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1.
Heteroblasty in Arabidopsis thaliana was analyzed in a variety of plants with mutations in leaf morphology using a tissue-specific β-glucuronidase gene marker.
Some mutants exhibited their mutant phenotypes specifically in foliage leaves. The phenotypes associated with the foliage-leaf-specific
mutations were also found to be induced ectopically in cotyledons in the presence of the lec1 mutation. Moreover, the features of an emf1lec1 double mutant showed that cotyledons can be partially converted into carpelloids. When heteroblastic traits were examined
in foliage leaves in the presence of certain mutations or natural deviations by histochemical analysis of the expression of
the tissue-specific marker gene, it was found that ectopic expression of the developmental program for the first foliage leaves
in lec1 cotyledons seemed to affect the heteroblastic features of the first set of foliage leaves, while foliage leaves beyond the
third position appeared normal. Similarly, in wild-type plants, discrepancies in heteroblastic features, relative to standard
features, of foliage leaves at early positions seemed to be eliminated in foliage leaves at later positions. These results
suggest that heteroblasty in foliage leaves might be affected in part by the heteroblastic stage of the preceding foliage
leaves but is finally controlled autonomously at each leaf position.
Received: 9 July 1999 / Accepted: 17 August 1999 相似文献
2.
A nonphotochemical-quenching-deficient mutant of Arabidopsis thaliana possessing normal pigment composition and xanthophyll-cycle activity 总被引:1,自引:0,他引:1
Higher-plant chloroplasts alter the distribution of absorbed radiant energy between photosynthesis and heat formation in
response to changing illumination level or environmental stress. Fluorescence imaging was used to screen 62 yellow-green T-DNA
insertion mutant lines of Arabidopsis thaliana (L.) Heynh. for reduced photoprotective nonphotochemical quenching (NPQ) capacity. Pulse-modulation fluorometry was employed
to characterize one line (denoted Lsr1−) that exhibited an approximately 50% reduction in NPQ compared to the wild type (WT). The loss in NPQ capacity was associated
with the ΔpH-dependent phase of quenching (qE). Under the growth conditions employed, pigment composition and levels of the
six photosystem-II light-harvesting chlorophyll a/b proteins were identical in mutant and WT. Changes in the in-vivo levels of the xanthophyll pigments violaxanthin, antheraxanthin,
and zeaxanthin in excess light were the same for mutant and WT. However, use of the violaxanthin de-epoxidase inhibitor dithiothreitol
indicated that a zeaxanthin-dependent component of NPQ was specifically reduced in the mutant. The mutant exhibited diminished
suppression of minimum fluorescence yield (F
o
) in intense light suggesting an altered threshold in the mechanism of response to light stress in the mutant. The NPQ-deficient
phenotype was meiotically transmissible as a semidominant trait and mapped near marker T27K12 on chromosome 1. The results
suggest that the mutant is defective in sensing the transthylakoid ΔpH that reports exposure to excessive illumination.
Received: 26 May 1999 / Accepted: 17 June 1999 相似文献
3.
4.
Leaf and minor vein structure were studied in Arabidopsis thaliana (L.) Heynh. to gain insight into the mechanism(s) of phloem loading. Vein density (length of veins per unit leaf area) is
extremely low. Almost all veins are intimately associated with the mesophyll and are probably involved in loading. In transverse
sections of veins there are, on average, two companion cells for each sieve element. Phloem parenchyma cells appear to be
specialized for delivery of photoassimilate from the bundle sheath to sieve element-companion cell complexes: they make numerous
contacts with the bundle sheath and with companion cells and they have transfer cell wall ingrowths where they are in contact
with sieve elements. Plasmodesmatal frequencies are high at interfaces involving phloem parenchyma cells. The plasmodesmata
between phloem parenchyma cells and companion cells are structurally distinct in that there are several branches on the phloem
parenchyma cell side of the wall and only one branch on the companion cell side. Most of the translocated sugar in A. thaliana is sucrose, but raffinose is also transported. Based on structural evidence, the most likely route of sucrose transport is
from bundle sheath to phloem parenchyma cells through plasmodesmata, followed by efflux into the apoplasm across wall ingrowths
and carrier-mediated uptake into the sieve element-companion cell complex.
Received: 5 October 1999 / Accepted: 20 November 1999 相似文献
5.
