A Paraquat-Inducible Protein B-like (pqiB) Gene From Chromobacterium Violaceum Confers Tolerance to Paraquat in Transgenic Tobacco

Abstract

Paraquat (1,1'-dimethyl-4,4'-bipyridinium dichloride) is a contact non-selective herbicide, widely used in agriculture in several countries. Proteins induced by paraquat have been the subject of great interest because of the possibility of conferring herbicide resistance when introduced into crops. In this work, we analyzed a paraquat-inducible protein B-like ( cvpqiB ) gene, isolated from Chromobacterium violaceum, in conferring tolerance to paraquat in transgenic tobacco. A DNA fragment containing the pqiB coding sequence was isolated from the C. violaceum ATCC12472 genome, inserted into the pCAMBIA1390 vector, under the control of the cauliflower mosaic virus (CaMV) 35S promoter, and used in Agrobacterium -mediated transformation of Nicotiana tabacum cv. Havana. Analysis of the regenerants revealed the incorporation of cvpqiB into the tobacco genome and its transmission in a Mendelian fashion to the progeny of transgenic plants. Sensitivity assays using tobacco leaves demonstrated that the transgenic plants were tolerant to concentrations up to 50 µM paraquat, whereas the wild-type (WT) plants exhibited intolerance to concentrations higher than 1 μM of the herbicide. Paraquat-treated leaves of the transgenic plants also exhibited significantly reduced electrolyte leakage and their chlorophyll content was not impacted as observed in the WT plants. Besides, in contrast to the WT, negligible amounts of hydrogen peroxide (H 2 O 2 ) were detected in paraquat-treated seedlings of the transgenic plants, as revealed by 3,3’-diaminobenzidine (DAB) staining. Collectively, these results indicate that the cvpqiB gene is functional in plants and may be further used in the genetic engineering of crop plants aiming paraquat tolerance.