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Fungal infection can affect crop yield. A plant protein found to counter fungal-induced interference with host metabolism illuminates antifungal defences and mechanisms that inhibit metabolic enzymes.A defence mechanism thwarts fungal interference with host metabolism., Author(s): Mary C. WildermuthAuthor Affiliations:Plants fight fungi using kiwellin proteins The authors studied infection of maize by the fungus Ustilago maydis , which can cause corn smut disease and results [...]

Abstract: Copines are evolutionarily conserved calcium-dependent membrane-binding proteins with potentially critical biological functions. In plants, the function of these proteins has not been analyzed except for in Arabidopsis thaliana where [...]

Molecular evolution of large protein families in closely related species can provide useful insights on structural functional relationships. Phylogenetic analysis of the grass-specific group II HKT genes identified two distinct [...]

Two-pore channels (TPCs) comprise a subfamily (TPC1-3) of eukaryotic voltage- and ligand-gated cation channels (1,2) with two non-equivalent tandem pore-forming subunits that dimerize to form quasi-tetramers. Found in vacuolar (3) [...]

Posttranslational modification is an important element in circadian clock function from cyanobacteria through plants and mammals. For example, a number of key clock components are phosphorylated and thereby marked for subsequent ubiquitination and degradation. Through forward genetic analysis we demonstrate that protein arginine methyltransferase 5 (PRMTS; At4g31120) is a critical determinant of circadian period in Arabidopsis. PRMT5 is coregulated with a set of 1,253 genes that shows alterations in phase of expression in response to entrainment to thermocycles versus photocycles in constant temperature. PRMT5 encodes a type II protein arginine methyltransferase that catalyzes the symmetric dimethylation of arginine residues (Rsme2). Rsme2 modification has been observed in many taxa, and targets include histones, components of the transcription complex, and components of the spliceosome. Neither arginine methylation nor PRMT5 has been implicated previously in circadian clock function, but the period lengthening associated with mutational disruption of prmt5 indicates that Rsme2 is a decoration important for the Arabidopsis clock and possibly for clocks in general. circadian rhythms | circadian clock | luciferase doi/ 10.1073/pnas.1011987107

Plants are unique in their ability to store proteins in specialized protein storage vacuoles (PSVs) within seeds and vegetative tissues. Although plants use PSV proteins during germination, before photosynthesis is fully functional, the roles of PSVs in adult vegetative tissues are not understood. Trafficking pathways to PSVs and lytic vacuoles appear to be distinct. Lyric vacuoles are analogous evolutionarily to yeast and mammalian lysosomes. However, it is unclear whether trafficking to PSVs has any analogy to pathways in yeast or mammals, nor is PSV ultrastructure known in Arabidopsis vegetative tissue. Therefore, alternative approaches are required to identify components of this pathway. Here, we show that an Arabidopsis thaliana mutant that disrupts PSV trafficking identified TERMINAL FLOWER 1 (TFL1), a shoot meristem identity gene. The tfl1-19/mtv5 (for 'modified traffic to the vacuole') mutant is specifically defective in trafficking of proteins to the PSV. TFL1 localizes to endomembrane compartments and colocalizes with the putative [delta]-subunit of the AP-3 adapter complex. Our results suggest a developmental role for the PSV in vegetative tissues. protein trafficking | vegetative tissue | adaptin

The GINS complex, which contains the four subunits SId5, Psf1, Psf2, and Psf3, is essential for both the initiation and progression of DNA replication in eukaryotes. GINS associates with the MCM2-7 complex and Cdc45 to activate the eukaryotic minichromosome maintenance helicase. It also appears to interact with and stimulate the polymerase activities of DNA polymerase [epsilon] and the DNA polymerase [alpha]-primase complex. To further understand the functional role of GINS, we determined the crystal structure of the full-length human GINS heterotetramer. Each of the four subunits has a major domain composed of an s-helical bundle-like structure. With the exception of Psf1, each of the other subunits has a small domain containing a three-stranded [beta]-sheet core. Each full-length protein in the crystal has unstructured regions that are all located on the surface of GINS and are probably involved in its interaction with other replication factors. The four subunits contact each other mainly through [alpha]-helices to form a ring-like tetramer with a central pore. This pore is partially plugged by a 16-residue peptide from the Psf3 N terminus, which is unique to some eukaryotic Psf3 proteins and is not required for tetramer formation. Removal of these N-terminal 16 residues of Psf3 from the GINS tetramer increases the opening of the pore by 80%, suggesting a mechanism by which accessibility to the pore may be regulated. The structural data presented here indicate that the GINS tetramer is a highly stable complex with multiple flexible surface regions. Cdc45 | DNA helicase | minichromosome maintenance complex | DNA polymerase

