Characterization Of BiP Gene Family Of Pepper (Capsicum Annuum L.)and The Role Of CaBiP1 In Response To Abiotic Stress

Adverse environments have detrimental negative impacts on crop growth and development by causing protein denaturation or misfolding,while BiP plays an important protective role by alleviating the endoplasmic reticulum(ER)stress induced by misfolded proteins.Meanwhile,BiP participates in unfolding protein response(UPR)induced by endoplasmic reticulum(ER)stress molecular chaperone,and is believed to take part in ER protective mechanism against protein misfolding.In this study,the sequences and expression patterns of three BiP genes,CaBiP1,CaBiP2 and CaBiP3,from pepper(Capsicum annuum L.),an important economic species as vegetable and spice,were characterized.Our results showed that all the functional and signal domains were detected in the three deduced pepper BiP proteins,but the motifs and exon-intron distribution in CaBiP3 were slightly different from those in CaBiP1 and CaBiP2.CaBiP1 and CaBiP2 were constitutively expressed in all the tested tissues under both normal and stressed conditions;however,CaBiP3 was mainly expressed under stress conditions.Ectopic expression of constitutive expression gene,CaBiP1 enhanced stress tolerance in transgenic Arabidopsis,revealed by the increased germination rate,root length,survival rate,soluble protein content,unfolding protein response(UPR),and by the decreased water loss rate.Function loss of CaBiP1 using the virus-induced gene silencing(VIGS)technique led to decreased tolerance to environment stresses(heat-,salt-and osmotic stress)and ER stress caused by dithiothreitol(DTT),marked by the increasing of H2O2 accumulation,malondialdehyde(MDA)content,relative electric leakage(REL),water loss rate,and by the reduction of the soluble protein content in the leaves..Overall,our results provide the basis for further studied about CaBiP family genes’ founction in different regulatory mechanisms and suggest that CaBi P1 plays an important role in regulating the abiotic stress resistance in pepper plants.