Abstract: Pyrroline-5-carboxylate reductase（P5CR），which catalyzes the final reaction of proline biosynthesis pathway，plays an important role in plant stress response. Totally 54 P5CR sequences were identified from 45 genome sequence available species（including cassava）by bioinformatic method，and their distribution and sequence characteristics were analyzed；neighbor-joining phylogenetic trees was constructed by MEGA software；and the expression levels of MeP5CR were evaluated in different tissues and in response to abiotic stresses by quantitative real-time PCR（qRT-PCR）method. The results showed that P5CR had a large difference in intron length，but there was no significant difference in amino acid length，exon number，isoelectric point，and molecular weight. There is only one copy of P5CR in most plants，such as in cassava，indicating that P5CR is evolutionarily conserved and originated from a single gene. However，there are 2-3 copies P5CR genes in some plants such as soybean and apple，indicating that P5CR genes experienced several duplication events during the evolution processes，and totally three different evolutionary patterns were revealed. Expression analysis revealed that MeP5CR expressed the highest in leaf，fibrous root，and storage root，but expressed the lowest in stem and petiole. MeP5CR was significantly induced by cold stress but greatly inhibited by drought stress. These findings suggest that MeP5CR is involved in drought and cold stresses at the transcriptional level，and it can be treated as a candidate to further study its functions in abiotic stress in cassava.

Key words: cassava（Manihot esculenta Crantz）, P5CR, evolution, abiotic stress, drought, cold