共查询到20条相似文献,搜索用时 15 毫秒
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Barre A Peumans WJ Menu-Bouaouiche L Van Damme EJ May GD Herrera AF Van Leuven F Rougé P 《Planta》2000,211(6):791-799
The pulp of ripe bananas (Musa acuminata) contains an abundant thaumatin-like protein (TLP). Characterization of the protein and molecular cloning of the corresponding
gene from banana demonstrated that the native protein consists of a single polypeptide chain of 200 amino acid residues. Molecular
modelling further revealed that the banana thaumatin-like protein (Ban-TLP) adopts an overall fold similar to that of thaumatin
and thaumatin-like PR-5 proteins. Although the banana protein exhibits an electrostatically polarized surface, which is believed
to be essential for the antifungal properties of TLPs, it is apparently devoid of antifungal activity towards pathogenic fungi.
It exhibits a low but detectable in vitro endo-β-1,3-glucanase (EC 3.2.1.x) activity. As well as being present in fruits,
Ban-TLP also occurs in root tips where its accumulation is enhanced by methyl jasmonate treatment of plants. Pulp of plantains
(Musa acuminata) also contains a very similar TLP, which is even more abundant than its banana homologue. Our results demonstrate for the
first time that fruit-specific (abundant) TLPs are not confined to dicots but occur also in fruits of monocot species. The
possible role of the apparent widespread accumulation of fruit-specific TLPs is discussed.
Received: 7 January 2000 / Accepted: 26 April 2000 相似文献
4.
Cell-specific expression of the mercury-insensitive plasma-membrane aquaporin NtAQP1 from Nicotiana tabacum 总被引:9,自引:0,他引:9
The aquaporin NtAQP1 from Nicotiana tabacum L. is insensitive to heavy-metal ions. In addition to water, the transport of urea or glycerol is facilitated by this plasma-membrane-located
water channel. Northern hybridization and whole-mount in situ hybridization revealed a high steady-state level of NtAQP1-RNA
in roots, a decreased content in shoots and a low content in leaves. By immunolocalization with an antibody targeted to the
N-terminus of the aquaporin, the localization of NtAQP1-protein at sites of expected high water transport rates from and to
the apoplast or symplast could be demonstrated. The specific pattern of NtAQP1 distribution in petioles strongly indicates
a transcellular movement of water.
Received: 12 August 1999 / Accepted: 27 December 1999 相似文献
5.
Specificity of the accumulation of mRNAs and proteins of the plasma membrane and tonoplast aquaporins in radish organs 总被引:13,自引:0,他引:13
Plant aquaporins occur in multiple isoforms and are distributed in both plasma membrane and tonoplast. We cloned cDNAs for
plasma-membrane aquaporins (PAQ1, 1b, 1c, 2, 2b, and 2c) of radish (Raphanus sativus L.). The amino acid sequences of the PAQs showed on average 63% sequence identity. Their sequences were 23% identical to
those of tonoplast aquaporins (γ- and δ-VM23). A comprehensive investigation of the aquaporin mRNAs, including VM23, in seedlings,
plants, flowers and seeds of radish showed a marked accumulation of all the mRNAs in hypocotyls and growing taproots. In other
organs, the mRNA level of each isoform varied according to the organ. In petals, stamens, pistils and sepals of flowers, the
levels of PAQ1, 1b, 1c and γ-VM23 mRNAs were high, and mRNAs of all aquaporins except for δ-VM23 were detected at high levels
in pericarps. The protein levels of aquaporins on the basis of the membrane protein were determined by immunoblotting. Proteins
PAQ1 and VM23 were detected in every organ except for the mature petiole. The PAQ2 protein level was especially high in green
cotyledons and leaves, but was extremely low in seedling cotyledons and hypocotyls. Proteins PAQ1, PAQ2 and VM23 were highly
accumulated in growing pericarps, but not in the immature seeds. These results indicate that the gene expression of the aquaporin
isoforms was individually regulated in an organ- and tissue-specific manner, and that the amounts of aquaporin protein, especially
PAQ2, are regulated in certain tissues at the translational level and by the rate of protein turnover.
Received: 10 February 2000 / Accepted: 30 June 2000 相似文献
6.
