6533b85dfe1ef96bd12bee8f

RESEARCH PRODUCT

Three cytochrome P450 genes are over-expressed in ryegrass (Lolium sp.) plants resistant to the ALS inhibitors iodosulfuron+mesosulfuron or pyroxsulam.

subject

description

One of the most intense abiotic stresses encountered by arable weeds infesting agricultural fields is herbicide application. Non-target-site based resistance (NTSR), which belongs to the weed herbicide stress response pathways, is an adaptive response to herbicides. Stress response is driven by gene regulation. It follows that NTSR is endowed by differences in the expression of a set of genes between sensitive and resistant plants. We developed an accurate and reliable quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assay to detect differences in gene expression in the major grass weed Lolium sp. using two ALS inhibitors (iodosulfuron+mesosulfuron and pyroxsulam). Resistant and sensitive plants from three populations were cloned, and tillers were collected and frozen before and at several time points after herbicide application. qPCR primers were designed for eight potential reference genes and for three potentially herbicide-responsive cytochrome P450s (CYPs). The stability of the candidate reference genes was assessed with BestKeeper, GeNorm and NormFinder. The three most stable genes under herbicide stress, capsine-phosphatase, glyceraldehyde-3-phosphate dehydrogenase and ubiquitin, were used to normalise the expression data of the CYP genes. Two CYP genes were constitutively over-expressed in resistant plants compared to sensitive plants (up to >8-fold). The expression of all three CYP genes increased after herbicide application, and the increase was most pronounced in some resistant plants. The variation in CYP expression patterns observed among plants confirms the hypothesis that NTSR involves complex and variable detoxification pathways.