| In this paper,the effects of cadmium stress on the physiological and molecular mechanisms of different genotypes tobacco were studied,two different genotypes of tobacco K326 and N.rustica were used as experimental materials,the tobacco K326 was the accumulation of cadmium in leaves,and tobacco(N.rustica)was the cadmium accumulation of root system.In this paper,the suitable cadmium concentration,photosynthesis,antioxidant system and transcriptional sequence of different genotypes of tobacco under cadmium stress were studied.The main findings are as follows:(1)under the 0 ?M cadmium treatment,the root length variation of two kinds of tobacco was the largest compared with 5 ?M,10 ?M,20 ?M cadmium treatment,and the root length variation was close to the maximum of cadmium stress without affecting the normal growth and development of tobacco under 5 ?M stress,under the stress of 5 ?M,the tobacco had obviously been inhibited,and the root length variation of tobacco(N.rustica)was more than that of the tobacco K326,and the root color is also deeper than that of K326,so the suitable concentration for tobacco stress treatment is 5 ?M.(2)Two tobacco genotypes of Nicoticna tabacum K326 and N.rustica were used as test materials,and two cadmium treatment gradients were set up for 0 M and 5 ?M.Cadmium stress could significantly inhibit the photosynthesis of two genotypes tobacco.Under cadmium stress,the chlorophyll content,carotenoid content,net photosynthetic rate,stomatal conductance,intercellular CO2 concentration and transpiration of K326 and N.rustica leaves decreased,but the stomatal limit was a trend.The difference of photosynthetic parameters and chlorophyll content between common tobacco K326 and N.rustica is also significant.(3)Under cadmium stress,the activity of SOD and POD in the root and leaf of two genotypes increased,and the activity of CAT in the two tobacco roots showed a downward trend,but the trend of expression in the leaves was different.The trend of K326 leaves showed a trend,and the leaf of N.rustica showed a downward trend.In general,cadmium stress has a significant effect on the antioxidant system of two genotypes tobacco,but the degree of resistance expressed in the root neutralization leaves of different genotypes of tobacco to cadmium stress is different,which may also be related to the accumulation of cadmium in different parts of the two tobacco.(4)A total of 12 samples of two genotypes of tobacco and cadmium were sequenced based on Illumina Hi Seq 2500 platform,and 87.63 Gb Clean data was obtained.the Clean data of each sample was not less than 6.17 Gb,and Q30 was not less than 93.27%.(5)Compared the 12 Clean data with the K326 reference genome,the ratio of the 6 clean reads to the K326 reference genome of the Nicoticna tabacum K326 was higher than 92.04%,the mapped ratio of Total was more than 70%,and the N.rustica of the 6 clean reads to the K326 reference genome was about 70%.Moreover,Nt C,Nt T,Nr C and Nr T had more than 0.92 R2 of biological duplication among four samples,which met the requirements of follow-up analysis.(6)There were 62 differentially expressed genes before and after cadmium treatment in the root of Nicoticna tabacum K326,including 38 up-regulated genes and 24 down-regulation genes.There were 26 differentially expressed genes before and after cadmium treatment in the root of N.rustica,including 17 up-regulated genes and 9 down-regulated genes.There were 30710 differentially expressed genes between Nicoticna tabacum K326 and N.rustica control,among which,19257 up regulation genes and down regulated groups were up.There were 11453 differentially expressed genes between the Nicoticna tabacum K326 and the tobacco N.rustica treated 5 ?M cadmium treatment,of which 18996 were up and 11298 were down regulated.There were 3692 specific differentially expressed genes in Nicoticna tabacum K326 before and after cadmium treatment.There were 3276 differentially expressed genes in tobacco N.rustica.(7)GO and KEGG enrichment analysis of differentially expressed genes showed that the concentration of differentially expressed genes between the control and treatment of tobacco N.rustica and Nicoticna tabacum K326 was basically the same.In the biological process,the metabolism of nitrogen compounds,the metabolic process of nitrogen compounds and the process of nitrogen compound metabolization were significantly enriched,and the cytoplasm and cytoplasm of the cell components were enriched,and the cytoplasm and cytoplasm were significantly enriched.on the Molecular function,oxidoreductase activity,antioxidant activity,nuclear transfer enzyme activity and ribosome structure composition were significantly enriched.The main pathways in KEGG are mainly sulfur metabolism,carbon metabolism,nitrogen metabolism,plant pathogen interaction,photosynthesis,photosynthesis,cysteine,plant hormone signaling,phenylpropane biosynthesis,RNA transport,splice body,ribosome,flavonoid biosynthesis,carotenoid biosynthesis and ABC transporter.The metabolic pathway of thiosulfate Xie Hetan was closely related to the abiotic stress of plant resistance to cadmium.The KEGG metabolic pathways,such as oxidoreductase activity,antioxidant activity and other GO units,and the biosynthesis of benzopropane biosynthesis and the biosynthesis of flavonoids were all closely related to the results of the study on the activity of tobacco antioxygenase at the early stage of this study.Some gene down-regulation in the metabolic pathway related to photosynthesis is also related to the decrease of photosynthetic pigment content in tobacco and the weakening of light and effect.(8)There are many transcription factors such as b ZIP,ERF,MYBb HLH,SBP,C2H2,NAC,WRKY in the roots of two genotypes tobacco,these transcription factors are closely related to the signal regulation related to cadmium tolerance,and most of these transcription factors are down regulated. |
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