Sorting of soluble proteins in the secretory pathway of plants

Hadlington, Jane L.; Denecke, Jürgen

doi:10.1016/s1369-5266(00)00114-x

Cited by 93 publications

(83 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…These results suggest that the pathway of PA accumulation may be much more complex than a minimal pathway that involves membranebound transporters transporting monomeric units into a preexisting vacuole. The presence of provacuolar intermediates suggests the need for the complex membrane targeting, and vesicle formation and fusion like those that accompany events in the secretory pathway (Bethke and Jones, 2000;Hadlington and Denecke, 2000).…”

Section: Discussionmentioning

confidence: 99%

Identification and Biochemical Characterization of Mutants in the Proanthocyanidin Pathway in Arabidopsis

et al. 2002

View full text Add to dashboard Cite

Proanthocyanidin (PA), or condensed tannin, is a polymeric flavanol that accumulates in a number of tissues in a wide variety of plants. In Arabidopsis, we found that PA precursors (detected histochemically using OsO 4 ) accumulate in the endothelial cell layer of the seed coat from the two-terminal cell stage of embryo development onwards. To understand how PA is made, we screened mature seed pools of T-DNA-tagged Arabidopsis lines to identify mutants defective in the synthesis of PA and found six tds (tannin-deficient seed) complementation groups defective in PA synthesis. Mutations in these loci disrupt the amount (tds1, tds2, tds3, tds5, and tds6) or location and amount of PA (tds4) in the endothelial cell layer. The PA intermediate epicatechin has been identified in wild type and mutants tds1, tds2, tds3, and tds5 (which do not produce PA) and tds6 (6% of wild-type PA), whereas tds4 (2% of wild-type PA) produces an unidentified dimethylaminocinnamaldehyde-reacting compound, indicating that the mutations may be acting on genes beyond leucoanthocyanidin reductase, the first enzymatic reduction step dedicated to PA synthesis. Two other mutants were identified, an allele of tt7, which has a spotted pattern of PA deposition and produces only 8% of the wild-type level of type PA as propelargonidin, and an allele of tt8 producing no PA. Spotted patterns of PA deposition observed in seed of mutants tds4 and tt7-3 result from altered PA composition and distribution in the cell. Our mutant screen, which was not exhaustive, suggests that the cooperation of many genes is required for successful PA accumulation.Flavonoids are a diverse group of plant secondary metabolites that accumulate in a wide variety of plant tissues and include anthocyanins, flavonols, and the polymeric flavanols known as proanthocyanidins (PAs; Fig. 1). Like their flavanol constituents, PAs are rich in hydrophobic aromatic rings and hydroxyl groups that can interact with biological molecules, particularly proteins, by hydrogen bonds and hydrophobic interactions. Because PAs are polymeric, their interaction with proteins is much stronger than that of monomeric flavanols, presumably because of a "chelate" effect where polymeric PAs can interact with large proteins at multiple sites, increasing the strength of overall molecular interaction as well as minimizing dissociation of the complex once it is formed (Fersht, 1985). This strong interaction of PAs with proteins is probably the basis of their main role in plants and their uses by man.Because PA content of dietary plants can have both positive and negative effects on animal nutrition (Waghorn and Jones, 1989), an important agricultural objective is to manipulate the level of PA in pasture legumes (Morris and Robbins, 1997). When present in bloat-safe forage legumes, PA can bind to and cause the precipitation of dietary proteins, inhibiting the formation of stable proteinaceous foams, thereby preventing bloat (Tanner et al., 1995). Increasing the PA content of pastures such as alfalfa (Medicago s...

show abstract

Section: Discussionmentioning

confidence: 99%

Identification and Biochemical Characterization of Mutants in the Proanthocyanidin Pathway in Arabidopsis

et al. 2002

View full text Add to dashboard Cite

show abstract

“…For this localization, the internal TM helix is required because without it, the MtLecRK1;1 fusion became stuck in the ER, and the MtLecRK7;2 fusion located mainly to the vacuole. These localizations are surprising because the default destination of soluble proteins in the secretory pathway is secretion (Barrieu and Chrispeels, 1999; Hadlington and Denecke, 2000), thus suggesting that the lectin-like domain fusions contain information for retention in the ER (for MtLecRK1;1) or sorting to the vacuole (for MtLecRK7;2). However, such sorting or retention signals could not be identified in the sequences.…”

