| Peroxidases, which are thought to play an important role in plant defense are induced by numerous biotic and abiotic stimuli, including pathogen and herbivore attacks. Examination of the changes of gene expressions that occur in the abundance of transcripts with putative representation of defense-associated and regulatory genes as result of Helicoverpa zea caterpillar herbivory on non-transgenic tomato plants and peroxidase over expressing tomato plants was conducted. To gain a new insight into the changes of gene expression underlying the correlation of both the defense system of peroxidases and herbivore attack on the tomato plants, four treatments were performed in this experiment: non-wounded/nontransgenic tomato plants (NW-NT, the control), caterpillar-wounded/non-transgenic tomato plants (caterpillar-NT), non-wounded/ peroxidase overexpressing transgenic tomato plants (NW-Trans), caterpillar-wounded/ peroxidase overexpressing transgenic tomato plants (Caterpillar-Trans) treatments. After tomato plants were fed on by Helicoverpa zea for 48 hours, it was frozen in liquid nitrogen. Total RNA was extracted from the frozen tomato plant tissues, mRNA was purified from total RNA, and then cDNA labeled with Cy-3 and Cy-5 was synthesized from mRNA catalyzed by the reverse transcriptase. The labeled cDNA was hybridized to microarray chips and scanned with a Gene Pix 4100 A microarray scanner.;The results from a microarray revealed a large number of changes of gene expression of the tomato plant genomes in the transcriptional activities that were affected by H. zea herbivory. The peroxidase overexpressing transgenic tomato plants also affect and alter expressions of specific genes quantitatively on a genomic scale in comparison of non-transgenic tomato plants. The gene groups that underwent altered expressions included plant defense and plant pathogen related genes; abiotic resistance; photosynthesis; growth, development, and fruit ripening; DNA, transcription and ribosomes; cellular structure; active oxygen and metabolism related proteins; detoxification; protein kinases; translation termination. The results demonstrated that caterpillars feeding on tomato plants may induce differential gene expression on plant defense and pathogen-related group such as multicystatin, pathogenesis-related protein, proteinase inhibitor, threonine deaminase and aspartic protease inhibitor. Furthermore, peroxidases may play a role in the induction of some of representative plant defense-related genes, such as arginine decarboxylase and cysteine proteinase. These results suggested that over expressions of one of the defense related enzyme in plants, peroxidase, could mediate the degree of some of the resistance-related gene expressions of tomato plants. Therefore, peroxidase activity is likely to be one of the important factors of determination of defense activity of tomato plants. |
