SEARCH · PubMed Health

Results for “Meristem”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10Linked to original sources

PubMed2000

Regulation of SUP expression identifies multiple regulators involved in arabidopsis floral meristem development.

During the course of flower development, floral homeotic genes are expressed in defined concentric regions of floral meristems called whorls. The SUPERMAN (SUP, also called FLO10) gene, which encodes a C2H2-type zinc finger protein, is involved in maintenance of the stamen/carpel whorl boundary (the boundary between whorl 3 and whorl 4) in Arabidopsis. Here, we show that the regulation of SUP expression in floral meristems is complex, consisting of two distinct phases, initiation and maintenance. The floral meristem identity gene LEAFY (LFY) plays a role in the initiation phase through at least two pathways, which differ from each other in the involvement of two homeotic genes, APETALA3 (AP3) and PISTILLATA (PI). AP3, PI, and another homeotic gene, AGAMOUS (AG), are further required for SUP expression in the later maintenance phase. Aside from these genes, there are other as yet unidentified genes that control both the temporal and spatial patterns of SUP expression in whorl 3 floral meristems. SUP appears to act transiently, probably functioning to trigger a genetic circuit that creates the correct position of the whorl 3/whorl 4 boundary.

AGAMOUS Protein, Arabidopsis↗

PubMed1995

The Arabidopsis AGL8 MADS box gene is expressed in inflorescence meristems and is negatively regulated by APETALA1.

MADS box genes encode putative transcription factors that play important roles in plant and animal development. In plants, MADS box genes are involved in the early step of specifying floral meristem identity as well as the later step of determining the fate of floral organ primordia. Here, we describe the isolation and characterization of a new MADS box gene from Arabidopsis, designated AGL8. Although AGL8 RNA does not accumulate during vegetative growth, it accumulates to high levels in the inflorescence apical meristem as well as in the inflorescence stem and cauline leaves. AGL8 RNA is excluded from the young flower primordia that arise on the flanks of the inflorescence meristem but later accumulates in the walls of the developing carpels. The lack of AGL8 RNA in floral meristems is due in part to the action of another MADS box gene, APETALA1, because AGL8 RNA does accumulate in apetala1 mutant flower primordia.

Amino Acid Sequence↗

PubMed1996

Identification of a meristem L1 layer-specific gene in Arabidopsis that is expressed during embryonic pattern formation and defines a new class of homeobox genes.

Homeobox genes are master regulatory genes that specify the body plan and control development of many eukaryotic organisms, including plants. We isolated and characterized a cDNA designated ATML1 (for Arabidopsis thaliana meristem L1 layer) that encodes a novel homeodomain protein. The ATML1 protein shares high sequence homology inside and outside of the homeodomain with both the Phalaenopsis O39 and the Arabidopsis GLABRA2 (GL2) homeodomain proteins, which together define a new class of plant homeodomain-containing proteins, designated HD-GL2. The ATML1 gene was first expressed in the apical cell after the first asymmetric division of the zygote and continued to be expressed in all proembryo cells until the eight-cell stage. In the 16-cell proembryo, the ATML1 gene showed a distinct pattern of expression, with its mRNA becoming restricted to the protoderm. In the torpedo stage of embryo development, ATML1 mRNA disappeared altogether but reappeared later only in the L1 layer of the shoot apical meristem in the mature embryo. After germination, this L1 layer-specific pattern of expression was maintained in the vegetative shoot apical meristem, inflorescence, and floral meristems, as well as in the young floral organ primordia. Finally, ATML1 mRNA accumulated in the protoderm of the ovule primordia and integuments and gradually became restricted in its expression to the endothelium surrounding the embryo sac. We propose that ATML1 may be involved in setting up morphogenetic boundaries of positional information necessary for controlling cell specification and pattern formation. In addition, ATML1 provides an early molecular marker for the establishment of both apical-basal and radial patterns during plant embryogenesis.

Amino Acid Sequence↗

PubMed2004

A novel Arabidopsis gene TONSOKU is required for proper cell arrangement in root and shoot apical meristems.

