title: Overexpression of TMAC2, a novel negative regulator of abscisic acid and salinity responses, has pleiotropic effects in Arabidopsis thaliana.
abstract: Phytohormone abscisic acid (ABA) regulates many aspects of plant development and growth. To explore the molecular mechanism of ABA, we identified the novel ABA-regulated genes in Arabidopsis thaliana by searching for genes possessing two or more ABREs (ABA-responsive elements). One of these genes, two or more ABREs-containing gene 2 (TMAC2) is highly induced by ABA and NaC1. Database searches revealed that TMAC2 encodes a protein with no domains of known function. Expression of TMAC2-GFP fusion protein in Arabidopsis mesophyll protoplasts indicated that TMAC2 is targeted to the nucleus. Although the gene has a basal level of expression in various Arabidopsis organs/tissues except for adult leaves, a high expression level was detected in roots. Constitutive overexpression of TMAC2 in plants resulted in the insensitivity to ABA and NaCl, suggesting that TMAC2 plays a negative role in ABA and salt stress responses. Furthermore, TMAC2-overexpressing plants exhibited the short roots, late flowering and starch-excess phenotypes. RT-PCR analysis showed that decreased expression of two floral- and one starch degradation-related genes, SOC1/AGL20 and SEP3/AGL9, and SEX1, respectively, may lead to altered phenotypes of TMAC2-overexpressing plants. Taken together, our data reveal that TMAC2 acts in the nucleus and is an important negative regulator of ABA and salt stress responses, and could play a critical role in controlling root elongation, floral initiation and starch degradation.
authors.affiliation: Department of Life Sciences, National Cheng Kung University, Tainan 701, Taiwan.
authors.forename: Ming-Der
authors.initials: MD
authors.lastname: Huang
authors.forename: Wen-Luan
authors.initials: WL
authors.lastname: Wu
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics*; D003001:Cloning, Molecular; D017124:Conserved Sequence; D017931:DNA Primers; D018506:Gene Expression Regulation, Plant; D007700:Kinetics; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics*; D011994:Recombinant Proteins / Q000737:chemistry; D015183:Restriction Mapping; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012965:Sodium Chloride / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D017931:DNA Primers; D009687:Nuclear Proteins; D011994:Recombinant Proteins; C521711:TMAC2 protein, Arabidopsis; D012965:Sodium Chloride; D000040:Abscisic Acid