Filament formation in vitro of a sieve tube protein from Cucurbita maxima and Cucurbita pepo

Kleinig, Hans; Thönes, Jochen; Dörr, Inge; Kollmann, Rainer

doi:10.1007/bf00388377

Cited by 47 publications

(23 citation statements)

References 14 publications

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“…The first P-proteins to be analyzed in detail were PP1 and the 24-kDa phloem lectin PP2, which are the main components of C. maxima exudates and are thought to be covalently linked (15). Cucurbits have long served as model plants in phloem research because their large phloem cells are well suited for microscopy and because they bleed profusely after injury, allowing the direct harvest of phloem exudates (51). Electron microscopy revealed the presence of P-protein filaments in C. maxima exudates (52); these filaments were assumed to be composed of PP1, although the ability of the protein to form stable structural components in vivo was debated because of its high turnover rate (53).…”

Section: Distribution Of Seo Genes Reveals the Uniformity Of P-proteinsmentioning

confidence: 99%

Sieve element occlusion(SEO) genes encode structural phloem proteins involved in wound sealing of the phloem

Ernst

Jekat

Zielonka

et al. 2012

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

100

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The sieve element occlusion (SEO) gene family originally was delimited to genes encoding structural components of forisomes, which are specialized crystalloid phloem proteins found solely in the Fabaceae. More recently, SEO genes discovered in various nonFabaceae plants were proposed to encode the common phloem proteins (P-proteins) that plug sieve plates after wounding. We carried out a comprehensive characterization of two tobacco (Nicotiana tabacum) SEO genes (NtSEO). Reporter genes controlled by the NtSEO promoters were expressed specifically in immature sieve elements, and GFP-SEO fusion proteins formed parietal agglomerates in intact sieve elements as well as sieve plate plugs after wounding. NtSEO proteins with and without fluorescent protein tags formed agglomerates similar in structure to native Pprotein bodies when transiently coexpressed in Nicotiana benthamiana, and the analysis of these protein complexes by electron microscopy revealed ultrastructural features resembling those of native P-proteins. NtSEO-RNA interference lines were essentially devoid of P-protein structures and lost photoassimilates more rapidly after injury than control plants, thus confirming the role of P-proteins in sieve tube sealing. We therefore provide direct evidence that SEO genes in tobacco encode P-protein subunits that affect translocation. We also found that peptides recently identified in fascicular phloem P-protein plugs from squash (Cucurbita maxima) represent cucurbit members of the SEO family. Our results therefore suggest a common evolutionary origin for P-proteins found in the sieve elements of all dicotyledonous plants and demonstrate the exceptional status of extrafascicular P-proteins in cucurbits.photoassimilate transport | wound response | exudation | phloem protein 1

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Section: Distribution Of Seo Genes Reveals the Uniformity Of P-proteinsmentioning

confidence: 99%

Sieve element occlusion(SEO) genes encode structural phloem proteins involved in wound sealing of the phloem

Ernst

Jekat

Zielonka

et al. 2012

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

100

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“…In Cucurbita spp., two predominant P-proteins, the phloem filament protein or phloem protein 1 (PP1) and the phloem lectin or phloem protein 2 (PP2), have been associated with the structural P-protein filaments (Cronshaw and Sabnis, 1990). In vitro studies have shown PP1 to be the primary structural protein capable of forming P-protein filaments (Kleinig et al, 1975), and PP2, a dimeric poly-GlcNAc-binding lectin, to be covalently linked to the filaments by disulfide bridges (Read and Northcote, 1983). The expression of PP1 and PP2 is developmentally related to defined stages of phloem differentiation .…”

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confidence: 99%

Diversity of the Superfamily of Phloem Lectins (Phloem Protein 2) in Angiosperms

et al. 2003

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Phloem protein 2 (PP2) is one of the most abundant and enigmatic proteins in the phloem sap. Although thought to be associated with structural P-protein, PP2 is translocated in the assimilate stream where its lectin activity or RNA-binding properties can exert effects over long distances. Analyzing the diversity of these proteins in vascular plants led to the identification ofPP2-like genes in species from 17 angiosperm and gymnosperm genera. This wide distribution of PP2 genes in the plant kingdom indicates that they are ancient and common in vascular plants. Their presence in cereals and gymnosperms, both of which lack structural P-protein, also supports a wider role for these proteins. Within this superfamily, PP2 proteins have considerable size polymorphism. This is attributable to variability in the length of the amino terminus that extends from a highly conserved domain. The conserved PP2 domain was identified in the proteins encoded by six genes from several cucurbits, celery (Apium graveolens), and Arabidopsis that are specifically expressed in the sieve element-companion cell complex. The acquisition of additional modular domains in the amino-terminal extensions of other PP2-like proteins could reflect divergence from its phloem function.

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“…In Cucurbita two phloem-specific proteins, termed PP1 and PP2, account for most of the exudate protein (19). It has been proposed that one or both proteins form the P-protein filaments seen in sieve elements by electron microscopy (13,19). Although the proteins have similar amino acid compositions (19,26,27), they differ in mol wt and other properties: PP1 has a…”

mentioning

confidence: 99%

“…molecule (20), and forms filaments upon oxidation (13). PP2 is a dimer of 48,000 Mr with six cysteine residues (20), and is a lectin (1,23).…”

mentioning

confidence: 99%

The Regulation of Gelation of Phloem Exudate from Cucurbita Fruit by Dilution, Glutathione, and Glutathione Reductase

Alosi¹,

Melroy²,

Park³

1988

Plant Physiol.

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Filament formation in vitro of a sieve tube protein from Cucurbita maxima and Cucurbita pepo

Cited by 47 publications

References 14 publications

Sieve element occlusion(SEO) genes encode structural phloem proteins involved in wound sealing of the phloem

Sieve element occlusion(SEO) genes encode structural phloem proteins involved in wound sealing of the phloem

Diversity of the Superfamily of Phloem Lectins (Phloem Protein 2) in Angiosperms

The Regulation of Gelation of Phloem Exudate from Cucurbita Fruit by Dilution, Glutathione, and Glutathione Reductase

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