State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
J Genet Genomics. 2014 Jun 20;41(6):327-38. doi: 10.1016/j.jgg.2014.04.004. Epub 2014 May 14.
Seed dormancy is an important agronomic trait in cereals. Using deep dormant (N22), medium dormant (ZH11), and non-dormant (G46B) rice cultivars, we correlated seed dormancy phenotypes with abscisic acid (ABA) and gibberellin (GA) metabolism gene expression profiles and phytohormone levels during seed development and imbibition. A time course analysis of ABA and GA content during seed development showed that N22 had a high ABA level at early and middle seed developmental stages, while at late developmental stage it declined to the level of ZH11; however, its ABA/GA ratio maintained at a high level throughout seed development. By contrast, G46B had the lowest ABA content during seed development though at early developmental stage its ABA level was close to that of ZH11, and its ABA/GA ratio peaked at late developmental stage that was at the same level of ZH11. Compared with N22 and G46B, ZH11 had an even and medium ABA level during seed development and its ABA/GA ratio peaked at the middle developmental stage. Moreover, the seed development time-point having high ABA/GA ratio also had relatively high transcript levels for key genes in ABA and GA metabolism pathways across three cultivars. These indicated that the embryo-imposed dormancy has been induced before the late developmental stage and is determined by ABA/GA ratio. A similar analysis during seed imbibition showed that ABA was synthesized in different degrees for the three cultivars. In addition, water uptake assay for intact mature seeds suggested that water could permeate through husk barrier into seed embryo for all three cultivars; however, all three cultivars showed distinct colors by vanillin-staining indicative of the existence of flavans in their husks, which are dormancy inhibition compounds responsible for the husk-imposed dormancy.
种子休眠是谷类作物的一个重要农艺性状。利用深休眠（N22）、中休眠（ZH11）和非休眠（G46B）水稻品种，我们将种子休眠表型与脱落酸（ABA）和赤霉素（GA）代谢基因表达谱和种子发育及吸胀过程中的植物激素水平相关联。种子发育过程中 ABA 和 GA 含量的时程分析表明，N22 在早期和中期种子发育阶段具有高 ABA 水平，而在晚期发育阶段其 ABA 水平下降到 ZH11 的水平；然而，其 ABA/GA 比值在整个种子发育过程中保持在高水平。相比之下，G46B 在种子发育过程中具有最低的 ABA 含量，尽管在早期发育阶段其 ABA 水平接近 ZH11，但其 ABA/GA 比值在晚期发育阶段达到峰值，与 ZH11 相同。与 N22 和 G46B 相比，ZH11 在种子发育过程中具有均匀且中等水平的 ABA，其 ABA/GA 比值在中期发育阶段达到峰值。此外，具有高 ABA/GA 比值的种子发育时间点在三个品种中也具有关键基因在 ABA 和 GA 代谢途径中的相对较高的转录水平。这表明胚胎诱导的休眠在晚期发育阶段之前已经被诱导，并且由 ABA/GA 比值决定。在种子吸胀过程中的类似分析表明，三个品种都在不同程度上合成了 ABA。此外，对完整成熟种子的吸水测定表明，水分可以通过外壳屏障渗透到种子胚中，对于所有三个品种都是如此；然而，所有三个品种在香草醛染色时都表现出不同的颜色，这表明它们的外壳中存在类黄酮，类黄酮是负责外壳诱导休眠的休眠抑制化合物。
