Genome-wide in silico identification and functional characterization of abscisic acid-regulated genes in Arabidopsis

• Main Authors: Ming-Der Huang, 黃明德
• Other Authors: Wen-Luan Wu
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/57990085882859839158

博士 === 國立成功大學 === 生命科學系碩博士班 === 95 === Abscisic acid (ABA) is a key phytohormone which regulates plant development and growth in many aspects. Functional analysis of the ABA-regulated gene promoter reveals a conserved ABA-responsive element (ABRE), which is recognized by a group of transcription factors with a bZIP domain. Although some ABA-regulated genes have been reported, the molecular mechanism of ABA signaling remained unknown. To facilitate the identification of ABA-regulated genes, we identify novel ABA-regulated genes in Arabidopsis thaliana using a bioinformatics approach. A computational search revealed that 137 of 26,207 genes possess two or more ABREs in Arabidopsis, and 31 genes encode unknown proteins. In an attempt to monitor the expression of these candidate genes in response to ABA, we selected 16 genes were and examined their expression by RT-PCR. Among these 16 genes, 12 candidates were up-regulated by ABA. In addition, Northern blot analysis indicated that some candidates were further shown to differentially respond to various stresses. To explore the functions of these ABA-regulated genes, we generated the transgenic Arabidopsis plants. One of these genes, TMAC1 (two or more ABREs containing gene 1), which encodes a PMP22-like protein, was up-regulated by ABA, salt, cold and wounding stresses; the results indicated that TMAC1 is a stress-related gene. Additionally, TMAC1 transcript rapidly increased in response to wounding in both wild-type and ABA-deficient mutant leaves and exogenous hydrogen peroxide (H2O2) stimulated TMAC1 expression. Thus, the signaling molecule ROS, rather than ABA, may be the intermediate of the signal transduction pathway leading to TMAC1 expression by wounding. TMAC2, which encodes a protein with no domains of known function, was highly induced by ABA and salt. Constitutive overexpression of TMAC2 in transgenic plants resulted in insensitivity of the plants to ABA and salt; the results suggested that TMAC2 plays a negative role in ABA and salt stress responses. Furthermore, TMAC2-overexpressing plants exhibited the phenotypes of short roots, late flowering and starch-excess leaves. Taken together, these results show that in silico identification of ABA-regulated genes by using data mining of Arabidopsis genome sequence is a fast and reliable approach to dissecting the function of these genes.