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ABSTRACT: We carried out activation tagging screen to isolate genes regulating abscisic acid (ABA) response. From the screen of approximately 10,000 plants, we isolated ca 100 ABA response mutants. We characterized one of the mutants, designated ahs1, in this study. The mutant is ABA-hypersensitive, and AtMYB52 was found to be activated in the mutant. Overexpression analysis to recapitulate the mutant phenotypes demonstrated that ATMYB confers ABA-hypersensitivity during postgermination growth. Additionally, AtMYB52 overexpression lines were drought-tolerant and their seedlings were salt-sensitive. Changes in the expression levels of a few genes involved in ABA response or cell wall biosynthesis were also observed. Together, our data suggest that AtMYB52 is involved in ABA response. Others previously demonstrated that AtMYB52 regulates cell wall biosynthesis; thus, our results imply a possible connection between ABA response and cell wall biosynthesis.
Molecules and Cells 03/2011; 31(5):447-54. · 2.18 Impact Factor
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ABSTRACT: ABF2 is a basic leucine zipper protein that regulates abscisic acid (ABA)-dependent stress-responsive gene expression. We carried out yeast two-hybrid screens to isolate genes encoding ABF2-interacting proteins in Arabidopsis (Arabidopsis thaliana). Analysis of the resulting positive clones revealed that two of them encode an AP2 domain protein, which is the same as AtERF48/DREB2C. This protein, which will be referred to as DREB2C, could bind C-repeat/dehydration response element in vitro and possesses transcriptional activity. To determine its function, we generated DREB2C overexpression lines and investigated their phenotypes. The transgenic plants were ABA hypersensitive during germination and seedling establishment stages, whereas primary root elongation of seedlings was ABA insensitive, suggesting developmental stage dependence of DREB2C function. The DREB2C overexpression lines also displayed altered stress response; whereas the plants were dehydration sensitive, they were freezing and heat tolerant. We further show that other AP2 domain proteins, DREB1A and DREB2A, interact with ABF2 and that other ABF family members, ABF3 and ABF4, interact with DREB2C. Previously, others demonstrated that ABF and DREB family members cooperate to activate the transcription of an ABA-responsive gene. Our result implies that the cooperation of the two classes of transcription factors may involve physical interaction.
Plant physiology 06/2010; 153(2):716-27. · 6.53 Impact Factor
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ABSTRACT: ARIA is an ARM repeat protein that is a positive regulator of ABA response. To identify ARIA-interacting proteins, we conducted yeast two-hybrid screening. One of the positive clones obtained from the screen encoded a protein kinase, AtNEK6, which belongs to the NIMA (Never In Mitosis, gene A)-related kinase family. We analyzed AtNEK6 over-expression (OX) and knockout (KO) lines to investigate its in vivo function. The AtNEK6 OX lines grew slowly, whereas the KO line germinated and grew faster than wild type plants. AtNEK6 also affected ABA and stress responses. During seed germination, AtNEK6 OX lines were hypersensitive to ABA and high osmolarity, whereas its KO line was partially insensitive to ABA and high osmolarity. Previously, AtNEK6 was shown to be involved in epidermal cell morphogenesis. Our results indicate that AtNEK6 is also involved in plant growth regulation and responses to ABA and high osmolarity during the seed germination stage.
Molecules and Cells 05/2010; 29(6):559-66. · 2.18 Impact Factor
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ABSTRACT: ADAP is an AP2-domain protein that interacts with ARIA, which, in turn, interacts with ABF2, a bZIP class transcription factor. ABF2 regulates various aspects of the abscisic acid (ABA) response by controlling the expression of a subset of ABA-responsive genes. Our expression analyses indicate that ADAP is expressed in roots, emerging young leaves, and flowers. We found that adap knockout mutant lines germinate more efficiently than wild-type plants and that the mutant seedlings grow faster. This suggests that ADAP is involved in the regulation of germination and seedling growth. Both germination and post-germination growth of the knockout mutants were partially insensitive to ABA, which indicates that ADAP is required for a full ABA response. The survival rates for mutants from which water was withheld were low compared with those for wild-type plants. The result shows that ADAP is necessary for the response to stress induced by water deprivation. Together, our data indicate that ADAP is a positive regulator of the ABA response and is also involved in regulating seedling growth. The role of ADAP is similar to that of ARIA, which is also a positive regulator of the ABA response. It appears that ADAP acts through the same ABA response pathway as ARIA.
Molecules and Cells 05/2009; 27(4):409-16. · 2.18 Impact Factor
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ABSTRACT: Phytohormone abscisic acid (ABA) regulates stress-responsive gene expression during vegetative growth, which is mediated largely by cis-elements sharing the ACGTGGC consensus. Although many transcription factors are known to bind the elements in vitro, only a few have been demonstrated to have in vivo functions and their specific roles in ABA/stress responses are mostly unknown. Here, we report that ABF2, an ABF subfamily member of bZIP proteins interacting with the ABA-responsive elements, is involved in ABA/stress responses. Its overexpression altered ABA sensitivity, dehydration tolerance, and the expression levels of ABA/stress-regulated genes. Furthermore, ABF2 overexpression promoted glucose-induced inhibition of seedling development, whereas its mutation impaired glucose response. The reduced sugar sensitivity was not observed with mutants of two other ABF family members, ABF3 and ABF4. Instead, these mutants displayed defects in ABA, salt, and dehydration responses, which were not observed with the abf2 mutant. Our data indicate distinct roles of ABF family members: whereas ABF3 and ABF4 play essential roles in ABA/stress responses, ABF2 is required for normal glucose response. We also show that ABF2 overexpression affects multiple stress tolerance.
The Plant Journal 11/2004; 40(1):75-87. · 6.16 Impact Factor
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ABSTRACT: Unfavourable environmental conditions, such as drought, freezing and high salinity, are major limiting factors of plant productivity. Plants perceive and respond adaptively to such 'abiotic stress' conditions, and the adaptive process is controlled mainly by the phytohormone, abscisic acid (ABA). The hormone, whose level increases under various stress conditions, functions as a signal to trigger adaptive responses that include changes in gene expression patterns. We have recently reported transcription factors that regulate the ABA-responsive gene expression. As ABA mediates adaptation to several common abiotic stresses, we investigated whether the transcription factors are involved in various stress responses. Here, we report that over-expression of ABF3, one of the factors, confers tolerance to chilling, freezing, high temperature and oxidative stress in addition to drought. Our results indicate that ABF3 is involved in multiple stress responses, and that it may be a useful genetic resource for the engineering of plant stress tolerance.
Plant Biotechnology Journal 10/2004; 2(5):459-66. · 5.44 Impact Factor
