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1.
François Mankessi Aubin R. Saya Frédéric Boudon Yann Guédon Fabienne Montes Marc Lartaud Jean-Luc Verdeil Olivier Monteuuis 《Trees - Structure and Function》2010,24(4):743-752
Shoot apical meristem (SAM) domes derived from five different outdoor and in vitro sources of juvenile and mature Eucalyptus urophylla × Eucalyptus grandis akin genotypes were compared. Overall measurements of SAM dome height H and diameter D ranged from 2 to 35 μm and 20 to 80 μm, with significant differences according to the various physiological origins of plant
material investigated. SAM domes from the mature trees “Mat” were taller than those from the rejuvenated ministock plants
“Rej”; from the in vitro microcuttings “IVM” of the same clone and also from the in vitro juvenile seedlings “IVJ”, whereas
outdoor seedlings “Juv” exhibited intermediate SAM dome height. SAM domes from the rejuvenated material “Rej”, from the in
vitro mature “IVM” and juvenile “IVJ” origins were also narrower than those from the outdoor seedlings “Juv” and to lesser
extent than those from the mature trees “Mat”. Overall, the mature source “Mat” displayed bigger and somehow sharper hemispherical
domes than those from “Rej” and “Juv”, physiologically more juvenile, or those from the in vitro origins “IVM” and “IVJ” which
looked flatter and smaller. SAM dome height, diameter D and H/D values varied also significantly according to the plastochron. More specifically, H, D, and H/D SAM differences between the five origins were not significant during the early plastochron phase corresponding to leaf initiation,
to become more salient as leaf structures started to elongate and to differentiate. This was particularly obvious for mature
tree “Mat” SAM dome shapes which showed at this stage much higher H/D values than the other SAM sources. A shape index S used for characterizing more accurately dome shape confirmed these trends. These observations provide additional arguments
to the view that juvenility in trees becomes more and more time- and shoot-tip restricted as ageing increases in the course
of time during the ontogenetical process and could be ultimately confined to the most organogenic phase of SAM, from which
shoot characteristics derive. 相似文献
2.
Hiroki Miwa Atsuko Kinoshita Hiroo Fukuda Shinichiro Sawa 《Journal of plant research》2009,122(1):31-39
The plant meristems, shoot apical meristem (SAM) and root apical meristem (RAM), are unique structures made up of a self-renewing
population of undifferentiated pluripotent stem cells. The SAM produces all aerial parts of postembryonic organs, and the
RAM promotes the continuous growth of roots. Even though the structures of the SAM and RAM differ, the signaling components
required for stem cell maintenance seem to be relatively conserved. Both meristems utilize cell-to-cell communication to maintain
proper meristematic activities and meristem organization and to coordinate new organ formation. In SAM, an essential regulatory
mechanism for meristem organization is a regulatory loop between WUSCHEL (WUS) and CLAVATA (CLV), which functions in a non-cell-autonomous manner. This intercellular signaling network coordinates the development of the
organization center, organ boundaries and distant organs. The CLAVATA3/ESR (CLE)-related genes produce signal peptides, which act non-cell-autonomously in the meristem regulation in SAM. In RAM, it has
been suggested that a similar mechanism can regulate meristem maintenance, but these functions are largely unknown. Here,
we overview the WUS–CLV signaling network for stem cell maintenance in SAM and a related mechanism in RAM maintenance. We also discuss conservation
of the regulatory system for stem cells in various plant species.
S. Sawa is the recipient of the BSJ Award for Young Scientist, 2007. 相似文献
3.
4.
Arabidopsis ACT2 represents an ancient class of vegetative plant actins and is strongly and constitutively expressed in almost all Arabidopsis sporophyte vegetative tissues. Using the beta glucuronidase report system, the studies showed that ACT2 5′ regulatory region was significantly more active than CaMV 35S promoter in Arabidopsis seedlings and gametophyte vegetative tissues of Physcomitrella patens. Its activity was also observed in rice and maize seedlings. Thus, the ACT2 5′ regulatory region could potentially serve as a strong regulator to express a transgene in divergent plant species. ACT2 5′ regulatory region contained 15 conserved sequence elements, an ancient intron in its 5′ un-translated region (5′ UTR),
and a purine-rich stretch followed by a pyrimidine-rich stretch (PuPy). Mutagenesis and deletion analysis illustrated that
some of the conserved sequence elements and the region containing PuPy sequences played regulatory roles in Arabidopsis. Interestingly, mutation of the conserved elements did not lead a dramatic change in the activity of ACT2 5′ regulatory region. The ancient intron in ACT2 5′ UTR was required for its strong expression in both Arabidopsis and P. patens, but did not fully function as a canonical intron. Thus, it was likely that some of the conserved sequence elements and gene
structures had been preserved in ACT2 5′ regulatory region over the course of land plant evolution partly due to their functional importance. The studies provided
additional evidences that identification of evolutionarily conserved features in non-coding region might be used as an efficient
strategy to predict gene regulatory elements. 相似文献
5.
