Stomatal guard

Zeiger, E. (1983). The biology of stomatal guard cells. Annual Review of Plant Physiology, 34, 441-75. 

Blatt, M.R., Thiel, G., and Trentham, D.R., 1990, Reversible inactivation of K+ channels of Vicia stomatal guard cells following the photolysis of caged inositol 1,4,5-trisphosphate. Nature 346 766-769. 

MacRobbie, E.A., 2000, ABA activates multiple Ca2+ fluxes in stomatal guard cells, triggering vacuolar K+ (Rb+) release. Proc. Natl. Acad. Sci. U.S.A. 97 12361-12368. 

Parmar, P.N., and Brearley, C.A., 1995, Metabolism of 3- and 4- phosphorylated phosphatidylinositols in stomatal guard cells of Commelina communis L. Plant J. 8 425033. Pennycooke, J.C., Jones, M.L., and Stushnoff, C., 2003, Down-regulating alpha-galactosidase enhances freezing tolerance in transgenic petunia. Plant Physiol. 133(2) 901-909. 

The physiological content of these equations will be taken up in Section 4.1, where the turgor regulation in stomatal guard cells has been discussed. 

In a recent review Cote and Crain [5] have pointed to three phenomena which they thought particularly convenient to study the physiological role of phosphoinositides in plants. These were 1) the turgor changes in stomatal guard cells, paiticulaiiy after a treatment with abscisic acid which provokes the closure of stomata, 2) the osmotic stress in Dunaliella salina or carrot cell cultures and 3) the deflagellation of Chlamydomonas reinhardtii after exposure of the alga to acid pH, elevated temperature or ethanol. Nevertheless the rates of apparition of inositolphosphates after stimulation have been found very different in various plant tissues (from 30 sec to 30 min). 

PATHWAY OF SYNTHESIS OF 3- AND 4-PHOSPHORYLATED PHOSPHOINOSITIDES IN STOMATAL GUARD CELLS OF COMMELINA COMMUNIS L. 

In the plant kingdom, the pathway of synthesis of 3- and 4-phosphorylated phosphoinositides has been described only in Spirodela polyrhiza L. [1]. If animal models of phosphoinositide metabolism are to be applied to plants, it is imperative to determine the route of synthesis of phosphoinositides in other members of the plant kingdom in which signaling functions for phosphoinositides and inositol phosphates have been implicated. Recently, we have rigorously identified 3- and 4-phosphorylated phosphoinositides in stomatal guard cells of Commelina communis L. [2]. In the present work we have set out to determine the metabolic route by which PtdIns(3,4)P and PtdIns(4,5)P synthesis occurs and to examine the metabolic relationship between 3- and 4-phosphoryrated lipids in stomatal guard cells. 

Figure 1 Incorporation of [ P]P into ATP pool ( ) and gamma-phospnate of ATP (O) in stomatal guard cells.

Figure 2 Hplc separation of (teacylation products from l 32p]p labelled stomatal guard cells.

Since the 3 phosphate of PtdIns(3,4)P is less stron y labelled than the 4 phosphate, synthesis of PtdIns(3,4)P in Conmmina communis L. occurs by successive 3- and 4-phosphorylation of Ptdms. In contrast to all animal and plants cell systems described to date, in stomatal guard cells PtcUns(3,4)P predominates, in labelling terms at least, over PuiIns(4,5)P PtdIns(4,5)P is synthesis in Commelina communis L. by successive 4- and3-phosphorylation of Ptdins. 

Parmar PN, Brearley CA. Identification of 3- and 4-phosphorylated phosphoinositides and inositol phosphates in stomatal guard cells of Commelina communis L. Plant J 1993 4 255-263. 

MACRCBBIE, E.A.C. 1988. Control of ion fluxes in stomatal guard cells. Botanica acta 101, 140-148. 

Stebbins, G. L., Shah, S. S., Jamin, D., and Jura, P. (1967). Changed orientation of the mitotic spindle of stomatal guard cell divisions in Hordeum vulgare. Am. J. Botany 54, 71-80. 

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