title: A subset of Arabidopsis RAV transcription factors modulates drought and salt stress responses independent of ABA.
abstract: Arabidopsis RAV1, RAV1L and RAV2/TEM2 are Related to ABI3/VP1 (RAV) transcription factors that contain both plant-specific B3 and AP2 domains. RAV1 was known to be a negative regulator of growth and its transcript level was repressed by brassinolide (BL). In this study, we found that the expressions of RAV1, and its closest homologs RAV1L and RAV2 were also regulated by other plant hormones, and especially repressed significantly by BL and abscisic acid (ABA), which mediate various abiotic stress responses in plants. Therefore, to further investigate the physiological functions of RAV1, RAV1L and RAV2 in abiotic stress responses, we isolated T-DNA insertional knockout mutants of each gene and produced transgenic plants overexpressing the RAVs. Under normal conditions, each single mutant showed slightly promoted growth patterns only at an early stage of development. In comparison, the RAV1-overexpressing plants exhibited strong growth retardation with semi-dwarfed stature. In drought conditions, RAVs-overexpressing transgenic plants exhibited higher transpirational water loss than the wild type. In salt conditions, seed germination of the RAVs-overexpressing transgenic plants was more inhibited than that of the wild type, while ravs mutants showed promoted seed germination. We also found that RAVs expressions were reduced by dryness and salt. RAV1-overexpressing plants showed the same patterns of increased expression as stress-inducible genes such as RD29A, RD29B and the genes encoding ABA biosynthetic enzymes, as did the wild type and rav1 mutant. However, the RAV1-overexpressing transgenic plants were insensitive to ABA, regardless of the higher accumulation of ABA even in normal conditions. Taken together, these results suggest that RAVs are versatile negative regulators for growth and abiotic stresses, drought and salt, and that negative regulatory effects of RAVs on abiotic stresses are likely to be operated independently of ABA.
authors.affiliation: Department of Life Systems, Sookmyung Women's University, Seoul 140-742, Korea These authors contributed equally to this article.
authors.forename: Minjie
authors.initials: M
authors.lastname: Fu
authors.affiliation: Department of Biological Sciences, Sookmyung Women's University, Seoul 140-742, Korea These authors contributed equally to this article.
authors.forename: Hyun Kyung
authors.initials: HK
authors.lastname: Kang
authors.affiliation: Department of Life Science, Chung-Ang University, Seoul 156-756, Korea.
authors.forename: Seung-Hyun
authors.initials: SH
authors.lastname: Son
authors.affiliation: Department of Life Science, Chung-Ang University, Seoul 156-756, Korea.
authors.forename: Seong-Ki
authors.initials: SK
authors.lastname: Kim
authors.affiliation: Department of Life Systems, Sookmyung Women's University, Seoul 140-742, Korea Department of Biological Sciences, Sookmyung Women's University, Seoul 140-742, Korea khnam514@sookmyung.ac.kr.
authors.forename: Kyoung Hee
authors.initials: KH
authors.lastname: Nam
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism* / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D057773:Cold Shock Proteins and Peptides / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D055864:Droughts; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D018525:Germination / Q000235:genetics; D009154:Mutation; D010937:Plant Growth Regulators / Q000378:metabolism / Q000494:pharmacology; D030821:Plants, Genetically Modified; D055049:Salt Tolerance / Q000502:physiology*; D013312:Stress, Physiological / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D057773:Cold Shock Proteins and Peptides; D004268:DNA-Binding Proteins; D010937:Plant Growth Regulators; C117695:RAV1 protein, Arabidopsis; C117696:RAV2 protein, Arabidopsis; C000595439:RD29B protein, Arabidopsis; C520629:RD29a protein, Arabidopsis; D014157:Transcription Factors; D000040:Abscisic Acid
keywords: ABA; Drought; Growth; RAV transcription factor; Salt; Seed germination