Molecular Analysis of OsLEA4 and Its Contributions to Improve E. coli Viability

OsLEA4 , a late embryogenesis abundant (LEA) protein gene from rice ( Oryza sativa L.), contains a 312-bp open reading frame encoding a putative polypeptide of 103 amino acids with a calculated molecular mass of 11.19 kDa and a theoretical p I of 10.04. OsLEA4 polypeptide is rich in Ala (22%), Lys (15%), Glu (9%), His (8%), Thr (8%), and Arg (7%) and lacking in Trp, Cys, Asn, and Phe residues. OsLEA4 protein contains a Pfam:LEA_1 domain architecture at positions 1–73 with three α-helical domains and without β-sheet domain. In silico predictions showed that OsLEA4 protein was strongly hydrophilic with the grand average of hydropathy value of −0.816 and instability index of 27.31. The hydrophilic regions were found in the conserved motif of OsLEA 4. OsLEA4 gene was introduced into Escherichia coli , and a fusion protein (∼29.4 kDa) was expressed after isopropylthio-β- d -galactoside inducting by sodium dodecyl sulfate–polyacrylamide gel electrophoresis analysis. OsLEA4 protein enhanced the tolerance of E. coli recombinant to high salinity, heat, freezing, and UV radiation, which suggested that OsLEA4 protein may play a protective role under stressed conditions. This is the first successful use of E. coli as a prokaryotic system for LEA production from rice.