Functional Identification Of A Hydrophilic Protein Dlp Required For Resistance To Abiotic Stresses In Deinococcus Radiodurans

Deinococcus radiodurans(DR)has attracted more attention for its superior resistance to abiotic stresses.Genome annotation showed that three genes(dr1372,dr0105 and dr1172)in D.radiodurans encode homo logs of plant desiccation resistance-associated Late Embryogenesis Abundant protein(LEA).Dlp(DR0105),classed into LEA3 family,is highly hydrophilic.Dlp,was identified functionally via bioinformatics and transcriptional profiles with the combination of phenotype identification,heterologus expression and enzymatic protection.The results obtained are as following,Dlp is 17.83 kDa,contains 163 amino acids,and rich in hydrophilic amino acids consists of 90.18%a-helix,which was predicted as a stable hydrophilic protein and classed into LEA3 familyby bio informatics analysis.The results of QRT-PCR showed that the expression of dlp gene was significantly down-regulated in?drRRA,which indicates that dlp was presumbly regulated by DrRRA,an identified response regulator.We predict that Dlp protein may be have some abiotic stress resistance like the most of LEA3 proteins,and related to salt tolerance,antioxidant,UV resistance and other abiotic stress resistance in D.radiodurans.To investigate the resistance function of Dlp,the dlp deletion mutant strain(Adlp)was obtained by fusion PCR,and the phenotype of the wild-type and Adlp mutant were tested under abiotic stress,the results showed that Adlp mutant became more sensitive to high-salt and oxidative stresses than wild-type,but their cell's UV radiation resistance was same.And also the heterologous expression strain E32a-dlp was constructed and showed that Dlp can significantly enhance the E.coli salt,drought and oxidative resistance.Theprotection of Dlp to MDH and LDH enzymes was measured under oxidative and freeze-thaw stressesin vitro.The data showed that both two enzymes were protected effectively by Dlp,which decreases the loss of enzymatic activities largely.In summary,Dlp can not increase the UV radiation resistance of D.radiodurans,however itcan enhanceD.radiodurans and E.coli resistance to abiotic stresses,such as salt and oxidative resistance,and protect enzymatic activity from abiotic stresses in a chaperone manner.