Section: Discussionmentioning

confidence: 99%

Characterization of Four Lectin-Like Receptor Kinases Expressed in Roots of Medicago truncatula. Structure, Location, Regulation of Expression, and Potential Role in the Symbiosis with Sinorhizobium meliloti

et al. 2003

View full text Add to dashboard Cite

To study the role of LecRK (lectin-like receptor kinase) genes in the legume-rhizobia symbiosis, we have characterized the four Medicago truncatula Gaernt. LecRK genes that are most highly expressed in roots. Three of these genes, MtLecRK7;1, MtLecRK7;2, and MtLecRK7;3, encode proteins most closely related to the Class A LecRKs of Arabidopsis, whereas the protein encoded by the fourth gene, MtLecRK1;1, is most similar to a Class B Arabidopsis LecRK. All four genes show a strongly enhanced root expression, and detailed studies on MtLecRK1;1 and MtLecRK7;2 revealed that the levels of their mRNAs are increased by nitrogen starvation and transiently repressed after either rhizobial inoculation or addition of lipochitooligosaccharidic Nod factors. Studies of the MtLecRK1;1 and MtLecRK7;2 proteins, using green fluorescent protein fusions in transgenic M. truncatula roots, revealed that they are located in the plasma membrane and that their central transmembrane-spanning helix is required for correct sorting. Moreover, their lectin-like domains appear to be highly glycosylated. Of the four proteins, only MtLecRK1;1 shows a high conservation of key residues implicated in monosaccharide binding, and molecular modeling revealed that this protein may be capable of interacting with Nod factors. However, no increase in Nod factor binding was found in roots overexpressing a fusion in which the kinase domain of this protein had been replaced with green fluorescent protein. Roots expressing this fusion protein however showed an increase in nodule number, suggesting that expression of MtLecRK1;1 influences nodulation. The potential role of LecRKs in the legumerhizobia symbiosis is discussed.The lectin-like receptor kinases (LecRKs) are a class of proteins originally described from Arabidopsis (Hervé et al., 1996). They have a structure similar to other plant receptor-like kinases (RLKs; Shiu and Bleecker, 2001;Cock et al., 2002) with an N-terminal targeting signal, a presumably extracellular domain, a single transmembrane (TM)-spanning helix, and a cytosolic kinase domain. The Arabidopsis genome contains over 610 RLKs that have been shown to be monophylogenetic with respect to the kinase domain and most closely related to the fruitfly (Drosophila melanogaster) Pelle and related animal cytoplasmic kinases (Shiu and Bleecker, 2001). In cases in which they have been tested, these kinases have been shown to have specificity for phosphorylation on Ser/Thr residues (Shiu and Bleecker, 2001).The plant RLKs can be grouped into more than 21 structural classes based on their extracellular domains (Shiu and Bleecker, 2001). The LecRKs represent one such class in which the extracellular domain is related to legume lectins. The Arabidopsis genome contains at least 42 LecRK sequences that have been grouped into three classes (A-C) plus an additional nine sequences of related soluble lectins (Barre et al., 2002). Searches in plant databases reveal that LecRK genes are widespread in higher plants, but apart from Arabidopsis (Hervé et al., 1996,...

show abstract

“…A family of BP-80 receptors (Ahmed et al, 1997;Hadlington and Denecke, 2000;Kirsch et al, 1994;Shimada et al, 1997) has been recognised for proteins destined for vacuoles. Indeed, the membranes of PAC in maturing pumpkin seeds are known to contain at least two BP-80-like proteins, PV72/PV82 (Shimada et al, 1997).…”

Section: Discussionmentioning

confidence: 99%

Sequence‐specific, Golgi‐dependent vacuolar targeting of castor bean 2S albumin

et al. 2003

View full text Add to dashboard Cite

SummaryThe targeting of the castor bean (Ricinus communis) 2S albumin precursor has been investigated by expressing cDNA in transformed tobacco (Nicotiana tabacum) leaf cells and by following biosynthesis in the native tissue. Correct targeting in both tissues was accompanied by processing of the precursor. Delivery to vacuoles was sensitive to brefeldin A (BFA) treatment in both tissues and to perturbation of COPII function in tobacco, supporting the view that transport through the Golgi is required. The targeting signal for this Golgi-dependent routing lies within the propeptide of the ®rst heterodimer of proalbumin. This propeptide directed a normally secreted reporter protein to the vacuoles of tobacco cells in a Golgidependent manner in vivo, unless a critical Leu residue was mutated, supporting the view that a sequencespeci®c signal was needed to target a seed storage protein to the vacuoles of a vegetative cell.

show abstract

Sorting of soluble proteins in the secretory pathway of plants

Cited by 93 publications

References 57 publications

Identification and Biochemical Characterization of Mutants in the Proanthocyanidin Pathway in Arabidopsis

Identification and Biochemical Characterization of Mutants in the Proanthocyanidin Pathway in Arabidopsis

Characterization of Four Lectin-Like Receptor Kinases Expressed in Roots of Medicago truncatula. Structure, Location, Regulation of Expression, and Potential Role in the Symbiosis with Sinorhizobium meliloti

Sequence‐specific, Golgi‐dependent vacuolar targeting of castor bean 2S albumin

Contact Info

Product

Resources

About