Ectopic overexpression of the hot pepperCat1 inArabidopsis enhances resistance to paraquat, but not to wounding

Abstract

We constructed transgenicArabidopsis plants that over-express hot pepperCaCat1 to gain more insight into that gene’s functional roles in response to abiotic stresses. Although all the homozygous transgenic lines accumulatedCaCat1 transcripts, their degree of catalase activity varied, from 1.1-fold to 1.9-fold. The germination rates for transgenic lines on MS plates containing >0.5 µM 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 µM paraquat. However, fresh weights for the latter were greater than those of the wild type. Moreover, one transgenic line showed lower H2O2 production than did the wild-type plants in response to paraquat treatment. These results revealed thatCaCat1 overexpression enhances paraquat resistance in transgenicArabidopsis. In response to wounding, however, our examination ofAtVSP1 expression, as defined by H2O2 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-regulateCaCat1 expression at the post-transcriptional level in transgenicArabidopsis in order to maintain the wound-signaling process in transgenic lines.