SHORT-ROOT paralogs mediate feedforward regulation of D-type cyclin to promote nodule formation in soybean

Nitrogen fixation in soybean takes place in root nodules that arise from de novo cell divisions in the root cortex. Although several early nodulin genes have been identified, the mechanism behind the stimulation of cortical cell division during nodulation has not been fully resolved. Here we provide evidence that two paralogs of soybean SHORT-ROOT (GmSHR) play vital roles in soybean nodulation. Expression of GmSHR4 and GmSHR5 (GmSHR4/5) is induced in cortical cells at the beginning of nodulation, when the first cell divisions occur. The expression level of GmSHR4/5 is positively associated with cortical cell division and nodulation. Knockdown of GmSHR5 inhibits cell division in outer cortical layers during nodulation. Knockdown of both paralogs disrupts the cell division throughout the cortex, resulting in poorly organized nodule primordia with delayed vascular tissue formation. GmSHR4/5 function by enhancing cytokinin signaling and activating early nodulin genes. Interestingly, D-type cyclins act downstream of GmSHR4/5, and GmSHR4/5 form a feedforward loop regulating D-type cyclins. Overexpression of D-type cyclins in soybean roots also enhanced nodulation. Collectively, we conclude that the GmSHR4/5-mediated pathway represents a vital module that triggers cytokinin signaling and activates D-type cyclins during nodulation in soybean.

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Integration of growth and patterning during vascular tissue formation in Arabidopsis

Science ◽

10.1126/science.1255215 ◽

2014 ◽

Vol 345 (6197) ◽

pp. 1255215 ◽

Cited By ~ 172

Author(s):

Bert De Rybel ◽

Milad Adibi ◽

Alice S. Breda ◽

Jos R. Wendrich ◽

Margot E. Smit ◽

...

Keyword(s):

Cell Migration ◽

Cell Division ◽

Pattern Formation ◽

Vascular Tissue ◽

Genetic Network ◽

Tissue Formation ◽

Cell Divisions ◽

Stable Pattern ◽

Auxin Distribution ◽

Theoretical Evidence

Coordination of cell division and pattern formation is central to tissue and organ development, particularly in plants where walls prevent cell migration. Auxin and cytokinin are both critical for division and patterning, but it is unknown how these hormones converge upon tissue development. We identify a genetic network that reinforces an early embryonic bias in auxin distribution to create a local, nonresponding cytokinin source within the root vascular tissue. Experimental and theoretical evidence shows that these cells act as a tissue organizer by positioning the domain of oriented cell divisions. We further demonstrate that the auxin-cytokinin interaction acts as a spatial incoherent feed-forward loop, which is essential to generate distinct hormonal response zones, thus establishing a stable pattern within a growing vascular tissue.

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Rapid accumulation of mutations in growing mycelia of a hypervariable fungus Schizophyllum commune

10.1101/781310 ◽

2019 ◽

Author(s):

Aleksandra V. Bezmenova ◽

Elena A. Zvyagina ◽

Anna V. Fedotova ◽

Artem S. Kasianov ◽

Tatiana V. Neretina ◽

...

Keyword(s):

Cell Division ◽

Mutation Rate ◽

De Novo ◽

Schizophyllum Commune ◽

Natural Populations ◽

Germline Cell ◽

Cell Divisions ◽

Mutation Burden ◽

Armillaria Gallica ◽

Very High

AbstractThe number of mutations that occur per nucleotide per generation varies between species by several orders of magnitude. In multicellular eukaryotes, the per generation mutation rate depends both on the per cell division mutation rate and on the number of germline cell divisions per generation. In a range of species, from fungi to humans, the number of germline cell divisions is lower than that of somatic cells, reducing the mutation burden on the offspring. The basidiomycete Schizophyllum commune has the highest level of genetic polymorphism known among eukaryotes. In a previous study, it was also found to have a high per generation mutation rate, probably contributing to its high polymorphism. However, this rate has been measured only in a breeding experiment on Petri dishes, and it is unclear how this result translates to natural populations. Here, we used an experimental design that measures the rate of accumulation of de novo mutations in a linearly growing mycelium. We show that S. commune accumulates mutations at a uniform rate of 1.4·10−7 substitutions per nucleotide per meter of growth, which is 3 orders of magnitude higher than the corresponding rates in the oak Quercus robur and the fungus Armillaria gallica. This figure is consistent with the estimate obtained before, and suggests the lack of a dedicated germline in this system. If so, even a low per cell division mutation rate can translate into a very high per generation mutation rate when the number of cell divisions between consecutive meioses is large.

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Temporal and Spatial Order of Events During the Induction of Cortical Cell Divisions in White Clover by Rhizobium leguminosarum bv. trifolii Inoculation or Localized Cytokinin Addition

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.2000.13.6.617 ◽

2000 ◽

Vol 13 (6) ◽

pp. 617-628 ◽

Cited By ~ 82

Author(s):

Ulrike Mathesius ◽

Celine Charon ◽

Barry G. Rolfe ◽

Adam Kondorosi ◽

Martin Crespi

Keyword(s):

White Clover ◽

Rhizobium Leguminosarum ◽

Cortical Cell ◽

Nodule Formation ◽

Cell Divisions ◽

Auxin Transport Inhibitor ◽

Chalcone Synthase Genes ◽

Nodule Initiation ◽

Inner Cortex

We examined the timing and location of several early root responses to Rhizobium leguminosarum bv. trifolii infection, compared with a localized addition of cytokinin in white clover, to study the role of cytokinin in early signaling during nodule initiation. Induction of ENOD40 expression by either rhizobia or cytokinin was similar in timing and location and occurred in nodule progenitor cells in the inner cortex. Inoculation of rhizobia in the mature root failed to induce ENOD40 expression and cortical cell divisions (ccd). Nitrate addition at levels repressing nodule formation inhibited ENOD40 induction by rhizobia but not by cytokinin. ENOD40 expression was not induced by auxin, an auxin transport inhibitor, or an ethylene precursor. In contrast to rhizobia, cytokinin addition was not sufficient to induce a modulation of the auxin flow, the induction of specific chalcone synthase genes, and the accumulation of fluorescent compounds associated with nodule initiation. However, cytokinin addition was sufficient for the localized induction of auxin-induced GH3 gene expression and the initiation of ccd. Our results suggest that rhizobia induce cytokinin-mediated events in parallel to changes in auxin-related responses during nodule initiation and support a role of ENOD40 in regulating ccd. We propose a model for the interactions of cytokinin with auxin, ENOD40, flavonoids, and nitrate during nodulation.

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Deciphering the transcriptomic insight during organogenesis in castor (Ricinus communis L.), jatropha (Jatropha curcas L.) and sunflower (Helianthus annuus L.)

10.1101/679027 ◽

2019 ◽

Author(s):

Sai Sudha Puvvala ◽

Tarakeswari Muddanuru ◽

Padmavathi AV Thangella ◽

Kumar Aniel O ◽

Navajeet Chakravartty ◽

...

Keyword(s):

Transcription Factors ◽

De Novo ◽

Ricinus Communis ◽

Differential Expression Analysis ◽

Regeneration Ability ◽

Oilseed Crop ◽

Rna Seq ◽

Cytokinin Signaling ◽

Short Root

AbstractBackgroundCastor is a non-edible oilseed crop with a multitude of pharmaceutical and industrial uses. Profitable cultivation of the crop is hindered by various factors and one of the approaches for genetic improvement of the crop belonging to a monotypic genus is to exploit biotechnological tools. The major limitation for successful exploitation of biotechnological tools is the in vitro recalcitrance of castor tissues. Response of castor tissues to in vitro culture is poor which necessitated study on understanding the molecular basis of organogenesis in cultured tissues of castor, through de novo transcriptome analysis, by comparing with two other crops (jatropha and sunflower) with good regeneration ability.ResultsRNA-seq analysis was carried out with hypocotyl explants from castor, jatropha and cotyledons from sunflower cultured on MS media supplemented with different concentrations of hormones. Genes that showed strong differential expression analysis during dedifferentiation and organogenic differentiation stages of callus included components of auxin and cytokinin signaling, secondary metabolite synthesis, genes encoding transcription factors, receptor kinases and protein kinases. In castor, many genes involved in auxin biosynthesis and homeostasis like WAT1 (Wall associated thinness), vacuolar transporter genes, transcription factors like short root like protein were down-regulated while genes like DELLA were upregulated accounting for regeneration recalcitrance. Validation of 62 differentially expressed genes through qRT-PCR showed a consensus of 77.4% with the RNA-Seq analysis.ConclusionThis study provides information on the set of genes involved in the process of organogenesis in three oilseed crops which forms a basis for understanding and improving the efficiency of plant regeneration and genetic transformation in castor.

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Anatomical comparison of wild-type and non-nodulating mutant chickpea (Cicer arietinum)

Canadian Journal of Botany ◽

10.1139/b90-152 ◽

1990 ◽

Vol 68 (6) ◽

pp. 1201-1207 ◽

Cited By ~ 4

Author(s):

Leslie J. Matthews ◽

Thomas M. Davis

Keyword(s):

Cell Division ◽

Cicer Arietinum ◽

Root Hair ◽

Root Nodule ◽

Cortical Cell ◽

Infection Process ◽

Nodule Formation ◽

Cell Infection ◽

Infection Threads ◽

Nodule Symbiosis

Non-nodulating chickpea (Cicer arietinum L.) mutant PM233B was characterized anatomically via comparison with its normally nodulating parent line ICC 640. Root hair and cortical cell infection threads, cortical cell division centers, and nodule formation were observed by light microscopy in serial root sections of ICC 640, but were absent in PM233B. Scanning electron microscope observations of inoculated root sections showed that ICC 640 and PM233B were indistinguishable in adsorption of chickpea Rhizobium strain CC1192. Thus, the rhizobial infection process was blocked in PM233B at a stage subsequent to root hair adsorption of bacteria, but prior to initiation of infection threads and root cortical cell division. Reciprocal shoot grafts between ICC 640 and PM233B demonstrated that the non-nodulation phenotype of PM233B was controlled by the root, and not the shoot, genotype. Key words: chickpea, Cicer arietinum, root nodule, symbiosis, non-nodulating mutant.

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De novo Cortical Cell Division Triggered by the Phytopathogen Rhodococcus fascians in Tobacco

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.2001.14.2.189 ◽

2001 ◽

Vol 14 (2) ◽

pp. 189-195 ◽

Cited By ~ 37

Author(s):

Carmem-Lara de O. Manes ◽

Marc Van Montagu ◽

Els Prinsen ◽

Koen Goethals ◽

Marcelle Holsters

Keyword(s):

Cell Division ◽

Host Plants ◽

De Novo ◽

Cortical Cell ◽

Multiple Shoot ◽

Infection Process ◽

Cortical Cells ◽

Shoot Primordia ◽

Gene Coding ◽

Rhodococcus Fascians

Plant growth, development, and morphology can be affected by several environmental stimuli and by specific interactions with phytopathogens. In many cases, plants respond to pathogenic stimuli by adapting their hormone levels. Here, the interaction between the phytopathogen Rhodococcus fascians and one of its host plants, tobacco, was analyzed phenotypically and molecularly. To elucidate the basis of the cell division modulation and shoot primordia initiation caused by R. fascians, tobacco plants were infected at leaf axils and shoot apices. Adventitious meristems that gave rise to multiple-shoot primordia (leafy galls) were formed. The use of a transgenic line carrying the mitotic CycB1 promoter fused to the reporter gene coding for β-glucuronidase from Escherichia coli (uidA), revealed that stem cortical cells were stimulated to divide in an initial phase of the leafy gall ontogenesis. Local cytokinin and auxin levels throughout the infection process as well as modulation of expression of the cell cycle regulator gene Nicta;CycD3;2 are discussed.

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Stimulated Virus Production in Vinblastine and Cytochalasin-Induced Multinucleate Cells

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100067923 ◽

1970 ◽

Vol 28 ◽

pp. 186-187

Author(s):

Krishan Awtar

Keyword(s):

Cell Division ◽

Normal Cell ◽

Virus Production ◽

Multinucleate Cells ◽

Daughter Cells ◽

Cell Divisions ◽

Nuclear Membranes ◽

Division 2 ◽

Vinblastine Sulfate

Exposure of cells to low sublethal but mitosis-arresting doses of vinblastine sulfate (Velban) results in the initial arrest of cells in mitosis followed by their subsequent return to an “interphase“-like stage. A large number of these cells reform their nuclear membranes and form large multimicronucleated cells, some containing as many as 25 or more micronuclei (1). Formation of large multinucleate cells is also caused by cytochalasin, by causing the fusion of daughter cells at the end of an otherwise .normal cell division (2). By the repetition of this process through subsequent cell divisions, large cells with 6 or more nuclei are formed.

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Effects of a Nod-factor-overproducing strain of Sinorhizobium meliloti on the expression of the ENOD40 gene in Melilotus alba

Canadian Journal of Botany ◽

10.1139/b02-076 ◽

2002 ◽

Vol 80 (9) ◽

pp. 907-915 ◽

Cited By ~ 6

Author(s):

Walter F Giordano ◽

Michelle R Lum ◽

Ann M Hirsch

Keyword(s):