Functional diversification of CLAVATA3-related CLE proteins in meristem maintenance in rice 总被引:4,自引:0,他引:4
Postembryonic development in plants depends on the activity of the shoot apical meristem (SAM) and root apical meristem (RAM). In Arabidopsis thaliana, CLAVATA signaling negatively regulates the size of the stem cell population in the SAM by repressing WUSCHEL. In other plants, however, studies of factors involved in stem cell maintenance are insufficient. Here, we report that two proteins closely related to CLAVATA3, FLORAL ORGAN NUMBER2 (FON2) and FON2-LIKE CLE PROTEIN1 (FCP1/Os CLE402), have functionally diversified to regulate the different types of meristem in rice (Oryza sativa). Unlike FON2, which regulates the maintenance of flower and inflorescence meristems, FCP1 appears to regulate the maintenance of the vegetative SAM and RAM. Constitutive expression of FCP1 results in consumption of the SAM in the vegetative phase, and application of an FCP1 CLE peptide in vitro disturbs root development by misspecification of cell fates in the RAM. FON1, a putative receptor of FON2, is likely to be unnecessary for these FCP1 functions. Furthermore, we identify a key amino acid residue that discriminates between the actions of FCP1 and FON2. Our results suggest that, although the basic framework of meristem maintenance is conserved in the angiosperms, the functions of the individual factors have diversified during evolution. 相似文献
6.
The HP1 family proteins are involved in several aspects of chromatin function and regulation in Drosophila, mammals and the
fission yeast. Here we investigate the localization of LHP1, the unique Arabidopsis thaliana HP1 homolog known at present time, to approach its function. A functional LHP1–GFP fusion protein, able to restore the wild-type
phenotype in the lhp1 mutant, was used to analyze the subnuclear distribution of LHP1 in both A. thaliana and Nicotiana tabacum. In A. thaliana interphase nuclei, LHP1 was predominantly located outside the heterochromatic chromocenters. No major aberrations were observed
in heterochromatin content or chromocenter organization in lhp1 plants. These data indicate that LHP1 is mainly involved in euchromatin organization in A. thaliana. In tobacco BY-2 cells, the LHP1 distribution, although in foci, slightly differed suggesting that LHP1 localization is determined
by the underlying genome organization of plant species. Truncated LHP1 proteins expressed in vivo allowed us to determine
the function of the different segments in the localization. The in foci distribution is dependent on the presence of the two
chromo domains, whereas the hinge region has some nucleolus-targeting properties. Furthermore, like the animal HP1β and HP1γ
subtypes, LHP1 dissociates from chromosomes during mitosis. In transgenic plants expressing the LHP1–GFP fusion protein, two
major localization patterns were observed according to cell types suggesting that localization evolves with age or differentiation
states. Our results show conversed characteristics of the A. thaliana HP1 homolog with the mammal HP1γ isoform, besides specific plant properties. 相似文献
7.
In common with most Old World Gesneriaceae; Streptocarpus Lindl. shows anisocotylous growth, i.e., the continuous growth of one cotyledon after germination. Linked to this phenomenon
is an unorthodox behaviour of the shoot apical meristem (SAM) that determines the growth pattern of acaulescent species (subgenus
Streptocarpus). In contrast caulescent species develop a conventional central post-embryonic SAM (mainly subgenus Streptocarpella). We used S. rexii Lindl. as a model to investigate anisocotyly and meristem initiation in Streptocarpus by using histological techniques and analyses of the expression pattern of the meristematic marker SrSTM1 during ontogeny. In contrast to Arabidopsis thaliana (L.) Heynh., S. rexii does not establish a SAM during embryogenesis, and the first evidence of a SAM-like structure occurs during post-embryonic
development on the axis (the petiolode) between the two cotyledons. The expression pattern of SrSTM1 suggests a function in maintaining cell division activity in the cotyledons before becoming localized in the basal meristem,
initially at the proximal ends of both cotyledons, later at the base of the continuously growing macrocotyledon, and the groove
meristem on the petiolode. The latter is equivalent to a displaced SAM seemingly originating de novo under the influence of
endogenous factors. Applied cytokinin retains SrSTM1expression in the small cotyledon, thus promoting isocotyly and re-establishment of a central post-embryonic SAM. Hormone-dependent
delocalization of the process of meristem development could underlie anisocotyly and the unorthodox SAM formation in Streptocarpus.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
8.
