Abstract
ABI5 is a critical transcription factor in regulation of crop seed maturation, dormancy, germination and post-germination. Sixteen copies of homologous sequences of ABI5 were identified in Chinese wheat line Zhou 8425B. Cultivars of two haplotypes TaABI5-A4a and TaABI5-A4bshowed significantly different seed dormancy. Based on two SNPs between the sequences of TaABI5-A4a and TaABI5-A4b, two complementary dominant sequence-tagged site (STS) markers were developed and validated in a natural population of 103 Chinese wheat cultivars and advanced lines and 200 recombinant inbred lines (RILs) derived from the Yangxiaomai/Zhongyou 9507 cross; the STS markers can be used efficiently and reliably to evaluate the dormancy of wheat seeds. The transcription level of TaABI5-A4b was significantly increased in TaABI5-A4a-GFPtransgenic rice lines compared with that in TaABI5-A4b-GFP. The average seed germination index of TaABI5-A4a-GFP transgenic rice lines were significantly lower than those of TaABI5-A4b-GFP. In addition, seeds of TaABI5-A4a-GFP transgenic lines had higher ABA sensitivity and endogenous ABA content, lower endogenous GA content and plant height, and thicker stem internodes than those of TaABI5-A4b-GFP. Allelic variation of TaABI5-A4 affected wheat seed dormancy and the gene function was confirmed in transgenic rice. The transgenic rice lines of TaABI5-A4a and TaABI5-A4b had significantly different sensitivities to ABA and contents of endogenous ABA and GA in mature seeds, thereby influencing the seed dormancy, plant height and stem internode length and diameter.