Plant cell activation

Interest in DG as a product of phospholipid degradation was stimulated by the discovery in the early 1980s of a phospholipid-dependent DG-stimulated and Ca2+-activated protein kinase, termed protein kinase C (PKC) [15], This kinase is ubiquitous in animal cells and is found in some plant cells. Activation of this enzyme by DG occurs by a shift in affinity for Ca2+ from the mM to the sub-juM range, which exists in stimulated cells. Further interest in the DG-activated PKC stimulatory pathway was aroused by the observation that this kinase is the intracellular receptor... 

PO performs vitally important functions in the plant cell and is mainly associated with the oxidation of phenolic compounds and with the formation and strengthening of the cell wall (Passardi et al., 2004). PO is involved in the oxidative transformation of molecules in growth-regulating or signalling activities and - as a result - can also perform regulatory functions in the cell. Plant POs are represented by genetically different proteins with the same enzymatic activity (Welinder et al., 2002). 

A number of chapters in this volume (especially Chapters 5 and 6) provide a more thorough discussion of osmotic adjustment by intact plants and tissues in response to environmental stress and the role of osmotically active solutes in this response. The following section focuses on the role of organic osmotica in the response of plant cells to salt stress. Cultured plant cells offer the opportunity to evaluate the effect of both internally synthesised and externally administered organic osmotica. 

Fig. 4.1 Sinigrin is an aliphatic glucosinolate that occurs at significant levels in the human diet, notably in mustard and Brussels sprouts. When brought into contact with myrosinase, derived either from plant cells or from colonic bacteria, it is broken down to yield a variety of products including the acrid, volatile, biologically active compoimd...

Sasaki, N. et al., Isolation and characterization of cDNAs encoding an enzyme with glucosyltransferase activity for cyc/o-dopa from four o clocks and feather cockscombs, Plant Cell Physiol., 46, 666, 2005. 

Many different glycosyltransferase activities involved in higher plant wall biosynthesis have been identified in cell free membrane fractions, but in only a few cases has glycosyltransferase activity been retained in detergent-solubilized preparations, and in even fewer cases have any purified polypeptides been identified as plant cell wall glycosyltransferases (29,33). 

These acidic molecules might result from either the lack of PMT activity or the action of PME, known to be present in most plant cell walls. Pectin methyltransferases and pectin methylesterases extracted from active and resting cells were therefore characterized. 

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