title: Abscisic acid regulates early seed development in Arabidopsis by ABI5-mediated transcription of SHORT HYPOCOTYL UNDER BLUE1.
abstract: Seed development includes an early stage of endosperm proliferation and a late stage of embryo growth at the expense of the endosperm in Arabidopsis thaliana. Abscisic acid (ABA) has known functions during late seed development, but its roles in early seed development remain elusive. In this study, we report that ABA-deficient mutants produced seeds with increased size, mass, and embryo cell number but delayed endosperm cellularization. ABSCISIC ACID DEFICIENT2 (ABA2) encodes a unique short-chain dehydrogenase/reductase that functions in ABA biosynthesis, and its expression pattern overlaps that of SHORT HYPOCOTYL UNDER BLUE1 (SHB1) during seed development. SHB1 RNA accumulation was significantly upregulated in the aba2-1 mutant and was downregulated by the application of exogenous ABA. Furthermore, RNA accumulation of the basic/region leucine zipper transcription factor ABSCISIC ACID-INSENSITIVE5 (ABI5), involved in ABA signaling, was decreased in aba2-1. Consistent with this, seed size was also increased in abi5. We further show that ABI5 directly binds to two discrete regions in the SHB1 promoter. Our results suggest that ABA negatively regulates SHB1 expression, at least in part, through the action of its downstream signaling component ABI5. Our findings provide insights into the molecular mechanisms by which ABA regulates early seed development.
authors.affiliation: State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, Shandong 271018, China.
authors.forename: Zhi Juan
authors.initials: ZJ
authors.lastname: Cheng
authors.forename: Xiang Yu
authors.initials: XY
authors.lastname: Zhao
authors.forename: Xing Xing
authors.initials: XX
authors.lastname: Shao
authors.forename: Fei
authors.initials: F
authors.lastname: Wang
authors.forename: Chao
authors.initials: C
authors.lastname: Zhou
authors.forename: Ying Gao
authors.initials: YG
authors.lastname: Liu
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xian Sheng
authors.initials: XS
authors.lastname: Zhang
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D000429:Alcohol Oxidoreductases / Q000235:genetics; D017360:Arabidopsis / Q000196:embryology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000502:physiology*; D050976:Basic-Leucine Zipper Transcription Factors / Q000502:physiology*; D012313:RNA / Q000378:metabolism; D012639:Seeds / Q000254:growth & development*; D014158:Transcription, Genetic / Q000502:physiology*
chemical_list: C409743:ABI5 protein, Arabidopsis; D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; C511745:SHB1 protein, Arabidopsis; D012313:RNA; D000040:Abscisic Acid; C469255:ABA2 protein, Arabidopsis; D000429:Alcohol Oxidoreductases