Cell division and cell differentiation are key processes in shoot development. The Arabidopsis thaliana (L.) Heynh. SCHIZOID (SHZ) gene appears to influence cell differentiation and cell division in the shoot. The shz-2 mutant is notable in that distinct phenotypes develop, depending on the environment in which the plants are grown. When shz-2 mutants are grown in petri dishes, callus develops from the petiole and hypocotyl. In contrast, when the mutants are grown
on soil, shoots appear externally stunted with malformed leaves. However, detailed examination of soil-grown mutants shows
that the two phenotypes are related. Soil-grown mutants form adventitious meristems, produce a large amount of vascular tissues
and have aberrant cell divisions in the meristem. Cells with abnormal cell-division patterns were found in the apical and
vascular meristems, suggesting SHZ influences cell division. Development of callus in petri dishes, development of adventitious meristems and aberrations in
leaves on soil suggest that SHZ influences cell differentiation. The distinct, but related phenotypes on soil and in petri dishes suggests that SHZ normally functions to regulate differentiation and/or cell division in a manner that is responsive to environmental conditions.
Received: 30 July 1999 / Accepted: 22 September 1999 相似文献
6.
Transgenic Nicotiana tabacum and Arabidopsis thaliana plants overexpressing allene oxide synthase 总被引:3,自引:0,他引:3
Allene oxide synthase (AOS), encoded by a single gene in Arabidopsis thaliana (L.) Heynh., catalyzes the first step specific to the octadecanoid pathway. Enzyme activity is very low in control plants,
but is upregulated by wounding, octadecanoids, ethylene, salicylate and coronatine (D. Laudert and E.W. Weiler, 1998, Plant
J 15: 675–684). In order to study the consequences of constitutive expression of AOS on the level of jasmonates, a complete
cDNA encoding the enzyme from A. thaliana was constitutively expressed in both A. thaliana and tobacco (Nicotiana tabacum L.). Overexpression of AOS did not alter the basal level of jasmonic acid; thus, output of the jasmonate pathway in the unchallenged
plant appears to be strictly limited by substrate availability. In wounded plants overexpressing AOS, peak jasmonate levels
were 2- to 3-fold higher compared to untransformed plants. More importantly, the transgenic plants reached the maximum jasmonate
levels significantly earlier than wounded untransformed control plants. These findings suggest that overexpression of AOS
might be a way of controlling defense dynamics in higher plants.
Received: 10 February 2000 / Accepted: 11 March 2000 相似文献
7.
The tryptophan auxotroph mutant trp3-1 of Arabidopsis thaliana (L.) Heynh., despite having reduced levels of l-tryptophan, accumulates the tryptophan-derived glucosinolate, glucobrassicin and, thus, does not appear to be tryptophan-limited.
However, due to the block in tryptophan synthase, the mutant hyperaccumulates the precursor indole-3-glycerophosphate (up
to 10 mg per g FW). Instability of indole-3-glycerophosphate leads to release of indole-3-acetic acid (IAA) from this metabolite
during standard workup of samples for determination of conjugated IAA. The apparent increase in “conjugated IAA” in trp3-1 mutant plants can be traced back entirely to indole-3-glycerophosphate degradation. Thus, the levels of neither free IAA
nor conjugated IAA increase detectably in the trp3-1 mutant compared to wild-type plants. Precursor-feeding experiments to shoots of sterile-grown wild-type plants using [2H]5-l-tryptophan have shown incorporation of label from this precursor into indole-3-acetonitrile and indole-3-acetic acid with
very little isotope dilution. It is concluded that Arabidopsis thaliana shoots synthesize IAA from l-tryptophan and that the non-tryptophan pathway is probably an artifact.
Received: 1 March 2000 / Accepted: 10 April 2000 相似文献
8.
When a brassinosteroid biosynthesis inhibitor, brassinazole (Brz), was applied at concentrations ranging from 0.1 to 2 μM,
Arabidopsis thaliana (L.) Heynh seedlings grown in the dark exhibited morphological features of light-grown plants, i.e. short hypocotyls, expanded
cotyledons, and true leaves, in a dose-dependent manner. Control (non Brz-treated) seedlings grown in the dark for 40 d did
not develop leaf primordia. However, treatment with the lowest concentration of Brz induced the development of leaf buds,
although it hardly induced any short hypocotyls, and treatment with the highest concentration of Brz induced both short hypocotyls
and leaves. Labeling experiments with the thymidine analogue 5-bromo-2′-deoxyuridine revealed that amplification of cell nuclei
and organellar nucleoids is activated in the shoot apical meristems of dark-grown Brz-treated seedlings. These results suggest
that Brz-treatment induces development of true leaves. Furthermore, condensation and scattering of plastid nucleoids, which
is known to occur during the differentiation of etioplasts into chloroplasts, was observed in the plastids of dark-grown Brz-treated
cotyledons. In addition, high levels of ribulose-1,5-bisphosphate carboxylase-oxygenase proteins accumulated in the plastids
of the cotyledons. Electron microscopy showed that the plastids were etioplasts with a prolamellar body and few thylakoid
membranes. These results suggest that Brz treatment in the dark induces the initial steps of plastid differentiation, which
occur prior to the development of thylakoid membranes. This is a novel presumed function of brassinosteroids. These cytological
changes seen in Brz-treated Arabidopsis were exactly the same as those seen in a brassinosteroid-biosynthesis-deficient mutant, det2, supporting the hypothesis that Brz has no side-effects except inhibiting brassinosteroid biosynthesis, and should prove
a useful tool in clarifying the role of brassinosteroids.
