scholarly journals A fern WUSCHEL-RELATED HOMEOBOX gene functions in both gametophyte and sporophyte generations

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Christopher E. Youngstrom ◽  
Lander F. Geadelmann ◽  
Erin E. Irish ◽  
Chi-Lien Cheng
Keyword(s):  
Stem Cells ◽  
Lateral Roots ◽  
Homeobox Gene ◽  
Genetic Networks ◽  
Land Plants ◽  
Seed Plants ◽  
Wild Type ◽  
Cell Fates ◽  
Cell Divisions ◽  
Gene Functions

Abstract Background Post-embryonic growth of land plants originates from meristems. Genetic networks in meristems maintain the stem cells and direct acquisition of cell fates. WUSCHEL-RELATED HOMEOBOX (WOX) transcription factors involved in meristem networks have only been functionally characterized in two evolutionarily distant taxa, mosses and seed plants. This report characterizes a WOX gene in a fern, which is located phylogenetically between the two taxa. Results CrWOXB transcripts were detected in proliferating tissues, including gametophyte and sporophyte meristems of Ceratopteris richardii. In addition, CrWOXB is expressed in archegonia but not the antheridia of gametophytes. Suppression of CrWOXB expression in wild-type RN3 plants by RNAi produced abnormal morphologies of gametophytes and sporophytes. The gametophytes of RNAi lines produced fewer cells, and fewer female gametes compared to wild-type. In the sporophyte generation, RNAi lines produced fewer leaves, pinnae, roots and lateral roots compared to wild-type sporophytes. Conclusions Our results suggest that CrWOXB functions to promote cell divisions and organ development in the gametophyte and sporophyte generations, respectively. CrWOXB is the first intermediate-clade WOX gene shown to function in both generations in land plants.

Asymmetric Numb distribution is critical for asymmetric cell division of mouse cerebral cortical stem cells and neuroblasts

Development ◽  
2002 ◽  
Vol 129 (20) ◽  
pp. 4843-4853 ◽  
Author(s):  
Qin Shen ◽  
Weimin Zhong ◽  
Yuh Nung Jan ◽  
Sally Temple
Keyword(s):  
Stem Cells ◽  
Cell Division ◽  
Progenitor Cells ◽  
Cortical Development ◽  
Cell Fates ◽  
Unequal Distribution ◽  
Asymmetric Cell Divisions ◽  
Neural Lineage ◽  
Cell Divisions ◽  
Β Tubulin

Stem cells and neuroblasts derived from mouse embryos undergo repeated asymmetric cell divisions, generating neural lineage trees similar to those of invertebrates. In Drosophila, unequal distribution of Numb protein during mitosis produces asymmetric cell divisions and consequently diverse neural cell fates. We investigated whether a mouse homologue m-numb had a similar role during mouse cortical development. Progenitor cells isolated from the embryonic mouse cortex were followed as they underwent their next cell division in vitro. Numb distribution was predominantly asymmetric during asymmetric cell divisions yielding a β-tubulin III− progenitor and a β-tubulin III+ neuronal cell (P/N divisions) and predominantly symmetric during divisions producing two neurons (N/N divisions). Cells from the numb knockout mouse underwent significantly fewer asymmetric P/N divisions compared to wild type, indicating a causal role for Numb. When progenitor cells derived from early (E10) cortex undergo P/N divisions, both daughters express the progenitor marker Nestin, indicating their immature state, and Numb segregates into the P or N daughter with similar frequency. In contrast, when progenitor cells derived from later E13 cortex (during active neurogenesis in vivo) undergo P/N divisions they produce a Nestin+ progenitor and a Nestin– neuronal daughter, and Numb segregates preferentially into the neuronal daughter. Thus during mouse cortical neurogenesis, as in Drosophila neurogenesis, asymmetric segregation of Numb could inhibit Notch activity in one daughter to induce neuronal differentiation. At terminal divisions generating two neurons, Numb was symmetrically distributed in approximately 80% of pairs and asymmetrically in 20%. We found a significant association between Numb distribution and morphology: most sisters of neuron pairs with symmetric Numb were similar and most with asymmetric Numb were different. Developing cortical neurons with Numb had longer processes than those without. Numb is expressed by neuroblasts and stem cells and can be asymmetrically segregated by both. These data indicate Numb has an important role in generating asymmetric cell divisions and diverse cell fates during mouse cortical development.

