- 期刊
Enantioselective Effects of Imazapyr on Resistant Arabidopsis thaliana GH90
抗依滅草阿拉伯芥突變品系GH90對依滅草之光學選擇性研究
摘要
The imidazolinone herbicide imazapyr is a chiral compound that targets acetolactate synthase (ALS). Imazapyr has been widely used for weed control since the early 1980s; however, some weed species are resistant to ALS-inhibiting herbicides. This study applied herbicide to the resistant mutant Arabidopsis thaliana GH90 to investigate the enantioselectivity of imazapyr. There was no observable effect on plant shoots exposed to (R,+)-imazapyr at a concentration of 0.01 mg L^(-1) or 1 mg L^(-1); however, exposure to (R,+)- imazapyr at the same concentration turned the shoot stems and leaves purple and resulted in plants of smaller size. At a herbicide concentration of 0.1 mg L^(-1), the total chlorophyll content was higher in samples exposed to (S,-)-imazapyr than in those exposed to rac- or (R,+)-imazapyr and did not differ from that of the controls. At a herbicide concentration of 1 mg L^(-1), proline and malonaldehyde (MDA) content was proportional to the concentration of rac- and (R,+)-imazapyr as follows: (R,+)-imazapyr ＞ rac-imazapyr ＞ (S,-)-imazapyr. Overall, (R,+)-imazapyr was more stressful to mutant A. thaliana GH90 plants than was racand (S,-)-imazapyr. The effect of the herbicides on ascorbate peroxidase activity was in the following order: (R,+)-imazapyr ＞ rac-imazapyr ＞ (S,-)-imazapyr. Total superoxide dismutase activity did not increase with an increase in the concentration of (R,+)-imazapyr, due to damage caused to plant cells and a reduction in enzyme synthesis. The effect of (R,+)- Imazapyr on reducing ALS activity exceeded that of rac- or (S,-)-imazapyr. The structure of ALS reveals clues by which to elucidate the enantioselectivity of imazapyr to imazapyrresistant A. thaliana GH90.
並列摘要
咪唑啉酮類（imidazolinone）除草劑依滅草（imazapyr），為一具有對掌性（chiral）化學結構的農藥，市場上是以消旋體形式販售。而依滅草之作用位置為乙醯乳酸合成酶（acetolactate synthase, ALS），自1980年代初即廣泛被應用於田間雜草管理，由於長期使用，目前已有雜草對抑制乙醯乳酸合成酶的除草劑產生抗藥性的情形，而抗性雜草是否對依滅草不同光學活性成分具有光學活性的選擇性，即為本文主要探討目標。由結果顯示，抗依滅草的阿拉伯芥（arabidopsis thaliana）突變品系GH90，在0.01 mg L^(-1)的各種除草劑依滅草處理下，皆未受影響；但在0.1 mg L^(-1)的處理下（R,+）-依滅草處理會造成葉部紫色植株矮小；而（S,-）-依滅草總葉綠素含量顯著高於外消旋（rac）-依滅草及（R,+）-依滅草，但與未以除草劑處理之對照組比較則無區別。GH90阿拉伯芥中之脯氨酸及丙二醛含量隨著外消旋（rac）-依滅草及（R,+）-依滅草施用量增加而增加，影響效應則以（R,+）-依滅草＞外消旋（rac）-依滅草＞（S,-）-依滅草，顯見（R,+）-依滅草對GH90阿拉伯芥造成較大生長壓力。抗壞血酸過氧化物酶活性以（R,+）-依滅草＞外消旋-依滅草＞（S,-）-依滅草的順序增加。而總超氧化物歧化酶（SOD）活性則不隨（R,+）-依滅草煙濃度的增加而增加，則是因為（R,+）-依滅草已對植物細胞造成損傷而減少酶的合成。（R,+）-依滅草比消旋（rac）-或（S,-）-依滅草更能降低ALS活性。由GH90阿拉伯芥ALS的結構亦可發現其對依滅草具有光學的選擇性。