Callose formation

Hinch, J. M., and Clarke, A. E., 1980, Callose formation in Zea mays as a response to infection with Phytophthora cinnamomi, Physiol. Plant Pathol. 21 113-124. 

Callose Formation. Deposits or papillae between host plasma membranes and cell walls are seen in plant tissues infected by fungi, nematodes and viruses (30). These deposits often react positively with the aniline blue fluorochrome and are believed to be composed of callose, a polysaccharide complex which may include 3-glucans containing 1,3- and 1,4-linkages (HL). 

The deposits may function in plugging or sealing the wound caused by injury due to the pathogen and may restrict the loss of molecules and ions and the movement of toxic substances into the tissues. Little is known about induction of the synthesis of the callose although membrane-bound plant 1,3-3-glucan synthetases have been described (112). Callose formation is induced by various chemical and physical stimuli (113, 114, 115) and there is evidence that membrane disruption (116, 117), such as may result from microbial infection, can initiate callose deposition. Whether the stimulus is provided by a specific binding to plasma membranes of microbial metabolites, such as... 

Kauss, H., Jeblik, W., and Domard, A. 1989. The degree of polymerization and A-acetylation of chitosan determine its ability to ehcit callose formation in suspension cells and protoplasts of Catharantus roseus. Planta 178 385-392. 

The ability of Ca -channel blockers to influence cytokinin-responses has also been used to adduce second messenger status for Ca. However, the metal ions La and Co are inevitably comparatively non-specific, and also affect both the physical properties of the wall and ethylene biosynthesis respectively. Ca -channel-blocking drugs such as verapamil and nifedipine could only begin to be trusted if their effect on Ca transport in the experimental material had been fully characterized. The discovery that these two Ca channel binders induce callose formation in cells of the liverwort Riella[ 6] indicates that they can facilitate Ca entry in some tissues. Verapamil and nifedipine induced callose in different, discrete regions of the cell which suggests the possibility of diversity within the Ca -channels, an added complication already apparent from the differential sensitivity of Ca -channels in tonoplast and endoplasmic reticulum membrane to inositol 1, 4, 5-trisphosphate [17, 18]. 

Most of the biochemical studies on polysaccharide synthesis to date have been concerned with the formation of homopolymers even when it is known that the synthesis of the homopolymer chain occurs in vivo as part of a heteropolysaccharide (4-6). Cytochemical investigations have made no such distinctions and the polymers located by these studies have nearly always been sites at which heteropolymers were present and where deposition in the wall occurred. The bulk of the polysaccharides that occur in the wall, with the exception of cellulose and callose, are heteropolymers. Generally the polysaccharides of the hemicelluloses and pectins are composed of poly-... 

The shift from phloem feeding to xylem feeding on resistant rices is not well understood. Auclair et al. (37) speculated that these differences were due to either the presence of a feeding deterrent in tissues adjacent to or within the sieve elements of resistant plants or the formation of callose or slime plugs in phloem in response to GLH probing. 

The nonprotein amino acid, / -aminobutyric acid (BABA) protected Arabidopsis against the oomycete pathogen Peronospora parasitica through activation of natural defence mechanisms of the plant such as callose deposition, the hepersensitive response, and the formation of the trailing necroses [158]. Seed treatment with BABA also shown to protect Pennisetum glaucum (pear millet) systematically from the attack of Sclerospora graminicola [159]. 

Deposition of the matrix substances and formation of the microfibrils are accompanied by a sequence of related processes that lead to the development and differentiation of the cell wall this sequence includes expansion of the wall, changes in the composition of the polysaccharides, organization and orientation of the different layers, deposition of callose for formation of pores in phloem, lignification (see p. 299), and other processes. Considerable information has been obtained about the mechanism of some of these processes and the factors that affect them this information has been reviewed by leading molecular biologists, and will very briefly be mentioned here because of its relevance to cell-wall formation and to the constitution of cell-wall polysaccharides of interest to carbohydrate chemists. According to the new concepts, the transformations of the cell wall are effected, or are assisted, by the presence of a variety of enzymes, proteins, and, perhaps, even ribonucleic acid to the extent that primary... 

The formation of callose as a response to wounding in C. roseus has been extensively studied (356,357), but unfortunately these data cannot be correlated with most of the studies on alkaloid production. However, there is evidence for a role of Ca + as second messenger in this process, as well as in the regulation of alkaloid biosynthesis through cytokinins (see later discussion). 

Stanghellini M E, Aragaki M 1966 Relation of periderm formation and callose deposition to an-thracnose resistance in papaya fruit. Phytopathology 56 444-450... 

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