A Study On Physiological And Molecular Responses Of Rhus Chinensis Stimulated By Schlechtendalia Chinensis

For the high content of tannin, horned gall is widely used in different fields such asmedicine, food and chemical industry. Horned gall is a special gall caused by the interactionbetween Rhus Chinensis and Schlechtendalia chinensis. Exploring physiologial and molecularresponses of the plant attacked by the aphids is significant for researches.With the detection of some protective enzymes and chemical components related tomembrane injury, we try to confirm the possibility of oxidative damage or membrane injury,and reflect the ecological relationship between them. Invertase activities and gene expressionwill show nutrient partitioning in the plant and their roles in gall formation at protein andnucletide level respectively. Responses of the plants are revealed by cDNA-AFLP attranscriptome level. Genes selected from this research will be useful for the detection of gallformation. The results of physiological and molecular responses mentioned above were asfollows:1. Protective enzyme and other physiological indicators in host plants during gallformation: Protective enzyme is a series of protevtive proteins when plants face with oxidativedamage. The comparision of SOD, POD and CAT between galled and ungalled leaves indifferent period showed no significant difference（P＜0.05）. Total soluable protein and prolineplays adjust role of membrane when it is damaged, while malonaldehyde (MDA) indicats theoxidative damage of lipid membrane. There was no significant difference found between galledand ungalled leaves for these three active substances. The results above showed us that afterfeeding of aphids and with the increase of aphid number, there seemed to be not any seriousoxidative damage or membrane injury. So the plants did not show usual protective activities. S.chinensis might be different frome other pests in plants, and the mutualistic relationship mightexist between this aphid and plant. In all of the results, there is only significant differercehappeded in the later stage for the change trend of soluable protein（P＜0.05）. This illustrated the changes of metabolism in plants induced by aphids, which might be caused by thesource-sink relationship or changes in the process of development.2. Activity of invertase during gall formation: Invertase is important in sucrosemetabolism, so it plays an impotant role in the adjustment of plant growth. In the detection offour kinds of invertase including vacuolar invertase, cytoplasmic invertase, cell wall acidinvertase and cell wall neutral enzyme, activities of vacuolar invertase and cell wall invertasein leaves decreased dramatically （P＜0.05）which proved that leaf growth negativelycorrelated with three kinds of enzymes. Cell wall invertase in galls was not detected whilevacuolar invertase decreased dramatically all the time. It indicated the negative correlationbetween gall development and vacuolar invertase. Different from the decrease of acid invertasein the cell, cytoplasmic invertase in galls increased with growth. Cytoplasmic invertase mightact as a sustain enzyme. Higher acid activies in galls and galled leaves might due to the sinkrole of galls. Ungalled leaves acted as souce tissue, and galls received nutrition frome them.Plant mediated the development by the control of different kinds of invertase, and acidinvertase should be quite important in partition.3. cDNA cloning and expression of invertase gene: cDNA cloning and analysis of geneexpression will be helpful for the control of gall growth and development. cDNA cloneencoding cytoplasmic invertase INV1, cell wall invertase INV2and vacuolar invertase INV3were isolated for the analysis of gene expression. Expression of INV2had its specificity intissue and development, and it played a positive role in gall formation. Expression of INV3ingalls and galled leaves decreased all the time, while it only decreased in ungalled leaves at thefast growth time of galls. This gene might be related to the fast growth and expansion of galls.The latter increase of INV1expression in galls might indicate its relationship with fast growthof galls. We can conclude that higher expression of INV2might be useful for the gall formation,while INV1and INV3should cause the fast growth of galls.4. Screening of genes in responses of the plant and analysis of gene function: Differentexpression of genes in different tissues can help us find the gall-formation-ralated genes, andanalysis of gene function is the base of the molecular mechanism of gall formation.64genes in early responses and71genes in responses during gall formation were selected by the methodof cDNA-AFLP respectively. These genes refered to photosynthesis, redox reaction, regulationof gene expression, secondary metabolism, signal transduction, transmembrane transport, stressreaction, cell fate, cell component and so on. Great changes in metabolic process and cellularprocess caused the formation of galls. Candidate genes taking part in biological regulation,cellular component biogenesis, cellular component organization, cellular process, developmentprocess, establishment of localization, localization, metabolic process, multicellular organismalprocess, pigmentation, reproduction and response to stimulus paved the way for researches onmolecular mechanism.