Urinary calcium excretion is strongly related to net renal acid excretion. The catabolism of dietary protein generates ammonium ion and sulfates from sulfur-containing amino acids. Bone citrate and carbonate are mobilized to neutralize these acids, so urinary calcium increases when dietary protein increases. Common plant proteins such as soy, corn, wheat and rice have similar total S per g of protein as eggs, milk and muscle from meat, poultry and fish. Therefore increasing intake of purified proteins from either animal or plant sources similarly increases urinary calcium. The effects of a protein on urinary calcium and bone metabolism are modified by other nutrients found in that protein food source. For example, the high amount of calcium in milk compensates for urinary calcium losses generated by milk protein. Similarly, the high potassium levels of plant protein foods, such as legumes and grains, will decrease urinary calcium. The hypocalciuric effect of the high phosphate associated with the amino acids of meat at least partially offsets the hypercalciuric effect of the protein. Other food and dietary constituents such as vitamin D, isoflavones in soy, caffeine and added salt also have effects on bone health. Many of these other components are considered in the potential renal acid load of a food or diet, which predicts its effect on urinary acid and thus calcium. 'Excess' dietary protein from either animal or plant proteins may be detrimental to bone health, but its effect will be modified by other nutrients in the food and total diet. KEY WORDS: * protein * bone * calcium * plant * animal

The characteristics of a phosphoprotein with a relative electrophoretic mobility of 12 kDa have been unknown during two decades of studies on redox-dependent protein phosphorylation in plant photosynthetic membranes. Digestion of this protein from spinach thylakoid membranes with trypsin and subsequent tandem nanospray-quadrupole-time-of-flight mass spectrometry of the peptides revealed a protein sequence that did not correspond to any previously known protein. Sequencing of the corresponding cDNA uncovered a gene for a precursor protein with a transit peptide followed by a strongly basic mature protein with a molecular mass of 8,640 Da. Genes encoding homologous proteins were found on chromosome 3 of Arabidopsis and rice as well as in ESTs from 20 different plant species, but not from any other organisms. The protein can be released from the membrane with high salt and is also partially released in response to light-induced phosphorylation of thylakoids, in contrast to all other known thylakoid phosphoproteins, which are integral to the membrane. On the basis of its properties, this plant-specific protein is named thylakoid soluble phosphoprotein of 9 kDa (TSP9). Mass spectrometric analyses revealed the existence of non-, mono-, di-, and triphosphorylated forms of TSP9 and phosphorylation of three distinct threonine residues in the central part of the protein. The phosphorylation and release of TSP9 from the photosynthetic membrane on illumination favor participation of this basic protein in cell signaling and regulation of plant gene expression in response to changing light conditions.

EID1, an F-box protein is discussed relative to phytochrome A-specific light signaling. Plants have evolved specific photoreceptors called phytochromes and even though the spectral properties of all phytochromes are very alike, they have distinct action modes. Likely EID1 acts by targeting activated components of the phyA signaling pathway to ubiquitin-dependent proteolysis.

A new member of the GRAS protein family, PAT1, has a role in phytochrome A (phy A) signal transduction. PAT1 acts in a dominant negative way to inhibit phyA signaling. A new Arabidopsis mutant, phytochrome A signal tranduction (pat)1-1, which shows greatly reduced responses in continuous far-red (FR) light, was identified. It is disrupted early in phyA signal transduction.

Several type III effector proteins from Pseudomonas syringae have been shown to be targeted to the host plasma membrane. In the same study it was shown that efficient membrane association enhances function. Plant innate immune systems evolved disease resistance genes to recognize some type III effectors, Avirulence (Avr) proteins.

