ena-STUDY-Australian Herbicide Resistance Initiative-11-10-2019-07:27:53:237-98
Herbicide metabolic resistance gene discovery in Lolium rigidum using RNA-Seq
Rapid and widespread evolution of multiple herbicide resistance in economically damaging global weed species endowed by increased capacity to metabolize (degrade) herbicides (metabolic resistance) is a great threat to herbicide sustainability and global food production. Metabolic resistance in the cross-pollinated weed species Lolium rigidum is well known but a molecular understanding has been lacking. We purified a metabolic diclofop-methyl and chlorsulfuron resistant (R) subset from a field evolved resistant L. rigidum population (SLR31).  The R, herbicide susceptible (S) and derived F2 populations were used in this study for candidate P450 gene discovery by RNA sequencing (RNA-Seq). A P450 gene CYP81A10v7 was identified with consistently higher expression in R vs. S plants. Transgenic rice overexpressing CYP81A10v7 gene were produced and found to be highly resistant to ACCase-inhibiting herbicides diclofop-methyl and tralkoxydim and the ALS-inhibiting herbicide chlorsulfuron, and moderately resistant to the HPPD-inhibiting herbicide mesotrione, PSII-inhibiting herbicides atrazine and chlorotoluron and the tubulin-inhibiting herbicide trifluralin. This herbicide cross-resistance profile in CYP81A10v7 transgenic rice generally reflects that evident in the R L rigidum subset containing CYP81A10v7. Furthermore, transgenic rice overexpressing the CYP81A10v7 gene displayed enhanced rates of diclofop-methyl and mesotrione metabolism. This is the first characterization of a single P450 gene in a weed species conferring cross-resistance to herbicides of at least five modes of action across seven herbicide chemistries.
Rapid and widespread evolution of multiple herbicide resistance in economically damaging global weed species endowed by increased capacity to metabolize (degrade) herbicides (metabolic resistance) is a great threat to herbicide sustainability and global food production. Metabolic resistance in the cross-pollinated weed species Lolium rigidum is well known but a molecular understanding has been lacking. We purified a metabolic diclofop-methyl and chlorsulfuron resistant (R) subset from a field evolved resistant L. rigidum population (SLR31).  The R, herbicide susceptible (S) and derived F2 populations were used in this study for candidate P450 gene discovery by RNA sequencing (RNA-Seq). A P450 gene CYP81A10v7 was identified with consistently higher expression in R vs. S plants. Transgenic rice overexpressing CYP81A10v7 gene were produced and found to be highly resistant to ACCase-inhibiting herbicides diclofop-methyl and tralkoxydim and the ALS-inhibiting herbicide chlorsulfuron, and moderately resistant to the HPPD-inhibiting herbicide mesotrione, PSII-inhibiting herbicides atrazine and chlorotoluron and the tubulin-inhibiting herbicide trifluralin. This herbicide cross-resistance profile in CYP81A10v7 transgenic rice generally reflects that evident in the R L rigidum subset containing CYP81A10v7. Furthermore, transgenic rice overexpressing the CYP81A10v7 gene displayed enhanced rates of diclofop-methyl and mesotrione metabolism. This is the first characterization of a single P450 gene in a weed species conferring cross-resistance to herbicides of at least five modes of action across seven herbicide chemistries.