Esterification Of Chlorophyllide Research Articles

Changing Ratios of Phototransformable Protochlorophyll and Protochlorophyllide of Bean Seedlings Developing in the Dark

Protochlorophyll (Pchl) and protochlorophyllide (Pchlide) are at comparable levels in 2-day-old (young) etiolated bean leaves (Phaseolus vulgaris L. var. Red Kidney). During subsequent development in the dark, both pigments increase, but the rate of Pchlide increase is greater than that of Pchl, leading to the commonly observed predominance of Pchlide beyond 7 days (old leaves). Both protopigments are phototransformable to their respective chlorophyll(ide) photoproducts throughout dark development. The rate of protopigment regeneration in young leaves after illumination is rapid and displays no lag, whereas this process in old leaves begins slowly and achieves only about one-fifth the rate of younger leaves. The rate of chlorophyllide esterification is also faster in the younger tissue. Since the proplastid-related properties of young bean leaves are quite similar to those of Euglena, young leaves and Euglena may represent an evolutionarily primitive case compared with older bean leaves which contain etioplasts. Since Euglena and young beans green perfectly well when exposed to light, the extensive modifications associated with prolonged dark growth do not seem to be obligatory for plastid development. The properties of older beans are viewed as being the consequence of prolonged etiolation which may provide a faster rate of plastid development and appearance of photosynthesis as the plant nears the limits of its stored reserves.

Control of chlorophyll synthesis by phytochrome

The rate of chlorophyllide esterification in mustard cotyledons can be increased by a pretreatment with 5 min red light applied 24 h prior to the protochlorophyll(ide)→chlorophyll(ide) photoconversion at 60 h after sowing. Simultaneously the red light pulse pretreatment leads to a decrease of the total amount of chlorophyll(ide) a in darkness. It has been proven that phytochrome (Pfr) is the photoeffector for both. Since the amounts of esterified chlorophyllide are determined by the ratio [chlorophyll a]/[chlorophyllide a+chlorophyll a] it is assumed that Pfr increases the rate of esterification indirectly via stimulating the decrease of chlorophyll(ide) a. The regulation of chlorophyll synthesis by Pfr does not seem to involve a control of esterification. The duration of the chlorophyllide esterification differs from the duration of the Shibata shift although both are greatly shortened by the red light pulse pretreatment. The effect of 5 min red light on the duration of the esterification is fully reversible by 5 min far-red light while the reversibility with respect to the Shibata shift is lost within 2 min [Jabben, M. and H. Mohr, Photochem. Photobiol. 22, 55-58 (1975)]. We conclude that the control of the chlorophyllide esterification and the control of the Shibata shift cannot be traced back to the same initial action of Pfr.

Macromolecular Physiology of Plastids: XIII. The Effect of Photoinactive Protochlorophyllide on the Function of Protochlorophyllide Holochrome

The barley mutant albina-f 17 produces only photoconvertible protochlorophyllide. It is a stringent mutant in a nuclear gene controlling protochlorophyllide synthesis. At partial as well as total photoconversion the chlorophyllide absorption maximum is located at 682–684 nm. The blue-shift to 672 nm and esterification to chlorophyll a is absent in the mutant. Supply of exogenous δ -amino-levulinic acid leads to the formation of initially inactive protochlorophyllide. The presence of this pigment causes the absorption maximum of newly formed chlorophyllide to be at 675 nm which subsequently is shifted to 672 nm. Initially non-convertible pigment is activated in a dark reaction after the first protochlorophyllide reduction. A comparison of these results with the behaviour of protochlorophyllide holochrome in wild type seedlings and mutant seedlings accumulating constitutively inactive protochlorophyllide allows the following deductions: The presence of inactive protochlorophyllide at the chlorophyllide holochrome is responsible for its 675 nm absorption and possibly causes release of chlorophyllide from the conversion site. Esterification of chlorophyllide is not a prerequisite for the reuse of the photoconversion sites.

Esterification and Spectral Shifts of Chlorophyll(ide) in Wildtype and Mutant Seedlings Developed in Darkness

AbstractSpectral changes and esterification (presumably with phytol) of newly formed chlorophyllide a in dark‐grown leaves of wildtype bean (Phaseolus vulgaris) and barley (Hordeum vulgare) and a number of chloroplast mutants in barley, were studied by spectrofluorimetry on leaves and on solvent extracts.The shift of the fluorescence emission maximum from 692–694 to 678 nm (excitation shift: 682–684 to 672 nm) and esterification of chlorophyllide a have a similar time course, and both processes are temperature dependent in a similar manner. After completion of the spectral shift and esterification, the fluorescence efficiency of chlorophyll a increases with a subsequent reaccumulation of protochlorophyllide. In leaves of mutants where the shift of fluorescence from 692 to 678 nm is lacking, esterification and the subsequent processes are also blocked. In leaves of mutants with a rapid shift of the fluorescence from 692 to 678 nm, or with direct photoconversion to chlorophyllide a with the fluorescence at 678 nm, esterification is also rapid.The results are interpreted as a sequence of molecular events involving a conformational relaxation of the chlorophyllide holochrome and a translocation of chlorophyll a to reaction centers of the photosystems.

Phytol Changes in Dark Grown Leaves of Barley after Varying Light Treatments

AbstractGas chromatographic determinations revealed a certain amount of free phytol in dark‐grown barley leaves. When a short light impulse or continuous light is given to the leaves, the phytol pool is partly emptied due to esterification of chlorophyllide a. The regeneration is slow during the first 2–3 hours. A pretreatment with light flashes followed by a dark period accelerates the regeneration, which stops however after approximately 30 min. Some evidence points to the existence of an acceptor for excess phytol entering at this stage.Connections between phytol changes during irradiation and the lag phase of chlorophyll formation are discussed.