Root apical meristem (RAM) and shoot apical meristem (SAM) are vital for the correct development of the plant. The direction, frequency, and timing of cell division must be tightly controlled in meristems. Here, we isolated new Arabidopsis mutants with shorter roots and fasciated stems. In the tonsoku (tsk) mutant, disorganized RAM and SAM formation resulted from the frequent loss of proper alignment of the cell division plane. Irregular cell division also occurred in the tsk embryo, and the size of cells in meristems and embryo in tsk mutant was larger than in the wild type. In the enlarged SAM of the tsk mutant, multiple centers of cells expressing WUSCHEL (WUS) were observed. In addition, expression of SCARECROW (SCR) in the quiescent center (QC) disappeared in the disorganized RAM of tsk mutant. These results suggest that disorganized cell arrangements in the tsk mutants result in disturbed positional information required for the determination of cell identity. The TSK gene was found to encode a protein with 1311 amino acids that possesses two types of protein-protein interaction motif, leucine-glycine-asparagine (LGN) repeats and leucine-rich repeats (LRRs). LGN repeats are present in animal proteins involved in asymmetric cell division, suggesting the possible involvement of TSK in cytokinesis. On the other hand, the localization of the TSK-GFP (green fluorescent protein) fusion protein in nuclei of tobacco BY-2 cells and phenotypic similarity of tsk mutants to other fasciated mutants suggest that the tsk mutation may cause disorganized cell arrangements through defects in genome maintenance.

Amino Acid Sequence↗

PubMed2006

Below-ground bud banks increase along a precipitation gradient of the North American Great Plains: a test of the meristem limitation hypothesis.

In perennial grasslands, the below-ground population of meristems (bud bank) plays a fundamental role in plant population dynamics. Here, we tested the 'meristem limitation hypothesis' prediction - that bud banks increase along an increasing precipitation/productivity gradient in North American grasslands - and assessed the seasonal dynamics of bud banks. We sampled bud and stem populations quarterly at six sites across a 1100 km gradient in central North America. Bud banks increased with average annual precipitation, which explained 80% of the variability between the sites. In addition, seasonal changes in grass bud banks were surprisingly similar across a 2.5-fold range in precipitation and a 4-fold range of productivity: densities peaked in March, decreased in June and increased slightly in September. Increasing meristem limitation may constrain vegetation responses to inter-annual changes in resources. An important consequence of this is that biomes with large bud banks may be the most responsive to environmental change. If meristem limitation represents an important constraint on productivity responses to environmental variability, then bud banks must be considered in developing predictive models for grassland responses to environmental change.

Acclimatization↗

PubMed2002

The control of spikelet meristem identity by the branched silkless1 gene in maize.

Most of the world's food supply is derived from cereal grains that are borne in a unique structure called the spikelet, the fundamental unit of inflorescence architecture in all grasses. branched silkless1 (bd1) is a maize mutation that alters the identity of the spikelet meristem, causing indeterminate branches to form in place of spikelets. We show that bd1 encodes a putative ERF transcription factor that is conserved in different grasses and is expressed in a distinct domain of the spikelet meristem. Its expression pattern suggests that signaling pathways regulate meristem identity from lateral domains of the spikelet meristem.

Alleles↗

PubMed2003

Shoot meristem: an ideal explant for Zea mays L. transformation.

We report on a rapid high-frequency somatic embryogenesis and plant regeneration protocol for Zea mays. Maize plants were regenerated from complete shoot meristem (3-4 mm) explants via organogenesis and somatic embryogenesis. In organogenesis, the shoot meristems were directly cultured on a high-cytokinin medium comprising 5-10 mg x L(-1) 6-benzylaminopurine (BAP). The number of multiple shoots produced per meristem varied from six to eight Plantlet regeneration through organogenesis resulted in just four weeks. Callus was induced in five days of incubation on an auxin-modified Murashige and Skoog (MS) medium. Prolific callus, with numerous somatic embryos, developed within 3-4 weeks when cultured on an auxin medium containing 5 mg 2,4-dichlorophenoxyacetic acid x L(-1). The number of multiple shoots varied from three to six per callus. Using R23 (Pioneer, Hi-Bred, Johnston, Iowa), the frequency of callus induction was consistently in excess of 80% and plant regeneration ranged between 47 and 64%. All regenerated plantlets survived in the greenhouse and produced normal plants. Each transgenic plant produced leaves, glumes, and anthers that uniformly expressed green fluorescent protein (GFP). The GFP gene segregated in the pollen. Based on this data it is concluded that the transgenics arose from single-cell somatic embryos. The rate of transfer DNA (T-DNA) transfer to complete shoot meristems of Zea mays was high on the auxin medium and was independent of using super-virulent strains of Agrobacterium.

