Biomedical subjects

Gwyneth C Ingram

Publications and source records attributed to Gwyneth C Ingram.

8 recordsLinked to original sources

PubMed2005

Keeping it together: co-ordinating plant growth.

One of the most important demands of multicellularity is the co-ordination of cell proliferation and cell growth to allow the ultimate differentiation of functional organs and tissues. In plants, endogenously and exogenously generated developmental signals hone a basic patterning plan to the demands of a changing environment throughout the lifecycle. Recent advances have started to identify many signalling pathways and intermediates that are potentially implicated in controlling plant growth in response to developmentally important signals. These include pathways that are conserved in other eukaryotes, such as the Target Of Rapamycin (TOR) pathway and lipid signalling via S6-Kinases, as well as pathways that contain plant-specific elements, such as ERECTA-class receptor kinases and TCP-class transcription factors. Understanding how these elements are integrated to give co-ordinated growth remains one of the major challenges in plant biology.

Cell Division↗

PubMed2005

Sending the right signals: regulating receptor kinase activity.

Knowledge of the functions of plant receptor-like-kinases (RLKs) is increasing rapidly, but how their cytoplasmic signalling activity is regulated and how signals are transduced to cytoplasmic or nuclear proteins remain important questions. Recent studies, particularly of the BRASSINOSTEROID INSENSITIVE1 RLK, have begun to shed light on the mechanistic details of RLK activation, including the possible role of ligand binding. Studies of this and other RLKs have also highlighted the potential importance of hetero-oligomerisation and receptor internalisation in RLK signalling. Finally, a range of potential regulatory proteins and putative downstream signalling substrates have been identified for various RLKs. Despite some similarities with animal receptor kinase signalling systems, mechanisms that affect the intracellular behaviour, regulation and interactions of RLKs appear to be very diverse, potentially explaining how signalling specificity is maintained at the cytoplasmic level.

Arabidopsis↗

PubMed2005

Plant development: spacing out stomatal pores.

How do plants generate the optimal spacing of stomatal pores on their surfaces to prevent excessive water-loss, whilst allowing efficient gas exchange? New research into the ERECTA family of receptor-like-kinases has provided an important link in the cell-cell signalling pathways controlling this process.

Arabidopsis Proteins↗

PubMed2005

ARABIDOPSIS CRINKLY4 function, internalization, and turnover are dependent on the extracellular crinkly repeat domain.

The study of the regulation and cellular dynamics of receptor kinase signaling in plants is a rapidly evolving field that promises to give enormous insights into the molecular control of signal perception. In this study, we have analyzed the behavior of the L1-specific receptor kinase ARABIDOPSIS CRINKLY4 (ACR4) from Arabidopsis thaliana in planta and have shown it to be present in two distinct compartments within cells. These represent protein export bodies and a population of internalized vesicles. In parallel, deletion analysis has shown that a predicted beta-propeller-forming extracellular domain is necessary for ACR4 function. Nonfunctional ACR4 variants with deletions or point mutations in this domain behave differently to wild-type fusion protein in that they are not internalized to the same extent. In addition, in contrast with functional ACR4, which appears to be rapidly turned over, they are stabilized. Thus, for ACR4, internalization and turnover are linked and depend on functionality, suggesting that ACR4 signaling may be subject to damping down via internalization and degradation. The observed rapid turnover of ACR4 sets it apart from other recently studied plant receptor kinases. Finally, ACR4 kinase activity is not required for protein function, leading us to propose, by analogy to animal systems, that ACR4 may hetero-oligomerize with a kinase-active partner during signaling. Plant and animal receptor kinases have distinct evolutionary origins. However, with other recent work, our study suggests that there has been considerable convergent evolution between mechanisms used to regulate their activity.

Arabidopsis↗

PubMed2005

Engrailed-ZmOCL1 fusions cause a transient reduction of kernel size in maize.