Lateral Root ◽

Sinorhizobium Meliloti ◽

Cortical Cell ◽

Host Cells ◽

Nodule Development ◽

Nodule Formation ◽

Additional Increase ◽

Nod Factor ◽

Melilotus Alba ◽

Different Strains

We have initiated studies on the molecular biology and genetics of white sweetclover (Melilotus alba Desr.) and its responses to inoculation with the nitrogen-fixing symbiont Sinorhizobium meliloti. Early nodulin genes such as ENOD40 serve as markers for the transition from root to nodule development even before visible stages of nodule formation are evident. Using Northern blot analysis, we found that the ENOD40 gene was expressed within 6 h after inoculation with two different strains of S. meliloti, one of which overproduces symbiotic Nod factors. Inoculation with this strain resulted in an additional increase in ENOD40 gene expression over a typical wild-type S. meliloti strain. Moreover, the increase in mRNA brought about by the Nod-factor-overproducing strain 24 h after inoculation was correlated with lateral root formation by using whole-mount in situ hybridization to localize ENOD40 transcripts in lateral root meristems and by counting lateral root initiation sites. Cortical cell divisions were not detected. We also found that nodulation occurred more rapidly on white sweetclover in response to the Nod-factor-overproducing strain, but ultimately there was no difference in nodulation efficiency in terms of nodule number or the number of roots nodulated by the two strains. Also, the two strains could effectively co-colonize the host when inoculated together, although a few host cells were occupied by both strains.Key words: ENOD40, Nod factor, Melilotus, Sinorhizobium, symbiosis.

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discordia mutations specifically misorient asymmetric cell divisions during development of the maize leaf epidermis

Development ◽

10.1242/dev.126.20.4623 ◽

1999 ◽

Vol 126 (20) ◽

pp. 4623-4633 ◽

Cited By ~ 2

Author(s):

K. Gallagher ◽

L.G. Smith

Keyword(s):

Cell Division ◽

Preprophase Band ◽

Cytochalasin D ◽

Leaf Epidermis ◽

Asymmetric Cell Divisions ◽

Maize Leaf ◽

Cell Divisions ◽

Cytoskeletal Structure ◽

Dividing Cells ◽

Preprophase Bands

In plant cells, cytokinesis depends on a cytoskeletal structure called a phragmoplast, which directs the formation of a new cell wall between daughter nuclei after mitosis. The orientation of cell division depends on guidance of the phragmoplast during cytokinesis to a cortical site marked throughout prophase by another cytoskeletal structure called a preprophase band. Asymmetrically dividing cells become polarized and form asymmetric preprophase bands prior to mitosis; phragmoplasts are subsequently guided to these asymmetric cortical sites to form daughter cells of different shapes and/or sizes. Here we describe two new recessive mutations, discordia1 (dcd1) and discordia2 (dcd2), which disrupt the spatial regulation of cytokinesis during asymmetric cell divisions. Both mutations disrupt four classes of asymmetric cell divisions during the development of the maize leaf epidermis, without affecting the symmetric divisions through which most epidermal cells arise. The effects of dcd mutations on asymmetric cell division can be mimicked by cytochalasin D treatment, and divisions affected by dcd1 are hypersensitive to the effects of cytochalasin D. Analysis of actin and microtubule organization in these mutants showed no effect of either mutation on cell polarity, or on formation and localization of preprophase bands and spindles. In mutant cells, phragmoplasts in asymmetrically dividing cells are structurally normal and are initiated in the correct location, but often fail to move to the position formerly occupied by the preprophase band. We propose that dcd mutations disrupt an actin-dependent process necessary for the guidance of phragmoplasts during cytokinesis in asymmetrically dividing cells.

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The growth of supernumerary legs in the cockroach

Development ◽

10.1242/dev.92.1.115 ◽

1986 ◽

Vol 92 (1) ◽

pp. 115-131

Author(s):

Paul R. Truby

Keyword(s):

Wound Healing ◽

Cell Division ◽

Rapid Rate ◽

Large Area ◽

Anteroposterior Axis ◽

Cell Divisions ◽

Leucophaea Maderae ◽

Different Types ◽

Local Cell

When the anteroposterior axis of a cockroach leg is reversed at a graft by exchanging a left leg for a right leg at the mid-tibia level, regeneration occurs in the region of the graft/host junction. This results in the formation of a pair of lateral supernumerary legs. In these experiments the patterns of cell division which take place during supernumerary leg formation were observed in sections of regenerating legs of the cockroach Leucophaea maderae. Early patterns of cell division resemble those seen in control grafts in which no axial reversal had been carried out during grafting. These cell divisions are associated with the process of wound healing. Later, a large area of the epidermis proximal to the graft/host junction becomes activated and shows a rapid rate of cell division. This area forms two outgrowths which grow by cell division throughout their epidermis to form the epidermis of the supernumerary legs. The results are more consistent with the view that the formation of supernumerary legs involves dedifferentiation of the epidermis in the region of the graft/host junction to form a blastema, rather than being due to local cell division at the point of maximum pattern discontinuity. This conclusion is used to offer an explanation for the range of different types of outcome of left-right grafts that has been observed.

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