Received: 10 February 2000 / Accepted: 11 April 2000 相似文献
9.
10.
11.
Two new oleosin isoforms with altered expression patterns in seeds of the Arabidopsis mutant fus3 总被引:1,自引:0,他引:1
Victor Kirik Kerstin Kölle Hans-Jörg Balzer Helmut Bäumlein 《Plant molecular biology》1996,31(2):413-417
Oleosins are proteins associated with lipid bodies mainly synthesised during seed development. Using a subtractive hybridisation approach two new members of the oleosin gene family of Arabidopsis thaliana have been isolated. The quantitative and temporal expression patterns of both genes are found to be affected in the fus3 mutant defective in late embryogenesis. This pattern is interpreted as a molecular marker for a mutant specific developmental change from a seed maturation toa germination pathway. 相似文献
12.
13.
Conditional identification of phosphate-starvation-response mutants in Arabidopsis thaliana 总被引:7,自引:0,他引:7
Plants have evolved elaborate metabolic and developmental adaptations to low phosphorus availability. Biochemical responses
to phosphate limitation include increased production and secretion of phosphate-acquisition proteins such as nucleases, acid
phosphatases, and high-affinity phosphate transporters. However, the signal transduction pathways that sense phosphate availability
and integrate the phosphate-starvation response in plants are unknown. We have devised a screen for conditional mutants in
Arabidopsis thaliana (L.) Heynh. to dissect signaling of phosphate limitation. Our genetic screen is based on the facultative ability of wild-type
Arabidopsis plants to metabolize exogenous DNA when inorganic phosphate is limiting. After screening 50,000 M2 seedlings, we isolated
22 confirmed mutant lines that showed severely impaired growth on medium containing DNA as the only source of phosphorus,
but which recovered on medium containing soluble inorganic phosphate. Characterization of nine such mutant lines demonstrated
an inability to utilize either DNA or RNA. One mutant line, psr1 (phosphate starvation response), had significantly reduced activities of phosphate-starvation-inducible isoforms of ribonuclease and acid phosphatase under
phosphate-limiting conditions. The data suggest that a subset of the selected mutations impairs the expression of more than
one phosphate-starvation-inducible enzyme required for utilization of exogenous nucleic acids, and may thus affect regulatory
components of a Pi starvation response pathway in higher plants.
Received: 23 September 1999 / Accepted: 10 November 1999 相似文献
14.
Characterisation of pea cytosolic glutathione reductase expressed in transgenic tobacco 总被引:4,自引:0,他引:4
Expression in transgenic tobacco (Nicotiana tabacum L.) of a pea (Pisum sativum L.) GOR2 cDNA, encoding an isoform of glutathione reductase (GOR2), resulted in a 3- to 7-fold elevation of total foliar glutathione
reductase (GR) activity. The enzyme encoded by GOR2 was confirmed to be extraplastidial in organelle fractionation studies and was considered most likely to be localised in
the cytosol. A partial purification of GOR2 was achieved but a standard affinity chromatography step, using adenosine-2′,5′-diphosphate-Sepharose
and often employed in the purification of GR from diverse sources, was unsuccessful with this isoform. Preparative isoelectric
focussing was employed as part of the purification procedure of GOR2 and a complete separation from plastidial/mitochondrial
glutathione reductase (GOR1) was achieved. The isoform GOR2 was shown to have a slower migration on non-denaturing polyacrylamide
gels compared with GOR1 and properties typical of GR enzymes from plant sources.
Received: 9 November 1999 / Accepted: 28 February 2000 相似文献
15.
Caesium-affected gene expression in Arabidopsis thaliana 总被引:5,自引:0,他引:5
16.
