Plant Molecular Biology and Biotechnology Division, CSIR-National Botanical Research Institute, Lucknow, UP, 226001, India; Department of Biochemistry, Banaras Hindu University, Varanasi, UP, 221005, India.
Plant Molecular Biology and Biotechnology Division, CSIR-National Botanical Research Institute, Lucknow, UP, 226001, India; Department of Biotechnology, Bhimtal Campus, Kumaun University, Nainital, Uttarakhand, 263001, India.
Plant Sci. 2023 Aug;333:111737. doi: 10.1016/j.plantsci.2023.111737. Epub 2023 May 20.
Methanol is noxious to insect pests, but most plants do not make enough of it to shield themselves from encroaching insects. Methanol emission is known to increase in the instance of herbivory. In the current study, we showed that Aspergillus niger pectin methylesterase over-expression increases methanol emission and confers resistance to polyphagous insect pests on transgenic cotton plants by impeding the possible methanol detoxification pathways. Transgenic plants emitted ∼11 fold higher methanol displaying insect mortality of 96% and 93% in Helicoverpa armigera and Spodoptera litura, respectively. The larvae were unable to survive and finish their life cycle and the surviving larvae exhibited severe growth retardation. Insects try to detoxify methanol via catalase, carboxylesterase and cytochrome P450 monooxygenase enzymes, amongst which cytochrome P450 plays a major role in oxidizing methanol to formaldehyde and formaldehyde to formic acid, which is broken down into carbon dioxide and water. In our study, catalase and esterase enzymes were found to be upregulated, but cytochrome P450 monooxygenase levels were not much affected. Leaf disc assays and In-planta bioassays also showed 50-60% population reduction in the sap sucking pests, such as Bemisia tabaci and Phenacoccus solenopsis. These findings imply that elevated methanol emissions confer resistance in plants against chewing and sap-sucking pests by tampering the methanol detoxification pathways. Such mechanism will be useful in imparting expansive resistance against pests in plants.
甲醇对害虫有毒害作用，但大多数植物自身产生的甲醇不足以保护其免受入侵昆虫的侵害。已知在受到草食性侵害时，甲醇的排放会增加。在目前的研究中，我们表明，黑曲霉果胶甲酯酶的过度表达增加了甲醇的排放，并通过阻碍可能的甲醇解毒途径，赋予了转基因棉花植株对多食性害虫的抗性。转基因植物排放的甲醇约增加了 11 倍，分别导致棉铃虫和斜纹夜蛾的死亡率达到 96%和 93%。幼虫无法存活并完成其生命周期，幸存的幼虫表现出严重的生长迟缓。昆虫试图通过过氧化氢酶、羧酸酯酶和细胞色素 P450 单加氧酶等酶来解毒甲醇，其中细胞色素 P450 在将甲醇氧化为甲醛和将甲醛氧化为甲酸方面起着主要作用，甲酸进一步分解为二氧化碳和水。在我们的研究中，发现过氧化氢酶和酯酶被上调，但细胞色素 P450 单加氧酶水平没有太大影响。叶片圆盘测定和体内生物测定也表明，在吸食汁液的害虫，如烟粉虱和棉红铃虫中，种群减少了 50-60%。这些发现表明，提高甲醇的排放使植物对咀嚼和吸食汁液的害虫具有抗性，因为这干扰了甲醇的解毒途径。这种机制将有助于赋予植物对害虫的广泛抗性。
