Proteomic analysis of long term salt responsive proteins in the halophyte Suaeda maritima

Abstract

A proteomic approach was carried out to identify proteins responsive to long term salt treatment in the halophyte Suaeda maritima. A 3-month-old S. maritima seedlings were hydroponically exposed to Modified Hoagland’s treated with salt solution of 200mM were grown for a period of 14 days in a growth chamber maintained at 24 ± 3°C, 70-75% relative humidity with 14 h light (200 μmol m s)/10 h dark cycle. The untreated set maintained in Modified Hoagland’s solution was considered as control with similar conditions. Proteins extracted from the leaves of S. maritima control and salt treated seedlings were separated by Two-Dimensional gel electrophoresis (2DE). Using PDquest software analysis, we observed ~ 50 protein spots were reproducibly detected on gels, out of which 18 differentially expressed protein spots showed at least two-fold differences on 2DE maps some of them were up-regulated and few others were down-regulated in treated compared with the control. From that, we identified 6 up-regulated protein spots shows the maximum level of fold differences and these protein spots were performed trypsin digestion and Matrix Assisted Laser Desorption Ionization -Time of Flight (MALDI-TOF) analysis. The results showed that S. maritima could withstand up to 200mM NaCl for long term period of 14 days by up regulating proteins that are mainly involved in protein transport, vesicle trafficking, heme/iron binding, protein folding and assembly, chromosome segregation, cell maintenance. Our study has identified salt responsive proteins such as RAB2B, CYP71A8, SCC3 that are not previously identified by expressed sequence tag analyses or transcriptome analyses in this species. This is the first report of proteome analysis and provides insights into the molecular mechanisms of long term salt tolerance in S. maritima.