Functional Study of ARABIDOPSIS A-FIFTEEN to Modulate Redox Homeostasis During Plant Development in Arabidopsis thaliana

• Main Authors: Guan-Hong Chen, 陳冠宏
• Other Authors: Fung-Fang Chen
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/82103834664628992008

博士 === 國立陽明大學 === 生化暨分子生物研究所 === 100 === Leaf senescence is a highly regulated developmental process and is coordinated by both developmetal and environmental factors. Many senescence-associated genes (SAGs) have been identified, but their roles in leaf senescence remain unclear. We have previously identified a sweet potato (Ipomoea batatas) SAG, named SPA15, whose function was unknown. To further understand the role of SPA15 in leaf senescence, we identified and characterized the orthologue of SPA15 in Arabidopsis thaliana and named it ARABIDOPSIS A-FIFTEEN (AAF). AAF was expressed in early senescent leaves and in tissues with highly proliferative activities. AAF was localized to the chloroplasts by transient expression in the Arabidopsis mesophyll protoplasts. Overexpression of AAF (AAF-OX) in Arabidopsis promoted but the T-DNA insertion mutant (aaf-KO) delayed age-dependent leaf senescence. Furthermore, stress-induced leaf senescence by continuous darkness was enhanced in AAF-OX but suppressed in aaf-KO. Transcriptome analysis of expression profiles revealed upregulated genes related to pathogen defense, senescence, and oxidative stress in 3-week-old AAF-OX plants. Indeed, elevated levels of reactive oxygen species (ROS) and enhanced sensitivity to oxidative and dark stress were apparent in AAF-OX but reduced in aaf-KO. ETHYLENE INSENSITIVE2 (EIN2) was required for the dark- and ROS-induced senescence phenotypes in AAF-OX and the induction of AAF expression by treatment with the immediate precursor of ethylene, 1-aminocyclopropane-1-carboxylic acid. Our results indicate the functional role of AAF is involved in redox homeostasis to regulate leaf senescence mediated by age and stress factors during Arabidopsis development. However, AAF is likely not involved in ethylene biosynthesis or ethylene triple response. Yeast two hybrid results showed two candidates might be interacted with AAF, and these results need more experimental proof to interprete the molecular function of AAF.