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Fucosyltransferase and the biosynthesis of storage and structural xyloglucan in developing nasturtium fruits

Young, developing fruits of nasturtium (Tropaeolum majus L.) accumulate large deposits of nonfucosylated xyloglucan (XG) in periplasmic spaces of cotyledon cells. This "storage" XG can be fucosylated by a nasturtium transferase in vitro, but this does not happen in vivo, even as a transitory signal for secretion. The only XG that is clearly fucosylated in these fruits is the structural fraction (approximately 1% total) that is bound to cellulose in growing primary walls. The two fucosylated subunits that are formed in vitro are identical to those found in structural XG in vivo. The yield of XG-fucosyltransferase activity from membrane fractions is highest per unit fresh weight in the youngest fruits, especially in dissected cotyledons, but declines when storage XG is forming. A block appears to develop in the secretory machinery of young cotyledon cells between sites that galactosylate and those that fucosylate nascent XG. After extensive galactosylation, XG traffic is diverted to the periplasm without fucosylation. The primary walls buried beneath accretions of storage XG eventually swell and lose cohesion, probably because they continue to extend without incorporating components such as fucosylated XG that are needed to maintain wall integrity.

Journal Article↗

[Changes in antioxidative system and cell ultrastructure in the fruit peels of apple during sunburn development].

Fruits from 6-year-old apple trees (Malus domestica Borkh cv. Fuji) were used as materials to test the changes of antioxidative system and cell ultrastructure of fruit peels during sunburn development. Fruit sunburn appeared in mid July, 2002. The process of apple fruit sunburn was divided into three phases (0 degrees : control): 1 degrees : bleaching, 2 degrees : brownness, and 3 degrees : necrosis. Fuji apple fruits in different sunburn state were picked. Phenolic compounds, membrane protective enzymes (SOD, POD, PPO, CAT), cell membrane lipid peroxidation and cell ultrastructure in fruit peel were studied. The result showed that the degree of cell membrane lipid peroxidation enhanced along with development of sunburn. The activity of membrane protective enzymes also increased remarkably. However, the cell structure kept its integrity, except some organelles which partly disassembled, and cytoplasm and vacuoles became enriched with electron-dense substances while fruit peels became pale. As peel became brown, chlorogenic acid, quercetin, rutin and myricetin accumulated, and cells of outer layers of the epidermis collapsed correspondingly, cell wall became thicker. It is suggested that changes in both cell ultrastructure and antioxidative system confirm that physiological state of fruit peels becomes disordered during sunburn development.

Antioxidants↗

Identification of a gene involved in polysaccharide export as a transcription target of FruA, an essential factor for Myxococcus xanthus development.

Fruiting body development in Myxococcus xanthus is a multicellular event that is coordinated by exchanging intercellular signals. FruA is a transcription factor essential for fruiting body development and is thought to play a key role in the C-signal pathway. Here we present the first identification of a gene regulated by FruA. The gene was isolated from a genomic library via in vitro selection in a DNA binding assay by using the DNA-binding domain of FruA tagged with His(8) at the C-terminal end (FruA-DBD-H(8)). The gene, named fdgA (FruA-dependent gene A), encodes a protein homologous to the outer-membrane auxiliary family protein involved in the polysaccharide export system. FruA-DBD-H(8) bound the upstream promoter region of the fdgA gene from nucleotide -89 to nucleotide -64 with respect to the transcription initiation site, which was required for the induction of fdgA expression during development. fdgA mRNA induced during development was absent in a fruA deletion strain. The deletion of fdgA resulted in defective fruiting body formation and reduced sporulation efficiency (1% that of the parent strain). Moreover, FruA was required for the developmental expression of sasA, which is also involved in the biosynthesis of the lipopolysaccharide O-antigen and is required for fruiting body development. Furthermore, the expression of both fdgA and sasA was partially dependent on the C-signal. These findings expand our understanding of the signal transduction pathway mediated by FruA during development in M. xanthus.

