The gene expression of insect-induced plant defense signal and plant defense chemicals

• Main Authors: Hsiang-Wei Huang, 黃翔瑋
• Other Authors: Shaw-Yhi Hwang
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/40942146998252829303

碩士 === 國立中興大學 === 昆蟲學系所 === 94 === Plant responses to herbivores are complex. Signaling cross-talk between wound- and pathogen-response pathways influences resistance of plants to insects and diseases. Jasmonic acid (JA) was identified as a component of fragrant oils and was first demonstrated to promote senescence of leaves in 1980’s, and were subsequently shown to be a class of plant growth regulator. In late 1990’s, new evidences indicate that JA is a key factor between chemical web on plant-insect interaction, and contend for the plant interior resources with salicylic acid (SA) signaling pathway which is induced by plant pathogens. The results of competition between JA and SA signaling pathways may influence the direction of plant defense compound biosynthesis. On the other hand, plants protect themselves against herbivores with diverse array of repellent or toxic secondary metabolites. Taking the cabbage plants as an example, toxic secondary metabolites glucosinolate-myrosinase system is dangerous to the insects which are polyphagous. Although we have already known about these, but still can not find out how to connect these chemical web together? What is the real relationship between insects feeding induce plant defense signal transduction and plant defense chemicals? In this work, we used Pieris rapae for insect model, and Arabidopsis thaliana for plant model, to design a series of biomolecular test. By the RT-PCR assay, we knew that after insect feeding, A. thaliana not only turns on the JA synthesis pathway in a short period of time, but also the glucosinolate synthesis pathway in the short term insect invasion test. If the action of insect feeding was not continuous, all the defense chemical biosynthesis would be stopped, to saving the interior resources. Fascinatingly, when the expression of genes which involve JA and glucosinolate biosynthesis decreased, the report gene of SA biosynthesis would be turned on at the same time. Following, in the long term insect invasion test, when we stopped the insect invasion, the gene involve in JA and glucosinolate biosynthesis would be turned off in a short time. Besides, the report gene of SA biosynthesis would be turned on at the same time, this result is similar to the short term insect invasion test. It suggests that there are some kinds of in vivo control for plant defense chemical biosynthesis, and SA may be the “brake” to stop the biosynthesis of these chemicals.