3 Salt stress
4 Germin and Germin like protein
5 Crystal Structure of Germin
6 Isoforms of Germin
7 Biochemical properties
8 Germin and germin like protein related genes
9 Salt induced gene expression of Germin
1. Crystal structure of germin
2. Amino acid sequence of germin
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This review summarizes the Germin and Germin like proteins (GLPs), in relation to the crystal structure, amino acid sequence, biochemical properties, differential expression of proteins of subfamily under the salt stress. The interactive effects of the alkaline and salt stress on the Germin and Germin like protein will be discussed.
Plants, unlike animals, are sessile (Shanker A. 2011), and cannot move from one place to another in response to the unusual environment or any biotic and abiotic stress, they encounters. To protect themselves they need to change in their internal environment to face the situation and to survive in it. There are many stresses in nature which occurs time to time at various extents, for example- Biotic stress – fungi, bacteria, viruses, nematodes, insects, animals etc. and Abiotic stress – drought, flood, high & low temperature, pH, salinity , sodicity, alkalinity, acidity, ion deficiencies and toxicities. Plants respond to these stresses by changes and modification in biophysical, biochemical, physiological, morphological and developmental processes (Caliskan. M; 2011). Salt stress is one of the major abiotic stresses faced by the plants. Soil salinity and alkalinity seriously affect about 932 million hectares of land globally, reducing productivity in about 100 million hectares in Asia (Rao et al. 2008, Wang et al. 2011).
Soil salinity in agriculture soils refers to the presence of high concentration of soluble salts in the soil moisture of the root zone. Soils are considered saline or salt affected when the electrical conductivity of water extracted (EC) from water-saturated soil samples from the root zone exceeds 4 dSm-1 (Richards, 1954). These high concentrations of soluble salts through their high osmotic pressures affect plant growth by restricting the uptake of water by the roots. Salinity can also affect plant growth because the high concentration of salts in the soil solution interferes with balanced absorption of essential nutritional ions by plants (Tester and Devenport, 2003). Reports have clearly demonstrated alkaline salts (NaHCO3 and Na2CO3) are more destructive to plants than neutral salts (NaCl and Na2SO4) (Shi and Sheng 2005, Shi and Wang 2005, Yang et al. 2008 a,b,c ; Wang et al. 2011). Salt stress in a soil generally involves osmotic stress and ion-induced injury (Munns 2002), there is an added high pH effect with alkali stress. A high-pH environment surrounding the roots can cause metal ions and phosphorus to precipitate, with loss of the normal physiological functions of the roots and destruction of the root cell structure (Li et al. 2009). Alkali stress can inhibit absorption of inorganic anions such as Cl–, NO3– and H2PO4–, greatly affect the selective absorption of K+-Na+, and break the ionic balance (Yang et al. 2007, 2008b, 2009). Thus, plants in alkaline soil must cope with physiological drought and ion toxicity, and also maintain intracellular ion balance and regulate pH outside the roots.( Wang et al. 2011)
GERMIN AND GERMIN LIKE PROTEIN
Germin and Germin-like proteins (GLPs) constitute a large and highly diverse family of developmentally regulated proteins showing a wide range of distribution ubiquitously from Myxomycetes to flowering plants. Germin was initially identified as a specific marker for the start of germination in wheat embryos, from which function it was given the name “Germin” (Thompson and Lane, 1980). Germin genes and their proteins were first detected in Germinating cereals (Grzelczak et al., 1985), but subsequently, Germin-like proteins were also identified in dicotyledonous angiosperms (Michalowski and Bohnerd, 1992), gymnosperms (Domon et al., 1995) and mosses (Yamahara et al., 1999).
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