2,4-Dichlorophenoxyacetic Acid↗

PubMed2004

The HALTED ROOT gene encoding the 26S proteasome subunit RPT2a is essential for the maintenance of Arabidopsis meristems.

In higher plants, post-embryonic development is dependent on the activity of the root and shoot apical meristem (RAM and SAM). The quiescent center (QC) in the RAM and the organizing center (OC) in the SAM are known to be essential for the maintenance of meristematic activity. To understand the mechanism that maintains post-embryonic meristems, we isolated an Arabidopsis mutant, halted root (hlr). In this mutant, the cellular organization was disrupted in post-embryonic meristems both in the root and in the shoot, and their meristematic activity was reduced or became abnormal. We showed that the mutant RAM lost its QC identity after germination, which was specified during embryogenesis, whereas the identity of differentiated tissues was maintained. In the post-embryonic SAM, the expression pattern of a typical OC marker gene, WUSCHEL, was disturbed in the mutant. These observations indicate that the HLR gene is essential to maintain the cellular organization and normal nature of the RAM and SAM. The HLR gene encodes RPT2a, which is a subunit of the 26S proteasome that degrades key proteins in diverse cellular processes. We showed that the HLR gene was expressed both in the RAM and in the SAM, including in the QC and the OC, respectively, and that the activity of proteasomes were reduced in the mutant. We propose that proteasome-dependent programmed proteolysis is required to maintain the meristem integrity both in the shoot and in the root.

Amino Acid Sequence↗

PubMed2004

The maize duplicate genes narrow sheath1 and narrow sheath2 encode a conserved homeobox gene function in a lateral domain of shoot apical meristems.

The narrow sheath (ns) phenotype of maize is a duplicate factor trait conferred by mutations at the unlinked loci ns1 and ns2. Recessive mutations at each locus together confer the phenotypic deletion of a lateral compartment in maize leaves and leaf homologs. Previous analyses revealed that the mediolateral axis of maize leaves is comprised of at least two distinct compartments, and suggest a model whereby NS function is required to recruit leaf founder cells from a lateral compartment of maize meristems. Genomic clones of two maize homeodomain-encoding genes were isolated by homology to the WUSCHEL-related gene PRESSED FLOWER (PRS). PRS is required for lateral sepal development in Arabidopsis, although no leaf phenotype is reported. Co-segregation of the ns phenotype with multiple mutant alleles of two maize PRS homologs confirms their allelism to ns1 and ns2. Analyses of NS protein accumulation verify that the ns-R mutations are null alleles. ns transcripts are detected in two lateral foci within maize meristems, and in the margins of lateral organ primordia. Whereas ns1 and ns2 transcripts accumulate to equivalent levels in shoot meristems of vegetative seedlings, ns2 transcripts predominate in female inflorescences. Previously undiscovered phenotypes in the pressed flower mutant support a model whereby the morphology of eudicot leaves and monocot grass leaves has evolved via the differential elaboration of upper versus lower leaf zones. A model implicating an evolutionarily conserved NS/PRS function during recruitment of organ founder cells from a lateral domain of plant meristems is discussed.