A cDNA fragment encoding a Lupinus albus. L. class-III chitinase, IF3, was isolated, using a cDNA probe from Cucumis sativus L., by in-situ plaque hybridization from a cDNA library constructed in the Uni-ZAP XR vector, with mRNAs isolated from mature
lupin leaves. The cDNA had a coding sequence of 293 amino acids including a 27-residue N-terminal signal peptide. A class-III
chitinase gene was detected by Southern analysis in the L. albus genome. Western blotting experiments showed that the IF3 protein was constitutively present during seed development and in
all the studied vegetative lupin organs (i.e., roots, hypocotyls and leaves) at two growth stages (7- and 20-d-old plants).
Accumulation of both the IF3 mRNA and IF3 protein was triggered by salicylic acid treatment as well as by abiotic (UV-C light
and wounding) and biotic stress conditions (Colletotrichum gloeosporioides infection). In necrotic leaves, IF3 chitinase mRNA was present at a higher level than that of another mRNA encoding a pathogenesis-related
(PR) protein from L. albus (a PR-10) and that of the rRNAs. We suggest that one role of the IF3 chitinase could be in the defense of the plant against
fungal infection, though our results do not exclude other functions for this protein.
Received: 15 March 1999 / Accepted: 12 July 1999 相似文献
7.
Phloem transport of amino acids in two Brassica napus L. genotypes and one B. carinata genotype in relation to their seed protein content 总被引:2,自引:0,他引:2
In order to investigate the relationship between the amino acid concentration in the phloem sap of leaves and the protein
content in seeds, two Brassica napus genotypes and one B. carinata genotype with low, medium and high seed protein contents were analyzed. Phloem sap was collected from the B. napus winter rapeseed breeding line DSV15 with 19% protein of dry weight in the seeds, the spring cultivar ‘Duplo’ with 25% protein
in the seeds and from the B. carinata line BRA1151/90 with 39% protein in the seeds by using the aphid-stylet technique. The total amino acid contents measured
in the phloem varied considerably among the three genotypes analysed, and correlated positively with their respective seed
protein contents. The total amino acid-to-sucrose ratio was lowest in B. napus line DSV15 which had the lowest seed protein content and highest in the B. carinata line BRA1151/90 which had the highest seed protein content. The amino-N translocation in the phloem during the light period
was about 2-fold higher in the B. carinata line BRA1151/90 than in the B. napus lines Dulpo and DSV15. Predominant amino acids in the phloem were glutamine and glutamate, followed by serine, aspartate,
and threonine. The amino acid patterns in the leaves resembled those in the phloem, although their absolute concentrations
were higher in the phloem than in the cytosol of mesophyll tissue. Furthermore, the concentration gradient of amino acids
between the cytosol of mesophyll cells and the phloem was higher in the B. carinata line BRA1151/90 than in the B. napus lines Duplo and DSV15. These results lead to the conclusion that the phloem translocation of amino-N and the phloem loading
process of amino acids are decisive factors for the protein content in the seeds of Brassica species.
Received: 28 November 1999 / Accepted: 10 April 2000 相似文献
8.
Microtubule organization plays an important role in plant morphogenesis; however, little is known about how microtubule arrays
transit from one organized state to another. The use of a genetically incorporated fluorescent marker would allow long-term
observation of microtubule behavior in living cells. Here, we have characterized a Nicotiana tabacum L. cv. Bright Yellow 2 (BY-2) cell line that had been stably transformed with a gfp-mbd construct previously demonstrated to label microtubules (J. Marc et al., 1998, Plant Cell 10: 1927–1939). Fluorescence levels
were low, but interphase and mitotic microtubule arrays, as well as the transitions between these arrays, could be observed
in individual gfp-mbd-transformed cells. By comparing several attributes of transformed and untransformed cells it was concluded that the transgenic
cells are not adversely affected by low-level expression of the transgene and that these cells will serve as a useful and
accurate model system for observing microtubule reorganization in vivo. Indeed, some initial observations were made that are
consistent with the involvement of motor proteins in the transition between the spindle and phragmoplast arrays. Our observations
also support the role of the perinuclear region in nucleating microtubules at the end of cell division with a progressive
shift of these microtubules and/or nucleating activity to the cortex to form the interphase cortical array.
Received: 2 June 1999 / Accepted: 13 August 1999 相似文献
9.
Ermel FF Follet-Gueye ML Cibert C Vian B Morvan C Catesson AM Goldberg R 《Planta》2000,210(5):732-740
The development of pectin structural features during the differentiation of cambial derivatives was investigated in aspen
(Populus tremula L. × P. tremuloides Michx.) using biochemical and immunocytochemical methods. Comparisons were also made between active and resting tissues.
