Ectopic Overexpression of the Hot Pepper Cat1 in Arabidopsis Enhances Resistance to Paraquat, but not to Wounding

摘要

We constructed transgenic Arabidopsis plants that over-express hot pepper CaCat1 to gain more insight into that gene's functional roles in response to abiotic stresses. Although all the homozygous transgenic lines accumulated CaCat1 transcripts, theirdegree of catalase activity varied, from 1.1-fold to 1.9-fold. The germination rates for transgenic lines on MS plates containing >0.5 mu M paraquat were higher than those recorded for the wild type, while no difference in germinability was noted between the wild type and those exposed to 0.2 uM paraquat. However, fresh weights for the latter were greater than those of the wild type. Moreover, one transgenic line showed lower H_2O_2 production than did the wild-type plants in response to paraquat treatment. These results revealed that CaCatl overexpression enhances paraquat resistance in transgenic Arabidopsis. In response to wounding, however, our examination of AtVSP1 expression, as defined by H_2O_2 levels, showed no difference between the WT and transgenic plants. Furthermore, catalase activities in our two transgenic lines decreased 2 h after this stress was applied, in both wounded and untreated leaves, further declining to levels similar to the wild type after 6 h. These results suggest that wounding may down-regulate CaCatl expression at the post-transcriptional level in transgenic Arabidopsis in order to maintain the wound-signaling process in transgenic lines.