Abscisic acid (ABA) response element (ABRE)-binding factors (ABFs) are basic region/leucine zipper motif (bZIP) transcription factors that regulate the expression of ABA-induced genes containing ABRE in their promoters. The amino acid sequence of the wheat bZIP protein, TaABI5, showed high homology to that of Arabidopsis ABA insensitive 5 (ABI5). TaABI5 was classified into the clade of ABI5s in Arabidopsis and rice, unlike TRAB1 of rice, Wabi5 of wheat, and HvABI5 of barley in the bZIP Group A family, by a phylogenetic analysis. TaABI5 was strongly expressed in seeds during the late ripening and maturing stages; however, its expression level markedly decreased after germination. An in situ hybridization analysis showed that TaABI5 mRNA accumulated in seed embryos, particularly the scutellum. In a transient assay using wheat aleurone cells, TaABI5 activated the promoter of Em containing ABRE, which is an embryogenesis abundant protein gene, indicating that TaABI5 acts as a transcription factor in wheat seeds. Furthermore, the seeds of transgenic Arabidopsis lines introduced with 35S:TaABI5 exhibited high sensitivity to ABA and the inhibition of germination. The seed dormancy of the transgenic Arabidopsis lines was stronger than that of Col. These results support TaABI5 playing an important role in mature seeds, particularly before seed germination, and acting as a functional ortholog to Arabidopsis ABI5.

中文翻译：

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TaABI5是拟南芥ABA不敏感5的小麦同源物，可控制种子发芽。

脱落酸（ABA）响应元件（ABRE）结合因子（ABFs）是基本区域/亮氨酸拉链基序（bZIP）转录因子，可调节启动子中包含ABRE的ABA诱导基因的表达。小麦bZIP蛋白TaABI5的氨基酸序列与拟南芥ABA不敏感5（ABI5）的同源性很高。通过系统进化分析，与水稻的TRAB1，小麦的Wabi5和大麦的HvABI5不同，TaABI5被分为拟南芥和水稻中的ABI5s进化枝。TaABI5在成熟和成熟后期在种子中强烈表达。但是，发芽后其表达水平明显下降。原位杂交分析表明TaABI5 mRNA积累在种子胚胎，特别是盾片中。在使用小麦糊粉细胞的瞬时分析中，TaABI5激活了含有ABRE的Em的启动子，ABRE是一种胚发生丰富的蛋白质基因，表明TaABI5充当小麦种子中的转录因子。此外，导入35S：TaABI5的转基因拟南芥品系的种子表现出对ABA的高敏感性和对发芽的抑制作用。转基因拟南芥品系的种子休眠性强于Col。这些结果支持TaABI5在成熟种子中发挥重要作用，尤其是在种子发芽之前，并充当拟南芥ABI5的功能直系同源物。TaABI5表现出对ABA的高敏感性和对发芽的抑制作用。转基因拟南芥品系的种子休眠性强于Col。这些结果支持TaABI5在成熟种子中发挥重要作用，尤其是在种子发芽之前，并充当拟南芥ABI5的功能直系同源物。TaABI5表现出对ABA的高敏感性和对发芽的抑制作用。转基因拟南芥品系的种子休眠性强于Col。这些结果支持TaABI5在成熟种子中发挥重要作用，尤其是在种子发芽之前，并充当拟南芥ABI5的功能直系同源物。