Profilin 1 Is Essential for Retention and Metabolism of Hematopoietic Stem Cells in Bone Marrow

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 1224-1224
Author(s):  
Junke Zheng ◽  
Chengcheng Zhang
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Conflicts Of Interest ◽  
Bone Marrow Failure ◽  
Actin Binding ◽  
Wild Type ◽  
Cell Fates ◽  
Hematopoietic Stem ◽  
Multiple Cell

Abstract Abstract 1224 How stem cells interact with the microenvironment to regulate their cell fates and metabolism is largely unknown. Here we show that, in a hematopoietic stem cell (HSC) -specific inducible knockout model, the cytoskeleton-modulating protein profilin 1 (pfn1) is essential for the maintenance of multiple cell fates and metabolism of HSCs. The deletion of pfn1 in HSCs led to bone marrow failure, loss of quiescence, increased apoptosis, and mobilization of HSCs in vivo. In reconstitution analyses, pfn1-deficient cells were selectively lost from mixed bone marrow chimeras. By contrast, pfn1 deletion did not significantly affect differentiation or homing of HSCs. When compared to wild-type cells, levels of expression of Hif-1a, EGR1, and MLL were lower and an earlier switch from glycolysis to mitochondrial respiration with increased ROS level was observed in pfn1-deficient HSCs. This switch preceded the detectable alteration of other cell fates. Importantly, treatment of pfn1-deficient mice with the antioxidant N-acetyl-l-cysteine reversed the ROS level and loss of quiescence of HSCs, suggesting that pfn1 maintained metabolism is required for the quiescence of HSCs. Furthermore, we demonstrated that expression of wild-type pfn1 but not the actin-binding deficient or poly-proline binding-deficient mutants of pfn1 rescued the defective phenotype of pfn1-deficient HSCs. This result indicates that actin-binding and proline-binding activities of pfn1 are required for its function in HSCs. Thus, pfn1 plays an essential role in regulating the retention and metabolism of HSCs in the bone marrow microenvironment. Disclosures: No relevant conflicts of interest to declare.

Sectors expressing the homeobox gene liguleless3 implicate a time-dependent mechanism for cell fate acquisition along the proximal-distal axis of the maize leaf

Development ◽  
1997 ◽  
Vol 124 (24) ◽  
pp. 5097-5106 ◽  
Author(s):  
G.J. Muehlbauer ◽  
J.E. Fowler ◽  
M. Freeling
Keyword(s):  
Cell Fate ◽  
Homeobox Gene ◽  
Longitudinal Axis ◽  
Cell Types ◽  
Transverse Dimension ◽  
Leaf Sheath ◽  
Wild Type ◽  
Cell Fates ◽  
Maize Leaf ◽  
Gradual Process

The longitudinal axis of the maize leaf is composed of, in proximal to distal order, sheath, ligule, auricle and blade. The semidominant Liguleless3-O (Lg3-O) mutation disrupts leaf development at the ligular region of the leaf midrib by transforming blade to sheath. In a previous study, we showed that leaf sectors of Lg3 mutant activity are cell nonautonomous in the transverse dimension and can confer several alternative developmental fates (Fowler, Muehlbauer and Freeling (1996) Genetics 143, 489–503). In our present study we identify five Lg3 sector types in the leaf: sheath-like with displaced ligule (sheath-like), sheath-like with ectopic ligule (ectopic ligule), auricle-like, macro-hairless blade and wild-type blade. The acquisition of a specific sector fate depends on the timing of Lg3 expression. Early Lg3 expression results in adoption of the sheath-like phenotype at the ligule position (a proximal cell fate), whereas later Lg3 expression at the same position results in one of the more distal cell fates. Furthermore, sheath-like Lg3 sectors exhibit a graded continuum of phenotypes in the transformed blade region from the most proximal (sheath) to the most distal (wild-type blade), suggesting that cell fate acquisition is a gradual process. We propose a model for leaf cell fate acquisition based on a timing mechanism whereby cells of the leaf primordium progress through a maturation schedule of competency stages which eventually specify the cell types along the proximal to distal axis of the leaf. In addition, the lateral borders between Lg3 ‘on’ sectors and wild-type leaf sometimes provide evidence of no spreading of the transformed phenotype. In these cases, competency stages are inherited somatically.

scholarly journals Homeobox transcription factor OsZHD2 promotes root meristem activity in rice by inducing ethylene biosynthesis

2020 ◽  
Vol 71 (18) ◽  
pp. 5348-5364
Author(s):  
Jinmi Yoon ◽  
Lae-Hyeon Cho ◽  
Wenzhu Yang ◽  
Richa Pasriga ◽  
Yunfei Wu ◽  
...  
Keyword(s):  
Root Meristem ◽  
Lateral Roots ◽  
Homeobox Gene ◽  
Ethylene Biosynthesis ◽  
Activation Tagging ◽  
Root Tip ◽  
Wild Type ◽  
Root Tips ◽  
Overexpression Line ◽  
Homeobox Transcription Factor

