Characterization of a new class of oleosins suggests a male gametophyte specific lipid storage pathway

Abstract

SummaryThe expression and sequences of two related antherspecific cDNAs (13 and C98) of Brassica napus (oilseed rape) were examined. These cDNAs were found to exhibit significant predicted amino acid sequence similarity with a group of seed-specific proteins, the oleosins, which are involved in oil body membrane structure. Pollen of 6. napus also contains oil bodies, and the synthesis and accumulation of these organelles correlates with expression of the 1 3 and C98 transcripts. The protein content of purified pollen oil bodies was or absence of possible oleosins. One major protein species of 14 kDa was identified and subjected t o N-terminal amino acid sequence determination. The sequence of this pollen oil body associated protein is homologous to the predicted sequence of one of the anther-specific cDNAs, 13, implying that this cDNA represents an anther-specific oleosin gene expressed in developing pollen. The expression of other genes active during seed oil body formation was also examined, and these were found to be specific t o the sporophyte, inferring the existence of specific components of the pathway of lipid synthesis and storage in the male gametophyte. These possibilities and the relationship between different oleosin genes are discussed. therefore examined in order to determine the presence

Molecular characterization of two Brassica napus genes related to oleosins which are highly expressed in the tapetum

“…In addition, highly conserved amino acids within this domain found in all oleosins are also well conserved in Sta 41-2 and Sta 41-9, especially when compared with oleosins isolated from B. napus pollen (Roberts et al, 1993) and with putative oleosins from A. thaliana anthers (De Oliveira et al, 1993). These conserved amino acids include three proline residues which are believed to be important for the formation of a loop in the hydrophobic tail of the oleosins which is embedded within the lipid fraction of the oil bodies (Huang, 1992;Murphy, 1993).…”

“…(b) Alignment of the most highly conserved amino acids from Sta 41-2, Sta 41-9, B. napus pollen oleosins C98 and 13 (Roberts et aL, 1993) and putative oleosins atgrp-6, atgrp-7 and atgrp-8 from A. thaliana anthers (De Oliveira et al, 1993). Conserved residue (*), conservative substitution (.).…”

“…Oleosins are believed to help stabilize the small oil bodies during dehydration and possibly provide binding sites for lipase activity upon germination. Recently, a novel class of oleosins was shown to be associated with the lipid bodies of B. napus pollen grains where they are believed to serve a similar function (Roberts et aL, 1993). Putative oleosins have also been reported in the anthers of Arabidopsis thaliana (De Oliveira et aL, 1993).…”

Characterization of anther‐expressed genes encoding a major class of extracellular oleosin‐like proteins in the pollen coat of Brassicaceae†

“…The major evidence for this was the purification of an oil body-associated protein from pollen protoplasts (Roberts et al, 1993b), and the temporal expression of the B. napus OInB;1 cDNA sequence. The B. napus OInB;1 sequence was assumed to be microspore expressed due to the detection of its transcript in buds of 5.9 mm in length, when the tapetal cell layer will have broken down .…”

“…Oleosin-like transcripts have also recently been identified in anther tissues (de Oliveira et al, 1993;Robert eta/., 1994;Roberts et al, 1993b;Ruiter et al, 1994). The proteins derived from such sequences are designated oleosin-like on the basis of sequence similarity with the conserved region of the seed oleosin protein family.…”