Modulation of the Biological Activity of a Tobacco LTP1 by Lipid Complexation

Abstract

Plant lipid transfer proteins (LTPs) are small, cysteine-rich proteins secreted into the extracellular space. They belong to the pathogenesis-related proteins (PR-14) family and are believed to be involved in several physiological processes including plant disease resistance, although their precise biological function is still unknown. Here, we show that a recombinant tobacco LTP1 is able to load fatty acids and jasmonic acid. This LTP1 binds to specific plasma membrane sites, previously characterized as elicitin receptors, and is shown to be involved in the activation of plant defense. The biological properties of this LTP1 were compared with those of LTP1-linolenic and LTP1-jasmonic acid complexes. The binding curve of the LTP1-linolenic acid complex to purified tobacco plasma membranes is comparable to the curve obtained with LTP1. In contrast, the LTP1-jasmonic acid complex shows a strongly increased interaction with the plasma membrane receptors. Treatment of tobacco plants with LTP1-jasmonic acid resulted in an enhancement of resistance toward Phytophthora parasitica. These effects were absent upon treatment with LTP1 or jasmonic acid alone. This work presents the first evidence for a biological activity of a LTP1 and points out the crucial role of protein-specific lipophilic ligand interaction in the modulation of the protein activity.

Arabidopsis LTPG Is a Glycosylphosphatidylinositol-Anchored Lipid Transfer Protein Required for Export of Lipids to the Plant Surface

“…As reported for several other LTPs (Buhot et al, 2004;Sawano et al, 2008), LTPG did bind to the fluorescent lipid reporter TNS. This lipid binding is not surprising because, although sequence similarity is low, the overall structural features of the protein predicted by the LTPG amino acid sequence resemble characterized LTPs (i.e., structure with four a-helices and four disulfide bonds).…”

“…The binding of this reporter is interesting because it is consistent with the hydrophobic cavity structural model (Kader, 1996). TNS binding to other, functionally uncharacterized, LTPs could be displaced by C 16 and C 18 unsaturated fatty acids (Buhot et al, 2004;Sawano et al, 2008), suggesting that aliphatics are capable of competing with TNS for the same hydrophobic binding cavity. In this case, the binding of the biologically relevant very-long-chain lipids, such as nonacosane, would be technically difficult to confirm due to solubility issues.…”

“…Fluorescent binding assays were performed essentially as previously described (Buhot et al, 2004). A 1 mM solution of TNS (Research Organics) was added incrementally to a 2-mL stirred cuvette at 258C containing 50 nM DLTPG.…”

Specific Adduction of Plant Lipid Transfer Protein by an Allene Oxide Generated by 9-Lipoxygenase and Allene Oxide Synthase

“…For example, it has been recently shown that LTPs can induce plant protection when they are loaded with jasmonic acid (but not with linolenic acid) (18) and that the cell wallloosening effect of LTP is modulated by lipid binding (9). Although LTPs typically bind lipids in a non-covalent way, we have previously found that an adduct is covalently bound to wheat LTP1 (19).…”

A Review: Biological and Technological Functions of Barley Seed Pathogenesis-Related Proteins (PRs)

“…NsLTPs may also be involved in cell signaling. Wheat ns-LTP1 is reported to interact with receptors of the fungal protein elicitin 20,38 . The complex of elicitin and ergosterol in the fungal cell wall needs to be recognized in order to trigger a plant response.…”