Active tissues, in particular cambial cells and phloem derivatives, were characterized by a high pectin content. Use of antibodies
raised against arabinan side chains of rhamnogalacturonan 1 (LM6), as well as biochemical analysis, revealed an obvious decrease
from the cortex to the differentiating xylem. Galactan side chains, detected with LM5 antibodies, were present mainly in the
cambial zone and enlarging xylem cells. In contrast, they were totally absent from sieve-tube cell walls. Image analysis of
LM5 immunogold labelling in the cambial zone showed a clustered distribution of galactan epitopes in the radial walls, a distribution
which might result from the association of two different periodic processes, namely the exocytosis of galactan and wall expansion.
Cessation of cambial activity was characterized by cell wall thickening accompanied by a sharp decrease in the relative amount
of pectin and a lowering of the degree of methylesterification. The data provide evidence that the walls of phloem and xylem
cells differ in their pectin composition even at a very early stage of commitment. These differences offer useful tools for
identifying the initial cells among their immediate neighbours.
Received: 12 June 1999 / Accepted: 20 October 1999 相似文献
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Zhang W Peumans WJ Barre A Astoul CH Rovira P Rougé P Proost P Truffa-Bachi P Jalali AA Van Damme EJ 《Planta》2000,210(6):970-978
A novel plant lectin was isolated from salt-stressed rice (Oryzasativa L.) plants and partially characterized. The lectin occurs as a natural mixture of two closely related isoforms consisting
of two identical non-covalently linked subunits of 15 kDa. Both isoforms are best inhibited by mannose and exhibit potent
mitogenic activity towards T-lymphocytes. Biochemical analyses and sequence comparisons further revealed that the rice lectins
belong to the subgroup of mannose-binding jacalin-related lectins. In addition, it could be demonstrated that the lectins
described here correspond to the protein products of previously described salt-stress-induced genes. Our results not only
identify the rice lectin as a stress protein but also highlight the possible importance of protein-carbohydrate interactions
in stress responses in plants.
Received: 27 July 1999 / Accepted: 11 November 1999 相似文献
12.
Recently, it has been shown that water fluxes across biological membranes occur not only through the lipid bilayer but also
through specialized water-conducting proteins, the so called aquaporins. In the present study, we investigated in young and
mature leaves of Brassica napus L. the expression and localization of a vacuolar aquaporin homologous to radish γ-tonoplast intrinsic protein/vacuolar-membrane
integral protein of 23 kDa (TIP/VM 23). In-situ hybridization showed that these tonoplast aquaporins are highly expressed
not only in developing but also in mature leaves, which export photosynthates. No substantial differences could be observed
between different tissues of young and mature leaves. However, independent of the developmental stage, an immunohistochemical
approach revealed that the vacuolar membrane of bundle-sheath cells contained more protein cross-reacting with antibodies
raised against radish γ-TIP/VM 23 than the mesophyll cells. The lowest labeling was detected in phloem cells. We compared
these results with the distribution of plasma-membrane aquaporins cross-reacting with antibodies detecting a domain conserved
among members of the plasma-membrane intrinsic protein 1 (PIP1) subfamily. We observed the same picture as for the vacuolar
aquaporins. Furthermore, a high density of gold particles labeling proteins of the PIP1 group could be observed in plasmalemmasomes
of the vascular parenchyma. Our results indicate that γ-TIP/VM 23 and PIP1 homologous proteins show a similar expression pattern.
Based on these results it is tempting to speculate that bundle-sheath cells play an important role in facilitating water fluxes
between the apoplastic and symplastic compartments in close proximity to the vascular tissue.
Received: 23 December 1999 / Accepted: 3 June 2000 相似文献
13.
The entry of calcium and magnesium from external sources into mycorrhizal roots of 3-year-old Norway spruce trees (Piceaabies [L.] Karst.) was monitored. Roots of intact plants were exposed for various periods of time, ranging from 2 min to 48 h,
to nutrient solutions which contained the stable-isotope tracers 25Mg and 44Ca. After labelling, samples of roots were excised from the plants, shock-frozen, cryosubstituted and embedded. The resulting
isotope composition in this material was analysed by a laser-microprobe-mass-analyser (LAMMA) at relevant positions within
cross-sections of the roots. For both elements, we determined (i) the fractions of the isotopes originating from the plant
prior to labelling, and (ii) the fraction of isotopes originating from the corresponding tracer that penetrated into the root.
