Premium
Biology and mechanisms of sulfonylurea resistance in Schoenoplectiella juncoides , a noxious sedge in the rice paddy fields of J apan
Author(s) -
Sada Yoshinao,
Uchino Akira
Publication year - 2017
Publication title -
weed biology and management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.351
H-Index - 36
eISSN - 1445-6664
pISSN - 1444-6162
DOI - 10.1111/wbm.12126
Subject(s) - sulfonylurea , biology , acetolactate synthase , gene , amino acid , genetics , amino acid substitution , enzyme , botany , mutation , biochemistry , microbiology and biotechnology , insulin
Schoenoplectiella juncoides is a noxious sedge weed in rice paddy fields that has evolved resistance to sulfonylurea ( SU ) herbicides. The molecular basis of resistance is amino acid substitutions at P ro 197 , T rp 574 or A sp 376 in the acetolactate synthase ( ALS ) enzyme, which is the target of SU s. Schoenoplectiella juncoides has two ALS genes and resistant plants have point mutations that cause amino acid substitutions in either encoded protein. Single‐nucleotide substitutions at the codon for P ro 197 in the ALS genes can cause six types of amino acid substitutions and all of these substitutions have been found in both ALS genes among J apanese SU ‐resistant biotypes. Whole‐plant herbicide responses differ among the amino acid substitution types. Furthermore, analyses of ALS activity in plant extracts show that the extracts’ responses to herbicides differ, depending on which ALS gene is mutated. The activity responses of the ALS extracts to the SU, imazosulfuron, showed double‐sigmoid curves with plateaus of ~30% inhibition for P ro 197 substitutions in ALS 1 and ~70% for P ro 197 substitutions in ALS 2. This indicates that ALS 1 and ALS 2 contribute to the responses with a proportion of 7:3. The double‐sigmoid curves can be reconstructed to show the responses of the resistant and susceptible enzymes separately by regression analysis. The resistance levels of the separate ALS 1 or ALS 2 mutated enzyme are highly correlated with the whole‐plant responses, with a relationship that the former is the square of the latter. This could provide a quantitative insight into the physiological basis of resistance.