Amino Acid Sequence↗

PubMed1997

ETTIN patterns the Arabidopsis floral meristem and reproductive organs.

ettin (ett) mutations have pleiotropic effects on Arabidopsis flower development, causing increases in perianth organ number, decreases in stamen number and anther formation, and apical-basal patterning defects in the gynoecium. The ETTIN gene was cloned and encodes a protein with homology to DNA binding proteins which bind to auxin response elements. ETT transcript is expressed throughout stage 1 floral meristems and subsequently resolves to a complex pattern within petal, stamen and carpel primordia. The data suggest that ETT functions to impart regional identity in floral meristems that affects perianth organ number spacing, stamen formation, and regional differentiation in stamens and the gynoecium. During stage 5, ETT expression appears in a ring at the top of the floral meristem before morphological appearance of the gynoecium, consistent with the proposal that ETT is involved in prepatterning apical and basal boundaries in the gynoecium primordium. Double mutant analyses and expression studies show that although ETT transcriptional activation occurs independently of the meristem and organ identity genes LEAFY, APETELA1, APETELA2 and AGAMOUS, the functioning of these genes is necessary for ETT activity. Double mutant analyses also demonstrate that ETT functions independently of the 'b' class genes APETELA3 and PISTILLATA. Lastly, double mutant analyses suggest that ETT control of floral organ number acts independently of CLAVATA loci and redundantly with PERIANTHIA.

Amino Acid Sequence↗

PubMed1998

The HOBBIT gene is required for formation of the root meristem in the Arabidopsis embryo.

In Arabidopsis, the root meristem originates from the hypophyseal cell and from an adjoining cell tier that is distinct at the heart stage of embryogenesis. We have analysed mutations in the HOBBIT (HBT) gene that is essential for root meristem formation. hbt embryos display incorrect hypophyseal cell development from the quadrant stage onward. At the heart stage, the adjoining cell tier of hbt embryos develops abnormally, in that the activation of cell division and the formation of a lateral root cap layer are disturbed. Strong hbt mutants give rise to seedlings that lack an anatomically recognisable quiescent centre and differentiated columella root cap cells, the cell types derived from the wild-type hypophysis. Furthermore, they have no mitotically active root meristem and lack a differentiated lateral root cap. Secondary roots of hbt mutants and roots obtained from cultured cells of hbt mutants have similar defects. Therefore the HBT gene is required for root meristem formation in different developmental contexts.

Arabidopsis↗

PubMed2006

WFL, a wheat FLORICAULA/LEAFY ortholog, is associated with spikelet formation as lateral branch of the inflorescence meristem.

FLORICAULA (FLO) of Antirrhinum and LEAFY (LFY) of Arabidopsis encode plant-specific transcription factors, which are necessary and sufficient to specify floral meristem identity. We isolated WFL, a wheat FLO/LFY ortholog, and analyzed its expression pattern. RT-PCR analysis indicated that WFL is expressed predominantly in young spike. The WFL expression pattern during reproductive development was analyzed in more detail by using in situ hybridization technique. WFL transcripts were observed in all layers of the young spike excepting spikelet initiation sites as axillary meristem. In the double-ridge stage, WFL transcripts were localized in the lower ridge but were absent in the upper ridge, where spikelet meristem initiates. The WFL expression pattern indicated that WFL is associated with spikelet formation rather than floral meristem identity in wheat. As development of floret proceeds, the WFL transcripts were detectable in the developing palea, but not in other floral organs, suggesting that WFL may play a novel role in developing palea in the wheat floret.

Flowering Tops↗

PubMed2000

[Study of the behavior of the vegetative meristem of alfa (Stipa tenacissima L.). Cytological and histological approaches].

The biological and cytological studies of the vegetative meristem of Stipa tenacissima L. gave clear indication about its structure. It was similar to what was previously described in several species. This meristem showed an axial apical zone constituted by sommital cells of both tunica and corpus, a sub-apical lateral zone, very chromophilous, representing the initial ring and a medullar meristem. The cytofluorimetric determination of DNA in interphasic nuclei of these three zones revealed that the nuclei of the apical and lateral zones were in S phase, announcing the beginning of mitosis and meaning that these zones were the centers of the foliar initiation. The medullar meristem was in dormancy: all the nuclei were in G1 phase.

DNA, Plant↗

PubMed2002

Use of meristem tip culture to eliminate carnation latent virus from carnation plants.