Plants acclimate to changes in light quantity by altering leaf-cell development and the accumulation of chloroplast components,
such that light absorption is favoured under limiting illumination, and light utilisation under non-limiting conditions. Previous
evidence suggests an involvement of a high-light photosynthetic redox signal in the down-regulation of the accumulation of
the light-harvesting complexes of photosystem II (Lhcb) and the expression of the Lhcb genes, and of a blue-light signal in the control of leaf development and in the increase in photosynthetic capacity, as affected
by the accumulation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). We examined the internal anatomy of leaves,
the ultrastructure of chloroplasts and accumulation of light-harvesting complexes and Rubisco in wild-type Arabidopsis thaliana (L.) Heynh. and in mutants in each of the three known blue-light photoreceptors, cryptochrome 1, cryptochrome 2 and phototropin,
as well as a mutant in both cryptochromes. Our results indicate an extensive capacity of the Arabidopsis mesophyll cells to adapt to high light fluence rate with an increase in palisade elongation. Under high light, chloroplasts
showed increased starch accumulation and reductions in the amount of granal thylakoids per chloroplast, in the proportion
of chlorophyll b relative to chlorophyll a, and in the accumulation of the major Lhcb polypeptides. The responses were similar
for all four mutants, with respect to their wild types. The results are consistent with either a complete redundancy in function
between cryptochromes and phototropin, or their absence of involvement in the light-quantity responses tested. We observed
minimal effects of light quantity on Rubisco accumulation over the range of fluence rates used, and conclude that elongation
of palisade mesophyll cells and accumulation of Rubisco are controlled separately. This indicates that light acclimation must
be the result of a number of individual elementary responses. Quantitative differences in the acclimatory responses were observed
between the Landsberg erecta and Columbia wild-type ecotypes used.
Received: 4 April 2000 / Accepted: 14 July 2000 相似文献
17.
Photoassimilates are used by plants for production of energy, as carbon skeletons and in transport of fixed carbon between
different plant organs. Many studies have been devoted to characterizing the factors that regulate photoassimilate concentrations
in different plant species. Most studies examining photoassimilate concentrations in C3 plants have focused on analyzing starch and soluble sugars. However, work presented here demonstrates that a number of C3 plants, including the popular model organism Arabidopsis thaliana (L.) Heynh., and agriculturally important plants, such as soybean, Glycine max (L.) Merr., contain significant quantities of fumaric acid. In fact, fumaric acid can accumulate to levels of several milligrams
per gram fresh weight in Arabidopsis leaves, often exceeding those of starch and soluble sugars. Fumaric acid is a component of the tricarboxylic acid cycle and,
like starch and soluble sugars, can be metabolized to yield energy and carbon skeletons for production of other compounds.
Fumaric acid concentrations increase with plant age and light intensity in Arabidopsis leaves. Moreover, Arabidopsis phloem exudates contain significant quantities of fumaric acid, raising the possibility that fumaric acid may function in
carbon transport.
Received: 11 February 2000 / Accepted: 1 April 2000 相似文献
18.
Temperature-dependent internode elongation in vegetative plants of Arabidopsis thaliana lacking phytochrome B and cryptochrome 1 总被引:1,自引:0,他引:1
Vegetative plants of Arabidopsis thaliana (L.) Heynh. form a compact rosette of leaves in which internode growth is virtually arrested. Rapid extension of the internodes
occurs after flower buds are present in the reproductive apex. Under natural radiation, continuous light from fluorescent
lamps, or short photoperiods of light from fluorescent lamps, plants of the phyB cry1 double mutant (lacking both phytochrome B and cryptochrome 1) did not form normal rosettes because all the internodes showed
some degree of elongation. Internode elongation was weak in the phyB single mutant and absent in the cry1 mutant, indicating redundancy between phytochrome B and cryptochrome 1. The absence of phytochrome A caused no effects. The
failure to form normal rosettes was conditional because internode elongation was arrested at low temperatures in all the mutant
combinations. In contrast, the temperature dependence of phytochrome B and cryptochrome 1 effects on hypocotyl growth was
weak. The elongation of the internodes in phyB cry1 was not accompanied by early flowering as showed by the lack of effects on the final number of leaves. Apex dissection indicated
that in phyB cry1 double mutants internode elongation anticipated the transition from the vegetative to the reproductive stage. Thus, stem
growth in Arabidopsis thaliana is not fully dependent on the program of reproductive development.
Received: 2 June 1999 / Accepted: 13 August 1999 相似文献
19.
20.
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