Identification, characterization, and expression profiling of salt-stress tolerant proton gradient regulator 5 (PGR5) in Gossypium arboreum

Salinity is among the significant abiotic stresses adversely affecting plant development and yield for a wide range of crops. For quantitative and qualitative expression studies of proton gradient regulator 5 (PGR5) under salt stress, differential display RT-PCR and rapid amplification of cDNA ends (RACE) were performed on salt-stress responsive Gossypium arboreum. Alignment of genomic and cDNA sequences revealed that the GPGR5 gene comprises a single open reading frame of 96 amino acids and contains no introns. Alignment of cotton GPGR5 complete amino acid sequence with PGR5 from other plants revealed the following identities: Gossypium raimondii (97%), Amaranthus hybridus (72%), Vitis vinifera (69%), Medicago truncatula (68%), Cucumis melo (62%), Arabidopsis thaliana ( 62%), Portulaca oleracea (61%), Portulaca grandiflora (60%), and Zea mays (55%). The expression profile was studied in different plant tissues (stem, leaf, and root) under the abiotic stresses salt, drought, and cold. The results showed a 7-fold increased expression of GPGR5 in leaf tissue in salt stress and almost no induction of transcription in root and stem tissues in salt stress. This gene has a good expression pattern under cold stress compared to salt and drought. In future studies, GPGR5 may be used as a prognostic marker for the development of abiotic-stress-tolerant plants.