Amino Acid Sequence↗

The Assimilation of Ureides in Shoot Tissues of Soybeans : 1. CHANGES IN ALLANTOINASE ACTIVITY AND UREIDE CONTENTS OF LEAVES AND FRUITS.

The ureides, allantoin and allantoic acid, are major forms of N transported from nodules to shoots in soybeans (Merr.). Little is known about the occurrence, localization, or properties of the enzymes involved in the assimilation of ureides in shoot tissues. We have examined the capacity of the shoot tissues to assimilate allantoin via allantoinase (EC 3.5.2.5) during leaf and fruit development in nodulated soybeans. Specific activity of allantoinase in leaves peaked during pod formation and early seed filling. In developing fruits allantoinase activity in the seeds was 2 to 4 times that in the pods when expressed on a fresh weight or organ basis. In seeds, the embryos contained the highest specific allantoinase activity. Stems and petioles also had appreciable allantoinase activity. With development, peaks in the amounts of allantoic acid, but not allantoin, were measured in both leaves and fruits suggesting that the assimilation of allantoic acid may be a limiting factor in ureide assimilation. Highest amounts of ureides were measured in the pith and xylem of stem tissues and in developing pod walls.

Journal Article↗

Pathways of glucose regulation of monosaccharide transport in grape cells.

Grape (Vitis vinifera) heterotrophic suspension-cultured cells were used as a model system to study glucose (Glc) transport and its regulation. Cells transported D-[14C]Glc according to simple Michaelis-Menten kinetics superimposed on first-order kinetics. The saturating component is a high-affinity, broad-specificity H+ -dependent transport system (Km = 0.05 mm). Glc concentration in the medium tightly regulated the transcription of VvHT1 (Vitis vinifera hexose transporter 1), a monosaccharide transporter previously characterized in grape berry, as well as VvHT1 protein amount and monosaccharide transport activity. All the remaining putative monosaccharide transporters identified so far in grape were poorly expressed and responded weakly to Glc. VvHT1 transcription was strongly repressed by Glc and 2-deoxy-D-Glc, but not by 3-O-methyl-D-Glc or Glc plus mannoheptulose, indicating the involvement of a hexokinase-dependent repression. 3-O-Methyl-D-Glc, which cannot be phosphorylated, and Glc plus mannoheptulose induced a decrease of transport activity caused by the reduction of VvHT1 protein in the plasma membrane without affecting VvHT1 transcript levels. This demonstrates hexokinase-independent posttranscriptional regulation. High Glc down-regulated VvHT1 transcription and Glc uptake, whereas low Glc increased those parameters. Present data provide an example showing control of plant sugar transporters by their own substrate both at transcriptional and posttranscriptional levels. VvHT1 protein has an important role in the massive import of monosaccharides into mesocarp cells of young grape berries because it was localized in plasma membranes of the early developing fruit. Protein amount decreased abruptly throughout fruit development as sugar content increases, consistent with the regulating role of Glc on VvHT1 expression found in suspension-cultured cells.

Biological Transport↗

The strawberry gene Cyf1 encodes a phytocystatin with antifungal properties.

An EST, encoding a strawberry phytocystatin (PhyCys) obtained from a developing fruit of Fragariaxananassa cv. Elsanta has been characterized. The corresponding gene (Cyf1) had three introns interrupting its ORF that codes for a protein (FaCPI-1) of 235 amino acid residues with a putative signal peptide of 29 residues and an estimated molecular mass for the mature protein of 23.1 kDa. This protein contains, besides a C-terminal extension, several motifs conserved in all members of the PhyCys superfamily: (i) a GG and LARFAV-like motifs towards the N-terminal part of the protein; (ii) the reactive site QVVAG, and (iii) a conserved PW, downstream of the reactive site. Northern blot and in situ hybridization analyses indicated that the Cyf1 gene was expressed in fully expanded leaves, in roots and in achenes, but not in the receptacle (pseudocarp) during fruit development. The recombinant FaCPI-1 protein expressed in E. coli efficiently inhibited papain (K(i) 1.9 x 10(-9) M) and less so cathepsin H (K(i) 4.7 x 10(-7) M) and cathepsin B (K(i) 3.3 x 10(-6) M), and was a good inhibitor of the in vitro growth of phytopathogenic fungi Botrytis cinerea (EC(50): 1.90 microM) and Fusarium oxysporum (EC(50): 2.28 microM).

