Morphogenetic factors

Most parasites have to survive prolonged periods of time apart from the host plant. Consequently, the formation of resting propagules, such as sclerotia, constitutes a critical part of the parasite s life cycle. Several observations indicate that formation of sclerotia may be stimulated by allelochemicals (, 9). Brandt and Reese (10) concluded that Verticillium dahliae produces a diffusible morphogenetic factor that stimulates production of microsclerotia. When low concentrations of the diffusible factor were added to cultures of the pathogen, the hyphae swelled and became constricted, septation was increased, and cell walls became thickened. 

Bone formation and resorption are influenced by several protein factors. For example, IGF-I stimulates formation of bone, but EGF promotes breakdown.256 Additional bone-derived growth factors and morphogenetic factors also have been described.256 257 A cartilage-inducing factor has been identified as TGF-p.258... 

Bone morphogenetic factors (DPP in Drosophila) Regulation of development Gastrulation Neurogenesis Chondrogenesis Development of eyes and wings and dorsalization in Drosophila... 

A different binding and activation mode is used by the bone marrow morphogenetic factor (see review Shah et al., 2001). In this case, the ligand BMP binds to and activates preformed heteromeric complexes of receptor types I and II. 

One of the ways in which auxin could affect MTs is through a control of their dynamic instability and turnover rates [53], the latter being characteristically rapid in plant cells [54]. We suggest that such effects could allow a swift alteration of auxin level to act as a potent morphogenetic factor since an auxin-related intervention into the pattern of MT assembly (Fig. 1), if confined only to certain cells, or even certain walls of a cell (or cells), might be sufficient to invoke a new structural framework for subsequent growth and... 

Meiners, S. et al., Role of morphogenetic factors in metastasis of mammary carcinoma cells. Oncogene, 16, 9, 1998. 

Neuropeptides constitute the largest and most diverse class of signaling substances known in metazoans. Over the last 20 yr it has become apparent that neuropeptides have important roles as neurohormones, neuromodulators, cytokines, morphogenetic factors, and possibly in some cases, as true neurotransmitters. Each neuropeptide may even be multifimctional and exist in several isoforms in a given animal species. In the search for functions of neuropeptides, it has been critical to be able to localize sites of synthesis and release. Immunocytochemistry (ICC) has been instrumental in the accurate mapping of the cellular and subcellular distribution of neuropeptides in tissue. Other immunological assays, such as radioimmunoassay (RIA) and immxmo-enzymatic assay (ELISA) provide powerful complements for quantification of neuropeptides. Several important discoveries related to neuropeptides have relied on ICC, for example Different neuropeptides have very specific distributions in small populations of neurons (1—3), neuropeptides are commonly colocalized with low-mol-wt neurotransmitters or other neuropeptides (4), the chemical diversity of neurons is far greater than previously suspected (2,3), and neuropeptide synthesis and release can be episodic (5). 

Special morphogenetic factors seem also to exist in other induction systems. In all vertebrate embryos organogenesis of the cartilageneous vertebral column has been found to depend on the inductive activity of the spinal cord and the notochord (Strudel, 1967). Semitic mesenchyme isolated from early chick embryos does not form cartilage in contrast to somites taken from older embryos. In isolated somitic mesenchyme from 2- to 3-day-old embryos the formation of cartilage can be induced by extracts from spinal cord and notochord (Strudel, 1962). The chemical nature of the inducer is not yet known. Metachromatic... 

It may be argued that morphogenetic factors regulate early embryo-genesis by interference with quite different processes. Binding of the factors to cytoplasmic membranes could lead to an activation of membrane-bound adenylcyclase and a release of cyclic adenylate as a second messenger (for reference see Sutherland et al., 1965 Jost and Rickenberg,... 

Inducing factors have already been extracted from cleavage stage embryos of Xenopus laevis (Faulhaber, 1972b). Neuralizing factor, which has been found in Triturus oocytes (Tiedemann, 1953) must be made on maternal messenger. It is not unlikely that other morphogenetic factors are also prelocated in the unfertilized egg. 

During the last decades it has been possible to isolate morphogenetic factors in a more or less purified state. The morphogenetic factors so far known are protein in nature. The factors which act in very early stages of development very probably channel the diflferentiation of pluri-... 

The few known examples already show that morphogenetic factors may regulate cell growth and differentiation at different levels and by different mechanism. The elucidation of their mechanism of action is closely connected with the further progress in the biochemistry of information transfer from the nucleus to the cytoplasm as well the biochemistry of cell membranes and other cell constituents. 

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