机械损伤对Bt玉米化学防御的系统诱导效应

植物在生长过程中形成了抵御机械损伤等外界胁迫的直接和间接防御体系,并具有明显的系统性特征。Bt(Bacillus thuringiensis)玉米(Zea mays)是全球商品化最快的抗虫转基因作物之一。机械损伤等外界胁迫对Bt玉米和常规玉米化学防御的系统诱导效应是否存在差异是值得探讨的问题。该文以两个不同转化事件的Bt玉米'5422Bt1'(Bt11)和'5422CBCL'(Mon810)以及它们共同的同源常规玉米'5422'幼苗为材料,对玉米第一叶进行机械损伤处理6h后,检测非损伤部位(第二叶和根系)中Bt蛋白含量、直接防御物质丁布(DIMBDA)含量及其调控基因(Bx1、Bx6和Bx9)表达、直接防御物质总酚含量及其调控基因(PAL)表达、直接防御蛋白调控基因(MPI和PR-2a)表达以及间接防御物质挥发物调控基因(FPS和TPS)表达的变化。结果表明,与健康植株相比,机械损伤对两个Bt玉米第二叶和根系的Bt蛋白含量均没有显著影响;机械损伤第一叶只能系统诱导常规玉米'5422'第二叶中PAL、TPS和根系中PAL、FPS基因的表达,使得第二叶丁布含量显著增加,但根中丁布含量及其调控基因Bx6和Bx9基因的表达量明显下降;而机械损伤能系统诱导Bt玉米'5422Bt1'第二叶中Bx6、PAL、PR-2a、TPS和根系中Bx6、Bx9、PAL、MPI、PR-2a、TPS基因的表达,使得第二叶丁布含量明显增加;对于另一Bt玉米'5422CBCL'而言,机械损伤能系统诱导第二叶中Bx9、PAL、PR-2a、TPS和根系中Bx6、PAL、MPI、TPS基因的表达,使得根系的总酚含量显著增加。由此可见,机械损伤对两个Bt玉米化学防御反应的系统诱导作用均强于常规玉米'5422',说明在机械损伤的系统诱导防御过程中,人工导入抗性(Bt基因)与自身化学防御过程之间的互作关系是协同的。

Systemic induced effects of mechanical wounding on the chemical defense of Bt corn (Zea mays)

Aims The major objective was to explore the difference in the systematic induced effects of mechanical wounding on Bt corn and conventional corn after the first leaf of corn seedlings was mechanically wounded.Methods Two Bt corns, ‘5422Bt1’ (Bt11) and ‘5422CBCL’ (Mon810), as well as their conventional corn ‘5422’ were used to detect changes in the content of direct defense chemical DIMBOA and expression of its genes (Bx1, Bx6 and Bx9), content of direct defense chemical total phenol and expression of its gene (PAL), direct defense protein genes (MPI and PR-2a), and the indirect defense chemical volatile genes (FPS and TPS) in the non-wounded parts (second leaf and roots) by employing chemical analysis and gene expression analysis methods after the first leaf of corn seedlings was mechanically wounded for 6 h.Important findings Mechanical wounding systematically induced the expression of PAL and TPS in the second leaf and PAL and FPS in the roots of conventional corn ‘5422’ as compared with the healthy plants, which significantly increased the DIMBOA content in the second leaf but reduced the DIMBOA content and its gene expression of Bx6 and Bx9 in the roots. In addition, mechanical wounding systematically induced the gene expression of Bx6, PAL, PR-2a and TPS in the second leaf and Bx6, Bx9, PAL, MPI, PR-2a and TPS in the roots of Bt corn ‘5422Bt1’, resulting in increased DIMBOA content of the second leaf. In terms of ‘5422CBCL’, mechanical wounding systematically induced the gene expression of Bx9, PAL, PR-2a and TPS in the second leaf and the gene expression of Bx6, PAL, MPI and TPS in the roots, which remarkably increased the total phenol content in the roots. The systematic induced effect of mechanical wounding on the chemical defense response is more obvious in the two Bt corns as compared with the conventional corn ‘5422’, suggesting that there is a synergistic relationship between the Bt gene introduction and chemical defense response during the systematic induced defense processes inflicted by mechanical wounding.