Cao Dechang, Xu Huimin, Zhao Yuanyuan, Deng Xin, Liu Yongxiu, Soppe Wim J J, Lin Jinxing
Key Laboratory for Genetics and Breeding of Forest Trees and Ornamental Plants of Ministry of Education, College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing 100083, China (D.C., H.X., Y.Z., J.L.).
Key Laboratory of Plant Resources, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China (X.D., Y.L., J.L.).
Plant Physiol. 2016 Dec;172(4):2347-2362. doi: 10.1104/pp.16.00384. Epub 2016 Oct 19.
Seeds with physiological dormancy usually experience primary and secondary dormancy in the nature; however, little is known about the differential regulation of primary and secondary dormancy. We combined multiple approaches to investigate cytological changes, hormonal levels, and gene expression dynamics in Cunninghamia lanceolata seeds during primary dormancy release and secondary dormancy induction. Light microscopy and transmission electron microscopy revealed that protein bodies in the embryo cells coalesced during primary dormancy release and then separated during secondary dormancy induction. Transcriptomic profiling demonstrated that expression of genes negatively regulating gibberellic acid (GA) sensitivity reduced specifically during primary dormancy release, whereas the expression of genes positively regulating abscisic acid (ABA) biosynthesis increased during secondary dormancy induction. Parallel analysis of RNA ends revealed uncapped transcripts for ∼55% of all unigenes. A negative correlation between fold changes in expression levels of uncapped versus capped mRNAs was observed during primary dormancy release. However, this correlation was loose during secondary dormancy induction. Our analyses suggest that the reversible changes in cytology and gene expression during dormancy release and induction are related to ABA/GA balance. Moreover, mRNA degradation functions as a critical posttranscriptional regulator during primary dormancy release. These findings provide a mechanistic framework for understanding physiological dormancy in seeds.
具有生理休眠的种子在自然界中通常会经历初次休眠和二次休眠；然而，关于初次休眠和二次休眠的差异调控知之甚少。我们结合多种方法，研究了杉木种子在初次休眠解除和二次休眠诱导过程中的细胞学变化、激素水平和基因表达动态。光学显微镜和透射电子显微镜显示，胚细胞中的蛋白体在初次休眠解除过程中融合，然后在二次休眠诱导过程中分离。转录组分析表明，负调控赤霉素（GA）敏感性的基因表达在初次休眠解除过程中特异性降低，而正调控脱落酸（ABA）生物合成的基因表达在二次休眠诱导过程中增加。RNA末端平行分析显示，所有单基因中有约55%的转录本无帽。在初次休眠解除过程中，观察到无帽mRNA与有帽mRNA表达水平的倍数变化之间呈负相关。然而，在二次休眠诱导过程中，这种相关性较弱。我们的分析表明，休眠解除和诱导过程中细胞学和基因表达的可逆变化与ABA/GA平衡有关。此外，mRNA降解在初次休眠解除过程中作为关键的转录后调节因子发挥作用。这些发现为理解种子生理休眠提供了一个机制框架。
