温度和CO2浓度升高下转Bt作物抗虫代谢补偿及协调机理研究

Atmospheric warming combined with carbon dioxide level increases simulatiously occur under climate change, which may have stimulatory (i.e., positive) or inhibitory (i.e., negative) effects on vegetative growth and metabolism of crop pants. So it becomes very important to study the growth and metabolism, especially the metabolic physiology and the regulation mechanism of inherent (including C- and N-based) and exogenous (i.e., Bt toxin) defence expression, and the changes in resistance ability against target and non-target insect pests for transgenic Bt crops under climate change. In this study, Cry1A Bt crops (including Cry1Ab Bt cotton cv. 33B vs. the parental line cv. DP5412, and Cry1Ab+Cry1Ac Bt rice cv. HH1 vs. the parental line cv. MH63) will be deployed in a completely randomized design with four treatment combinations of two CO2 levels (ambient and double-ambient) and two temperature levels (ambient and ambient+0-1.5 C increase). The following objectives will be investigated for the Cry1Ab+Cry1Ac Bt rice and Cry1Ab Bt cotton grown under elevated temperature and carbon dioxide, that is: (1) the plant physiological and molecular biological mechanisms of the general decrease in exogenous Bt toxin content in plant tissues; (2) the metabolic compensation of inherent defence (including C- and N-based secondary defensive chemicals) for the decrease of exogenous Bt toxin, and the regulation mechanism of the two types of chemical defences, based on the growth and differentiation balance hypothesis (ab. GDBH); (3) the associated resistance mechanism against target and non-target insect pests, and the assessment on population dynamics of insect pests and the yield loss of transgenic Bt crops. The results will be important in developing the management strategies of target and non-target insect pests of transgenic Bt crops under climate change of atmospheric warming and carbon dioxide level rising.

温度和二氧化碳浓度同步升高是当前气候变化的主要特点，由此带来的对转Bt作物生长代谢，尤其是内（外）源抗虫代谢生理及其协调机制，以及对靶标害虫和非靶标害虫的抗虫性影响等亟待明确。本研究以Cry1A型转Bt水稻和转Bt棉花为研究对象，以温度和二氧化碳浓度升高的联合作用为主导因子，开展相关研究：（1）外源Bt毒素表达量降低的植物生理学和分子生物学机理；（2）外源Bt蛋白和内源次生防卫物质之间的代谢补偿及其协调机制，以及基于生长-分化平衡假说的植物防卫机理研究；（3）靶标害虫和非靶标害虫的协调抗虫机理研究及其种群暴发危害和作物经济产量损失评估。最终，服务于气候变化下转Bt作物（水稻和棉花）的靶标害虫和非靶标害虫的有效治理。

温度和CO2浓度同步升高是全球气候变化的主要特点，由此带来的对转Bt作物内（外）源抗虫代谢生理及其协调机制和抗虫性影响等问题亟待明确。本研究结合氮肥水平管理，重点开展了温度和CO2浓度升高下转Bt作物抗虫代谢补偿及协调机理研究。首先，从基因和蛋白水平明确了温度和 CO2浓度升高对转Bt水稻外源蛋白表达量影响，揭示了CO2浓度升高下转Bt水稻Bt毒素表达量降低的植物生理学（“稀释效应”）和分子生物学（外源基因“甲基化沉默”）机理。研究表明：温度和CO2浓度升高对转Bt水稻外源蛋白表达量有负面影响，适当施用N肥（1/4N~1N）下CO2浓度升高会上调外源Bt毒素表达量。与对照CO2相比，N素匮乏（即1/8N）或过量（即2N）水平下高CO2浓度导致转Bt水稻外源基因编码区甲基化水平显著提高。与对照CO2相比，高CO2浓度下转Bt棉花和转Bt水稻叶片中外源Bt基因编码区甲基化频率都显著增加。可见，N肥施用可改善未来CO2浓度升高下转Bt水稻面临的N素限制。其次，评价了温度和CO2浓度升高联合作用下转Bt作物的非靶标害虫暴发危害风险及其种间竞争。研究表明，稻飞虱对温度和CO2浓度升高的反应受Bt水稻品系影响。相比褐飞虱和灰飞虱，高温下CO2浓度升高提高了转Cry1Ab/Ac基因型Bt水稻上白背飞虱发生量。此外，CO2浓度和温度都高时，转Cry1Ab基因型Bt水稻降低了白背飞虱发生量。与对照亲本相比，CO2浓度和温度升高下转Cry1Ab基因型Bt水稻对白背飞虱的抗性比转Cry1Ab/Ac基因型Bt水稻高。因此，生产中应同时使用不同类型的Bt水稻以获得最佳抗虫效果。另一方面，与对照CO2相比，高CO2浓度下棉花叶片膨压和叶可溶性成分的增加有利于其刺吸取食危害，这也致使成蚜鲜重、繁殖力和种群丰度增加。可见，CO2浓度升高可通过改变寄主植物组织显微结构和可溶性组分进而影响刺吸类害虫的取食行为。最终，评估了CO2和温度升高下转Bt水稻及其对照亲本经济产量。研究表明，转Bt水稻的千粒重和百丛稻谷产量随CO2浓度升高而提高，且仅在高氮水平下随温度升高而产量增加。