The chromophore-binding properties of the higher plant light-harvesting protein CP29 have been studied by using site-directed mutagenesis of pigment-binding residues. Overexpression of the apoproteins in bacteria was followed by reconstitution in vitro with purified pigments, thus obtaining a family of mutant CP29 proteins lacking individual chromophore-binding sites. Biochemical characterization allowed identification of the eight porphyrins and two xanthophyll-binding sites. It is shown that the four porphyrin-binding sites (A1, A2, A4, and A5) situated in the central, twofold-symmetrical domain of the protein are selective for Chl-a, whereas the four peripheral sites (A3, B3, B5, and B6) have mixed Chl-a-Chl-b specificity. Within a site, porphyrin coordination by glutamine increases affinity for Chl-b as compared with glutamate. Xanthophyll site L1 is occupied by lutein, whereas site L2 can bind violaxanthin or neoxanthin. The protein is relatively stable when site L2 site is empty, suggesting that xanthophylls can be exchanged during operation of xanthophyll cycle-dependent photoprotection mechanism. Differential absorption spectroscopy allowed determination of transition energy levels for individual chromophores, thus opening the way to calculation of energy-transfer rates between Chl in higher plant antenna proteins.

The Arabidopsis thaliana NPR1 has been shown to be a key regulator of gene expression during the onset of a plant disease-resistance response known as systemic acquired resistance. The npr1 mutant plants fail to respond to systemic acquired resistance-inducing signals such as salicylic acid (SA), or express SA-induced pathogenesis-related (PR) genes. Using NPR1 as bait in a yeast two-hybrid screen, we identified a subclass of transcription factors in the basic leucine zipper protein family (AHBP-1b and TGA6) and showed that they interact specifically in yeast and in vitro with NPR1. Point mutations that abolish the NPR1 function in A. thaliana also impair the interactions between NPR1 and the transcription factors in the yeast two-hybrid assay. Furthermore, a gel mobility shift assay showed that the purified transcription factor protein, AHBP-1b, binds specifically to an SA-responsive promoter element of the A. thaliana PR-1 gene. These data suggest that NPR1 may regulate PR-1 gene expression by interacting with a subclass of basic leucine zipper protein transcription factors.

Plant cell vacuoles may have either storage or degradative functions. Vegetative storage proteins (VSPs) are synthesized in response to wounding and to developmental switches that affect carbon and nitrogen sinks. Here we show that VSPs are stored in a unique type of vacuole that is derived from degradative central vacuoles coincident with insertion of a new tonoplast intrinsic protein (TIP), [Delta]-TIP, into their membranes. This finding demonstrates a tight coupling between the presence of [Delta]-TIP and acquisition of a specialized storage function and indicates that TIP isoforms may determine vacuole identity.

The mechanisms involved in the posttranslational targeting of membrane proteins are not well understood. The light-harvesting chlorophyll proteins (LHCP) of the thylakoid membrane are a large family of hydrophobic proteins that are targeted in this manner. They are synthesized in the cytoplasm, translocated across the chloroplast envelope membranes into the stroma, bound by a stromal factor to form a soluble intermediate, 'transit complex', and then integrated into the thylakoid membrane by a GTP dependent reaction. Signal recognition particle (SRP), a cytoplasmic ribonucleoprotein, is known to mediate the GTP dependent cotranslational targeting of proteins to the endoplasmic reticulum. We show that chloroplasts contain an SRP consisting of, cpSRP54, a homologue of SRP54 and a previously undescribed 43-kDa polypeptide (cpSRP43) instead of an RNA. We demonstrate that both subunits of cpSRP are required for the formation of the transit complex with LHCP. Furthermore, cpSRP54, cpSRP43, and LHCP are sufficient to form a complex that appears to be identical to authentic transit complex. We also show that the complex formed between LHCP and cpSRP, together with an additional soluble factor(s) are required for the proper integration of LHCP into the thylakoid membrane. It appears that the expanded role of cpSRP in posttranslational targeting of LHCP has arisen through the evolution of the 43-kDa protein.

The protein oxyR acts as a global regulator for peroxide stress response and an understanding of it could play an important part in plant-microbe interactions. An oxyR gene mutant from the microbe Xanthomonas campestris was isolated and characterized. The gene was found to have a unique organization and transcriptional regulation. Some of the results indicate that oxyR mutants accumulate both H2O2 and organic peroxides that are consistent with the observation that ocyR mutants in Escherichia coli have higher levels of peroxides than a wild-type strain.

The alpha-TIP (tonoplast intrinsic proteins) and the TIP-Ma27 antibodies defines the functional implications of the compartments of protein vacuoles. The alpha-TIP defines a compartment for protecting storage-type proteins from enzyme degradation. The TIP-Ma27 defines a separate acidic lytic compartment. Barley lectin vacuolar proteins were detected in alpha-TIP vacuoles while aleurain proteins were contained in TIP-Ma27. This mechanism indicates a receptor-mediated pathway for two separate vacuolar compartments.