Amino Acid Sequence↗

Expression of the urease gene of Agaricus bisporus: a tool for studying fruit body formation and post-harvest development.

Fruit body initials of Agaricus bisporus contain high levels of urea, which decrease in the following developmental stages until stage 4 (harvest) when urea levels increase again. At storage, the high urea content may affect the quality of the mushroom, i.e. by the formation of ammonia from urea through the action of urease (EC 3.5.1.5). Despite the abundance of urea in the edible mushroom A. bisporus, little is known about its physiological role. The urease gene of A. bisporus and its promoter region were identified and cloned. The coding part of the genomic DNA was interrupted by nine introns as confirmed by cDNA analysis. The first full homobasidiomycete urease protein sequence obtained comprised 838 amino acids (molecular mass 90,694 Da, pI 5.8). An alignment with fungal, plant and bacterial ureases revealed a high conservation. The expression of the urease gene, measured by Northern analyses, was studied both during normal development of fruit bodies and during post-harvest senescence. Expression in normal development was significantly up-regulated in developmental stages 5 and 6. During post-harvest senescence, the expression of urease was mainly observed in the stipe tissue; expression decreased on the first day and remained at a basal level through the remaining sampling period.

Agaricus↗

Divergent fructokinase genes are differentially expressed in tomato.

Two cDNA clones (Frk1 and Frk2) encoding fructokinase (EC 2.7.1.4) were isolated from tomato (Lycopersicon esculentum). The Frk2 cDNA encoded a deduced protein of 328 amino acids that was more than 90% identical with a previously characterized potato (Solanum tuberosum) fructokinase. In contrast, the Frk1 cDNA encoded a deduced protein of 347 amino acids that shared only 55% amino acid identity with Frk2. Both deduced proteins possessed and ATP-binding motif and putative substrate recognition site sequences identified in bacterial fructokinases. The Frk1 cDNA was expressed in a mutant yeast (Saccharomyces cerevisiae) line, which lacks the ability to phosphorylate glucose and fructose and is unable to grow on glucose or fructose. Mutant cells expressing Frk1 were complemented to grow on fructose but not glucose, indicating that Frk1 phosphorylates fructose but not glucose, and this activity was verified in extracts of transformed yeast. The mRNA corresponding to Frk2 accumulated to high levels in young, developing tomato fruit, whereas the Frk1 mRNA accumulated to higher levels late in fruit development. The results indicate that fructokinase in tomato is encoded by two divergent genes, which exhibit a differential pattern of expression during fruit development.

Amino Acid Sequence↗

Permanent gases inside healthy and microbially infected cotton fruit during development.

Permanent gases inside developing cotton fruit (Gossypium hirsutum L.) were, by weight, 46% nitrogen, 29% oxygen, 4% argon and 20% carbon dioxide, whereas plant canopy air assayed at 73% nitrogen, 25% oxygen, 2% argon and 0.3% carbon dioxide. Light exposure, fruit age, and mild infection (Erwinia) had no compositional effect but aggressive infection (Aspergillus) raised carbon dioxide content to 31% by weight and correspondingly lowered oxygen to 17%. Respiration with oxygen replenishment except during aggressive infection accounted for the fruit gas compositions.

Fruit↗

Significance of photosynthetic and respiratory exchanges in the carbon economy of the developing pea fruit.