The flowering integrator gene FLOWERING LOCUS T (FT) in Arabidopsis thaliana is conserved between diverse plant species and is thought to be the flowering signal ‘‘florigen’’, a universal long-distance
mobile signal. In soybean, two FT homologs having a function to induce flowering in Arabidopsis have been identified. In this study, we showed that the expression
of FT from Arabidopsis by the Apple latent spherical virus (ALSV) vector promoted precocious flowering and terminated vegetative growth in a wide range of genotypes of soybean, without
using a short-day treatment. Four determinate and two indeterminate cultivars, infected with ALSV expressing FT (FT-ALSV), set flower buds on shoot apices and terminated vegetative growth at the fourth- to seventh-node stages under long-day
conditions. In contrast, non-infected, healthy plants did not set flower buds on shoot apices at the same stage under the
same conditions. After flowering, soybean cultivars infected with FT-ALSV, belonging to different maturity groups and stem
growth habits, matured and produced seeds. The results suggest that the basic flowering pathway controlled by FT in A. thaliana might also be conserved in soybean. A system for precocious flowering and shortening of generation time using FT-ALSV would
be a useful and novel technology for efficient soybean breeding. 相似文献
9.
Shaobai Huang Nicolas L. Taylor Reena Narsai Holger Eubel James Whelan A. Harvey Millar 《Plant molecular biology》2010,72(3):331-342
Complex II plays a central role in mitochondrial metabolism as a component of both the electron transport chain and the tricarboxylic
acid cycle. However, the composition and function of the plant enzyme has been elusive and differs from the well-characterised
enzymes in mammals and bacteria. Herewith, we demonstrate that mitochondrial Complex II from Arabidopsis and rice differ significantly
in several aspects: (1) Stability—Rice complex II in contrast to Arabidopsis is not stable when resolved by native electrophoresis
and activity staining. (2) Composition—Arabidopsis complex II contains 8 subunits, only 7 of which have homologs in the rice
genome. SDH 1 and 2 subunits display high levels of amino acid identity between two species, while the remainder of the subunits
are not well conserved at a sequence level, indicating significant divergence. (3) Gene expression—the pairs of orthologous
SDH1 and SDH2 subunits were universally expressed in both Arabidopsis and rice. The very divergent genes for SDH3 and SDH4 were co-expressed in both species, consistent with their functional co-ordination to form the membrane anchor. The plant-specific
SDH5, 6 and 7 subunits with unknown functions appeared to be differentially expressed in both species. (4) Biochemical regulation -succinate-dependent
O2 consumption and SDH activity of isolated Arabidopsis mitochondria were substantially stimulated by ATP, but a much more minor
effect of ATP was observed for the rice enzyme. The ATP activation of succinate-dependent reduction of DCPIP in frozen-thawed
and digitonin-solubilised mitochondrial samples, and with or without the uncoupler CCCP, indicate that the differential ATP
effect on SDH is not via the protonmotive force but likely due to an allosteric effect on the plant SDH enzyme itself, in
contrast to the enzyme in other organisms. 相似文献
10.
11.
Rice (Oryza sativa ssp. indica) is an important economic crop in many countries. Although a variety of conventional methods have been developed to improve
this plant, manipulation by genetic engineering is still complicated. We have established a system of multiple shoot regeneration
from rice shoot apical meristem. By use of MS medium containing 4 mg L−1 thidiazuron (TDZ) multiple shoots were successfully developed directly from the meristem without an intervening callus stage.
