Cadman Cassandra S C, Toorop Peter E, Hilhorst Henk W M, Finch-Savage William E
Warwick HRI, Warwick University, Wellesbourne, Warwick CV35 9EF, UK.
Plant J. 2006 Jun;46(5):805-22. doi: 10.1111/j.1365-313X.2006.02738.x.
Physiologically dormant seeds, like those of Arabidopsis, will cycle through dormant states as seasons change until the environment is favourable for seedling establishment. This phenomenon is widespread in the plant kingdom, but has not been studied at the molecular level. Full-genome microarrays were used for a global transcript analysis of Arabidopsis thaliana (accession Cvi) seeds in a range of dormant and dry after-ripened states during cycling. Principal component analysis of the expression patterns observed showed that they differed in newly imbibed primary dormant seeds, as commonly used in experimental studies, compared with those in the maintained primary and secondary dormant states that exist during cycling. Dormant and after-ripened seeds appear to have equally active although distinct gene expression programmes, dormant seeds having greatly reduced gene expression associated with protein synthesis, potentially controlling the completion of germination. A core set of 442 genes were identified that had higher expression in all dormant states compared with after-ripened states. Abscisic acid (ABA) responsive elements were significantly over-represented in this set of genes the expression of which was enhanced when multiple copies of the elements were present. ABA regulation of dormancy was further supported by expression patterns of key genes in ABA synthesis/catabolism, and dormancy loss in the presence of fluridone. The data support an ABA-gibberelic acid hormone balance mechanism controlling cycling through dormant states that depends on synthetic and catabolic pathways of both hormones. Many of the most highly expressed genes in dormant states were stress-related even in the absence of abiotic stress, indicating that ABA, stress and dormancy responses overlap significantly at the transcriptome level.
生理休眠种子，如拟南芥的种子，会随着季节变化在不同休眠状态间循环，直到环境适宜幼苗生长。这种现象在植物界广泛存在，但尚未在分子水平上进行研究。利用全基因组微阵列对拟南芥（生态型Cvi）种子在循环过程中的一系列休眠和干燥后熟状态进行了全局转录分析。对观察到的表达模式进行主成分分析表明，与循环过程中存在的维持初级和次级休眠状态的种子相比，实验研究中常用的新吸收的初级休眠种子的表达模式有所不同。休眠和后熟种子似乎具有同样活跃但不同的基因表达程序，休眠种子中与蛋白质合成相关的基因表达大幅降低，这可能控制着萌发的完成。鉴定出一组442个核心基因，它们在所有休眠状态下的表达均高于后熟状态。脱落酸（ABA）反应元件在这组基因中显著富集，当元件的多个拷贝存在时，其表达增强。ABA合成/分解代谢关键基因的表达模式以及氟啶酮存在下的休眠丧失进一步支持了ABA对休眠的调控。数据支持一种ABA-赤霉素激素平衡机制，该机制控制着通过休眠状态的循环，这取决于两种激素的合成和分解代谢途径。即使在没有非生物胁迫的情况下，休眠状态下许多表达量最高的基因也与胁迫相关，这表明ABA、胁迫和休眠反应在转录组水平上有显著重叠。
