title: Arabidopsis SAG protein containing the MDN1 domain participates in seed germination and seedling development by negatively regulating ABI3 and ABI5.
abstract: Three proteins containing a midasin homologue 1 (MDN1) domain from the yeast Solanum chacoense and Arabidopsis thaliana have important functions in yeast survival, seed development, and female gametogenesis. In this study, a novel protein containing the MDN1 domain from Arabidopsis negatively regulated abscisic acid (ABA) signalling during seed germination. Seeds of a T-DNA insertion line of this gene exhibited increased sensitivity to ABA during seed germination and seedling development (named sag). By contrast, seeds with overexpressed AtSAG (OX2) were less sensitive to ABA. The seeds of the sag mutant showed similar sensitivity to high concentrations of mannitol and NaCl during these stages. AtSAG was also highly expressed in germinating seeds. However, ABA-induced AtSAG expression remained almost unchanged. ABA-responsive marker genes, including ABI3, ABI5, Em1, Em6, RD29A, and RAB18, were upregulated in sag mutants but were downregulated in OX2. Genetic analyses indicated that the function of AtSAG in ABA signalling depended on ABI3 and ABI5. The expression of some target genes of ABI3 and ABI5, such as seed storage protein and oleosin genes, was induced higher by ABA in sag mutants than in wild-type germinated seeds, even higher than in abi5 mutants. This finding indicated that other regulators similar to ABI3 or ABI5 played a role during these stages. Taken together, these results indicate that AtSAG is an important negative regulator of ABA signalling during seed germination and seedling development.
authors.affiliation: State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, Shandong, PR China.
authors.forename: Changtian
authors.initials: C
authors.lastname: Chen
authors.forename: Changai
authors.initials: C
authors.lastname: Wu
authors.forename: Jiaming
authors.initials: J
authors.lastname: Miao
authors.forename: Yunxue
authors.initials: Y
authors.lastname: Lei
authors.forename: Dongxiao
authors.initials: D
authors.lastname: Zhao
authors.forename: Dan
authors.initials: D
authors.lastname: Sun
authors.forename: Guodong
authors.initials: G
authors.lastname: Yang
authors.forename: Jinguang
authors.initials: J
authors.lastname: Huang
authors.forename: Chengchao
authors.initials: C
authors.lastname: Zheng
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D018525:Germination; D008353:Mannitol / Q000494:pharmacology; D016254:Mutagenesis, Insertional; D010937:Plant Growth Regulators / Q000494:pharmacology*; D030821:Plants, Genetically Modified; D017434:Protein Structure, Tertiary; D036226:Seedlings / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D015398:Signal Transduction; D012965:Sodium Chloride / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
chemical_list: C091601:ABI3 protein, Arabidopsis; C409743:ABI5 protein, Arabidopsis; D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D010937:Plant Growth Regulators; D014157:Transcription Factors; D008353:Mannitol; D012965:Sodium Chloride; D000040:Abscisic Acid
keywords: Abscisic acid; AtSAG; MDN1 domain; drought; salt; seed germination