Full TGIF Record # 22336
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Publication Type:
i
Refereed
Author(s):Lee, Keunmyoung; Huang, Anthony H. C.
Author Affiliation:Department of Botany and Plant Sciences, University of California
Title:Genomic nucleotide sequence of a Brassica napus 20-kilodalton oleosin gene
Source:Plant Physiology. Vol. 96, No. 4, August 1991, p. 1395-1397.
Publishing Information:Lancaster, PA: American Society of Plant Physiologists
Keywords:TIC Keywords: Genes; Brassica
Abstract/Contents:"The storage triacylglycerols in seeds are confined to discrete spherical organelles called oil bodies (10). Each oil body of 1 u(mu)m diameter contains a matrix of triacylglycerols surrounded by a layer of phospholipids embedded with abundant and unique proteins called oleosins (2,6). Oleosins are hydrophobic proteins of low Mr ranging from 16 to 26 kD, depending on the isoforms and plant species. They are present in the seeds of both dicotyledons and monocotyledons. Their possible functions include stabilizing the oil bodies in an aqueous environment and providing signal recognition for the specific binding of lipase during germination. The partial amino acid sequences of the oleosins from maize (16kD) (9) and Brassica (20 kD) (4) and the complete amino acid sequences of the oleosins from maize (18 KD) (5) and carrot (19 kD) (1) have been deduced from their cDNA and genomic sequences, respectively. Here we report the complete nucleotide sequence of Brassica napus oleosin gene (Fig 1; Table 1). The Brassica oleosin gene possesses one intron, wheras all the previously reported oleosin genes (two from maize and one from carrot) do not contain introns. The intron in theBrassica oleosin gene occurs between the two exons encoding the central hydrophobic domain and the C-terminal domain, respectively. The deduced amino acid sequence of the Brassica oleosin shows the same three basic structural domains that are common to the four sequenced oleosins. These three domains are an N-terminal hydrophilic domain, a central hydrophobic domain, and a C-terminal amphipathic domain. The Brassica oleosin shares significant homology in amino acid sequences at the central hydrophobic domain, but not at the other two domains, with the other reported oleosins. The Brassica oleosin does not possess appreciable cleavable signal sequence at the N-terminus, and this is in agreement with its Mr of 20,000 estimated by SDS-PAGE being similar to its Mr of 20,682 derived from the amino acid sequence. The N-terminal amino acid sequence of the Brassica oleosin bears little similarity with those of maize 18-kD oleoins and carrot 19-kD oleosin. This is intriguing, because the maize 18-kD oleosin is correctly targeted to the seed oil bodies in Brassica transformed with the maize oleosin gene(3). Presumably, the intracellular targeting signal for oleosin resides in the highly conserved central hydrophobic domain or in the yet-unidentified secondary structures in the N- or C-terminus. Earlier, we identified at least two isoforms of oleosins in seeds from different, and within the same, species (8). The two isoforms are distinguishable immunologically, and in general, one isoform has a Mr higher than that of the other isoform within the same species. The Brassisc 20-kD oleosin and the maize 16-kD oleosin apparently belong to the same "low Mr" isoform, wheras the carrot 19-kD and maize 18-kD represent the "high Mr" isoform. This category is revealed in a comparison of the amino acid sequences among the oleosins: 48% identical amino acid residues between the two high Mr oleosins (maize 18-kD oleosin and carrot 19-kD oleosin), 51% between the two low Mr oleosins (maize 16-kD oleosin and rapeseed 20-kD oleosin), 37% between the two maize oleosins, and 33% or less between any other pair of high and low Mr oleosins. The findings that each pair of oleosin isoforms are more related between themselves than to the other oleosin isoforms explains our earlier observation of their immunological kinship(8)."
Language:English
References:10
Note:Figures
Tables
ASA/CSSA/SSSA Citation (Crop Science-Like - may be incomplete):
Lee, K., and A. H. C. Huang. 1991. Genomic nucleotide sequence of a Brassica napus 20-kilodalton oleosin gene. Plant Physiol. 96(4):p. 1395-1397.
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