The nutritional economy of the developing fruit of Pisum sativum L. (cv. Greenfeast) was studied in terms of intake of translocate, incorporation of C and N into dry matter, transpiration, and CO(2) exchanges of the fruit with its external and internal atmospheres. The environmental conditions were 12-hr days (22 C, 850 mueinsteins m(-2) sec(-1) at fruit level); 12-hr nights of 15 C.Between 6 and 30 days after anthesis, pod photosynthesis resulted in small gains of CO(2) from the external atmosphere, and assimilated most of the CO(2) respired by the fruit during the day. From then until maturity (40 days) the fruit lost CO(2) during the day. Night losses of CO(2) increased with fruit age.The gas cavity of the fruit contained 0.15 to 1.5% (v/v) CO(2). Lower levels were maintained in the day than at night. CO(2) levels were influenced by fruit age, radiant flux, and temperature. Labeled CO(2) injected into the gas cavity was fixed by the pod but not by seeds in the light, and by neither pod nor seeds in darkness. Dark-to-light or light-to-dark transfer of a fruit promoted rapid changes in CO(2) and O(2) levels of the gas space, consistent with a shift in the assimilation-respiration balance of the pod.The fruit transpired 27.6 cm(3) H(2)O per gram dry matter accumulated. Daytime ventilation was greatest 12 to 15 days after anthesis and declined as pod photosynthesis became increasingly involved in the retrieval of CO(2) respired by pod and seeds. Most, 69% by weight, of the translocate from the parent plant was converted to dry matter of seeds; nearly half, 45%, to useful seed reserves (sugar plus starch-protein-oil, 45:20:1). Illumination resulted in a fruit requiring 16% less translocate than if laying down an equal amount of dry matter in darkness.

Journal Article↗

Cloning and characterization of two hydrophobin genes differentially expressed during fruit body development in Lentinula edodes.

Hydrophobins play important roles in morphogenesis and pathogenesis in fungi and fruit development in mushrooms. Two genes encoding hydrophobins (Le.hyd1 and Le.hyd2) were isolated during sequencing of random clones from a primordial cDNA library of Lentinula edodes. The nucleotide sequences of these two genes were determined. These two genes are 760 and 738 bp in length and the deduced amino acid sequences are homologous to various fungal hydrophobins with characteristic cysteine spacing. These hydrophobin genes are Class I hydrophobins judging by their conserved domains and hydropathy patterns. The transcript level of Le.hyd1 is high in primordium and that of Le.hyd2 is high in dikaryotic mycelial tissues. Poor expression of these two genes in monokaryotic parents indicates that these two genes are under mating-type regulation. We thus suggest that differential expression of these two L. edodes hydrophobins during fruit development may contribute to their distinct roles in fruiting of this mushroom.

Amino Acid Sequence↗

Guanosine pentaphosphate and guanosine tetraphosphate accumulation and induction of Myxococcus xanthus fruiting body development.

Development of multicellular fruiting bodies of Myxococcus xanthus can be induced by limitation of any of a number of different classes of amino acids. Investigated were amino acids that wild-type strains of M. xanthus are unable to synthesize (isoleucine, leucine, and valine), can synthesize at a low rate (phenylalanine), or can normally synthesize at an adequate rate (tryptophan and serine). In general, gradual rather than abrupt starvation for an essential amino acid was required for the induction of fruiting. Perhaps gradual starvation in general minimizes antagonism between amino acids present in the medium, as was documented for valine starvation. The previously reported induction of fruiting by a high concentration of threonine was shown to be specifically reversed by lysine. Threonine addition may starve cells for lysine by feedback inhibition of aspartokinase activity. Starvation for carbon-energy sources or inorganic phosphate also induced fruiting. As in other bacteria, amino acid starvation of M. xanthus leads to increases in cellular guanosine polyphosphate, usually consisting of large increases in the amount of guanosine pentaphosphate with smaller increases in the level of guanosine tetraphosphate. Guanosine polyphosphate accumulation is thus shown to be correlated with nutritional conditions that induce fruiting, and therefore may serve as an intracellular signal to trigger cells to end vegetative growth and initiate fruiting body development.

