Carrera Esther, Holman Tara, Medhurst Anne, Peer Wendy, Schmuths Heike, Footitt Steven, Theodoulou Frederica L, Holdsworth Michael J
Centro de Genomica, Instituto Valenciano de Investigaciones Agrarias, Valencia, Spain.
Plant Physiol. 2007 Apr;143(4):1669-79. doi: 10.1104/pp.107.096057. Epub 2007 Feb 23.
Phase II of germination represents a key developmental stage of plant growth during which imbibed seeds either enter stage III of germination, completing the germination process via radicle protrusion, or remain dormant. In this study, we analyzed the influence of the peroxisomal ATP-binding cassette transporter COMATOSE (CTS) on the postimbibition seed transcriptome of Arabidopsis (Arabidopsis thaliana) and also investigated interactions between gibberellin (GA) and CTS function. A novel method for analysis of transcriptome datasets allowed visualization of developmental signatures of seeds, showing that cts-1 retains the capacity to after ripen, indicating a germination block late in phase II. Expression of the key GA biosynthetic genes GA3ox1 and 2 was greatly reduced in cts seeds and genetic analysis suggested that CTS was epistatic to RGL2, a germination-repressing DELLA protein that is degraded by GA. Comparative analysis of seed transcriptome datasets indicated that specific cohorts of genes were influenced by GA and CTS. CTS function was required for expression of the flavonoid biosynthetic pathway. Confocal imaging demonstrated the exclusive accumulation of flavonoids in the epidermis of wild-type seeds. In contrast, flavonoids were absent from cts and kat2-1 mutant seeds, but accumulated following the application of sucrose, indicating an essential role for beta-oxidation in inducing flavonoid biosynthetic genes. These results demonstrate that CTS functions very late in phase II of germination and that its function is required for the expression of specific gene sets related to an important biochemical pathway associated with seedling establishment and survival.
种子萌发的第二阶段是植物生长过程中的一个关键发育阶段，在此期间，吸胀的种子要么进入萌发的第三阶段，通过胚根突出完成萌发过程，要么保持休眠状态。在本研究中，我们分析了过氧化物酶体ATP结合盒转运蛋白COMATOSE（CTS）对拟南芥（Arabidopsis thaliana）吸胀后种子转录组的影响，并研究了赤霉素（GA）与CTS功能之间的相互作用。一种分析转录组数据集的新方法能够可视化种子的发育特征，结果表明cts-1保留了后熟的能力，这表明在第二阶段后期存在萌发障碍。关键的GA生物合成基因GA3ox1和GA2在cts种子中的表达大幅降低，遗传分析表明CTS对RGL2上位，RGL2是一种抑制萌发的DELLA蛋白，可被GA降解。种子转录组数据集的比较分析表明，特定的基因群组受GA和CTS影响。黄酮类生物合成途径的表达需要CTS功能。共聚焦成像显示黄酮类化合物在野生型种子的表皮中特异性积累。相比之下，cts和kat2-1突变体种子中没有黄酮类化合物，但在施加蔗糖后会积累，这表明β-氧化在诱导黄酮类生物合成基因方面起着重要作用。这些结果表明，CTS在种子萌发的第二阶段非常后期发挥作用，其功能对于与幼苗建立和存活相关的重要生化途径的特定基因集的表达是必需的。
