Intracellular localization of a lipid transfer protein in Vigna unguiculata seeds

Abstract

Lipid transfer proteins (LTP) facilitate transfer of lipids between membranes in vitro. Up to now, they have been found to be localized basically in the plant cell wall and in compartments linked to lipid metabolism, such as glyoxysomes. Accordingly, LTP are considered to be involved in the plant defence against pathogen microbes and lipid metabolism. We herein show, by immunoelectron microscopy, that besides the cell wall, LTP are localized in the lumen of organelles which we suggest to be the protein storage vacuoles, as well as in vesicles similar to the lipid‐containing ones and in the extracellular space of Vigna unguiculata seeds. To further characterize these organelles, we performed subcellular fractionation of membranes isolated from imbibed seeds on a sucrose‐density gradient. The analysis of these fractions revealed that the lightest membrane vesicles, derived probably from PSV, contain LTP, α‐TIP and K+ independent PPiase, but not γ‐TIP and K+ stimulated PPiase. The presence of LTP and vicilins (typical storage protein) in the lumen of these vesicles was confirmed by immunoelectron microscopy. Taken together, the data suggest that the intracellular LTP in the V. unguiculata seeds are localized in protein storage vacuoles and in lipid‐containing vesicles.

OsC6, Encoding a Lipid Transfer Protein, Is Required for Postmeiotic Anther Development In Rice

“…In addition, LTPs contain a signal peptide at the N terminus, generally 21 to 27 amino acids for the LTP1 family and 27 to 35 amino acids for the LTP2 family (Carvalho and Gomes, 2007), allowing mature LTP peptides to enter the secretory pathway. Consistently, several LTP1 members from Arabidopsis (Thoma et al, 1993), Brassica oleracea var italica (Pyee et al, 1994), Ricinus communis (Tsuboi et al, 1992), and Vigna unguiculata (Carvalho et al, 2004) are localized at the cell wall, while the extracellular localization of these LTPs was not in line with the assumed function of these proteins in cell cytoplasm (Carvalho and Gomes, 2007).…”

Expression of recombinant EARLI1, a hybrid proline-rich protein of Arabidopsis, in Escherichia coli and its inhibition effect to the growth of fungal pathogens and Saccharomyces cerevisiae

“…AlLTPs from Allium species are localized in endomembrane compartments (Yi et al, 2009), while a LTP in germinating sunflower seeds was found in both intracellular and extracellular localizations (Pagnussat et al, 2009). Moreover, a LTP from castor bean (Ricinus communis) was localized in the glyoxysome matrix (Tsuboi et al, 1992), and a LTP from Vigna unguiculata seeds in the protein storage vacuoles (Carvalho et al, 2004). Another exception is the apparent chloroplast localization of RlemLTP, a rough lemon nsLTP with antifungal activity against Alternaria alternata and Fusarium oxysporum.…”

Defense Proteins from Vigna Unguiculata Seed Exudates: Characterization and Inhibitory Activity Against Fusarium Oxysporum

“…In the last years, several proteins such as trypsin and papain inhibitors (Xavier-Filho et al 1989), variant vicilins (7S globulin storage proteins) , glucan hydrolases represented by chitinases and b-1,3-glucanase (Gomes et al 1996), antimicrobial peptides identified as lipid transfer proteins (LTP) and defensins (Carvalho et al 2001(Carvalho et al , 2004 were found in seeds of cowpea. These proteins are commonly linked to plant defense mechanisms.…”