Amino Acids↗

Membrane-associated protein kinase activities in the developing mesocarp of grape berry.

Fruit development is a process involving various signals and gene expression. Protein phosphorylation catalyzed by protein kinases is known to play a key role in eukaryotic cell signalling and so may be involved in the regulation of fruit development. Using the method of exogenous substrate phosphorylation, we characterised the calcium-dependent and calmodulin-independent protein kinase (CDPK) activity and the myelin basic protein (MBP)-phosphoralating activity that could be due to a mitogen-activated protein kinase (MAPK)-like activity in the developing mesocarp of grape berry. The CDPK activity was shown to be predominantly localised in the plasma membrane, while the MAPK-like activity was predominantly associated with endomembranes. The assays of bivalent cation requirement showed that Mn2+ could to a certain extent replace Mg2+ in the incubation system for the protein kinase activities. Both CDPK and MAPK-like activities were resistant to heat treatment. The activities of the two enzymes were fruit developmental stage-specific with the highest activities of both enzymes in the lag growth phase before the ripening stage, suggesting strongly the important roles of the detected CDPK and MAPK-like activities in the fruit development.

Calcium↗

Proline accumulation in developing grapevine fruit occurs independently of changes in the levels of delta1-pyrroline-5-carboxylate synthetase mRNA or protein.

Mature fruit of grapevine (Vitis vinifera) contains unusually high levels of free proline (Pro; up to 24 micromol or 2.8 mg/g fresh weight). Pro accumulation does not occur uniformly throughout berry development but only during the last 4 to 6 weeks of ripening when both berry growth and net protein accumulation have ceased. In contrast, the steady-state levels of both the mRNA encoding V. vinifera Delta1-pyrroline-5-carboxylate synthetase (VVP5CS), a key regulatory enzyme in Pro biosynthesis, and its protein product remain relatively uniform throughout fruit development. In addition, the steady-state protein levels of Pro dehydrogenase, the first enzyme in Pro degradation, increased throughout early fruit development but thereafter remained relatively constant. The developmental accumulation of free Pro late in grape berry ripening is thus clearly distinct from the osmotic stress-induced accumulation of Pro in plants. It is not associated with either sustained increases in steady-state levels of P5CS mRNA or protein or a decrease in steady-state levels of Pro dehydrogenase protein, suggesting that other physiological factors are important for its regulation.

1-Pyrroline-5-Carboxylate Dehydrogenase↗

The energy-conserving and energy-dissipating processes in mitochondria isolated from wild type and nonripening tomato fruits during development on the plant.

Bioenergetics of tomato (Lycopersicon esculentum) development on the plant was followed from the early growing stage to senescence in wild type (climacteric) and nonripening mutant (nor, non-climacteric) fruits. Fruit development was expressed in terms of evolution of chlorophyll a content allowing the assessment of a continuous time-course in both cultivars. Measured parameters: the cytochrome pathway-dependent respiration, i.e., the ATP synthesis-sustained respiration (energy-conserving), the uncoupling protein (UCP) activity-sustained respiration (energy-dissipating), the alternative oxidase(AOX)-mediated respiration (energy-dissipating), as well as the protein expression of UCP and AOX, and free fatty acid content exhibited different evolution patterns in the wild type and nor mutant that can be attributed to their climacteric/nonclimacteric properties, respectively. In the wild type, the climacteric respiratory burst observed in vitro depended totally on an increse in the cytochrome pathway activity sustained by ATP synthesis, while the second respiratory rise during the ripening stage was linked to a strong increase in AOX activity accompanied by an overexpression of AOX protein. In wild type mitochondria, the 10-microM linoleic acid-stimulated UCP-activity-dependent respiration remained constant during the whole fruit development except in senescence where general respiratory decay was observed.