All rice cultivars tested responded well on the medium and regenerated to plantlets that were readily transferred to soil
within 5–8 weeks. The tissue culture system was suitable for Agrobacterium-mediated transformation and different factors affecting transformation efficiency were investigated. Agrobacterium strain EHA105 containing the plasmid pCAMBIA1301 was used. The lowest concentration of hygromycin B in combined with either
250 mg L−1 carbenicillin or 250 mg L−1 cefotaxime to kill the rice shoot apical meristem was 50 mg L−1 and carbenicillin was more effective than cefotaxime. Two-hundred micromolar acetosyringone had no effect on the efficiency
of transient expression. Sonication of rice shoot apical meristem for 10 s during bacterial immersion increased transient
GUS expression in three-day co-cultivated seedlings. The gus gene was found to be integrated into the genome of the T0 transformant plantlets. 相似文献
12.
Developmental role and auxin responsiveness of Class III homeodomain leucine zipper gene family members in rice 总被引:2,自引:0,他引:2
Members of the Class III homeodomain leucine zipper (Class III HD-Zip) gene family are central regulators of crucial aspects of plant development. To better understand the roles of five Class III HD-Zip genes in rice (Oryza sativa) development, we investigated their expression patterns, ectopic expression phenotypes, and auxin responsiveness. Four genes, OSHB1 to OSHB4, were expressed in a localized domain of the shoot apical meristem (SAM), the adaxial cells of leaf primordia, the leaf margins, and the xylem tissue of vascular bundles. In contrast, expression of OSHB5 was observed only in phloem tissue. Plants ectopically expressing microRNA166-resistant versions of the OSHB3 gene exhibited severe defects, including the ectopic production of leaf margins, shoots, and radialized leaves. The treatment of seedlings with auxin quickly induced ectopic OSHB3 expression in the entire region of the SAM, but not in other tissues. Furthermore, this ectopic expression of OSHB3 was correlated with leaf initiation defects. Our findings suggest that rice Class III HD-Zip genes have conserved functions with their homologs in Arabidopsis (Arabidopsis thaliana), but have also acquired specific developmental roles in grasses or monocots. In addition, some Class III HD-Zip genes may regulate the leaf initiation process in the SAM in an auxin-dependent manner. 相似文献
13.
14.
Kai J. Müller Jinxing Lin Rainer Fischer Dirk Prüfer 《Central European Journal of Biology》2006,1(2):263-274
The tobacco knox1 genes tokn1 and tokn2 were isolated and their neomorphic capacities were tested while expressed in tobacco and potato. In addition, their neomorphic
capacities were compared to barley bkn3 transgenic plant material. While tokn2 and bkn3 induced epiphylly in tobacco and supercompound leaves in potato, tokn1 failed to produce such prominent knox1 specific phenotypes. In wild type tobacco, alleles of the tokn genes were found to be expressed within distinct zones of the shoot apical meristem (SAM), leaving out regions that correlated
with leaf founder cells [1]. In contrast, the expression of the tokn genes was detected throughout the meristem and in leaf primordia of epiphyllous shoots that developed in tobacco over-expressing
the barley hooded gene bkn3. It was determined that such extended expression domains of resident tobacco knox1 genes were mediated through an enhanced expression domain of bkn3 within the tissue confined to the epiphylls, and this contributed to “repeated epiphylly”, i.e. an iterated development of
epiphyllous shoots on leaves of progenitor epiphylls. 相似文献
15.
Tinde Van Andel 《Economic botany》2010,64(1):1-10
African Rice (
Oryza glaberrima
Steud.): Lost Crop of the Enslaved Africans Discovered in Suriname. African rice (Oryza glaberrima Steud.) was introduced to the Americas during the slave trade years and grown by enslaved Africans for decades before mechanical
milling devices facilitated the shift towards Asian rice (O. sativa L.). Literature suggests that African rice is still grown in Guyana and French Guiana, but the most recent herbarium voucher
dates from 1938. In this paper, evidence is presented that O. glaberrima is still grown by Saramaccan Maroons both for food and ritual uses. Saramaccan informants claim their forefathers collected
their first “black rice” from a mysterious wild rice swamp and cultivated these seeds afterwards. Unmilled spikelets (grains
with their husk still attached) are sold in small quantities for ancestor offerings, and even exported to the Netherlands
to be used by Maroon immigrants. Little is known of the evolution of O. glaberrima, before and after domestication. Therefore, more research is needed on the different varieties of rice and other “lost crops”
grown by these descendants of enslaved Africans who escaped from plantations in the 17th and 18th centuries and maintained
much of their African cultural heritage in the deep rainforest. 相似文献
16.
