Evolutionary History of the Non-Specific Lipid Transfer Proteins

Abstract

The non-specific lipid transfer proteins (nsLTPs) are small, basic proteins characterized by a tunnel-like hydrophobic cavity, capable of transferring various lipid molecules between lipid bilayers. Most nsLTPs are synthesized with an N-terminal signal peptide that localizes the protein to the apoplastic space. The nsLTPs have only been identified in seed plants, where they are encoded by large gene families. We have initiated an analysis of the evolutionary history of the nsLTP family using genomic and EST information from non-seed land plants and green algae to determine: (1) when the nsLTP family arose, (2) how often new nsLTP subfamilies have been created, and (3) how subfamilies differ in their patterns of expansion and loss in different plant lineages. In this study, we searched sequence databases and found that genes and transcripts encoding nsLTPs are abundant in liverworts, mosses, and all other investigated land plants, but not present in any algae. The tertiary structures of representative liverwort and moss nsLTPs were further studied with homology modeling. The results indicate that the nsLTP family has evolved after plants conquered land. Only two of the four major subfamilies of nsLTPs found in flowering plants are present in mosses and liverworts. The additional subfamilies have arisen later, during land plant evolution. In this report, we also introduce a modified nsLTP classification system.

Abundant Type III Lipid Transfer Proteins in Arabidopsis Tapetum Are Secreted to the Locule and Become a Constituent of the Pollen Exine

“…Plant lipid transfer proteins (LTPs) are so termed because, in the initial studies, the proteins were shown to transfer phospholipids and fatty acids between membranes in vitro (Kader, 1996;Boutrot et al, 2008;Edstam et al, 2011). LTPs have a low molecular mass, 6 to 10 kD, and usually a high pI, 8 to 12.…”

“…Although LTPs were thought to function in lipid transfer between subcellular membranes, subsequent findings have shown that their nascent polypeptides possess an N-terminal endoplasmic reticulum (ER)-targeting signal peptide (Boutrot et al, 2008;Edstam et al, 2011). Thus, LTPs are likely secreted to the cell exterior for functioning.…”

“…Numerous functions of LTPs in diverse cells or tissues have been documented or proposed. LTPs could play a role in long-distance signaling in the vascular system, pathogen defense on the organism surface, symbiotic association between plants and microbes, formation of epidermis surface lipids, seed endosperm lipid recycling, and protection of protease digestion during programmed cell death, cell wall extension, and pollen tube and style track recognition (Edstam et al, 2011).…”

“…LTPs are present, depending on the growth condition and environment, in diverse or restricted organs, tissues, and cells, including callus, maturing and germinating seeds, leaves, roots, stems, ovaries, anthers, and pollen (Boutrot et al, 2008;Edstam et al, 2011). The localization of LTP transcripts in anthers has been extensively reported, in part because anthers are essential for producing pollen and contain abundant metabolically active and secretory tapetum cells to which the transcripts could locate.…”

Regulation of gene expression for defensins and lipid transfer protein in Scots pine seedlings by necrotrophic pathogen Alternaria alternata (Fr.)

“…Plant lipid transfer proteins are small basic proteins, which are able to bind hydrophobic compounds in vitro and encoded by large multigene families (Carvalho and Gomes 2007;Kader et al 2007;Edstam et al 2011). LTPs are involved in key processes in plant physiology, such as cell wall organization, stabilization of membranes, signal transduction, plant growth and development (sexual reproduction, seed development and germination) (Nielsen et al 1996;Maldonado et al 2002).…”