The movement of proteins into the peroxisomal lumen involves the recognition of a peroxisomal targeting signal (PTS) by its cognate receptors. The receptors target the proteins to the translocation pathway. Proteins without a PTS associate with the PTS-containing proteins to penetrate the peroxisome. The PTS1 receptors of yeast and humans are structurally similar. In human peroxisomal diseases, the translocation of proteins is defective. Peroxisomes are able to translocate oligomeric proteins unlike the mitochondria and chloroplast.

Pollen tube growth is directed and physically and chemically assisted by pistil tissues. Important components of pollination involve the extracellular matrix of pollen and pistil, pollen cytoskeleton, signal transduction molecules, and mechanisms of pollen tube guidance. Extracellular matrix transmitting tissue-specific arabinogalactan proteins, such as TTS protein in tobacco, have been found to induce tube growth and attract pollen tubes in vitro. During pollination several physiological, molecular and developmental responses occur in pistil tissues which help in pollen germination, tube growth and pollen tube entrance in the embryo sacs.

The kinetic behavior of orally ingested 18O-cholesterol was compared with that of orally ingested 13[C.sub.5]-cholesterol in two normocholesterolemic men and the hypocholesterolemic effect of soy protein was demonstrated in 12 hypercholesterolemic men. Our results indicated no difference in the metabolism of orally ingested 18O- and 13[C.sub.5]-cholesterol. The use of 18O-cholesterol and 13[C.sub.5]-cholesterol also allowed simultaneous estimation of fractional rates of cholesterol synthesis using the 2[H.sub.2]O method, which were calculated to be 5.76 and 8.17%/d for the two normocholesterolemic subjects. The percent reduction in plasma cholesterol levels was found to be greater when the hypercholesterolemic men were placed on a soy protein diet than on an animal protein diet. INDEXING KEY WORDS: cholesterol; synthesis; absorption; human; stable isotopes; hypocholesterolemia; soy protein

A large body of literature indicates that protein from soybeans reduces blood cholesterol concentrations in experimental animals as well as in humans. The mechanism and component of soy responsible has not been established fully. Some suggest that when soy protein is fed, cholesterol absorption and/or bile acid reabsorption is impaired. This is observed in some animal species, such as rabbits and rats, but not in humans nor when amino acids replace intact soy protein. Others propose that changes in endocrine status, such as alteration in insulin:glucagon ratio and thyroid hormone concentrations, are responsible. The metabolic changes that have been observed on soy protein feeding in a variety of animal models, and in some cases humans, include increased cholesterol synthesis, increased bile acid synthesis (or fecal bile acid excretion), increased apolipoprotein B or E receptor activity and decreased hepatic lipoprotein secretion and cholesterol content, which are associated with an increased clearance of cholesterol from the blood. One hypothesis suggests amino acid composition or proportionality of soy causes changes in cholesterol metabolism (possibly via the endocrine system). Others have proposed that nonprotein components (such as saponins, fiber, phytic acid, minerals and the isoflavones) associated with soy protein affect cholesterol metabolism either directly or indirectly. INDEXING KEY WORDS: soy protein; cholesterol; saponins; phytic acid; isoflavones; trypsin inhibitor

To study the mechanism of dyslipoproteinemia, lipoproteins [very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL)] were isolated from stroke patients and healthy persons by ultracentrifugation. Lipoproteins were dialyzed into copper dichloride solution to study the effects of soycreme administration on lipoprotein peroxidation. Blood was drawn from 15 patients with cerebral thrombosis who were not administered soycreme, 10 patients with cerebral thrombosis who were administered soycreme and 11 healthy persons. The lipoproteins were dialyzed into 5 mol/l copper dichloride solution for various lengths of time, and then lipid constituents in the lipoproteins were measured by thin-layer chromatography. After the dialysis, percentages of cholesteryl ester and triglyceride in various lipoproteins decreased significantly (P < 0.05 or 0.01) in both patient groups and in healthy persons. Spot (X.sub.1) was found between triglyceride and free fatty acid on the thin-layer chromatography, and spot (X.sub.2) was located between free fatty acid and free cholesterol after dialysis. Spots (X.sub.1) and (X.sub.2) reflect lipoprotein peroxidation. Percentages of these spots were higher in VLDL, LDL and HDL in the patient groups than in the healthy subjects. Soycreme administration suppressed the appearance of spots (X.sub.1) and (X.sub.2). Furthermore, blood cholesterol concentrations were reduced by the administration of soy protein. Thus, soy may be useful in the prevention and/or treatment of atherosclerosis. INDEXING KEY WORDS: soy protein; peroxidized lipoprotein; peroxidized low density lipoprotein; protection of peroxidized lipoprotein