Adenosine Triphosphate↗

The phenolics of fruits. VII. The phenolics of cherries and plums and the changes in catechins and hydroxycinnamic acid derivatives during the development of fruits.

Quantitative data of hydroxycinnamic acids, hydroxybenzoic acids and hydroxycoumarins (after hydrolysis of derivatives) and of catechins are given. -Large quantities of catechins and hydroxycinnamic acid derivatives are found in the young fruit. Related to mg per kg fresh weight these concentrations soon decline sharply, especially during the progressive growth of the fruits. Related to mg per fruit, the concentrations of catechins increase progressively with fruit development, showing a loss when reaching maturity. The concentrations of hydroxycinnamic acids increase in a similar manner, but show in part a remarkable loss when examined after removal of the harder seeds.

Benzopyrans↗

[Changes in glycosidases and cellulase activities, and cell wall composition in strawberry fruits during development and ripening].

Experiments were carried out with two strawberry (Fragaria x nanassa Duch.) cultivars Fengxiang and Hongfeng, with different softening characteristics during growth, ripening and postharvest storage. The fruits were harvested at different stages of growth and ripening, as assessed by size and the coloration of the surface of the fruits. We selected the following stages: small and green (S1), large and green (S2), white (S3), reddish (S4), and fully red (S5). The main results were as follows. Both alpha- and beta-galactosidase activities were changed with ripening of strawberry fruits (Fig.1A, B). Of the strawberry cultivars tested, no correlation was found between glucosidase activity and fruit ripening (Fig.1C, D). Alpha-mannosidase is an enzyme being ionically bound with cell wall and its activities is correlated with the softening of strawberry fruits (Fig.1E, F). No beta-mannosidase has been detected in strawberry. The activities of cellulase increased as the strawberry fruits developed from stage of small and green to stage of overripe (Fig.2A). The activities of PME increased during the development of strawberry fruits (Fig.2B). Endo-PG was not detected in strawberry, and exo-PG was not related to fruit ripening (Fig.2C). Changes in cell wall component contents were clearly related to the changes in the firmness of strawberry fruits. The increase in soluble pectin, together with reduction of ionically bound pectin content, covalently bound pectin content (Fig.3A, B) and cellulose (Fig.3A, B) resulted in softening of strawberry fruits.

Cell Wall↗

Enhanced expression of a novel dioxygenase during the early developmental stage of tomato fruit.

Most previous efforts to isolate genes that are expressed during fruit development have focused on fruit ripening. As a result, information is lacking on fruit genes that are specifically expressed at early developmental stages. Using a cDNA subtraction technique, we isolated fruit-specific genes that are expressed during the cell expansion phase of tomato (Lycopersicon esculentum Mill) fruit development. One of the isolated cDNAs, LeODD, is transiently expressed 15 days after flowering in a nearly fruit-specific manner during the initial period of cell expansion. Southern blot analysis indicated that LeODD is encoded by a single gene. LeODD is homologous to 2-oxoglutarate-dependent dioxygenase genes, and the key amino acid residues in the binding sites for ferrous iron and 2-oxoglutarate are completely conserved. The amino acid sequence identity between LeODD and other 2-oxoglutarate-dependent dioxygenases is relatively low, suggesting that LeODD is a novel enzyme of this family. Another of the isolated cDNAs, LeGLO2, is also highly expressed at 15 days after flowering. LeGLO2 is thought to be a novel glycolate oxidase isoform that functions in fruit. 2-Oxoglutarate, the cosubstrate of LeODD, could be supplied by a LeGLO2-mediated glycolate pathway in immature fruit. The coordinate expression of LeODD and LeGLO2 may play a role in the biosynthesis of a metabolite, such as a plant hormone or secondary metabolite, that is required during the initial period of the cell expansion phase of fruit development.

Amino Acid Sequence↗