Transcript Profiling of Non‐Target‐Site Imidazolinone Resistance in Imisun Sunflower

Abstract

Imidazolinone resistance found in a wild sunflower (Helianthus annuus L.) population was successfully transferred to a cultivated inbred line developing ‘Imisun’ sunflowers. Genetic regulation of this trait has been reported to involve two genes: Imr1, an allelic variant of ahasl1 locus that codes for acetohydroxyacid synthase catalytic subunit, and the modifier Imr2, whose identity remains unknown, but it could be related to non‐target‐site resistance such as xenobiotic metabolism. The aim of the present study was to characterize the gene expression of resistant and susceptible sunflower lines in response to imazethapyr herbicide by complementary DNA amplified fragment‐length polymorphism (cDNA‐AFLP). Three assays were performed to determine (i) optimal herbicide treatment concentration, (ii) duration of herbicide treatment, and (iii) in vitro acetohydroxyacid synthase activity to assess enzyme inhibition levels. An important number of genes related to metabolism of xenobiotics and stress was found: cytochrome P450 monooxygenases, UDP‐glucuronosyl/UDP‐glucosyltransferases, glycosyltransferases, and ATP‐binding cassette transporters, among others. These results suggest that non‐target‐site resistance mechanisms may contribute to herbicide resistance in Imisun sunflower and could be related to the modifier gene Imr2. Using cDNA‐AFLP, we were able to detect candidate detoxification‐related genes potentially involved in imidazolinone resistance in sunflower.

Stress response and detoxification mechanisms involved in non‐target‐site herbicide resistance in sunflower

“…Recent transcriptomic characterization by complementary DNA‐amplified fragment length polymorphism has allowed detecting sequences related to imazethapyr metabolism in sunflower leaves that corresponded to four gene families: ABC transporters, glycosyltransferases, P450s, and UDP‐glucuronosyl/UDP‐glucosyltransferases (Gil, Ochogavía, et al., 2018). In addition, RNA sequencing analysis has allowed identifying detoxification genes potentially related to imazethapyr resistance in sunflower: cytochrome P450 monooxygenases, ABC transporters, UDP‐glucuronosyl and UDP‐glucosyltransferases, glycosyltransferases, and GSTs (Gil, Nestares, et al., 2018).…”

“…In addition to target‐site resistance (TSR) mechanisms, Imisun sunflowers present non‐target‐site resistance (NTSR) to IMI herbicides (Breccia et al., 2017; Gil, Nestares, et al., 2018; Gil, Ochogavía, Vega, Felitti, & Nestares, 2018; Sala et al., 2012). Although TSR mechanisms in sunflower are well described (Breccia, Vega, Felitti, Picardi, & Nestares, 2013; Kolkman et al., 2004; Sala et al., 2012; Vega et al., 2009, 2012), the nature of NTSR mechanisms has not yet been fully characterized but could be related to xenobiotic metabolism (Gil & Nestares, 2019).…”

“…In particular, P450s have been shown to be involved in the metabolism of different types of herbicides in several crops and weed species (Siminszky, 2006; Yu & Powles, 2014) by carrying out in vivo experiments using P450 inhibitors such as tetcyclacis, 1‐aminobenzotriazole (ABT), piperonyl butoxide (PBO), and malathion (Beckie & Tardif, 2012; Letouzé & Gasquez, 2003; Yang et al., 2016). Previous studies involving plant growth response and transcriptomic analysis have described the participation of P450s and other gene families in the metabolism of herbicides in the genus Helianthus (Balabanova, Remans, Vassilev, Cuypers, & Vangronsveld, 2018; Breccia et al., 2017; Didierjean et al., 2002; Gil, Nestares, et al., 2018; Gil, Ochogavía, et al., 2018; Kaspar, Grondona, Leon, & Zambelli, 2011).…”

Decoding Non-Target-Site Herbicide Resistance in Sunflower: The Beginning of the Story

“…These constraints are overcame by alternative methods based on sequencing or PCR amplification (Breyne et al, 2003). A transcript profiling characterization of NTSR by cDNA-AFLP methodology was carried out in Imisun sunflower confirming the contribution of these mechanisms in imazethapyr resistance (Gil et al, 2018a) (Table 2). An important number of genes related to metabolism of xenobiotics and stress was found: P450 monooxygenases, UDP-glucuronosyl/UDP-glucosyltransferases, glycosyltransferases and ATP-binding cassette transporters, among others, suggesting that herbicide detoxification processes are involved in imidazolinone resistance in sunflower.…”

“…Two mechanisms of AHAS-inhibitor herbicide resistance coexist in sunflower: an altered target site and enhanced herbicide metabolism (Sala et al, 2012b). The presence of NTSR mechanisms in sunflower resistant lines that are related specifically to herbicide metabolism has been suggested in several works (Balabanova et al, 2018;Breccia et al, 2017;Gil et al, 2018a;Kolkman et al, 2004) although very few genes endowing NTSR have been identified to date.…”