Both divalent cations rapidly penetrated across the cortical apoplast and reached the endodermis. After 2 min of exposure
to the labelling solution, an initial transient gradient of the tracers could be observed within the root cortex. Subsequently,
calcium as well as magnesium equilibrated between the apoplast of the entire cortex and the external tracer with a half-time,
t1/2, of about 3 min. In contrast, the kinetics of radial movement into the vascular stele showed a delay with a t1/2 of 100–120 min. We take this as strong evidence that there exists a free apoplastic path for divalent cations in the cortex
and that the endodermis is a major barrier to the further passage of Mg and Ca into the xylem. While 25Mg in the labelling solution exchanged rapidly with Mg in the cortical apoplast, the exchange across the plasma membrane with
Mg present in the protoplasm of the same cortical cells was almost 2 orders of magnitude slower. The kinetics of Ca and Mg
entry at +6 °C were similar to those obtained at a root temperature of +22 °C.
Received: 23 December 1998 / Accepted: 17 September 1999 相似文献
14.
Pectin methyltransferase (PMT) catalyzing the transfer of the methyl group from S-adenosyl-L-methionine (SAM) to the C-6 carboxyl group of galactosyluronic acid residues in pectin was found in a membrane preparation
of etiolated hypocotyls from 6-d-old soybean (Glycinemax Merr.). The enzyme was maximally active at pH 6.8 and 35–40 °C, and required 0.5% (w/v) Triton X-100. The incorporation of
the methyl group was significantly enhanced by addition of a pectin with a low (22%) degree of methyl-esterification (DE)
as exogenous acceptor substrate. The apparent Michaelis constants for SAM and the pectin (DE22) were 0.23 mM and 66 μg · ml−1, respectively. Attachment of the methyl group to the carboxyl group of the pectin via ester linkage was confirmed by analyzing
radiolabeled product from incubation of the enzyme with [14C]methyl SAM and the acceptor pectin. Size-exclusion chromatography showed that both enzymatic hydrolysis with a pectin methylesterase
and a mild alkali treatment (saponification) led to the release of radioactive methanol from the product. Enzymatic hydrolysis
of the product with an endopolygalacturonase degraded it into small pectic fragments with low relative molecular mass, which
also supports the idea that the methyl group is incorporated into the pectin. The soybean hypocotyls were fractionated into
their cell wall components by successive extraction with water, EDTA, and alkali treatment. Among the resulting polysaccharide
fractions, high PMT activity was observed when a de-esterified polysaccharide derived from the EDTA-soluble fraction (the
pectic fraction) was added as an alternative acceptor substrate, indicating that the enzyme may be responsible for producing
methyl-esterified pectin in vivo.
Received: 10 September 1999 / Accepted: 11 October 1999 相似文献
15.
A microsomal preparation from suspension-cultured potato stem cells (Solanum tuberosum L. cv. AZY) was incubated with [14C]acetyl-CoA resulting in a precipitable radiolabeled product. Analysis of the product revealed that it consisted mostly of
acetylated proteins and cell wall polysaccharides, including xyloglucan, homogalacturonan and rhamnogalacturonan I. Thus,
acetyl-CoA is a donor-substrate for the O-acetylation of wall polysaccharides. A rhamnogalacturonan acetylesterase was used to develop an assay to measure and characterize
rhamnogalacturonan O-acetyl transferase activity in the microsomal preparation. Using this assay, it was shown that the transferase activity was
highest during the linear growth phase of the cells, had a pH-optimum at pH 7.0, a temperature optimum at 30 °C, an apparent
K
m of 35 μM and an apparent V
max of 0.9 pkat per mg protein. Further analysis of the radiolabeled acetylated product revealed that it had a molecular mass
>500 kDa.
Received: 3 July 1999; Accepted: 27 September 1999 相似文献
16.
An arabinogalactan-protein (AGP) was purified from differentiating xylem of loblolly pine (Pinus taeda L.) and the N-terminal sequence used to identify a cDNA clone. The protein, PtaAGP3, was not coded for by any previously identified AGP-like genes. Moreover, PtaAGP3 was abundantly and preferentially expressed in differentiating xylem. The encoded protein contains four domains, a signal
peptide, a cleaved hydrophilic region, a region rich in serine, alanine, and proline/hydroxyproline, and a hydrophobic C-terminus.
