title: The Arabidopsis RING finger E3 ligase RHA2b acts additively with RHA2a in regulating abscisic acid signaling and drought response.
abstract: We have previously shown that the Arabidopsis (Arabidopsis thaliana) RING-H2 E3 ligase RHA2a positively regulates abscisic acid (ABA) signaling during seed germination and postgerminative growth. Here, we report that RHA2b, the closest homolog of RHA2a, is also an active E3 ligase and plays an important role in ABA signaling. We show that RHA2b expression is induced by ABA and that overexpression of RHA2b leads to ABA-associated phenotypes such as ABA hypersensitivity in seed germination and seedling growth, enhanced stomatal closure, reduced water loss, and, therefore, increased drought tolerance. On the contrary, the rha2b-1 mutant shows ABA-insensitive phenotypes and reduced drought tolerance. We provide evidence showing that a rha2a rha2b-1 double mutant generally enhances ABA insensitivity of rha2b-1 in seed germination, seedling growth, and stomatal closure, suggesting that RHA2b and RHA2a act redundantly in regulating ABA responses. Genetic analyses support that, like RHA2a, the RHA2b action in ABA signaling is downstream of a protein phosphatase 2C, ABA-INSENSITIVE2 (ABI2), and in parallel with that of the ABI transcription factors ABI3/4/5. We speculate that RHA2b and RHA2a may have redundant yet distinguishable functions in the regulation of ABA responses.
authors.affiliation: State Key Laboratory of Plant Genomics, National Centre for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Hongmei
authors.initials: H
authors.lastname: Li
authors.forename: Hongling
authors.initials: H
authors.lastname: Jiang
authors.forename: Qingyun
authors.initials: Q
authors.lastname: Bu
authors.forename: Qingzhen
authors.initials: Q
authors.lastname: Zhao
authors.forename: Jiaqiang
authors.initials: J
authors.lastname: Sun
authors.forename: Qi
authors.initials: Q
authors.lastname: Xie
authors.forename: Chuanyou
authors.initials: C
authors.lastname: Li
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism* / Q000494:pharmacology; D000222:Adaptation, Physiological / Q000187:drug effects; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D055864:Droughts; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D018525:Germination / Q000187:drug effects; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D054046:Plant Stomata / Q000187:drug effects / Q000502:physiology; D054829:RING Finger Domains; D012639:Seeds / Q000187:drug effects / Q000254:growth & development; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D000040:Abscisic Acid; C474016:RHA2a protein, Arabidopsis; C561283:RHA2b protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases