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PubMed2001

Control of axillary bud initiation and shoot architecture in Arabidopsis through the SUPERSHOOT gene.

The aerial architecture of flowering plants is determined to a large extent by shoot growth and shoot branching arising from the initiation and growth of axillary meristems. We have identified an Arabidopsis mutant, supershoot (sps), which is characterized by a massive overproliferation of shoots, such that a single plant can generate 500 or more inflorescences. Analysis of the mutant plants shows that the primary defect is because of an increase in the number of meristems formed in leaf axils, together with release of bud arrest, resulting in reiterative branch formation from rosette and cauline leaves. The SPS gene is shown here to encode a cytochrome P450, and together with a 3- to 9-fold increase in levels of Z-type cytokinins in sps mutant plants, indicate a role for SPS in modulating hormone levels. The expression pattern of SPS, with strong expression at the leaf axils, correlates well with the phenotypic defects. Our results indicate that control of shoot branching in Arabidopsis may be accomplished in part by suppression of axillary meristem initiation and growth through the localized attenuation of cytokinin levels at sites of bud initiation.

Arabidopsis↗

PubMed2002

Regulation of squalene synthase, a key enzyme of sterol biosynthesis, in tobacco.

Squalene synthase (SS) represents a putative branch point in the isoprenoid biosynthetic pathway capable of diverting carbon flow specifically to the biosynthesis of sterols and, hence, is considered a potential regulatory point for sterol metabolism. For example, when plant cells grown in suspension culture are challenged with fungal elicitors, suppression of sterol biosynthesis has been correlated with a reduction in SS enzyme activity. The current study sought to correlate changes in SS enzyme activity with changes in the level of the corresponding protein and mRNA. Using an SS-specific antibody, the initial suppression of SS enzyme activity in elicitor-challenged cells was not reflected by changes in the absolute level of the corresponding polypeptide, implicating a post-translational control mechanism for this enzyme activity. In comparison, the absolute level of the SS mRNA did decrease approximately 5-fold in the elicitor-treated cells, which is suggestive of decreased transcription of the SS gene. Study of SS in intact plants was also initiated by measuring the level of SS enzyme activity, the level of the corresponding protein, and the expression of SS gene promoter-reporter gene constructs in transgenic plants. SS enzyme activity, polypeptide level, and gene expression were all localized predominately to the shoot apical meristem, with much lower levels observed in leaves and roots. These later results suggest that sterol biosynthesis is localized to the apical meristems and that apical meristems may be a source of sterols for other plant tissues.

Animals↗

PubMed2003

Expression studies of gibberellin oxidases in developing pumpkin seeds.

Two cDNA clones, 3-ox and 2-ox, have been isolated from developing pumpkin (Cucurbita maxima) embryos that show significant amino acid homology to gibberellin (GA) 3-oxidases and 2-oxidases, respectively. Recombinant fusion protein of clone 3-ox converted GA(12)-aldehyde, GA(12), GA(15), GA(24), GA(25), and GA(9) to GA(14)-aldehyde, GA(14), GA(37), GA(36), GA(13), and GA(4), respectively. Recombinant 2-ox protein oxidized GA(9), GA(4), and GA(1) to GA(51), GA(34), and GA(8), respectively. Previously cloned GA 7-oxidase revealed additional 3beta-hydroxylation activity of GA(12). Transcripts of this gene were identified in endosperm and embryo of the developing seed by quantitative reverse transcriptase-polymerase chain reaction and localized in protoderm, root apical meristem, and quiescent center by in situ hybridization. mRNA of the previously cloned GA 20-oxidase from pumpkin seeds was localized in endosperm and in tissues of protoderm, ground meristem, and cotyledons of the embryo. However, transcripts of the recently cloned GA 20-oxidase from pumpkin seedlings were found all over the embryo, and in tissues of the inner seed coat at the micropylar end. Previously cloned GA 2beta,3beta-hydroxylase mRNA molecules were specifically identified in endosperm tissue. Finally, mRNA molecules of the 3-ox and 2-ox genes were found in the embryo only. 3-ox transcripts were localized in tissues of cotyledons, protoderm, and inner cell layers of the root apical meristem, and 2-ox transcripts were found in all tissues of the embryo except the root tips. These results indicate tissue-specific GA-biosynthetic pathways operating within the developing seed.

Cloning, Molecular↗

PubMed1992

Growth, Gravitropism, and Endogenous Ion Currents of Cress Roots (Lepidium sativum L.) : Measurements Using a Novel Three-Dimensional Recording Probe.

A novel, three-dimensional recording, vibrating probe was used for measuring the density and direction of the endogenous ionic current of cress roots (Lepidium sativum L.) bathed in low salt media (artificial pond water, APW). Roots submerged in regular APW and growing vertically show the following current pattern. Current of 0.7 microampere/square centimeter density enters or leaves the root cap; the current changes direction frequently. Current of 1.6 microamperes/square centimeter enters the meristem zone most of the time. Maximum current with a density of 2.2 microamperes/square centimeter enters the apical elongating zone, i.e. between 0.8 and 1.2 millimeters behind the root tip. The current density decreases to 1.4 microamperes/square centimeter at 2 millimeters, i.e. in the central elongating zone, and to 1.0 microampere/square centimeter at 3 millimeters, i.e. in the basal elongating zone. The current direction changes from inward to predominantly outward between 1.2 and 3 millimeters behind the tip. Measurements on opposite flanks of the roots indicate that the current pattern is fairly symmetrical. After placing the roots horizontally, the density of the endogenous current remains stable, but the current direction changes at the root cap and in the meristem zone. The current leaves the root on the upper side and enters on the lower side, causing a highly asymmetrical current pattern at the very tip. The current pattern at the upper and lower side further away from the tip remains the same as in vertical roots. Roots submerged in low Ca(2+) APW show a very different current pattern, no gravitropism, and no change of the current pattern after horizontal orientation. In these roots current enters the root cap and the basal elongating zone and leaves the apical elongating zone. Three conclusions are drawn from these results: First, plant roots elongate by two different modes of growth that are correlated with different current directions. They grow by cytoplasmic enlargement at sites of inward current and by turgor-driven elongation at sites of outward current. Second, a change in the current pattern at the root cap and in the meristem zone is a clear indicator of later gravitropism. Third, Ca(2+) ions are involved in the gravistimulated change in the current pattern, probably affecting the activity of plasmalemma H(+)-ATPases.

Journal Article↗

PubMed2004

Efficient virus-induced gene silencing in roots using a modified tobacco rattle virus vector.

Due to their capability of eliciting a form of posttranscriptional gene silencing (termed virus-induced gene silencing or VIGS), plant viruses are increasingly used as reverse-genetics tools for functional characterization of plant genes. RNA viruses have been shown to trigger silencing in a variety of host plants, including members of Solanacae and Arabidopsis (Arabidopsis thaliana). Several factors affect the silencing response, including host range and viral tropism within the plant. The work presented here demonstrates that a modified tobacco rattle virus (TRV) vector retaining the helper protein 2b, required for transmission by a specific vector nematode, not only invades and replicates extensively in whole plants, including meristems, but also triggers a pervasive systemic VIGS response in the roots of Nicotiana benthamiana, Arabidopsis, and tomato (Lycopersicon esculentum). This sustained VIGS response was exemplified by the silencing of genes involved in root development (IRT1, TTG1 [transparent testa glabra], RHL1 [root hairless1], and beta-tubulin), lateral root-meristem function (RML1 [root meristemless1]), and nematode resistance (Mi). Roots of silenced plants exhibit reduced levels of target mRNA and phenocopy previously described mutant alleles. The TRV-2b vector displays increased infectivity and meristem invasion, both key requirements for efficient VIGS-based functional characterization of genes in root tissues. Our data suggest that the TRV helper protein 2b may have an essential role in the host regulatory mechanisms that control TRV invasion.

Animals↗

PubMed1994

Nonvascular, Symplasmic Diffusion of Sucrose Cannot Satisfy the Carbon Demands of Growth in the Primary Root Tip of Zea mays L.