The effects of dietary protein on plasma cholesterol concentrations are well documented: animal proteins (casein) are hypercholesterolemic compared with plant proteins (soy protein). Although this effect of protein source on plasma cholesterol has been shown in many species, the mechanism is not completely understood. This paper reviews the relationship between dietary protein source and plasma thyroxine concentration. The basic premise is that feeding soy protein lowers plasma cholesterol concentration by causing an increase in plasma thyroxine concentrations. The metabolic changes involving cholesterol that occur when soy protein is fed are discussed. These changes are consistent with changes induced by elevating thyroxine. Data are presented from animal studies showing that feeding soy protein to laboratory animals consistently elevates plasma thyroxine concentrations. Furthermore, this elevation in plasma thyroxine concentrations precedes the change in plasma cholesterol concentrations: a necessary requirement for hypothesizing a causative effect. Possible mechanisms as to how a dietary protein source affects plasma thyroxine are also presented. INDEXING KEY WORDS: soy protein; casein; thyroxine; cholesterol

The T-urf13 gene, which encodes the URF13 protein in the mitochondria of male-sterile maize carrying the Texas cytoplasm (cms-T), was cloned in a baculovirus expression system. URF13 interacts with fungal T toxin or methomyl to permeabilize the plasma membranes of insect cells. In addition, URF13 is toxic when expressed in either cell cultures or insect larvae, even without T toxin or methomyl. The results indicate that male sterility and toxin sensitivity in cms-T maize may be due to independent mechanisms.

Developing wheat endosperm from early to mid-maturation was subjected to ultrastructural analysis to determine the route of wheat storage proteins to the protein bodies inside vacuoles. The results showed that most wheat storage proteins are formed within rough endoplasmic reticulum. They are transported as intact protein bodies to the vacuoles via a novel route which does not include the Golgi apparatus.

In higher plants the production of starch is orchestrated by chloroplast-localized biosynthetic enzymes, namely starch synthases, ADP-glucose pyrophosphorylase, and starch branching and debranching enzymes. Diurnal regulation of these enzymes, as well as starch-degrading enzymes, influences both the levels and composition of starch, and is dependent in some instances upon phosphorylation-linked regulation. The phosphoserine/threonine-binding 14-3-3 proteins participate in environmentally responsive phosphorylation-related regulatory functions in plants, and as such are potentially involved in starch regulation. We report here that reduction of the subgroup of Arabidopsis 14-3-3 proteins by antisense technology resulted in a 2- to 4-fold increase in leaf starch accumulation. Dark-governed starch breakdown was unaffected in these 'antisense plants,' indicating an unaltered starch-degradation pathway and suggesting a role for 14-3-3 proteins in regulation of starch synthesis. Absorption spectra and gelatinization properties indicate that the starch from the antisense plants has an altered branched glucan composition. Biochemical characterization of protease-treated starch granules from both Arabidopsis leaves and maize endosperm showed that 14-3-3 proteins are internal intrinsic granule proteins. These data suggest a direct role for 14-3-3 proteins in starch accumulation. The starch synthase III family is a possible target for 14-3-3 protein regulation because, uniquely among plastid-localized starch metabolic enzymes, all members of the family contain the conserved 14-3-3 protein phosphoserine/threonine-binding consensus motif. This possibility is strengthened by immunocapture using antibodies to DU1, a maize starch synthase III family member, and direct interaction with biotinylated 14-3-3 protein, both of which demonstrated an association between 14-3-3 proteins and DU1 or DU1-like proteins.

