Transcriptomic Responses To Salt Stress And ABA In Nicotiana Tabacum

Nicotiana tobacum which has the characteristics of short growth cycle,relatively strong adaptability,thorough research on stress resistance,and obvious plant characteristics plays an important role in molecular genetics and biotechnology.With the development of sequencing technology,tobacco genome provides a raw data for the response of tobacco to abiotic stress.K326,a flue-cured tobacco variety,was selected as the material in this study.Hoagland nutrient solution was used to balance the tobacco material.Salt stress and Abscisic acid(ABA)induction were applied to the tobacco material.Each treatment was threated three times.The differentially expressed genes(DEGs)in tobacco under two different treatments were analyzed by transcriptome sequencing.The enrichment function of DEGs was annotated by GO database.The functions of DEGs mainly concentrated in the process of protein binding,catalytic activity,biological regulation and stress response.DEGs which were treated by ABA uniquely showed signal transduction and transcription function.Transcription studies on specificity and generality of DEGs in tobacco showed that there were common genes regulating osmotic stress in both treatments.Specific genes played a key role in their respective treatments.79,974 SSR were found in 184,134 transcript assembled sequences,and the frequency of SSR was 43.43%.The sliding window of one SSR site was 10.32 kb,and the length of SSR accounted for genome size was 0.21%.Transcriptome of SSR accounted for only a small part of genomic SSR.Low GC contents in SSR and high proportion of triple repetition of dimer and tripolymer were found to be closely related to the codons and played an important role in tobacco transcription.Alternative splicing analysis indicated that A3 SS was most common under tobacco stress,and RI was relatively high,while MEX was little.The frequency and quantity of tobacco alternative splicing events were very similar under different treatments.Mitogen-activated protein kinase(MAPK)cascade pathway plays a major role in plant growth and development,cell proliferation and hormone physiology,as well as in biological and abiotic stress signals.There are two different pathways in tobacco after salt stress.Salt which created direct stress response enters the MAPK cascade reaction.All pathway genes are up-regulated and activated,which is not directly affected by ABA regulation.The CAT2 gene family is regulated by ABA induction into the cascade reaction to realize the salt resistance response of tobacco.Receptor binding with ABA by regulating the Pyrabactin Resistance/Pyr1-Like(PYR/PYL)gene family,then with protein phosphatase(PP2C)and protein kinase(SnRK2)signal was go into cascade reaction.In this study,whether or not ABA was applied,tobacco would respond to salt stress through two ways when plants were exposed to salt stress.In the co-expression network analysis of tobacco during treatments,the de-redundant gene sets of transcripts were clustered into 22 modules.The characteristics of gene expression were calculated by comparing the similarity and correlation of genes between modules.The correlation of different modules in the whole tobacco network were analyzed,and 22 modules were divided into four sub-groups with similar functions.The results of functional analysis of different treatments showed that modules played different key roles under different treatments.Modules with more gene distribution played an important role in both treatments,while modules with similar blueviolet only played an auxiliary regulatory role under the single treatment of abscisic acid.