Multiple Metabolic Enzymes Can Be Involved in Cross-Resistance to 4-Hydroxyphenylpyruvate-Dioxygenase-Inhibiting Herbicides in Wild Radish.

Abstract

A wild radish population (R) has been recently confirmed to be cross-resistant to 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicides without previous exposure to these herbicides. This cross-resistance is endowed by enhanced metabolism. Our study identified one 2-oxoglutarate/Fe(II)-dependent dioxygenase gene (Rr2ODD1) and two P450 genes (RrCYP704C1 and RrCYP709B1), which were significantly more highly expressed in R versus susceptible (S) plants. Gene functional characterization using Arabidopsis transformation showed that overexpression of RrCYP709B1 conferred a modest level of resistance to mesotrione. Ultra-performance liquid chromatography-tandem mass spectrometry analysis showed that tissue mesotrione levels in RrCYP709B1 transgenic Arabidopsis plants were significantly lower than that in the wild type. In addition, overexpression of Rr2ODD1 or RrCYP704C1 in Arabidopsis endowed resistance to tembotrione and isoxaflutole. Structural modeling indicated that mesotrione can bind to CYP709B1 and be easily hydroxylated to form 4-OH-mesotrione. Although each gene confers a modest level of resistance, overexpression of the multiple herbicide-metabolizing genes could contribute to HPPD-inhibiting herbicide resistance in this wild radish population.