Arabinogalactan proteins (AGPs) are proteoglycans of higher plants, which are implicated in growth and development. We recently have shown that two AGPs, NaAGP1 (from Nicotiana alata styles) and PcAGP1 (from Pyrus communis cell suspension culture), are modified by the addition of a glycosylphosphatidylinositol (GPI) anchor. However, paradoxically, both AGPs were buffer soluble rather than membrane associated. We now show that pear suspension cultured cells also contain membrane-bound GPI-anchored AGPs. This GPI anchor has the minimal core oligosaccharide structure, D-Man[Alpha](1-2)-D-Man[Alpha](1-6)-D-Man[Alpha](1-4)-D-GIcN-inositol, which is consistent with those found in animals, protozoa, and yeast, but with a partial [Beta](1-4)-galactosyl substitution of the 6-1inked Man residue, and has a phosphoceramide lipid composed primarily of phytosphingosine and tetracosanoic acid. The secreted form of PcAGP1 contains a truncated GPI lacking the phosphoceramide moiety, suggesting that it is released from the membrane by the action of a phospholipase D. The implications of these findings are discussed in relation to the potential mechanisms by which GPI-anchored AGPs may be involved in signal transduction pathways.

Isoflavones are similar to estrogen in structural and functional properties. However, there are still arguments that the similarity might cause sexual dimorphic characteristics in males. To investigate the five-generation effects of isoflavones consumption on sexual dimorphic behavior and maturation in Sprague-Dawley rats, 24 males and 24 females [first generation (Gl)] were randomly divided into four groups: control (CON, no isoflavones) and three commercially available regimens; cow's milk (CM, no isoflavones), nutritional-modified soymilk and cow's milk mixture (MSC, 15 mg/d isoflavones), and soymilk (SM, 24 mg/d isoflavones). The first offspring of each generation were fed each regimen after weaning, and this was continued through the fifth generation (G2-G5). Spatial memory and open-field activity was measured by the Morris water-maze test and by the open-field activity test using video-tracking system, respectively; body weight increase of dams and pups and reproductive outcome were measured; and the histomorphology of sex organ-related tissues was examined. SPSS for Windows was used for data description and Kruskal-Wallis tests. No offspring were in the CM group because of low hematocrit levels. The exploratory action (rearing and learning) of CON males was less frequent than that of females. The learning activity (G2, 18.5, P = 0.04; G3, 11.2, P = 0.03; G4, 10.7, P = 0.02) of SM males was more frequent than CON and MSC. The higher maternal body weight increase during pregnancy (P = 0.055) and longer first parturition day (P= 0.086) were shown in MSC over generations. Litter size was significantly higher in G2 MSC (12.9, P = 0.02) than in CON (8.42) and SM (8.57). The body weight increase of pups seemed to be low in SM and MSC, but no differences were noted in the survival rate and sex of pups. Other variables will be analyzed and discussed. The data assessed so far revealed no significant sexual dimorphic behavior and maturation differences over generations except the learning frequency of SM males.

Tetrapyrroles such as chlorophylls and bacteriochlorophylls play a fundamental role in the energy absorption and transduction activities of photosynthetic organisms. Because of these molecules, however, photosynthetic organisms are also prone to photooxidative damage. They had to evolve highly efficient strategies to control tetrapyrrole biosynthesis and to prevent the accumulation of free intermediates that potentially are extremely destructive when illuminated. In higher plants, the metabolic flow of tetrapyrrole biosynthesis is regulated at the step of [Delta]-aminolevulinic acid synthesis. This regulation previously has been attributed to feedback control of Glu tRNA reductase, the first enzyme committed to tetrapyrrole biosynthesis, by heme. With the recent discovery of chlorophyll intermediates acting as signals that control both nuclear gene activities and tetrapyrrole biosynthesis, it seems likely that heme is not the only regulator of this pathway. A genetic approach was used to identify additional factors involved in the control of tetrapyrrole biosynthesis. In Arabidopsis thaliana, we have found a negative regulator of tetrapyrrole biosynthesis, FLU, which operates independently of heme and seems to selectively affect only the M[g.sup.2+] branch of tetrapyrrole biosynthesis. The identity of this protein was established by map-based cloning and sequencing the FLU gene. FLU is a nuclear-encoded plastid protein that, after import and processing, becomes tightly associated with plastid membranes. It is unrelated to any of the enzymes known to be involved in tetrapyrrole biosynthesis. Its predicted features suggest that FLU mediates its regulatory effect through interaction with enzymes involved in chlorophyll synthesis.

Andrea Spear* Heavy metals can accumulate in plants and are often complexed with soluble peptides, derivatives of glutathione (GSH), called phytochelatins ranging in size from 3,000-10,000 MW. We called this [...]