A successful protocol for meristem tip culture to eliminate carnation latent virus from carnation cv. scania has been described . The virus was found to be mechanically transmissible to Chenopodium quinoa, C. amaranticolor, Dianthus barbatus and Saponaria vaccaria. Murashige and Skoog'smedium (MS) supplemented with NAA (1.0 microM) and Kn (20.0 microM) proved best for meristem establishment and microshoots were rooted in MS medium supplemented with IBA (5.0 microM). Meristems measuring 0.1 and-0.2 mm yielded virus free plants and larger meristems were not effective.

Adenine↗

PubMed2006

The rice FON1 gene controls vegetative and reproductive development by regulating shoot apical meristem size.

Most plant organs develop from meristems. Rice FON1, which is an ortholog of Clv1, regulates stem cell proliferation and organ initiation. The point muta-tions, fon1-1 and fon1-2, disrupt meristem balance, resulting in alteration of floral organ numbers and the architecture of primary rachis branches. In this study, we identified two knockout alleles, fon1-3 and fon1-4, generated by T-DNA and Tos17 insertion, respectively. Unlike the previously isolated point mutants, the null mutants have alterations not only of the reproductive organs but also of vegetative tissues, producing fewer tillers and secondary rachis branches. The mutant plants are semi-dwarfs due to delayed leaf emergence, and leaf senescence is delayed. SEM analysis showed that the shoot apical meristems of fon1-3 mutants are enlarged. These results indicate that FON1 controls vegetative as well as reproductive development by regulating meristem size.

Aging↗

PubMed2002

What the Distribution of Cell Lengths in the Root Meristem Does and Does Not Reveal About Cell Division.

Roots have long been realized to be useful material for studies of cell division. Despite this long history of use, the behavior of cells in the meristem is often misinterpreted. A common error is to argue that differences in cell length reflect differences in cell division rate. In this article we explain the fallacy behind this argument and show how the analysis of cell length distribution can lead to insight about the root meristem. These observations support a model for the root meristem where cells of various tissues grow at the same relative growth rate and divide at the same frequency, indicating that these growth parameters are built into the cells at a fundamental level. The differences in cell length between various tissues appear to arise at their formation, first at the tissue initials and ultimately in the seed. Length differences among mature cells may be enhanced by differences in the location within the meristem where division ceases. Discovering mechanisms regulating the length of initial cells and the position where cells cease division requires a realistic understanding of how growth constrains the division behavior of dividing cells.

Journal Article↗

PubMed1992

LEAFY controls floral meristem identity in Arabidopsis.

The first step in flower development is the generation of a floral meristem by the inflorescence meristem. We have analyzed how this process is affected by mutant alleles of the Arabidopsis gene LEAFY. We show that LEAFY interacts with another floral control gene, APETALA1, to promote the transition from inflorescence to floral meristem. We have cloned the LEAFY gene, and, consistent with the mutant phenotype, we find that LEAFY RNA is expressed strongly in young flower primordia. LEAFY expression procedes expression of the homeotic genes AGAMOUS and APETALA3, which specify organ identify within the flower. Furthermore, we demonstrate that LEAFY is the Arabidopsis homolog of the FLORICAULA gene, which controls floral meristem identity in the distantly related species Antirrhinum majus.

Amino Acid Sequence↗

PubMed1996

Identification of two MADS box genes that are expressed in the apical meristem of the long-day plant Sinapis alba in transition to flowering.

To understand the molecular mechanisms involved in the transition from vegetative to reproductive growth, the photoperiodic-controlled induction of flowering in the long-day plant Sinapis alba was used to screen for regulatory genes which are expressed upon induction in the apical meristem. By using the conserved MADS box-encoding region of the organ identity gene AGAMOUS, the genes SaMADS A and SaMADS B were identified which are expressed in transition stages of mustard. RNA blot analysis has confirmed that the transcript levels of both genes are drastically increased shortly after the induction of flowering and that both genes are expressed earlier than the known MADS box genes. In situ hybridization studies have shown that the expression of the genes is restricted to the apical meristem of induced plants during early phases of reproductive development. The expression of SaMADS A is first detectable in the central zone of the meristem, a region where the earliest changes of an evoked meristem could be detected by classical physiological methods, suggesting that SaMADS A may have an important function during the transition to flowering.

Amino Acid Sequence↗