Nonspecific Lipid Transfer Proteins Relate To Plant Stress Tolerance

Waxes form a continuous lipid membrance covering the epidermal cells of all aerial plant organs. It mainly comprised of lony-chain aliphatic compounds derived from very long chain fatty acids that are enlongedsfrom C16- or C18 -long fatty acids in ER by many fatty acid elongation (FAE) complexs. The chemical and physical properties of cuticular waxes indicate that they have vital functions for plant life. The primary role of cuticular waxes is to restrict non-stomatal waterloss. Waxes also have many other functions, such as protection against UV radiation and resisting bacterial and fungal pathogenes. Wax precursors are synthesized in the plastids and enlongated to very long acyl-CoA chains as direct processors in ER. Once the very long acyl-CoA chains are synthesized, they are converted to cuticular waxes by four different pathways. It is not know how cuticular waxes reach the epidermal surface from intracellular. The pathway most likely involves endoplastric reticulum, transport vesicles, substrate ligands, vesicle receptors and many other secretory factors. However, there are many evidances provid that nonspecific lipid transfer proteins (nsLTPs) may be involved in wax transport to the surface.Nonspecific lipid transfer proteins (nsLTPs) are small, soluble, basic proteins that can bind and catalyze transfer of lipids in vitro, however, we do not know their functions in vivo. A large number of these proteins have been isolated and their primary and secondary structures have been identified. These results showed these proteins have a high degree of similarity; they are basic and cysteine-rich proteins with a signal peptide and a common pattern of eight cysteines that engaged in four disulphide bridges holding together four a helices and stabilizing the structural fold. A hydrophobic central cavity in which can occupied by lipids is found between the four helices. However, it has been difficult to draw any conclusions about the in vivo activity of nsLTPs from their lipid binding properties because it is unknown which ligands, if any, are bound to nsLTPs in vivo. These proteins are ubiquitous in the plant kingdom where they form a multiple genetic family. They have been suggested to be involved in different aspects of plant physiology and cell biology through their ability to bind and/or carry lipophilic compounds, including the formation of cutin by transporting the hydrophobic cutin monomers to the apoplast and the defence of plants against pathogens as antimicrobial agents and in flowering. Also nsLTPs have been suggested to be important in several types of plant stress response including responses to drought, and temperature changes and cold and environmental changes. However, in fact, nsLTPs are extracellular proteins, so there is yet no direct demonstration of an in vivo function. Despite their implication in thesediverse aspects of plant biology, it is not clear which specific role nsLTPs play here, because in a given plant, several nsLTP genes can be found, and they are often specifically expressed in both time and tissue. Also individual nsLTP genes are induced under a variety of conditions. It is not clear whether the various nsLTPs have functional overlap. If this is the case, it may prove difficult to use genetic approaches in determining the function of nsLTPs.we have identified a nucleotide sequence from ESTs (Expressed Sequence Tags) acquired form a cDNA library of Thellungiella halophila treated with 200mM/NaCl by the large-scale partial sequencing of randomly selected cDNA clones. This sequence emergences fourteen times from 1000 ESTs library indicts that it is a middle affluently gene in cDNA library. The cDNA of 634 basepairs contains an open reading frame of 339 nucleotides encoding a novel nonspecific lipid transfer protein .The first 23 amino acids constitute the putative signal peptide, characteristic for targeting to the secretory pathway. We analyzed their sequence characterizations, genomic structures and transcription levels under many stresses. The predicted amino acid s...