Involvement of OpsLTP1 from Opuntia streptacantha in abiotic stress adaptation and lipid metabolism

Abstract

Plant lipid transfer proteins (LTPs) exhibit the ability to transfer lipids between membranes in vitro, and have been implicated in diverse physiological processes associated to plant growth, reproduction, development, biotic and abiotic stress responses. However, their mode of action is not yet fully understood. To explore the functions of the OpsLTP1 gene encoding a LTP from cactus pear Opuntia streptacantha Lem., we generated transgenic Arabidopsis thaliana (L.) Heynh. plants to overexpress OpsLTP1 and contrasted our results with the loss-of-function mutant ltp3 from A. thaliana under abiotic stress conditions. The ltp3 mutant seeds showed impaired germination under salt and osmotic treatments, in contrast to OpsLTP1 overexpressing lines that displayed significant increases in germination rate. Moreover, stress recovery assays showed that ltp3 mutant seedlings were more sensitive to salt and osmotic treatments than wild-type plants suggesting that AtLTP3 is required for stress-induced responses, while the OpsLTP1 overexpressing line showed no significant differences. In addition, OpsLTP1 overexpressing and ltp3 mutant seeds stored lower amount of total lipids compared with wild-type seeds, showing changes primarily on 16C and 18C fatty acids. However, ltp3 mutant also lead changes in lipid profile and no over concrete lipids which may suggest a compensatory activation of other LTPs. Interestingly, linoleic acid (18:2ω6) was consistently increased in neutral, galactoglycerolipids and phosphoglycerolipids of OpsLTP1 overexpressing line indicating a role of OpsLTP1 in the modulation of lipid composition in A. thaliana.