Characterization of Oleosins in the Pollen Coat of Brassica oleracea

Ruiter, Rene K.; Eldik, G.J. van; Herpen, Rinus M. A. Van; Schrauwen, J. A. M.; Wullems, G. J.

doi:10.2307/3870448

Cited by 15 publications

(20 citation statements)

References 26 publications

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“…These earlier studies have shown that the oleosin genes are expressed in the florets (24,25) or that the encoded oleosins are present on the pollen surface (19). The expression of the T genes in the florets and the subsequent location of the oleosins on the pollen surface are consistent with the findings in Brassica, that the T oleosins are synthesized in the tapetum and then transferred to the pollen surface (13,14,17,18).…”

Section: Resultssupporting

confidence: 78%

A Novel Group of Oleosins Is Present Inside the Pollen ofArabidopsis

Kim

Hsieh

Ratnayake

et al. 2002

Journal of Biological Chemistry

163

153

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In plants, subcellular triacylglycerol granules in seeds (oil bodies) and floral tapetum (tapetosomes) are stabilized by amphipathic structural protein called oleosin. We hereby report a novel group of oleosins that is present inside the pollen of Arabidopsis thaliana. We have used the conserved sequence of oleosins to locate, via the DNA database, all 16 oleosin genes in the Arabidopsis genome. The oleosin genes can be divided into three groups according to their sequences and tissue-specific expressions, as probed by RNA blot hybridization and reverse transcriptase-PCR. The first group includes eight genes specifically expressed in the floret tapetum. The second group includes five genes specifically expressed in maturing seeds. The third, novel group includes three genes expressed in both maturing seeds and floral microspores, which will become pollen. Transgenic study using the promoter of one of these genes attached to a reporter gene has provided corroborative evidence for the specific expression of the gene in the microspores in the florets. One of the pollen oleosins can be identified by microsequencing and specific immunoblotting. Pollen oleosins synthesized by recombinant bacteria can collaborate with phospholipids in stabilizing reconstituted oil bodies. Thus, pollen has oleosins to stabilize the abundant subcellular oil bodies. Seed oil bodies and floret tapetosomes have been isolated from the miniature Arabidopsis plants, and the success indicates that the organelles can be subjected to future biochemical and genetic studies.

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Section: Resultssupporting

confidence: 78%

A Novel Group of Oleosins Is Present Inside the Pollen ofArabidopsis

Kim

Hsieh

Ratnayake

et al. 2002

Journal of Biological Chemistry

163

153

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“…Most of the other Arabidopsis tapetum oleosins are smaller (10-23 kD), but one has 115 kD. As expected, Brassica has a similar oleosin gene system (Roberts et al, 1994;Ross and Murphy, 1996;Ruiter et al, 1997), and the most active ortholog gene produces a major oleosin of 45 or 48 kD (from the Brassica rapa AA genome or Brassica oleracea CC genome, respectively). Genes encoding the tapetum oleosins have undergone rapid evolution, likely because the constraints for protein structures and thus functions are not high.…”

Section: Oleosins In Tapetum Cells and The Novel Organelle Tapetosomementioning

confidence: 78%

Endoplasmic Reticulum, Oleosins, and Oils in Seeds and Tapetum Cells

2004

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Diverse organisms contain neutral lipids in subcellular particles for food reserves and other purposes. These lipid particles are present in seeds, flowers, pollen and fruit of higher plants, the vegetative and reproductive organs of primitive plants, algae, fungi, nematodes, mammalian glands and brown adipose tissue of mammals, and bacteria. Of all these lipid particles, the oil bodies (OBs) in seeds are the most prominent and best studied.Seeds of most plant species store oils (triacylglycerols [TAGs]) as a food reserve for germination and postgerminative growth. TAGs are present in small subcellular spherical OBs of approximately 1 mm in diameter. Each OB has a matrix of TAGs surrounded by a layer of phospholipids (PLs) and structural proteins termed oleosins. The small size of OBs provides a large surface area per unit TAG, which would facilitate lipase binding and lipolysis during germination. OBs inside the cells of mature seeds or in isolated preparations are remarkably stable and do not aggregate or coalesce. This stability is in contrast to the instability of artificial liposomes made from amphipathic and neutral lipids; the liposomes gradually coalesce after formation. Seed OBs are stable because their surface is shielded by a layer of oleosins. In maturing seeds, TAGs, PLs, and oleosins are synthesized in the endoplasmic reticulum (ER), from which budding OBs are released.Research on seed OBs and oleosins has been reviewed by Huang (1992, and an earlier

