUR17与SAUR50对PP2C-D1的拮抗调控：SAUR50 inhibits PP2C-D1, while SAUR17 has a higher affinity to PP2C-D1 without inhibiting its activity. We demonstrate that PP2C-D1 predominantly associates with SAUR17 in etiolated seedlings, which shields it from inhibitory SAURs such as SAUR50.

结果5-光下去黄化机制：Light signals turn off SAUR17 and up-regulate a subgroup of SAURs including SAUR50 at the inner side of the hook and cotyledon cells, causing cell expansion and consequently unfolding the hook and cotyledons.

 摘  要 

拟南芥小苗在黑暗下发芽之后，会经历黄化，并发育出顶钩、闭合的子叶以及能够快速伸长的下胚轴。一旦感知到光，小苗会经历去黄化，包括顶钩和子叶的张开。本文中，作者鉴定拟南芥中SAUR17是黄化下游的效应子，作用于黄化中小苗顶端结构的形成，即顶钩和闭合子叶。SAUR17在顶钩和子叶中高表达，并且受到光的抑制。小苗的顶端器官中同样还表达一群其他受到光诱导的SAURs，其中就包括SAUR50，作用于促进顶钩和子叶的张开。黄化或去黄化的顶端结构发育需要不对称的差异细胞生长。作者发现顶端发育过程中SAUR17和SAUR50相反的作用很大程度上是来自于其对PP2C-D1蛋白的拮抗调控，PP2C-D1蛋白是一个磷酸酶，能够在黑暗条件下抑制细胞扩张和促进顶钩发育。SAUR50会抑制PP2C-D1，而SAUR17与PP2C-D1的亲和力更高，但是不会抑制PP2C-D1。作者发现在黄化苗中，PP2C-D1主要与SAUR17相关联，从而保护其免受诸如SAUR50等抑制因子的抑制作用。光信号会在顶钩内层细胞以及子叶细胞中，关闭SAUR17、上调包括SAUR50等在内的一群SAURs，导致细胞扩张，从而展开顶钩和子叶。