Nonvascular, symplasmic transport of sucrose (Suc) was investigated theoretically in the primary root tip of maize (Zea mays L. cv WF9 x Mo 17) seedlings. Symplasmic diffusion has been assumed to be the mechanism of transport of Suc to cells in the root apical meristem (R.T. Giaquinta, W. Lin, N.L. Sadler, V.R. Franceschi [1983] Plant Physiol 72: 362-367), which grow apical to the end of the phloem and must build all biomass with carbon supplied from the shoot or kernel. We derived an expression for the growth-sustaining Suc flux, which is the minimum longitudinal flux that would be required to meet the carbon demands of growth in the root apical meristem. We calculated this flux from data on root growth velocity, area, and biomass density, taking into account construction and maintenance respiration and the production of mucilage by the root cap. We then calculated the conductivity of the symplasmic pathway for diffusion, from anatomical data on cellular dimensions and the frequency and dimensions of plasmodesmata, and from two estimates of the diffusive conductance of a plasmodesma, derived from independent data. Then, the concentration gradients required to drive a growth-sustaining Suc flux by diffusion alone were calculated but were found not to be physiologically reasonable. We also calculated the hydraulic conductivity of the plasmodesmatal pathway and found that mass flow of Suc solution through plasmodesmata would also be insufficient, by itself, to satisfy the carbon demands of growth. However, much of the demand for water to cause cell expansion could be met by the water unloaded from the phloem while unloading Suc to satisfy the carbon demands of growth, and the hydraulic conductivity of plasmodesmata is high enough that much of that water could move symplasmically. Either our current understanding of plasmodesmatal ultrastructure and function is flawed, or alternative transport mechanisms must exist for Suc transport to the meristem.

Journal Article↗

PubMed1998

Analysis of cell division and elongation underlying the developmental acceleration of root growth in Arabidopsis thaliana.

To investigate the relation between cell division and expansion in the regulation of organ growth rate, we used Arabidopsis thaliana primary roots grown vertically at 20 degreesC with an elongation rate that increased steadily during the first 14 d after germination. We measured spatial profiles of longitudinal velocity and cell length and calculated parameters of cell expansion and division, including rates of local cell production (cells mm-1 h-1) and cell division (cells cell-1 h-1). Data were obtained for the root cortex and also for the two types of epidermal cell, trichoblasts and atrichoblasts. Accelerating root elongation was caused by an increasingly longer growth zone, while maximal strain rates remained unchanged. The enlargement of the growth zone and, hence, the accelerating root elongation rate, were accompanied by a nearly proportionally increased cell production. This increased production was caused by increasingly numerous dividing cells, whereas their rates of division remained approximately constant. Additionally, the spatial profile of cell division rate was essentially constant. The meristem was longer than generally assumed, extending well into the region where cells elongated rapidly. In the two epidermal cell types, meristem length and cell division rate were both very similar to that of cortical cells, and differences in cell length between the two epidermal cell types originated at the apex of the meristem. These results highlight the importance of controlling the number of dividing cells, both to generate tissues with different cell lengths and to regulate the rate of organ enlargement.

Arabidopsis↗

PubMed1998

Characterization of a maize tonoplast aquaporin expressed in zones of cell division and elongation.

We studied aquaporins in maize (Zea mays), an important crop in which numerous studies on plant water relations have been carried out. A maize cDNA, ZmTIP1, was isolated by reverse transcription-coupled PCR using conserved motifs from plant aquaporins. The derived amino acid sequence of ZmTIP1 shows 76% sequence identity with the tonoplast aquaporin gamma-TIP (tonoplast intrinsic protein) from Arabidopsis. Expression of ZmTIP1 in Xenopus laevis oocytes showed that it increased the osmotic water permeability of oocytes 5-fold; this water transport was inhibited by mercuric chloride. A cross-reacting antiserum made against bean alpha-TIP was used for immunocytochemical localization of ZmTIP1. These results indicate that this and/or other aquaporins is abundantly present in the small vacuoles of meristematic cells. Northern analysis demonstrated that ZmTIP1 is expressed in all plant organs. In situ hybridization showed a high ZmTIP1 expression in meristems and zones of cell enlargement: tips of primary and lateral roots, leaf primordia, and male and female inflorescence meristems. The high ZmTIP1 expression in meristems and expanding cells suggests that ZmTIP1 is needed (a) for vacuole biogenesis and (b) to support the rapid influx of water into vacuoles during cell expansion.

Amino Acid Sequence↗

PubMed2000

Identification and characterization of three orchid MADS-box genes of the AP1/AGL9 subfamily during floral transition.

Gene expressions associated with in vitro floral transition in an orchid hybrid (Dendrobium grex Madame Thong-In) were investigated by differential display. One clone, orchid transitional growth related gene 7 (otg7), encoding a new MADS-box gene, was identified to be specifically expressed in the transitional shoot apical meristem (TSAM). Using this clone as a probe, three orchid MADS-box genes, DOMADS1, DOMADS2, and DOMADS3, were subsequently isolated from the TSAM cDNA library. Phylogenetic analyses show that DOMADS1 and DOMADS2 are new members of the AGL2 subfamily and SQUA subfamily, respectively. DOMADS3 contains the signature amino acids as with the members in the independent OSMADS1 subfamily separated from the AGL2 subfamily. All three of the DOMADS genes were expressed in the TSAM during floral transition and later in mature flowers. DOMADS1 RNA was uniformly expressed in both of the inflorescence meristem and the floral primordium and later localized in all of the floral organs. DOMADS2 showed a novel expression pattern that has not been previously characterized for any other MADS-box genes. DOMADS2 transcript was expressed early in the 6-week-old vegetative shoot apical meristem in which the obvious morphological change to floral development had yet to occur. It was expressed throughout the process of floral transition and later in the columns of mature flowers. The onset of DOMADS3 transcription was in the early TSAM at the stage before the differentiation of the first flower primordium. Later, DOMADS3 transcript was only detectable in the pedicel tissues. Our results suggest that the DOMADS genes play important roles in the process of floral transition.

Amino Acid Sequence↗

PubMed2000

Production and characterization of diverse developmental mutants of Medicago truncatula.

The diploid annual legume Medicago truncatula has been developed as a tractable genetic system for studying biological questions that are unique to, or well suited for study in legume species. An efficient mutagenesis protocol using ethyl-methyl sulfonate and a polymorphic ecotype with properties appropriate for use as a mapping parent are described. Isolation and characterization of three developmental mutants are described. The mtapetala mutation results in homeotic conversions of floral organ whorls 2 and 3 into sepals and carpelloid structures, respectively, similar to mutations in the apetala3/pistillata genes of Arabidopsis. The palmyra mutation primarily affects seedling shoot meristem initiation, and thus phenocopies meristem function mutations identified in Arabidopsis such as the zwille locus. The phenotype of the palmyra and mtapetala double mutant is additive, with seedling shoot meristems and floral organs indistinguishable from those of the single palmyra and mtapetala mutants, respectively. These results are consistent with a lack of genetic interaction between these loci. A third mutant, speckle, is characterized by spontaneous necrotic lesion formation on leaves, root, and stems, similar to necrosis mutants identified in other plant species. In addition to documenting the efficient mutagenesis of M. truncatula, the availability of developmental mutants that phenocopy characterized Arabidopsis mutants will provide a basis for establishing orthologous gene function between M. truncatula and Arabidopsis, once the genes responsible are cloned. Moreover, the male-sterile, female-fertile nature of the mtapetala mutant provides a convenient tool for genetic analyses in M. truncatula.

Amino Acid Sequence↗

PubMed1980

Changes of Endogenous Gibberellin-like Substances with Sex Reversal of the Apical Inflorescence of Corn.

In developing apical meristems of corn, the level of acidic, ethyl acetate-soluble gibberellin (GA)-like substances increased to a maximum of 108 micrograms GA(3)-equivalents per kilogram dry weight of tissue at inflorescence initiation, and then fell rapidly. At anthesis, only a trace (0.2 microgram per kilogram) of GA-like activity remained in the apical (male) inflorescences, whereas moderate activity (32 micrograms per kilogram), mostly of a nonpolar nature, was present in lateral, female, inflorescences.A sex reversal of the apical inflorescence, from male to female, was elicited by reducing the ambient light intensity. Higher levels of GA-like substances, particularly those eluting from a SiO(2) partition column in the nonpolar region, were observed at all harvests in the reverting meristems; levels increased to 180 micrograms per kilogram at inflorescence initiation, then dropped to 122 micrograms per kilogram in the apical (female), reverted meristems. This increase in endogenous GA-like activity with reversion to the female inflorescence is consistent with observations that (a) reversion can be obtained with exogenous application of GA(3) and (b) maleness is enhanced in GA-deficient mutants of maize. Endogenous GAs may thus play a key role in the control of sexuality of corn.

Journal Article↗

PubMed1988

Mechanisms of starvation tolerance in pearl millet.

The response of pearl millet (Pennisetum glaucum [L.]) seedlings to prolonged starvation was investigated at the biochemical and ultrastructural level. After 2 days of darkness the bulk of the seedling carbohydrate reserves were depleted. After 8 days in the dark the respiratory rate had declined to less than 50% of its initial value and the plants had lost half of their total protein content. Unlike the situation with carbohydrate depletion, protein loss was restricted to specific organs. The secondary leaf and stem (including the apical meristem) showed little or no protein loss during this period. In the primary leaf, seed, and roots, protein loss was substantial. In spite of the high rate of protein degradation in the primary leaf and roots, these organs showed no ultrastructural changes suggestive of tissue, cellular, or subcellular degradation. In addition, ribulose bisphosphate carboxylase was not preferentially degraded during starvation and only a small decline in chlorophyll content was observed after 8 days in the dark. During the period from 8 to 14 days, cell death started at the tip of the primary leaf and gradually spread downward. Both shoot and root meristems remained alive up to 14 days. Consequently, the eventual death of the plant was due to the loss of the carbohydrate-producing regions rather than the meristems. We suggest that these results provide an explanation for the high degree of starvation tolerance exhibited by pearl millet.

Journal Article↗

PubMed1992

Effects and Absorption of Sethoxydim in Cell Cycle Progression of Corn (Zea mays) and Pea (Pisum sativum).

The mechanisms of selective herbicidal action of sethoxydim were investigated by using cultured root tips of corn (Zea mays L. cv Goldencrossbantam) and pea (Pisum sativum L. cv Alaska). Meristematic cells in the cultured roots were arrested in G(1) and G(2) of the cell division cycle by sucrose starvation and resumed growth and cell division (proliferation) when sucrose was provided. Corn root growth after sucrose addition was inhibited by sethoxydim at concentrations of 0.01 micromolar and greater when roots were treated in the presence of sucrose but was not inhibited at 10 micromolar sethoxydim when they were treated during sucrose starvation. Greater absorption of [(14)C]sethoxydim into the meristematic region of corn roots was observed when cells were in proliferative condition but not when they were arrested by sucrose starvation, whereas no greater absorption of the herbicide into pea meristems was observed in either growth condition. In the cell cycle study, greater absorption of [(14)C]sethoxydim into the corn root meristem was observed at a certain limited time before S (DNA synthesis) stage. The physiological effects and the greater absorption of sethoxydim clearly depended on cell cycle progression of corn root meristem, whereas fatty acid synthesis, as well as its inhibition by sethoxydim, was not associated with either cell cycle progression or greater absorption of the herbicide.

Journal Article↗

PubMed2004

Heterogeneous expression patterns and separate roles of the SEPALLATA gene LEAFY HULL STERILE1 in grasses.

SEPALLATA (SEP) genes exhibit distinct patterns of expression and function in the grass species rice (Oryza sativa) and maize (Zea mays), suggesting that the role of the genes has changed during the evolution of the family. Here, we examine expression of the SEP-like gene LEAFY HULL STERILE1 (LHS1) in phylogenetically disparate grasses, reconstruct the pattern of gene expression evolution within the family, and then use the expression patterns to test hypotheses of gene function. Our data support a general role for LHS1 in specifying determinacy of the spikelet meristem and also in determining the identity of lemmas and paleas; these two functions are separable, as is the role of the gene in specifying floret meristems. We find no evidence that LHS1 determines flower number; it is strongly expressed in all spikelet meristems even as they are producing flowers, and expression is not correlated with eventual flower number. LHS1 expression in only the upper flowers of the spikelet appears to be the ancestral state; expression in all flowers is derived in subfamily Pooideae. LHS1 expression in pistils, stamens, and lodicules varies among the cereals. We hypothesize that LHS1 may have affected morphological diversification of grass inflorescences by mediating the expression of different floral identity genes in different regions of the floret and spikelet.

Evolution, Molecular↗

PubMed1989

Tobacco genes expressed during in vitro floral initiation and their expression during normal plant development.

Since the transition from vegetative to floral development in plants is likely to be influenced by gene expression in several plant organs, we have used an in vitro system, the tobacco "thin cell layer" system as a model for investigating gene expression associated with the initiation of flowering in higher plants. cDNA cloning has been used to identify mRNAs abundant during thin cell layer floral initiation. These genes are expressed in thin cell layer explants initiating floral meristems but not in thin cell layer explants initiating vegetative shoot meristems or possessing roots. Two of these genes are expressed transcriptionally in incipient floral apices during normal plant development. Transcripts of these genes, plus a third gene, occur at low levels in several plant organs and at high levels in the roots, with the maximum levels of root expression reached just prior to the formation of floral meristems.

