Several salt-induced proteins have been identified in plant species and classified into two categories proteins, which accumulate only due to salt stress, and stress associated proteins, which also accumulate in response to heat, cold, drought, water logging, and high and low mineral nutrients. Studies of Farghaly et al., (2013), Hurkman et al., (1989) and Mansour et al (2000) revealed as salinity stress induced insignificant change in the soluble proteins of the tolerant and sensitive wheat cultivars. A higher content of soluble proteins has been observed in salt tolerant than in salt sensitive cultivars of sunflower (Ashraf et al., 1995), finger millet (Uma et al., 1995) and rice (Pareek et al., 1997). In contrast, in lentil Ashraf and Waheed (1993) reported that leaf soluble proteins decreased due to salt stress in all lines, irrespective of their salt tolerance. Ashraf and Harris (2004) reported that the proteins produced under salt stress are not always associated with salt tolerance, thus using proteins as salt tolerant indicators depending on the nature of the plant species or cultivar. The protein degradation under saline environment has been attributed to the decrease in protein synthesis, accelerated proteolysis, decrease in availability of amino acids and denaturation of enzymes involved in protein synthesis (Jaleel et al., 2007; Lakhdar et al., 2008; Dagar et al., 2004).
Increased protein content in at ontogeny stage is an altered phenomenon explained through Kagale et al., 2007 i.e, increasing protein content under salt stress involves the activation of transcription and translational processes of specific stress tolerance genes. Similarly, Gomathi et al. (2013) also reported the differential accumulation of proteins and enhanced expression of polypeptides (15 kDa, 28 kDa and 72 kDa) in sugarcane, which was related to salinity tolerance. Protein content was observed to increase approximately two folds in seedlings under 80mM NaCl concentration and also showed higher accumulation in 45 and 60 days old plants under salt treatment when compared to control in rice Singh et al., 1985. Tuna et al., (2014) look at endorse that the NaCl treatment at 125 mM reduced soluble protein content material and electrolyte leakage.
Proteins are considered to be the building blocks of life and, in addition to their nutritional role, have other functions in living organisms. It is important to understand the structure of the protein molecules that determine its function. Proteins are molecules that form peptide chains. A protein molecule can consist of one polypeptide chain or several chains. Each polypeptide chain consists of long, continuous bundles of amino acids held together by peptide bonds. These bonds are formed between the carboxyl group of an amino acid and the adjacent amino acid group. The type and number of these amino acids lead to the formation of different types of proteins. Proteins are synthesized in the cellular cytoplasm through a process called translation.
All the vital activities of plants are done with the intervention and effect of proteins, and any reaction to external and internal factors depends on whether the plant has a mechanism to produce supporting proteins or not. This feature is different in different plants and even in different plants or varieties in different regions. Therefore, these plant or climatic differences prevent it from being clearly stated that the amount of some proteins can be an indicator of resistance or sensitivity to an external or internal factor.
P protein content significantly decreased in plants treated with 80 mM of sodium chloride and increased in plants grown in 160 mM. One characteristic of saline stress is the removal of potassium ions by plant roots, which causes a physiological imbalance because potassium is necessary for protein synthesis.