Identification And Expression Of AREB/ABFs Gene Family In Corchorus Olitorius L. Under Salt And Drought Stress With Exogenous ABA

Jute(Corchorus L.)is an annual plant of Malvaceae family,which is the most important natural fiber after cotton for the amount produced,versatility,and multiple uses.However,jute has been exposed to severe losses at yield and quality levels due to the increase of salt and drought conditions,affecting its worldwide development and production to certain extent.The AREB/ABF(ABA-responsive element-binding protein/AREB-binding factor)gene subfamily members induce ABA expression and play vital role in its signaling pathway,which can enhance the adaptation of plant under biotic and abiotic stresses.In this study,the morphological characteristics in two jute cultivars Cvlv(CL)and Nangyang Changguo(NC)were tested under salt and drought stress with and without ABA.Besides,the phylogenetic analysis and protein prediction of ABF relative with abscisic acid(ABA)were conducted by MEGA-X,Pfam and SMART databases.Moreover,the ABF genes were identified by BLAST,then expression pattern of AREB/ABF genes were analyzed in jute seedlings of different tissues and time points under salt(ST)and drought(PEG)stress using q RT-PCR technique.It was observed that CL had a better response to both stresses than NC.Furthermore,the growth of seedlings of both cultivars were greatly enhanced under ST+ABA and PEG+ABA treatments,and their agronomy traits including plant height and survival rate were improved notably compared with the seedlings under stress conditions without ABA.Eight CoABF genes from AREB/ABF members in the jute genome were identified based on 9 represent genes from Arabidopsis thaliana.The phylogenetic tree was performed with the multiple alignments of 90 AREB/ABF proteins from 8representatives species(Arabidopsis thaliana,Oryza sativa subsp.Japonica,Hibiscus cannabinus,Gossypium raimondii,Theobroma cacao,Corchorus capsularis,and Corchorus olitorius),which were classified into four groups(A,B,C,and D).Most of the CoABF proteins clustered with amino acids of Corchorus capsularis and shared recent common ancestors with the Theobroma cacao L.Meanwhile,the CoABF1 protein was solely related to Theobroma cacao L.The gene structure indicated the distribution of the exon/intron conserved by each group,except in group D,which had a slight difference in the exon numbers between genes.Also,the conserved motifs were predicted from the CoABF proteins,finding that motifs 1 and 2 were in all of the amino acid sequences with strong conservation of the b ZIP domain.Moreover,the prediction of the cis-elements showed the response of CoABF genes to the light,hormone,and stress elements.The analysis revealed that CoABF1,3,7,and 8 induced the reaction of the element AREB,which highlighted the expression of the abscisic acid in the plant.The results of the gene duplication indicated the interaction of two gene pairs with a Ka/Ks ratio of 0.25,indicating a clear purifying selection and a moderately ancient divergence.Meanwhile,the genetic evolution of the AREB/ABF members between jute-cotton,and jute-cacao indicated a clear purification selection in both relationships.Although the results of divergence time were different between relationships,the variance time was more ancient with cotton than with cacao.The expression profiling of the CoABF genes was induced through the tissues(leaf,stem,and root)of two jute cultivars(CL and NC)at different times(2h,4h,8h,12 h,and 24h)under 5 treatments(ABA,PEG,PEG+ABA,ST,and ST+ABA).Among the eight genes,CoABF3 and CoABF7 showed the best activity level in NC and CL with ABA.The expressions of these two genes were greatly activated in the CL seedlings,especially in the stem and leaf,having a gradual increase throughout time.Meanwhile,in the NC cultivar,the expression profiling of CoABF3 and CoABF7 were especially induced in the stem with a maximum level at 8h and 24 h,respectively.To examine the expression changes of the CoABF3 and CoABF7 genes,we analyzed the samples under salt and drought stress with and without ABA.Thus,both genes were significantly expressed in CL under PEG+ABA,although CoABF3 was highly activated in leaf(12h)and stem(4h),whereas CoABF7 was induced greatly in leaf and stem at 2h and 8h respectively.However,CoABF3 was solely expressed in the stem of NC,showing the highest activity under PEG+ABA at 8h.Besides,up-regulation of these genes was observed in both cultivars under PEG+ABA compared with the expression under PEG.Conversely,the expression profiles of both genes were solely activated in CL seedlings under ST and ST+ABA throughout time,although these two activity levels were slightly different between treatments.Nevertheless,in the NC cultivar,the expressions of CoABF3 and CoABF7 were induced in the stem and root under ST+ABA,reaching the maximum peak at 8h.Hence,the expressions of both genes were up-regulated in the NC seedlings under ST+ABA solution.In this study,we found CoABF3 and CoABF7 were significantly expressed in both cultivars under abiotic stress with ABA,which revealed the strong effect of ABA and also the ABA signaling pathway during the influences of the stresses in jute seedlings.This research can provide theoretical foundation for creating new jute germplasm with high resistance to abiotic stress by molecular biological method.