Study On The Regulatory Mechanism Of Arabidopsis Genes At1g18740 And At5g52250 Genes In ABA Signaling

Abscisic acid plays an important role in the regulation of plant growth and development, such as seed dormancy, germination, root growth and other processes. When plants are threatened by environmental stresses, the level of ABA is increased and induces the expression of a series of stress-responsive genes. The increased level of ABA also leads to stomatal closure, leaf senescence and other physiological responses, such that plants make responses to environmental stresses and improve the ability to tolerate the stresses. In this study, we used the model plant species Arabidopsis thaliana to explore the roles of two unknown Arabidopsis genes At1g18740 and At5g52250in the ABA signaling pathway. Experimental results show that:1. The T-DNA insertional mutants of At1g18740 (plant number 993) exhibited enhanced tolerance to drought stress, increased sensitivity to exogenous ABA treatment, and accelerated dark-induced leaf senescence. However, the T-DNA insertional mutants of At5g52250 (plant number 638) had no such phenotypic changes.2. The double mutant of 993 and 638 exhibited further enhanced sensitivity to exogenous ABA compared to wild-type and single mutants. The seed germination and primary root elongation were strongly inhibited by exogenous ABA in the double mutant. The double mutant also showed delayed germination and insensitivity to stratification, and accelerated dark-induced leaf senescence in comaprison to wild-type and single mutants. In addition, the bolting time of the double mutant was significantly delayed.3. Analysis of the expression pattern of At1g18740 and At5g52250 in wild-type using qRT-PCR indicated that both genes are induced by exogenous ABA and suppressed by stratification in seeds.4. qRT-PCR analysis of the expression patterns of ABA signaling-related genes and catabolism-related genes were carried out in wildtype and mutants under normal growth condition and exogenous ABA treatment. The results showed that the expression of ABF and ABI genes, which are involved in the ABA signaling pathway, was significantly increased in single mutants and double mutant with or without exogenous ABA treatment. The expression of ABI genes in the double mutant was increased more than others. The ABA catabolism-related genes CYP707As were noticeably increased in all mutants except CYP707A4.5. qRT-PCR analysis of the expression patterns of ABA signaling-related genes, biosynthesis- and catabolism-related genes was performed in Arabidopsis seeds with or without stratification. The results showed that the expression of ABFs, ABIs and NCED9 were suppressed in wild-type seeds by stratification, and two single mutants also showed similar results. In double mutant seeds, the expression of ABF1, ABF3, ABI1, ABI3, ABI5 and NCED9 showed no significant decrease.Taken together, the results showed that At1g18740 and At5g52250 act as negative regulators in ABA signaling pathway. The mechanism of the negative regulation may be achieved by regulating the expression of ABIs and ABFs.