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“…Thus, the high levels of change observed in the GRPs are unusual and do not reflect a genomic region with an elevated divergence rate. The most variable feature of these genes is exon 2, which contains abundant overlapping repetitive motifs (Tables 1 and 4); the domain encoded by this exon resides in the pollen coat (16)(17)(18) and likely contacts the stigma.…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, it was not clear whether these rapid changes were a consequence of a particularly dynamic genomic region or instead were specific to GRP genes. We address these questions, assessing changes in the GRPs relative to their genomic neighbors in near (5-8 MY diverged) and more distant relatives (15)(16)(17)(18)(19)(20). This work provides insight into the molecular genetic mechanisms that drive the evolution of genes required for compatible mating and shows that rapid evolution of the GRPs is driven by their repetitive nature.…”

mentioning

confidence: 99%

“…The first exon encodes a lipid-binding oleosin domain, and the second exon encodes a glycine-rich repetitive domain (15). Before the coat is deposited on the pollen surface, the oleosin domain is cleaved, leaving the repetitive domain available for interaction with the stigma (16)(17)(18). Five of the eight A. thaliana GRPs have been detected in the pollen coat (GRP14 and GRP16-GRP19; ref.…”

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confidence: 99%

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Comparisons of pollen coat genes across Brassicaceae species reveal rapid evolution by repeat expansion and diversification

Fiebig

Kimport

Preuss

2004

Proc. Natl. Acad. Sci. U.S.A.

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Reproductive genes and traits evolve rapidly in many organisms, including mollusks, algae, and primates. Previously we demonstrated that a family of glycine-rich pollen surface proteins (GRPs) from Arabidopsis thaliana and Brassica oleracea had diverged substantially, making identification of homologous genes impossible despite a separation of only 20 million years. Here we address the molecular genetic mechanisms behind these changes, sequencing the eight members of the GRP cluster, along with 11 neighboring genes in four related species, Arabidopsis arenosa, Olimarabidopsis pumila, Capsella rubella, and Sisymbrium irio. We found that GRP genes change more rapidly than their neighbors; they are more repetitive and have undergone substantially more insertion͞ deletion events while preserving repeat amino acid composition. Genes flanking the GRP cluster had an average K a͞Ks Ϸ 0.2, indicating strong purifying selection. This ratio rose to Ϸ0.5 in the first GRP exon, indicating relaxed selective constraints. The repetitive nature of the second GRP exon makes alignment difficult; even so, K a͞Ks within the Arabidopsis genus demonstrated an increase that correlated with exon length. We conclude that rapid GRP evolution is primarily due to duplication, deletion, and divergence of repetitive sequences. GRPs may mediate pollen recognition and hydration by female cells, and divergence of these genes could correlate with or even promote speciation. We tested crossspecies interactions, showing that the ability of A. arenosa stigmas to hydrate pollen correlated with GRP divergence and identifying A. arenosa as a model for future studies of pollen recognition.T raits mediating reproduction often undergo rapid evolution, effectively restricting successful mating to a subset of available partners. Rapidly changing genes regulate sperm storage, sperm-egg binding, cell fusion, and spermatogenesis (1). In some cases, a selective advantage promotes divergence (positive selection); in other cases, relaxed selective constraints allow rapid change (neutral selection). On occasion, evolutionary changes are so great, or the species studied are sufficiently divergent, that homologs cannot be identified, and the nature of the selective pressures cannot be assessed (2, 3). Both mathematical models and experimental data demonstrate that rapid changes in sexual traits have the capacity to drive speciation and that the coevolution of genes encoding male and female traits can lead to reproductive isolation (4-9).In some plant families, highly divergent genes limit inbreeding through self-incompatibility; many molecules required for selfpollen recognition have been identified (10, 11). In contrast, few components that allow plants to discriminate interspecific pollen are understood. Identifying molecules that regulate this selective process has agricultural applications; the ability to control gene flow between species would facilitate the creation of new hybrids and the containment of genetically modified varieties. Here, we examined a rapid...

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Characterization of Oleosins in the Pollen Coat of Brassica oleracea

Cited by 15 publications

References 26 publications

A Novel Group of Oleosins Is Present Inside the Pollen ofArabidopsis

A Novel Group of Oleosins Is Present Inside the Pollen ofArabidopsis

Endoplasmic Reticulum, Oleosins, and Oils in Seeds and Tapetum Cells

Comparisons of pollen coat genes across Brassicaceae species reveal rapid evolution by repeat expansion and diversification

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