Nostoc flagelliforme is a kind of terrestrial nitrogen-fixing cyanobacteria being strong drought ecological adaptability.An unknown protein related to drought-tolerant,named hypothetical protein NXL-01,has been discovered by the proteomic analysis under drought stress.NXL-01 gene was cloned by designed degeneracy primers based on identified amino acid sequences.A full length of 327 bp DNA was obtained(GenBank access number:HM854288).Bioinformatics analysis showed that the NXL-01 gene was highly conservative.The secondary structure of NXL-01 was made up of α helix and random coil.It was a hydrophilic outside membrane protein with five Ser phosphorylation sites and one Thr phosphorylation site.NXL-01 was expressed in E.coli,and a 12.4 kD heterologous protein was observed.RT-PCR showed that mRNA level of NXL-01 gradually increased,consistent with the expression trend of NXL-01 in N.flagelliforme under drought stress.