AUTHOR=Zhang Yi , Chen Liping , Song Wen , Cang Tao , Xu Mingfei , Wu Changxing 

TITLE=Diverse mechanisms associated with cyhalofop-butyl resistance in Chinese sprangletop (Leptochloa chinensis (L.) Nees): Characterization of target-site mutations and metabolic resistance-related genes in two resistant populations

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.990085

DOI=10.3389/fpls.2022.990085

ISSN=1664-462X

ABSTRACT=<p>Resistance of Chinese sprangletop (<italic>Leptochloa chinensis</italic> (L.) Nees) to the herbicide cyhalofop-butyl has recently become a severe problem in rice cultivation. However, the molecular mechanisms of target-site resistance (TSR) in cyhalofop-butyl<italic>-</italic>resistant <italic>L. chinensis</italic> as well as the underlying non-target-site resistance (NTSR) have not yet been well-characterized. This study aimed to investigate cyhalofop-butyl resistance mechanisms using one susceptible population (LC-S) and two resistant populations (LC-1701 and LC-1704) of <italic>L. chinensis.</italic> We analyzed two gene copies encoding the entire carboxyltransferase (CT) domain of chloroplastic acetyl-CoA carboxylase (ACCase) from each population. Two non-synonymous substitutions were detected in the resistant <italic>L. chinensis</italic> populations (Trp<sup>2027</sup>-Cys in the <italic>ACCase</italic>1 of LC-1701 and Leu<sup>1818</sup>-Phe in the <italic>ACCase</italic>2 of LC-1704), which were absent in LC-S. As Trp<sup>2027</sup>-Cys confers resistance to ACCase-inhibiting herbicides, the potential relationship between the novel Leu<sup>1818</sup>-Phe mutation and cyhalofop-butyl resistance in LC-1704 was further explored by single-nucleotide polymorphism (SNP) detection. Metabolic inhibition assays indicated that cytochrome P450 monooxygenases (P450s) and glutathione <italic>S</italic>-transferases (GSTs) contributed to cyhalofop-butyl resistance in specific resistant populations. RNA sequencing showed that the P450 genes <italic>CYP71Z18</italic>, <italic>CYP71C4</italic>, <italic>CYP71C1</italic>, <italic>CYP81Q32</italic>, and <italic>CYP76B6</italic> and the GST genes <italic>GSTF11</italic>, <italic>GSTF1</italic>, and <italic>GSTU6</italic> were upregulated in at least one resistant population, which indicated their putative roles in cyhalofop-butyl resistance of <italic>L. chinensis</italic>. Correlation analyses revealed that the constitutive or inducible expression patterns of <italic>CYP71C4</italic>, <italic>CYP71C1</italic>, <italic>GSTF1</italic>, and <italic>GSTU6</italic> in <italic>L. chinensis</italic> were strongly associated with the resistant phenotype. For this reason, attention should be directed towards these genes to elucidate metabolic resistance to cyhalofop-butyl in <italic>L. chinensis</italic>. The findings of this study improve the understanding of mechanisms responsible for resistance to ACCase-inhibiting herbicides in grass-weed species at the molecular level, thus aiding in the development of weed management strategies that delay the emergence of resistance to this class of pest control products.</p>