Identification and characterization of salt-responsive proteins in mango (Mangifera indica L.)

Abstract: Increasing salinity is a cause of concern for meeting UN sustainable development goals and needs urgent mitigation strategies. The widespread use of salinity tolerant rootstocks in salt-sensitive fruits provides long-term solutions to the harsh effects of soil salinization. Polyembryonic mango cultivar 13-1, a salinity-tolerant variety from Israel, was used to unravel initial salt adaptive mechanism by imposing a salinity screen at 200mM NaCl. Differentially accumulated proteins were separated through 2-D electrophoresis (pH gradient 4.0-7.0), and identified through properties of pI and molecular weight by annotation against Citrus isoelectric focusing database. Protein spots (309) were detected on Coomassie-stained gels and about 22 spots were found differentially expressed in control and stress. Overproduction of stress-related proteins like polygalacturonase (97 kDa/4.9PI) and alcohol dehydrogenase (38kDa/5.6PI) is linked to enhanced cell wall integrity, transpiration rate regulation and ionic maintenance in adaptability mechanism. The upregulated phenylpropanoid pathway proteins p-coumaroyl ester, Flavanone3-hydroxylase-2 and UDP-glycosyl transferase are also involved in stress alleviation through flavonoid accumulation. Glutathione S-transferase was also identified with 2.21-fold accumulation in plants exposed to salinity stress, thereby elucidating its role in oxidative stress mitigation. Cell wall and cytoskeleton metabolism-related proteins were also found to be associated with salinity adaptation in mango cv 13-1. Differential accumulation of proteins implicated in signal transduction pathway, transcription regulation and hormone signaling were also identified. Thus, role of differentially expressed proteins under initial salinity stress conditions provide new insights molecular adjustment mechanisms orchestrated by mango rootstock variety by hormone signaling, osmotic arrangements, cytoskeleton modifications, phenol accumulation and transcription regulation.