Abstract Root meristem activity is the most critical process influencing root development. Although several factors that regulate meristem activity have been identified in rice, studies on the enhancement of meristem activity in roots are limited. We identified a T-DNA activation tagging line of a zinc-finger homeobox gene, OsZHD2, which has longer seminal and lateral roots due to increased meristem activity. The phenotypes were confirmed in transgenic plants overexpressing OsZHD2. In addition, the overexpressing plants showed enhanced grain yield under low nutrient and paddy field conditions. OsZHD2 was preferentially expressed in the shoot apical meristem and root tips. Transcriptome analyses and quantitative real-time PCR experiments on roots from the activation tagging line and the wild type showed that genes for ethylene biosynthesis were up-regulated in the activation line. Ethylene levels were higher in the activation lines compared with the wild type. ChIP assay results suggested that OsZHD2 induces ethylene biosynthesis by controlling ACS5 directly. Treatment with ACC (1-aminocyclopropane-1-carboxylic acid), an ethylene precursor, induced the expression of the DR5 reporter at the root tip and stele, whereas treatment with an ethylene biosynthesis inhibitor, AVG (aminoethoxyvinylglycine), decreased that expression in both the wild type and the OsZHD2 overexpression line. These observations suggest that OsZHD2 enhances root meristem activity by influencing ethylene biosynthesis and, in turn, auxin.

scholarly journals Haploid induction by a maize cenh3 null mutant

2021 ◽  
Vol 7 (4) ◽  
pp. eabe2299 ◽  
Author(s):  
Na Wang ◽  
Jonathan I. Gent ◽  
R. Kelly Dawe
Keyword(s):  
Histone H3 ◽  
Null Mutation ◽  
Null Mutant ◽  
Wild Type ◽  
Haploid Induction ◽  
Cell Divisions ◽  
Gamete Formation ◽  
Simplified Method ◽  
Single Cross ◽  
Subsequent Loss

The production of haploids is an important first step in creating many new plant varieties. One approach used in Arabidopsis involves crossing plants expressing different forms of centromeric histone H3 (CENP-A/CENH3) and subsequent loss of genome with weaker centromeres. However, the method has been ineffective in crop plants. Here, we describe a greatly simplified method based on crossing maize lines that are heterozygous for a cenh3 null mutation. Crossing +/cenh3 to wild-type plants in both directions yielded haploid progeny. Genome elimination was determined by the cenh3 genotype of the gametophyte, suggesting that centromere failure is caused by CENH3 dilution during the postmeiotic cell divisions that precede gamete formation. The cenh3 haploid inducer works as a vigorous hybrid and can be transferred to other lines in a single cross, making it versatile for a variety of applications.

Dynamics of Telomeric DNA Turnover in Yeast

Genetics ◽  
2002 ◽  
Vol 160 (1) ◽  
pp. 63-73
Author(s):  
Michael J McEachern ◽  
Dana Hager Underwood ◽  
Elizabeth H Blackburn
Keyword(s):  
Kluyveromyces Lactis ◽  
Mutant Gene ◽  
Dna Repeats ◽  
Wild Type ◽  
Telomeric Dna ◽  
Cell Divisions ◽  
Dna Turnover ◽  
Length Regulation ◽  
Turn Over

Abstract Telomerase adds telomeric DNA repeats to telomeric termini using a sequence within its RNA subunit as a template. We characterized two mutations in the Kluyveromyces lactis telomerase RNA gene (TER1) template. Each initially produced normally regulated telomeres. One mutation, ter1-AA, had a cryptic defect in length regulation that was apparent only if the mutant gene was transformed into a TER1 deletion strain to permit extensive replacement of basal wild-type repeats with mutant repeats. This mutant differs from previously studied delayed elongation mutants in a number of properties. The second mutation, TER1-Bcl, which generates a BclI restriction site in newly synthesized telomeric repeats, was indistinguishable from wild type in all phenotypes assayed: cell growth, telomere length, and in vivo telomerase fidelity. TER1-Bcl cells demonstrated that the outer halves of the telomeric repeat tracts turn over within a few hundred cell divisions, while the innermost few repeats typically resisted turnover for at least 3000 cell divisions. Similarly deep but incomplete turnover was also observed in two other TER1 template mutants with highly elongated telomeres. These results indicate that most DNA turnover in functionally normal telomeres is due to gradual replicative sequence loss and additions by telomerase but that there are other processes that also contribute to turnover.

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