Molecular cloning and characterization of a flower-specific class III peroxidase gene in G. hirsutum.

A fundamental focus of plant biology is to understand the relationship between flowering and plant reproduction, but it is also of practical interest in agriculture. To investigate the genes involved in flowering, reproduction and male sterility, DDRT-PCR was performed in vegetative and reproductive tissues of the cotton genic male sterile line LangA. A 683 bp partial peroxidase cDNA was amplified from cotton (G. hirsutum) pollen, using degenerate oligonucleotide primers and arbitrary primers in DDRT-PCR. The full-length cDNA clone, designated Ghpod (cDNA GenBank accession number: EU196676), was isolated using 5'-RACE strategy and a partial 5'-UTR was isolated applying TAIL-PCR. Ghpod was characterized as a mature 330 amino acid protein, containing all evolutionarily conserved residues present in different members of the plant peroxidase family. The molecular mass of this unprocessed and unmodified deduced protein was estimated to be 35.54 kDa, and the pI value was 4.34. According to the Ghpod protein localization prediction by PSORT, Ghpod may be secreted extracellularly. Unlike other cotton class III peroxidases, Ghpod was expressed exclusively in reproductive organs, particularly pollen. A genomic DNA fragment encoding Ghpod was also cloned and fully sequenced, revealing a "three intron" structural organization in a category of genes belonging to a normal class III plant secretory peroxidase. In conclusion, the flower-specific expression of Ghpod, predominantly in pollen, suggested that the peroxidase is involved in the male reproductive processes of angiosperms.