ZmOCL1 is the founding member of the ZmOCL (Outer Cell Layer) family encoding putative transcription factors of the HD-ZIP IV class. It is expressed in the L1 cell layer of the embryo and several other tissues of maize. After determination of the intron/exon structure a mutator insertion was isolated in the upstream region. No notable phenotypes and wildtype levels of ZmOCL1 transcript were observed in homozygous mutant plants. In contrast transgenic plants carrying a fusion of the repressor domain of the Drosophila Engrailed gene with the DNA binding and dimerisation domains of ZmOCL1 showed a transient reduction of embryo, endosperm and kernel size that was most obvious around 15 DAP. An inverse relationship was observed between the degree of size reduction and the expression level of the transcript. In reciprocal crosses the size reduction was only observed when the transgenic plants were used as females and no expression of male transmitted transgenes was detected. Smaller kernels resembled younger kernels of wild-type siblings indicating that interference with ZmOCL1 function leads to an overall slow-down of early kernel development. Based on marker gene analysis ZmOCL1 may act via a modification of gibberellin levels. Phylogenetic analyses based on the intron/exon structure and sequence similarities of ZmOCL1 and other HD-ZIP IV proteins from maize, rice and Arabidopsis helped to identify orthologues and suggested an evolution in the function of individual genes after the divergence of monocots and dicots.

Binding Sites↗

PubMed2005

AtDEK1 is essential for specification of embryonic epidermal cell fate.

The specification of epidermal (L1) identity occurs early during plant embryogenesis. Here we show that, in Arabidopsis, AtDEK1 encodes a key component of the embryonic L1 cell-layer specification pathway. Loss of AtDEK1 function leads to early embryo lethality characterized by a severe loss of cell organization in the embryo proper and abnormal cell divisions within the suspensor. Markers for L1 identity, ACR4 and ATML1, are not expressed in homozygous mutant embryos. In order to clarify the function of AtDEK1 further, an RNAi knockdown approach was used. This allowed embryos to partially complete embryogenesis before losing AtDEK1 activity. Resulting seedlings showed a specific loss of epidermal cell identity within large portions of the cotyledons. In addition, meristem structure and function was systematically either reduced or entirely lost. AtDEK1 expression is not restricted to the L1 epidermal cell layer at any stage in development. This is consistent with AtDEK1 playing an upstream role in the continuous generation or interpretation of positional information required for epidermal specification. Our results not only identify a specific role for AtDEK1 during embryogenesis, but underline the potential key importance of L1 specification at the globular stage for subsequent progression through embryogenesis.

Arabidopsis↗

PubMed2004

Between the sheets: inter-cell-layer communication in plant development.

The cells of plant meristems and embryos are arranged in an organized, and sometimes extremely beautiful, layered pattern. This pattern is maintained by the controlled orientation of cell divisions within layers. However, despite this layered structure, cell behaviour during plant development is not lineage dependent, and does not occur in a mosaic fashion. Many studies, both classical and recent, have shown that plant cell identity can be re-specified according to position, allowing plants to show remarkable developmental plasticity. However, the layered structure of meristems and the implications of this during plant development, remain subjects of some speculation. Of particular interest is the question of how cell layers communicate, and how communication between cell layers could allow coordinated developmental processes to take place. Recent research has uncovered several examples both of the molecular mechanisms by which cell layers can communicate, and of how this communication can infringe on developmental processes. A range of examples is used to illustrate the diversity of mechanisms potentially implicated in cell-layer communication during plant development.

Cell Communication↗

PubMed2003

The Arabidopsis ACR4 gene plays a role in cell layer organisation during ovule integument and sepal margin development.

The mechanisms regulating cell layer organisation in developing plant organs are fundamental to plant growth, but remain largely uninvestigated. We have studied the receptor kinase-encoding ARABIDOPSIS CRINKLY4 gene and shown that its expression is restricted to the L1 cell layer of most meristems and organ primordia, including those of the ovule integuments. Insertion mutations show that ARABIDOPSIS CRINKLY4 is required for regulation of cellular organisation during the development of sepal margins and ovule integument outgrowth. We show that ARABIDOPSIS CRINKLY4 encodes a functional kinase that, in ovules and possibly other tissues, is abundant in anticlinal and the inner periclinal plasma membrane of 'outside' cells. We propose that ARABIDOPSIS CRINKLY4 may be involved in maintaining L1 cell layer integrity by receiving and transmitting signals from neighbouring L1 cells and/or from underlying cell layers.

Arabidopsis↗