Department of Biological Sciences, KAIST, Daejeon 305-701, Korea.
Plant Cell Physiol. 2013 Apr;54(4):555-72. doi: 10.1093/pcp/pct017. Epub 2013 Feb 1.
Seed dormancy, a seed status that prohibits germination even in the presence of inductive germination signals, is a poorly understood process. To identify molecular components that regulate seed dormancy, we screened T-DNA insertion lines and identified a mutant designated honsu (hon). HON loss-of-function mutants display deep seed dormancy, whereas HON-overexpressing lines display shallow seed dormancy. HON encodes a seed-specific group A phosphatase 2C (PP2C) and is one of the major negative regulators of seed dormancy among group A PP2Cs. Like other PP2C family members, HON interacts with PYR1/RCAR11 in the presence of ABA. Our analysis indicates that HON inhibits ABA signaling and activates gibberellic acid signaling, and both of these conditions must be satisfied to promote the release of seed dormancy. However, HON mRNA levels are increased in mutants displaying deep seed dormancy or under conditions that deepen seed dormancy, and decreased in mutants displaying shallow seed dormancy or under conditions that promote the release of seed dormancy. Taken together, our results indicate that the expression of HON mRNA is homeostatically regulated by seed dormancy.
种子休眠是一种阻止种子发芽的种子状态，即使存在诱导发芽信号也是如此，这是一个尚未被充分理解的过程。为了鉴定调控种子休眠的分子组成部分，我们筛选了 T-DNA 插入系，并鉴定出一个命名为 hon 的突变体。HON 功能丧失突变体表现出深度休眠，而 HON 过表达系表现出浅休眠。HON 编码一种种子特异性 A 组磷酸酶 2C（PP2C），是 A 组 PP2C 中主要的负调控因子之一。与其他 PP2C 家族成员一样，HON 在存在 ABA 的情况下与 PYR1/RCAR11 相互作用。我们的分析表明，HON 抑制 ABA 信号并激活赤霉素信号，这两种情况必须同时满足才能促进种子休眠的释放。然而，在表现出深度休眠的突变体或在加深种子休眠的条件下，HON mRNA 水平增加，而在表现出浅休眠的突变体或在促进种子休眠释放的条件下，HON mRNA 水平降低。总之，我们的结果表明，HON mRNA 的表达受到种子休眠的动态调控。
