Genome-wide identification and expression analysis of polyamine oxidase genes in upland cotton (Gossypium hirsutum L.)

Many reports showed that polyamine oxidase (PAO) genes play crucial roles in various abiotic and biotic stresses response. In this study, 12 putative PAO genes (GhPAO1–GhPAO12) were identified in upland cotton (Gossypium hirsutum L.) genome using the released genome database. A total of 349 cis-acting factors involved in hormone and stress response were predicted in 1.5-kb promoter regions at the upstream region of GhPAOs. These GhPAOs can be divided into four major groups when compared with their counterparts in Arabidopsis thaliana. Transcriptional level of GhPAOs were detected by qRT-PCR showing the highest levels in roots. Although GhPAOs exhibited various responses to NaCl treatment, the highest expression level was observed from 3 or 6 h after treatment. To further elucidate GhPAOs functions, GhPAO3 were selected for genetic transformation in Arabidopsis. The content of spermine was significantly decreased in transgenic Arabidopsis lines, whereas the content of putrescine was enhanced, which indicates a potential role of GhPAO3 in the conversion of spermidine and spermine. Discrepancy of salt resistance were observed in germination and seedling stage, which might be controlled by H2O2 concentration threshold. This study provides a valuable insight of the PAO genes in upland cotton response to abiotic stress.