G-Box Binding Factor1 Reduces CATALASE2 Expression and Regulates the Onset of Leaf Senescence in Arabidopsis    

Abstract

Hydrogen peroxide (H 2 O 2 ) is discussed as being a signaling molecule in Arabidopsis (Arabidopsis thaliana) leaf senescence. Intracellular H 2 O 2 levels are controlled by the H 2 O 2 -scavenging enzyme catalase in concert with other scavenging and producing systems. Catalases are encoded by a small gene family, and the expression of all three Arabidopsis catalase genes is regulated in a senescence-associated manner. CATALASE2 (CAT2) expression is down-regulated during bolting time at the onset of leaf senescence and appears to be involved in the elevation of the H 2 O 2 level at this time point. To understand the role of CAT2 in senescence regulation in more detail, we used CAT2 promoter fragments in a yeast one-hybrid screen to isolate upstream regulatory factors. Among others, we could identify G-Box Binding Factor1 (GBF1) as a DNA-binding protein of the CAT2 promoter. Transient overexpression of GBF1 together with a CAT2:b-glucuronidase construct in tobacco (Nicotiana benthamiana) plants and Arabidopsis protoplasts revealed a negative effect of GBF1 on CAT2 expression. In gbf1 mutant plants, the CAT2 decrease in expression and activity at bolting time and the increase in H 2 O 2 could no longer be observed. Consequently, the onset of leaf senescence and the expression of senescence-associated genes were delayed in gbf1 plants, clearly indicating a regulatory function of GBF1 in leaf senescence, most likely via regulation of the intracellular H 2 O 2 content.Tolerance against oxidative stress and life span are strikingly correlated in many organisms ranging from Caenorhabditis to mammals

Role of Intracellular Hydrogen Peroxide as Signalling Molecule for Plant Senescence

“…Insertion of a T-DNA into the GBF1 gene revealed a loss of CAT2 down-regulation and resulted in the loss of a hydrogen peroxide increase during bolting time. These gbf1 mutant plants exhibit a delayed onset of senescence (Smykowski et al, 2010). Consequently, the idea suggests itself that CAT2 knock-out plants also have a senescence phenotype.…”

“…The transcription factor responsible for this down-regulation was isolated by a yeast-one hybrid screen and turned out to be a member of the bZIP transcription factor family, namely GBF1. If GBF1 is knocked out by a T-DNA insertion, the down-regulation of CAT2 during bolting time is abolished, the hydrogen peroxide peak during bolting time disappears and senescence is delayed (Smykowski et al, 2010). This hydrogen peroxide peak is discussed to trigger senescence induction by activating the systemic expression of the senescence-related transcription factors e.g.…”

Functional Approaches to Study Leaf Senescence in Sunflower

“…Figure 3 shows Arabidopsis alignments and putative sunflower ORE1 proteins against Pfam NAC domain. Others relevant in-silico candidates for a putative sunflower SAG are: RAV1 gene, a transcription factor whose expression is closely associated with leaf maturation and senescence (Woo et al 2010), which has been detected with a high score level and statistically low E-value, and CAT2, a member of a small gene H 2 O 2 detoxifying enzyme family, widely characterized in Arabidopsis (Gergoff et al 2010;Smykowski et al 2010), although not yet tested in sunflower. Fig.…”

Transcription Pattern of Catalase Gene from Gynostemma pentaphyllum (Thunb.) Makino during Various Abiotic Stresses

“…CAT (oxidoreductase, EC 1.11.1.6) is a tetrameric heme-containing intracellular enzyme which can rapidly degrade two molecules of H 2 O 2 to water and molecular oxygen [3]. CAT, the first antioxidant enzyme to be discovered and characterized in plants, is found in almost all aerobic organisms and serves to break down hydrogen peroxide rapidly [2]. In contrast to animals, CAT in plants was encoded by a small gene family.…”

“…Plants contain several types of antioxidant enzymes that are able to control ROS concentrations during fluctuating environmental conditions. A complex antioxidant defense system has been developed with several antioxidant enzymes such as ascorbate peroxidase (APX), catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), peroxidase (POD) and glutathione-Stransferase (GST) [2]. CAT (oxidoreductase, EC 1.11.1.6) is a tetrameric heme-containing intracellular enzyme which can rapidly degrade two molecules of H 2 O 2 to water and molecular oxygen [3].…”