Cells, Cultured↗

PubMed1998

A recessive heterochronic mutation, plastochron1, shortens the plastochron and elongates the vegetative phase in rice

We describe two recessive alleles of a rice heterochronic gene, plastochron1-1 (pla1-1) and pla1-2, that reduce the length of the plastochron to approximately half that of the wild type. Because the onset of the reproductive phase in pla1 was not temporally affected, the number of leaves produced in the vegetative phase was nearly twice that produced in the wild type. Panicle development was severely disturbed in pla1 mutants. In pla1-1, many primordia of primary rachis branches were converted into vegetative shoots. These ectopic shoots repeated the initiation of panicle development and the conversion of primary rachis branches into shoots. In the weak allele pla1-2, however, only the basal one or two primordia developed as vegetative shoots, and the remaining primordia developed to produce a truncated panicle. These results indicate that both vegetative and reproductive programs are expressed simultaneously during the reproductive phase of pla1; however, the degree varied depending on the strength of the allele. Accordingly, pla1 is a heterochronic mutation that extends the vegetative period. The shoot apical meristem of pla1 was larger than that of the wild type, although the shape was not modified. An in situ hybridization experiment using the histone H4 gene as a probe revealed that cell divisions are accelerated in the pla1 meristem. The PLA1 gene is considered to regulate the duration of the vegetative phase by controlling the rate of leaf production in the meristem.

Journal Article↗

PubMed1990

Developmental and environmental regulation of a bean chalcone synthase promoter in transgenic tobacco.

Regulatory properties of a 1.4-kilobase promoter fragment of the bean chalcone synthase CHS8 gene were examined by analysis of glucuronidase (GUS) activity in transgenic tobacco containing a CHS8-GUS gene fusion. The promoter was highly active in the root apical meristem and in petals, exclusively in those cells of the inner epidermis that accumulate anthocyanins. The gene fusion was only weakly expressed in other floral organs, mature leaves, and stems. The early stages of seedling development were characterized by an apparent wound induction of the promoter in the endosperm and strong expression in the immature root, which became localized to the apical meristem and perivascular tissue at the root-hypocotyl junction. The promoter became active during lateral root formation in both the new root and damaged tissue of the main root. The gene fusion was also expressed in greening cotyledons and primary leaves but not in the shoot apical meristem. Light modulated expression in the cotyledons and root-shoot junction but had no effect on other aspects of the developmental program. Wounding or fungal elicitor treatment of mature leaves activated the promoter in a well-defined zone adjacent to the stress site. Stress induction occurred in mesophyll and vascular tissues as well as in the epidermis. We conclude that the CHS8 promoter contains cis-elements required to establish temporal and spatial control of flavonoid biosynthesis during development and in response to diverse environmental stimuli.

Acyltransferases↗

PubMed1991

Characterization of cis-acting sequences regulating root-specific gene expression in tobacco.

The expression of the tobacco root-specific gene TobRB7 was characterized. Gel blot hybridizations to RNA isolated from various tobacco tissues demonstrated that steady-state TobRB7 mRNA is not detected in expanded leaf, stem, or shoot apex tissue. To determine the spatial pattern of expression, in situ hybridization to root sections revealed that TobRB7 expression is localized to root meristem and immature central cylinder regions. The 5' flanking region of the gene was studied with respect to its ability to direct root-specific expression. Deletions of 5' flanking sequence were fused to the beta-glucuronidase (GUS) reporter gene and transformed into tobacco. Our data demonstrated that sequences 636 base pairs from the site of transcription initiation are sufficient to direct the root-specific GUS expression in transgenic tobacco, whereas sequences 299 base pairs from the site of transcription initiation fail to direct root-specific expression. A negative regulatory element was apparent between 813 base pairs and 636 base pairs 5' of the transcription initiation site. Histochemical localization of GUS activity in transgenic plants was consistent with in situ hybridization results: GUS activity was localized to the root meristem and central cylinder regions. GUS activity appeared 2 days post-germination in the primary root meristem. In lateral roots, GUS activity was detected from the time of initiation.

Amino Acid Sequence↗