Lipid transfer proteins (LTPs) constitute a pervasive class of small proteins implicated in many biological and physiological processes, including seed development, germination, cuticle formation, and abiotic stress responses. In this study, we explored the role of Arabidopsis LTP12 protein in mitigating environmental stresses. To address this, we analyzed the T-DNA knockout mutant ltp12, focusing on its responses to salinity and osmotic stress. Utilizing antioxidant enzyme assays, phenotypic analyses (including water loss, chlorophyll content, seed germination rates, root length, and relative water content), and lipid profile analysis via Thin Layer Chromatography (TLC), we found that ltp12 mutants showed reduced catalase and peroxidase activities and poorer hydration, chlorophyll content, germination, and growth under stress, compared to wild-type Col-0 plants. Mutants delayed vegetative-to-floral phase transition compared to wild-type. Additionally, lipid analysis indicated that the wild-type plants had increased phospholipids under high osmotic stress, suggesting LTP12's involvement in lipid reorganization during stress responses.

SIP470, a putative tobacco lipid transfer protein, was identified in a yeast two-hybrid screen to interact with SABP2. SABP2 is a critical role in SA-mediated signaling in tobacco and other plants. In vitro studies using purified recombinant SIP470 confirmed that it is a lipid binding protein. In an attempt to determine its role in mediating stress responses, Arabidopsis T-DNA insertion knockout lines lacking SIP470 homolog were used for the analysis. These mutant plants were defective in basal resistance against microbial pathogens. Expression of defense gene PR-1 was also delayed in these mutant plants. Interestingly, these mutant plants were not defective in inducing systemic acquired resistance. Besides biotic stress, these mutant plants also showed increased susceptibility to abiotic stresses. To directly study the role of SIP470 in tobacco plants, transgenic tobacco lines, with reduced levels of SIP470 expression, were generated using RNAi and transgenic lines overexpressing SIP470 were also generated.

SABP2-interacting protein 470 (SIP470), a non-specific lipid transfer protein (nsLTP), was discovered in a yeast two-hybrid screening using SABP2 as bait and tobacco leaf proteins as prey. SABP2 is an important enzyme in systemic acquired resistance that converts salicylic acid to methyl salicylate. Localization studies are an important aspect to understanding the biological function of proteins. nsLTPs are generally considered apoplastic proteins and has been localized intracellularly and extracellularly. Transient expression shows highest expression of SIP470-eGFP at 2 days post infiltration into Nicotiana benthamiana. Confocal microscopy showed localization near the periphery of the cell. Subcellular localization using differential centrifugation showed that SIP470 is localized in the mitochondria. Mitochondria membranes are rich in lipids and have shown lipid exchange with the endoplasmic reticulum in mammalian systems. Co-localization of SIP470-eGFP+mCherry did not express complete co-localization in the targeted organelles. Co-localization pattern suggests possible localization in the endoplasmic reticulum.