Fast phototransformation of the 636 nm‐emitting protochlorophyllide form in epicotyls of dark‐grown pea (Pisum sativum)

Abstract

The phototransformation of protochlorophyllide forms was studied in epicotyls of dark-germinated pea (Pisum sativum L. cv. Zsuzsi) seedlings. Middle segments were illuminated with white or 632.8 nm laser flash or continuous light at room temperature and at À15 C. At low light intensities, photoreduction could be distinguished from bleaching. 77 K fluorescence emission spectra were measured, difference spectra of illuminated and nonilluminated samples were calculated and/or the spectra were deconvoluted into Gaussian components. The 629 nm-emitting protochlorophyllide form, P629 (Pxxx where xxx is the fluorescence emission maximum), was inactive. For short-period (2-100 ms) and/or low-intensity (0.75-1.5 mmol m À2 s À1 ) illumination, particularly with laser light, the transformation of P636 into the 678 nm-emitting chlorophyllide form, C678 (Cxxx where xxx is the fluorescence emission maximum), was characteristic. This process was also found when the samples were cooled to À15 C. The transformation of P644 into C684 usually proceeded in parallel with the process above as a result of the strong overlap of the excitation bands of P636 and P644. The Shibata shift of C684 into a short-wavelength form, C675-676, was observed. Long-period (20-600 s) and/or high-intensity (above 10 mmol m À2 s À1 ) illumination resulted in the parallel transformation of P655 into C692. These results demonstrate that three flash-photoactive protochlorophyllide forms function in pea epicotyls. As a part of P636 is flash photoactive, its protochlorophyllide molecule must be bound to the active site of a monomer protein unit [Bö ddi B, Kis-Petik K, Kaposi AD, Fidy J, Sundqvist C (1998) The two short wavelength protochlorophyllide forms in pea epicotyls are both monomeric. Biochim Biophys Acta 1365: 531-540] of the NADPH:protochlorophyllide oxidoreductase (EC 1.3.1.33). Dynamic interconversions of the protochlorophyllide forms into each other, and their regeneration, were also found, which are summarized in a scheme.Abbreviations -Chl, chlorophyll; Chlide, chlorophyllide; Cxxx, chlorophyllide form with fluorescence emission maximum at xxx nm; Pchl, protochlorophyllide ester, i.e. 'protochlorophyll'; Pchlide, protochlorophyllide; Pxxx, protochlorophyllide or protochlorophyll form with fluorescence emission maximum at xxx nm; PLB, prolamellar body; POR, NADPH: protochlorophyllide oxidoreductase enzyme (POR, EC 1.3.1.33); PT, prothylakoid.

Proteomic analysis of the etioplast inner membranes of wheat (Triticum aestivum) by two‐dimensional electrophoresis and mass spectrometry

“…The plastids of mesocotyles can be regarded as proplastids or poorly developed etioplasts, and this tissue fails to develop chloroplasts when irradiated (Virgin 1996). The Pchlide fluorescence spectrum from a typical mesocotyle tissue shows a peak at 632 nm, representing mainly non‐phototransformable Pchlide (Kósa et al 2005), whereas mature etioplasts with fully developed PLBs are characterized by Pchlide fluorescence spectra dominated by a peak at 656 nm (Ryberg and Sundqvist 1982). This spectral form of Pchlide, the so‐called phototransformable Pchlide, represents aggregates of the ternary complex of POR, Pchlide and NADPH, which may accumulate in darkness also in green leaves (Amirjani and Sundqvist 2004).…”

Proteomic analysis of highly purified prolamellar bodies reveals their significance in chloroplast development

“…The main reason for the formation of different spectral forms of Pchlide is differences in the association between Pchlide, NADPH and the POR protein and the aggregation of this pigment-protein complex (Ryberg and Sundqvist 1991;Schoefs and Franck 2003). Pchlide F633 can only to a limited amount be phototransformed to Chlide (Kósa et al 2005), while Pchlide F657 is readily transformed with a short (ms) flash of light. This phototransformable form of Pchlide is present in ternary complexes of POR, Pchlide and NADPH and is by far the most abundant Pchlide form in PLBs (e.g.…”

Etioplasts with protochlorophyll and protochlorophyllide forms in the under‐soil epicotyl segments of pea (Pisum sativum) seedlings grown under natural light conditions

“…The dimeric and oligomeric forms are photoactive while the monomeric forms are considered as ‘non‐photoactive’ which can convert to Chlide only indirectly. The exception is the 636 nm form; a part of which transforms directly into Chlide (Kósa et al ).…”