Abstract
Plant ascorbate peroxidases (APXs), enzymes catalyzing the dismutation of H2O2 into H2O and O2, play an important role in reactive oxygen species homeostasis in plants. The rice genome has eight OsAPXs, but their physiological functions remain to be determined. In this report, we studied the function of OsAPX2 gene using a T-DNA knockout mutant under the treatment of drought, salt and cold stresses. The Osapx2 knockout mutant was isolated by a genetic screening of a rice T-DNA insertion library under 20% PEG-2000 treatment. Loss of function in OsAPX2 affected the growth and development of rice seedlings, resulting in semi-dwarf seedlings, yellow-green leaves, leaf lesion mimic and seed sterility. OsAPX2 expression was developmental- and spatial-regulated, and was induced by drought, salt, and cold stresses. Osapx2 mutants had lower APX activity and were sensitive to abiotic stresses; overexpression of OsAPX2 increased APX activity and enhanced stress tolerance. H2O2 and MDA levels were high in Osapx2 mutants but low in OsAPX2-OX transgenic lines relative to wild-type plants after stress treatments. Taken together, the cytosolic ascorbate peroxidase OsAPX2 plays an important role in rice growth and development by protecting the seedlings from abiotic stresses through scavenging reactive oxygen species.
Highlights
Reactive oxygen species (ROS) control various signaling pathways in plants involved in stress and pathogen responses, photosynthesis, programmed cell death, hormonal action, growth and development [1,2]
In this study, using both the Osapx2 knockout mutants and the Osapx2 overexpression lines, we demonstrated that OsAPX2 plays an important role in tolerance to abiotic stresses in rice
We found that the Osapx2 knockout mutants exhibited a pleiotropic phenotype including semi-dwarf, severe leaf minic lesion and male-sterility (Figure 4-A,E)
Summary
Reactive oxygen species (ROS) control various signaling pathways in plants involved in stress and pathogen responses, photosynthesis, programmed cell death, hormonal action, growth and development [1,2]. ROS damage is one of the major mechanisms underlying the biotic and abiotic stresses including drought, high light, wounding, salt, or pathogen infection [4,5,6]. Studies have shown that APXs play an important role in removing ROS in plants [1]. In Arabidopsis, cytosolic APXs (cAPXs) are critical for cellular H2O2 homeostasis and play an important role in oxidative protection of chloroplasts under abiotic stresses, including high light, heat, methyl viologen and drought stress [9,10]. Arabidopsis APX1 is important for plant growth and development since mutation of APX1 leads to the accumulation of H2O2, inhibition of plant growth and photosynthesis, delay of flowering, and enhanced protein oxidation under high light [10]. APX2 expression is induced under high light, heat stresses and wounding conditions [11,12]. Thylakoid-bound APXs (tAPXs) are essential for photosynthetic activity and photoprotection under photooxidative stress in Arabidopsis [14]
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