Faculty Opinions recommendation of Chromatin organization and cell fate switch respond to positional information in Arabidopsis.

Plant development and responses to environmental cues largely depend on mobile signals including microRNAs (miRNAs) required for post-transcriptional silencing of specific genes. Short-range cell-to-cell transport of miRNA in developing tissues and organs is involved in transferring positional information essential for determining cell fate. Among other RNA species, miRNAs are found in the phloem sap. Long-distance transport of miRNA via the phloem takes a part in regulation of physiological responses to changing environmental conditions. As shown for regulation of inorganic phosphorus and sulfate homeostasis, mature miRNAs rather than miRNAs precursors are transported in the phloem as signaling molecules. Here, a bioinformatics analysis of transcriptomic data for Cucurbita maxima phloem exudate RNAs was carried out to elucidate whether miRNA precursors could also be present in the phloem. We demonstrated that the phloem transcriptome contained a subset of C. maxima pri-miRNAs that differed from a subset of pri-miRNA sequences abundant in a leaf transcriptome. Differential accumulation of pri-miRNA was confirmed by PCR analysis of C. maxima phloem exudate and leaf RNA samples. Therefore, the presented data indicate that a number of C. maxima pri-miRNAs are selectively recruited to the phloem translocation pathway. This conclusion was validated by inter-species grafting experiments, in which C. maxima pri-miR319a was found to be transported across the graft union via the phloem, confirming the presence of pri-miR319a in sieve elements and showing that phloem miRNA precursors could play a role in long-distance signaling in plants.

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Successive specification of Drosophila neuroblasts NB 6-4 and NB 7-3 depends on interaction of the segment polarity genes wingless, gooseberry and naked cuticle

Development ◽

10.1242/dev.128.17.3253 ◽

2001 ◽

Vol 128 (17) ◽

pp. 3253-3261 ◽

Cited By ~ 1

Author(s):

Nirupama Deshpande ◽

Rainer Dittrich ◽

Gerhard M. Technau ◽

Joachim Urban

Keyword(s):

Cell Fate ◽

Cell Lineage ◽

Positional Information ◽

Dorsoventral Patterning ◽

Expression Domain ◽

Direct Role ◽

Segment Polarity Genes ◽

Segment Polarity ◽

Unique Identity

The Drosophila central nervous system derives from neural precursor cells, the neuroblasts (NBs), which are born from the neuroectoderm by the process of delamination. Each NB has a unique identity, which is revealed by the production of a characteristic cell lineage and a specific set of molecular markers it expresses. These NBs delaminate at different but reproducible time points during neurogenesis (S1-S5) and it has been shown for early delaminating NBs (S1/S2) that their identities depend on positional information conferred by segment polarity genes and dorsoventral patterning genes. We have studied mechanisms leading to the fate specification of a set of late delaminating neuroblasts, NB 6-4 and NB 7-3, both of which arise from the engrailed (en) expression domain, with NB 6-4 delaminating first. In contrast to former reports, we did not find any evidence for a direct role of hedgehog in the process of NB 7-3 specification. Instead, we present evidence to show that the interplay of the segmentation genes naked cuticle (nkd) and gooseberry (gsb), both of which are targets of wingless (wg) activity, leads to differential commitment to NB 6-4 and NB 7-3 cell fate. In the absence of either nkd or gsb, one NB fate is replaced by the other. However, the temporal sequence of delamination is maintained, suggesting that formation and specification of these two NBs are under independent control.

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Genes that control dorsoventral polarity affect gene expression along the anteroposterior axis of the Drosophila embryo

Development ◽

10.1242/dev.99.3.327 ◽

1987 ◽

Vol 99 (3) ◽

pp. 327-332 ◽

Cited By ~ 1

Author(s):

S.B. Carroll ◽

G.M. Winslow ◽

V.J. Twombly ◽

M.P. Scott

Keyword(s):

Gene Expression ◽

Cell Fate ◽

Maternal Effect ◽

Positional Information ◽

Drosophila Embryo ◽

Dorsoventral Polarity ◽

Anteroposterior Axis ◽

Positional Marker ◽

Control Pattern ◽

The Relationship

At least 13 genes control the establishment of dorsoventral polarity in the Drosophila embryo and more than 30 genes control the anteroposterior pattern of body segments. Each group of genes is thought to control pattern formation along one body axis, independently of the other group. We have used the expression of the fushi tarazu (ftz) segmentation gene as a positional marker to investigate the relationship between the dorsoventral and anteroposterior axes. The ftz gene is normally expressed in seven transverse stripes. Changes in the striped pattern in embryos mutant for other genes (or progeny of females homozygous for maternal-effect mutations) can reveal alterations of cell fate resulting from such mutations. We show that in the absence of any of ten maternal-effect dorsoventral polarity gene functions, the characteristic stripes of ftz protein are altered. Normally there is a difference between ftz stripe spacing on the dorsal and ventral sides of the embryo; in dorsalized mutant embryos the ftz stripes appear to be altered so that dorsal-type spacing occurs on all sides of the embryo. These results indicate that cells respond to dorsoventral positional information in establishing early patterns of gene expression along the anteroposterior axis and that there may be more significant interactions between the different axes of positional information than previously determined.

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Patterning of the angiosperm female gametophyte through the prism of theoretical paradigms

Biochemical Society Transactions ◽

10.1042/bst20140036 ◽

2014 ◽

Vol 42 (2) ◽

pp. 332-339 ◽

Cited By ~ 3

Author(s):

Dmytro S. Lituiev ◽

Ueli Grossniklaus

Keyword(s):

Cell Fate ◽

Female Gametophyte ◽

Positional Information ◽

Cell Types ◽

Theoretical Frameworks ◽

Cell Specification ◽

Distinct Cell ◽

Dynamical Nature ◽

Theoretical Paradigms ◽

Lines Of Evidence

The FG (female gametophyte) of flowering plants (angiosperms) is a simple highly polar structure composed of only a few cell types. The FG develops from a single cell through mitotic divisions to generate, depending on the species, four to 16 nuclei in a syncytium. These nuclei are then partitioned into three or four distinct cell types. The mechanisms underlying the specification of the nuclei in the FG has been a focus of research over the last decade. Nevertheless, we are far from understanding the patterning mechanisms that govern cell specification. Although some results were previously interpreted in terms of static positional information, several lines of evidence now show that local interactions are important. In the present article, we revisit the available data on developmental mutants and cell fate markers in the light of theoretical frameworks for biological patterning. We argue that a further dissection of the mechanisms may be impeded by the combinatorial and dynamical nature of developmental cues. However, accounting for these properties of developing systems is necessary to disentangle the diversity of the phenotypic manifestations of the underlying molecular interactions.

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Specification of cell fate in the developing eye of Drosophila

Development ◽

10.1242/dev.113.supplement_1.123 ◽

1991 ◽

Vol 113 (Supplement_1) ◽

pp. 123-130 ◽

Cited By ~ 1

Author(s):

Ernst Hafen ◽

Konrad Basler

Keyword(s):

Tyrosine Kinase ◽

Cell Fate ◽

Photoreceptor Cell ◽

Nuclear Protein ◽

Single Cells ◽

Photoreceptor Cells ◽

Positional Information ◽

Cellular Interactions ◽

Eye Imaginal Disc

Determination of cell fate in the developing eye of Drosophila depends on cellular interactions. In the eye imaginal disc, an initially unpatterned epithelial sheath of cells, single cells are specified in regular intervals to become the R8 photoreceptor cells. Genes such as Notch and scabrous participate in this process suggesting that specification of ommatidial founder cells and the formation of bristles in the adult epidermis involve a similar mechanism known as lateral inhibition. The subsequent steps of ommatidial assembly involve a different mechanism: undetermined cells read their position based on the contacts they make with neighbors that have already begun to differentiate. The development of the R7 photoreceptor cell is best understood. The key role seems to be played by sevenless, a receptor tyrosine kinase on the surface of the R7 precursor. It transmits the positional information – most likely encoded by boss on the neighboring R8 cell membrane – into the cell via its tyrosine kinase that activates a signal transduction cascade. Two components of this cascade – Sos and sina – have been identified genetically, sina encodes a nuclear protein whose expression is not limited to R7. Constitutive activation of the sevenless kinase by overexpression results in the diversion of other ommatidial cells into the R7 pathway, suggesting that activation of the sevenless signalling pathway is sufficient to specify R7 development.

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The role of atoh1 genes in the development of the lower rhombic lip during zebrafish hindbrain morphogenesis

10.1101/719997 ◽

2019 ◽

Author(s):

Ivan Belzunce ◽

Cristina Pujades

Keyword(s):

Cell Proliferation ◽

Progenitor Cells ◽

Cell Fate ◽

Cell Lineage ◽

Positional Information ◽

Neuronal Population ◽

Dependent Manner ◽

Rhombic Lip ◽

Differentiation Gene

ABSTRACTBACKGROUNDThe Lower Rhombic Lip (LRL) is a transient neuroepithelial structure of the dorsal hindbrain, which expands from r2 to r7, and gives rise to deep nuclei of the brainstem, such as the vestibular and auditory nuclei and most posteriorly the precerebellar nuclei. Although there is information about the contribution of specific proneural-progenitor populations to specific deep nuclei, and the distinct rhombomeric contribution, little is known about how progenitor cells from the LRL behave during neurogenesis and how their transition into differentiation is regulated.RESULTSIn this work, we investigated the atoh1 gene regulatory network operating in the specification of LRL cells, and the kinetics of cell proliferation and behavior of atoh1a-derivatives by using complementary strategies in the zebrafish embryo. We unveiled that atoh1a is necessary and sufficient for specification of LRL cells by activating atoh1b, which worked as a differentiation gene to transition progenitor cells towards neuron differentiation in a Notch-dependent manner. This cell state transition involved the release of atoh1a-derivatives from the LRL: atoh1a progenitors contributed first to atoh1b cells, which are committed non-proliferative precursors, and to the lhx2b-neuronal lineage as demonstrated by cell fate studies and functional analyses. Using in vivo cell lineage approaches we showed that the proliferative cell capacity, as well as their mode of division, relied on the position of the atoh1a progenitors within the dorsoventral axis.CONCLUSIONSOur data demonstrates that the zebrafish provides an excellent model to study the in vivo behavior of distinct progenitor populations to the final neuronal differentiated pools, and to reveal the subfunctionalization of ortholog genes. Here, we unveil that atoh1a behaves as the cell fate selector gene, whereas atoh1b functions as a neuronal differentiation gene, contributing to the lhx2b neuronal population. atoh1a-progenitor cell dynamics (cell proliferation, cell differentiation, and neuronal migration) relies on their position, demonstrating the challenges that progenitor cells face in computing positional information from a dynamic two-dimensional grid in order to generate the stereotyped neuronal structures in the embryonic hindbrain.

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