Different Expression Of Protein And Genes In Roots And Leaves Of Flue-cured Tobacco Under Water Stress

Water-culture experiments and pot experiments were employed to study the differently expressed proteins and genes in tobacco leaves and roots under drought and osmotic stress with PEG6000 from 2005 to 2006.The results were as follows:1.Some large-molecule proteins were induced under drought stress in pot experiments. The proteins with 21 KD molecular weight were always induced when drought stress occurred at roots spreading stage and were positively correlated with the decreasing of water content.2.In order to study the drought resistance defense mechanism in the tobacco plant,the changes of gene expression in osmotic stressed tobacco(Nicotiana tabacum L)leaves were analyzed by cDNA microarray analysis.RNAs of tobacco leaves with or without(CK)PEG treatment for 48 h under-1.2 MPa were extracted and subjected to analysis of cDNA microarray based on Arabidopsis genomic sequence.There were about 135 differently expressed genes(with ratio values≥2 or≤0.5)among 31 182 genes set in a microarray plate,in which 50 appeared to be up-regulated and 85 appeared to be down-regulated by osmotic stress.Functional analysis showed that some were defensive genes such as trehalose synthase(ATTPS11)and universal stress protein(USP),and the others were related to replication,transcription,translation and protein folding including bZIP family transcription factors,zinc finger proteins,histone H1-3,DREB1C,the WRKY,molecular chaperones and so on.All genes mentioned above were up-regulated by osmotic stress.Gene of MAPKK (Atlg51660),a key player in signal transduction pathway,was up-regulated dramatically by 3.94 times.Among down-regulated genes there were 6 genes of light harvesting complex in photosystemⅠand photosystemⅡ,including lhca3,lcb1,lcb2,lcb5,lcb6 and lcb4.2.The gene lcb6(Atlg15820)was most down-regulated by 3.9 times.In addtion,38 unknown function genes were also detected in the experiment.The functions of those genes in plant osmotic stress response need to be elucidated in the future.3.The changes of gene expression in osmotic stressed tobacco(Nicotiana tabacum L) roots were analyzed by cDNA microarray analysis.There were about 126 differently expressed genes(with ratio values≥2 or≤0.5)among 31182 genes set in a microarray plate, in which 79 genes were up-regulated and 47 down-regulated by osmotic stress.Among up-regulated genes,a lot of them such as ABA responsive protein,calcium signaling responsive protein and protein kinase were found in signaling transduction pathway, suggesting that signaling transduction in roots under osmotic stress be activating. Meanwhile,some hydrolase genes in relation to membrane system and transporter were also up-regulated under osmotic stress.But some genes regulating normal plant growth and development,such as the genes of gibberellin-responsive protein,nitrate reductase 2(NR2) and so on,were down regulated.Some genes of E3 ubiquitin ligase,the key components in ubiquitin-mediated protein degradation pathway,were also down regulated.Moreover,58 unknown function genes were also detected in the experiment.The functions of those genes in plant osmotic stress response needed to be elucidated in the future.By analyzing the differently expressed genes some valuable information underlining plant osmotic stress response were highlighted.4.By analyzing the differently expressed genes in tobacco leaves and roots,it was found that some up-regulated genes in tobacco leaves were mainly functional genes under osmotic stress,which in tobacco roots were genes which took part in signaling transduction pathway. However,whether in tobacco leaves or in tobacco roots,all of the down-regulated genes could be those which could inhibit tobacco from normally physiological metabolisms.5.The results showed that it was possible for us to study the changes of tobacco(Nicotiana tabacum L)gene expression with cDNA microarray of Arabidopsis thaliana before new cDNA microarray of tobacco were developed.The results explained some potential biological rules by analyzing the differently expressed genes and provided some valuable information on stress physiology research of tobacco for us.