中科院最新PNAS文章

　　种子从休眠向萌发转变是植物生命周期中的一个关键转折点。种子休眠是高等植物长期进化选择的结果，对于植物物种繁衍和渡过恶劣环境条件具有关键性作用。在农业生产方面，种子的休眠性能有效地防止种子成熟后在潮湿环境下穗发芽而导致产量和品质下降。前人的研究表明，ABA是唯一已知的能诱导和维持种子休眠的激素。

中科院上海生命科学研究院植物生理生态研究所何祖华研究组经过多年的研究发现，生长素是第二个可以诱导和维持种子休眠的激素。相关研究成果于8月28日在线发表在《美国科学院院报》（PNAS）上。

何祖华研究组在研究生长素（auxin）介导的植物免疫（抗病性）与生长发育的关系中发现，从上游到下游的一系列auxin信号缺失突变体的种子休眠性都不同程度的减弱，而且auxin合成缺陷的突变体的休眠性也减弱了，新鲜种子很容易发芽。相反，auxin合成过量突变体的种子休眠性得到了显著的提高。

ABI3是种子休眠的一个关键调控因子，进一步研究发现，auxin通过下游ARF10和ARF16转录因子调控了ABI3基因的表达，从而控制了种子的休眠性。研究证明，auxin和ABA两种信号途径是诱导和维持种子休眠所必需的。这些发现拓展了种子休眠的分子调控网络，为改良农作物种子的休眠性，解决穗发芽问题提供了新的思路。

原文摘要：

Auxin controls seed dormancy through stimulation of abscisic acid signaling by inducing ARF-mediated ABI3 activation in Arabidopsis

The transition from dormancy to germination in seeds is a key physiological process during the lifecycle of plants. Abscisic acid (ABA) is the sole plant hormone known to maintain seed dormancy; it acts through a gene expression network involving the transcription factor ABSCISIC ACID INSENSITIVE 3 (ABI3). However, whether other phytohormone pathways function in the maintenance of seed dormancy in response to environmental and internal signals remains an important question. Here, we show that the plant growth hormone auxin, which acts as a versatile trigger in many developmental processes, also plays a critical role in seed dormancy in Arabidopsis. We show that disruptions in auxin signaling in MIR160-overexpressing plants, auxin receptor mutants, or auxin biosynthesis mutants dramatically release seed dormancy, whereas increases in auxin signaling or biosynthesis greatly enhance seed dormancy. Auxin action in seed dormancy requires the ABA signaling pathway (and vice versa), indicating that the roles of auxin and ABA in seed dormancy are interdependent. Furthermore, we show that auxin acts upstream of the major regulator of seed dormancy, ABI3, by recruiting the auxin response factors AUXIN RESPONSE FACTOR 10 and AUXIN RESPONSE FACTOR 16 to control the expression of ABI3 during seed germination. Our study, thus, uncovers a previously unrecognized regulatory factor of seed dormancy and a coordinating network of auxin and ABA signaling in this important process.