Genome-wide identification and expression of Oryza sativa haloacid dehalogenase genes associated with oxadiazon metabolism

Plant haloacid dehalogenases (HADs) comprise a superfamily of proteins that facilitate the hydrolysis and dehalogenation processes for the detoxification and metabolism of organic contaminants. However, it remains entirely unknown how harmful agrochemicals stimulate HAD production in rice. In this study, the expression of 37 HAD-coding genes is revealed and 4 HAD-differentially expressed genes (DEGs) are identified in oxadiazon-treated rice transcriptome datasets. Chromosomal location and collinearity analyses show that 37 HAD expression genes are unevenly distributed on 12 rice chromosomes. Although these 37 HAD genes do not exhibit intraspecific collinearity, 5 and 25 rice HAD genes demonstrate collinearity relationships with Arabidopsis and soybean, respectively. However, only one DEG (Os05g0457800) shows a collinearity relationship with Arabidopsis and soybean. In addition, these rice HAD genes (including four HAD DEGs) exhibit a range of gene structures, cis-elements, motif compositions, and conserved domains that allow them to encode a range of biotic and abiotic stress responses. A docking analysis between oxadiazon and four HAD DEGs reveals amino acid residues implicated in oxadiazon binding. HAD activity in rice roots and shoots is found to be stimulated when 0.05–0.25 mg L⁻¹ oxadiazon stress is applied, which is 2- and 9.2-fold higher than the control, respectively. These findings show that these HAD genes respond effectively to oxadiazon stress and comprise a set of candidate genes (especially these four HAD DEGs) for the further characterization of pesticide metabolism and degradation.