In Arabidopsis, catalase （CAT） genes encode a small family of proteins including CAT1, CAT2 and CAT3, which catalyze the decomposition of hydrogen peroxide （H2O2） and play an important role in controlling homeostasis of reactive oxygen species （ROS）. Here, we analyze the expression profiles and activities of three catalases under different treatments including drought, cold, oxidative stresses, abscisic acid and salicylic acid in Arabidopsis. Our results reveal that CAT1 is an important player in the removal of H2O2 generated under various environmental stresses. CAT2 and CAT3 are major H2O2 scavengers that contribute to ROS homeostasis in light or darkness, respectively. In addition, CAT2 is activated by cold and drought stresses and CAT3 is mainly enhanced by abscisic acid and oxidative treatments as well as at the senescence stage. These results, together with previous data, suggest that the network of transcriptional control explains how CATs and other scavenger enzymes such as peroxidase and superoxide dismutase may be coordinately regulated during development, but differentially expressed in response to different stresses for controlling ROS homeostasis.
Exogenous abscisic acid(ABA)can inhibit root growth and promote formation of more root hairs in the root tip of Arabidopsis.However,the molecular mechanisms that underlie root ABA signaling are largely unknown.We report here that hydrogen peroxide(H2O2)reduces the root growth of wild type, and the phenotype of H2O2 on the root growth is similar to ABA response.Meanwhile ABA-induced changes in the morphology of root system can be partly reversed by ascorbic acid in wild type and abolished in NADPH oxidase defective mutant atrbohF and atrbohC.Further,ABA can induce H2O2 accumulation in the root cells and enhance transcription level of OXI1,which is necessary for many more AOS-dependent processes such as root hair growth in Arabidopsis.Our results suggest that H2O2 as an important signal molecule is required for the ABA-regulated root growth and development in Arabidopsis.
BAI LingZHOU YunZHANG XiaoRanSONG ChunPengCao MingQing
