The TsnsLTP4, a Nonspecific Lipid Transfer Protein Involved in Wax Deposition and Stress Tolerance

Nonspecific lipid transfer proteins (nsLTPs), a group of small, basic proteins that are ubiquitously distributed throughout the plant kingdom, are thought to participate in cutin formation as well as in defense reactions against abiotic and biotic stresses. However, whether nsLTPs are involved in cuticular wax deposition remains unknown. We identified a salt-induced gene, TsnsLTP4, encoding an nsLTP from Thellungiella salsuginea. TsnsLTP4 expression was significantly induced by salt, polyethylene glycol (PEG), abscisic acid (ABA), and high (37 degrees C) and low (4 degrees C) temperatures. Transgenic onion epidermal cells transiently expressing a TsnsLTP4-DsRed fusion protein demonstrated that TsnsLTP4 was targeted to the cell wall. Overexpression of TsnsLTP4 in transgenic Arabidopsis plants resulted in increased epicuticular wax deposition, particularly of wax components with a carbon chain length of more than C27. Moreover, the amount of wax deposited was strongly reduced in RNA interference (RNAi)-knockdown TsnsLTP4 transgenic T. salsuginea lines. Cuticle permeability was inversely related to the expression level of TsnsLTP4. Further analyses indicated that overexpression of TsnsLTP4 resulted in significantly enhanced drought and salt tolerance in transgenic Arabidopsis. In summary, our studies suggested that TsnsLTP4 may play a role in wax deposition and in plant tolerance against abiotic stresses.