Rapid progress in studies on flower development has resulted in refining the classical ‘ABC model’ into a new ‘ABCDE model’
to explain properly the regulation of floral organ identity. Conservation of E-function for flower organ identity among the
dicotyledonous (dicot) plants has been revealed. However, its conservation in monocotyledonous (monocot) plants remains largely
unknown. Here, we show the conservation of E-function in rice (Oryza sativaL.) by characterizing tissue culture-induced mutants of two MADS-box genes, OsMADS1and OsMADS5, which form a subclade within the well-supported clade of SEP-genes (E-function) phylogeny. Severe loss-of-function mutations of OsMADS1cause complete homeotic conversion of organs (lodicules, stamens, and carpels) of three inner whorls into lemma- and palea-like
structures. Such basic deformed structure is reiterated along with the pedicel at the center of the same floret, indicating
the loss of determinacy of the flower meristem. These phenotypes resemble the phenotypes caused by mutations of the dicot
E-class genes, such as the Arabidopsis SEP123(SEPALLATA1/2/3) and the petunia FBP2(Floral Binding Protein 2), suggesting that OsMADS1play a very similar role in rice to that of defined E-class genes in dicot plants. In case of the loss-of-function mutation of OsMADS5, no defect in either panicles or vegetative organs was observed. These results demonstrate that OsMADS1clearly possesses E-function, and so, E-function is fundamentally conserved between dicot plants and rice, a monocot model
plant. 相似文献
17.
18.
Acaulescent species of Streptocarpus Lindl. show unusual patterns of growth, characterized by anisocotyly (i.e. the unequal growth of cotyledons after germination)
and lack of a conventional embryonic shoot apical meristem (SAM). A SAM-like structure appears during post-embryonic development
on the axis of the continuously growing cotyledon. Since we have shown previously that KNOX genes are involved in this unusual morphology of Streptocarpus rexii, here we investigated the expression pattern of WUSCHEL (WUS), which is also required for the indeterminacy of the SAM, but is expressed independently from KNOX in Arabidopsis thaliana. In A. thaliana WUSCHEL is involved in the maintenance of the stem cell fate in the organizing centre. The expression pattern of the WUS ortholog in S. rexii (SrWUS) strongly deviates from that of the model plant, suggesting a fundamentally different spatial and temporal regulation of signalling
involved in meristem initiation and maintenance. In S. rexii, exogenous application of growth regulators, i.e. gibberellin (GA3), cytokinin (CK) and a gibberellin biosynthesis inhibitor (PAC), prevents anisocotyly and relocates meristematic cells to
a position of conventional SAMs; this coincides with a re-localization of the two main pathways controlling meristem formation,
the SrWUS and the KNOX pathways. Our results suggest that the establishment of a hormone imbalance in the seedlings is the basis of
anisocotyly, causing a lateral dominance of the macrocotyledon over the microcotyledon. The peculiar morphogenetic program
in S. rexii is linked to this delicate hormone balance and is the result of crosstalk between endogenous hormones and regulatory genes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
19.
20.
The AP1/FUL clade of MADS box genes have undergone multiple duplication events among angiosperm species. While initially identified as
having floral meristem identity and floral organ identity function in Arabidopsis, the role of AP1 homologs does not appear to be universally conserved even among eudicots. In comparison, the role of FRUITFULL has not been extensively explored in non-model species. We report on the isolation of three AP1/FUL genes from cultivated spinach, Spinacia oleracea L. Two genes, designated SpAPETALA1-1 (SpAP1-1) and SpAPETALA1-2 (SpAP1-2), cluster as paralogous genes within the Caryophyllales AP1 clade. They are highly differentiated in the 3′, carboxyl-end encoding region of the gene following the third amphipathic
alpha-helix region, while still retaining some elements of a signature AP1 carboxyl motifs. In situ hybridization studies also demonstrate that the two paralogs have evolved different temporal and
spatial expression patterns, and that neither gene is expressed in the developing sepal whorl, suggesting that the AP1 floral organ identity function is not conserved in spinach. The spinach FRUITFULL homolog, SpFRUITFULL (SpFUL), has retained the conserved motif and groups with Caryophyllales FRUITFULL homologs. SpFUL is expressed in leaf as well as in floral tissue, and shows strong expression late in flower development, particularly in
the tapetal layer in males, and in the endothecium layer and stigma, in the females. The combined evidence of high rates of
non-synonymous substitutions and differential expression patterns supports a scenario in which the AP1 homologs in the spinach AP1/FUL gene family have experienced rapid evolution following duplication.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献