Expression of CYP76C6 Facilitates Isoproturon Metabolism and Detoxification in Rice

Abstract

Agricultural chemical residues in farmland and crops is one of the serious public issues that constantly threatens crop production, food security, and human health. Understanding their decay mechanism in crops for accelerating their degradative metabolism is important. In this study, a rice uncharacterized cytochrome P450 gene encoding CYP76C6 was functionally identified in rice exposed to isoproturon (IPU). To verify the role of CYP76C6 in rice resistance to IPU toxicity, CYP76C6 overexpression (OEs) and knockout mutant rice by CRISPR/Cas9 were generated through genetic transformation and gene-editing technologies. Assessment of growth and physiological responses revealed that the growth of OE lines was improved, the IPU-induced cellular damage was attenuated, and IPU accumulation was significantly repressed, whereas the Cas9 lines displayed a contrasting phenotype compared to the wild-type. Both relative contents of IPU metabolites and conjugates in OE lines were reduced and those in Cas9 line were increased, suggesting that CYP76C6 plays a critical role in IPU degradation. Our study unveils a new regulator, together with its mechanism for IPU decay in rice crops, which will be used in reality to reduce environmental risks in food safety and human health.

Molecular Responses and Degradation Mechanisms of the Herbicide Diuron in Rice Crops

“…For instance, LOC_Os08g39730 ( CYP76C6 ) is the P450 gene with the highest expression in shoots and roots under the two DU concentrations (Figure ). The overexpression of CYP76C6 in rice was verified to attenuate the toxicity of phenylurea herbicides isoproturon (IPU) via the increments of metabolite contents, such as C -hydroxylated IPU and N -demethylated IPU . In addition, LOC_Os01g43710 encoding CYP72A18, a rice cytochrome P450 that catalyzes (ω-1)-hydroxylation of the herbicide pelargonic acid, was found to be higher transcription by 1.17-, 2.56-, 2.88-, and 3.05-fold in shoots and roots of rice under two concentrations of DU treatment.…”

“…These metabolic processes were divided into four phases, according to the types of enzyme-catalyzed reactions . In Phase I, cytochrome P450s, hydrolase, esterase, and monooxygenase are responsible for the dealkylation, hydroxylation, and dehalogenation of intermediates in plants, which is considered to be the first step of xenobiotic detoxification . Plant cytochrome P450s belonging to the largest family of enzymatic proteins have been found to participate in mediating the metabolism of xenobiotics or herbicides .…”

“…The overexpression of CYP76C6 in rice was verified to attenuate the toxicity of phenylurea herbicides isoproturon (IPU) via the increments of metabolite contents, such as C-hydroxylated IPU and N-demethylated IPU. 36 In addition, LOC_Os01g43710 encoding CYP72A18, a rice cytochrome P450 that catalyzes (ω-1)-hydroxylation of the herbicide pelargonic acid, 37 was found to be higher transcription by 1.17-, 2.56-, 2.88-, and 3.05-fold in shoots and roots of rice under two concentrations of DU treatment. Based on hydroxylated and demethylated DU derivatives (TP 249, TP 219, and TP 205) detected in rice (Figure 6), either CYP76C6-or CYP72A18-encoded P450 enzymes may have contributed to the metabolism of DU in rice.…”

“…35 In Phase I, cytochrome P450s, hydrolase, esterase, and monooxygenase are responsible for the dealkylation, hydroxylation, and dehalogenation of intermediates in plants, which is considered to be the first step of xenobiotic detoxification. 36 Plant cytochrome P450s belonging to the largest family of enzymatic proteins have been found to participate in mediating the metabolism of xenobiotics or herbicides. 9 In rice, a handful of P450s have been identified to have positive responses to DU stress (Figure 5).…”

Phytoremediation of isoproturon‐contaminated sites by transgenic soybean

“…Furthermore, soybean, an economic crop, can fix nitrogen via symbiosis to reduce the need for synthetic fertilizers. IPU can exhibit toxicities to non‐target plants, such as preventing root and leaf growth, reducing chlorophyll content, and inhibiting photosynthetic efficiency (Yin et al ., 2008 ; Zhai et al ., 2022 ). In our study, TS soybeans expressing the bacterial N‐ demethylase PdmAB showed improved IPU tolerance than non‐TS soybeans (Figure 2 ).…”