It is postulated to contain a GPI (glycosylphosphatidylinositol) anchor site. If the protein is cleaved at the putative GPI
anchor site, as has been observed in other classical AGPs, all but the Ser-Ala-Pro/Hyp-rich domain may be missing from the
mature protein. Xylem-specific AGPs are hypothesized to be involved in xylem development.
Received: 29 July 1999 / Accepted: 19 August 1999 相似文献
17.
Fruit-specific lectins from banana and plantain 总被引:6,自引:0,他引:6
Peumans WJ Zhang W Barre A Houlès Astoul C Balint-Kurti PJ Rovira P Rougé P May GD Van Leuven F Truffa-Bachi P Van Damme EJ 《Planta》2000,211(4):546-554
One of the predominant proteins in the pulp of ripe bananas (Musa acuminata L.) and plantains (Musa spp.) has been identified as a lectin. The banana and plantain agglutinins (called BanLec and PlanLec, respectively) were
purified in reasonable quantities using a novel isolation procedure, which prevented adsorption of the lectins onto insoluble
endogenous polysaccharides. Both BanLec and PlanLec are dimeric proteins composed of two identical subunits of 15 kDa. They
readily agglutinate rabbit erythrocytes and exhibit specificity towards mannose. Molecular cloning revealed that BanLec has
sequence similarity to previously described lectins of the family of jacalin-related lectins, and according to molecular modelling
studies has the same overall fold and three-dimensional structure. The identification of BanLec and PlanLec demonstrates the
occurrence of jacalin-related lectins in monocot species, suggesting that these lectins are more widespread among higher plants
than is actually believed. The banana and plantain lectins are also the first documented examples of jacalin-related lectins,
which are abundantly present in the pulp of mature fruits but are apparently absent from other tissues. However, after treatment
of intact plants with methyl jasmonate, BanLec is also clearly induced in leaves. The banana lectin is a powerful murine T-cell
mitogen. The relevance of the mitogenicity of the banana lectin is discussed in terms of both the physiological role of the
lectin and the impact on food safety.
Received: 1 December 1999 / Accepted: 31 January 2000 相似文献
18.
Seeds of Cichorium intybus L. var. foliosum cv. Flash were sown in acid-washed vermiculite and grown in a controlled-environment growth chamber. After 1 month of growth,
plantlets did not contain sucrose:sucrose 1-fructosyltransferase (1-SST), the key enzyme in fructan biosynthesis. No fructan
could be observed. Some of the plants were submitted to drought for 2 weeks. Glucose, fructose and sucrose concentrations
increased in roots and leaves of stressed plants and the fructan concentration in roots and leaves was ten times higher than
in control plants. The onset of fructan synthesis coincided with the increase in 1-SST activity in roots. Expression of the
1-SST gene could be observed in roots and leaves of stressed plants.
Received: 12 July 1999 / Accepted: 16 October 1999 相似文献
19.
Mechanisms of primordium formation during adventitious root development from walnut cotyledon explants 总被引:7,自引:0,他引:7
In walnut (Juglans regia L.), an otherwise difficult-to-root species, explants of cotyledons have been shown to generate complete roots in the absence
of exogenous growth regulators. In the present study, this process of root formation was shown to follow a pattern of adventitious,
rather than primary or lateral, ontogeny: (i) the arrangement of vascular bundles in the region of root formation was of the
petiole type; (ii) a typical root primordium was formed at the side of the procambium within a meristematic ring of actively
dividing cells located around each vascular bundle; (iii) the developing root apical meristem was connected in a lateral way
with the vascular bundle of the petiole. This adventitious root formation occurred in three main stages of cell division,
primordium formation and organization of apical meristem. These stages were characterized by expression of LATERAL ROOT PRIMORDIUM-1 and CHALCONE SYNTHASE genes, which were found to be sequentially expressed during the formation of the primordium. Activation of genes related
to root cell differentiation started at the early stage of primordium formation prior to organization of the root apical meristem.
The systematic development of adventitious root primordia at a precise site gave indications on the positional and biochemical
cues that are necessary for adventitious root formation.
Received: 30 July 1999 / Accepted: 16 February 2000 相似文献