Overexpressing of a novel wheat prolyl aminopeptidase gene enhances zinc stress tolerance in transgenic Arabidopsis thaliana

A common wheat cDNA encoding a prolyl aminopeptidase (PAP, EC 3.4.11.5) was cloned by RT-PCR method and has been named as TaPAP1. The cDNA of TaPAP1 is 1,173 bp in length and encodes a predicted protein of 391 amino acids with a molecular mass and isoelectric point were 43.9 kDa and 7.94, respectively. Alignment of protein sequence indicated that TaPAP1 was evolutionarily conserved among other plants. Real-time PCR analysis revealed that TaPAP1 was predominantly expressed in seedling roots and up-regulated by various abiotic stresses, such as salt, drought, cold, copper and zinc. Compared to wild type plants, zinc-stressed TaPAP1 transgenic Arabidopsis displayed higher survival rate, the fresh weight, photosynthetic efficiency, proline levels, and PAP activity. Our results suggested that TaPAP1 controlled plant tolerance to zinc stress by means of improving the proline levels and PAP enzyme activity. Subcellular localization analysis showed that protein TaPAP1 is localized mainly in the cytoplasm. In conclusion, a novel cDNA sequence encoding wheat PAP gene was successfully obtained and the results showed that TaPAP1 is involved in the plant response to zinc stress, indicating a potential use in the transgenic breeding to improve heavy metal resistance in crop species.