Chloroplast biogenesis 88. Protochlorophyllide b occurs in green but not in etiolated plants.
It has recently been reported that protochlorophyllide (Pchlide) b is an abundant pigment in barley etioplasts but is rather unstable, as it is rapidly converted to Pchlide a by 7-formyl reductase during pigment extraction with conventional 80% acetone (Reinbothe, S., Pollmann, S., and Reinbothe, C. (2003) J. Biol. Chem. 278, 800-806). It has also been claimed that extraction of barley etioplasts with 100% acetone containing 0.1% diethyl pyrocarbonate prevents the conversion of Pchlide b to Pchlide a and leads to the detection of large amounts of Pchlide b in the isolated etioplasts. In this work the extraction protocol of Reinbothe et al. is compared with the more conventional 80% aqueous acetone extraction method. No Pchlide b was detected either in etiolated barley leaves or isolated barley etioplasts irrespective of the extraction protocol. On the other hands, small amounts of Pchlide b were detected in green barley leaves and isolated chloroplasts, extracted either with 80% acetone or 100% acetone containing 0.1% diethyl pyrocarbonate. It is concluded that the proposed occurrence of a light-harvesting POR-Pchlide-a,b complex in etiolated plant tissues is untenable, and its ensuing consequences and implications, for the greening process, are irrelevant.
Laboratory of Plant Biochemistry and Photobiology, Natural Resources and Environmental Sciences, University of Illinois, Urbana, Illinois 61801, USA.
Vladimir L
VL
Kolossov
Constantin A
CA
Rebeiz
D000096:Acetone / Q000737:chemistry / Q000494:pharmacology; D002734:Chlorophyll / Q000737:chemistry; D002736:Chloroplasts / Q000378:metabolism*; D004047:Diethyl Pyrocarbonate / Q000494:pharmacology; D001467:Hordeum / Q000378:metabolism; D008027:Light; D018462:Photobiology; D010860:Pigments, Biological / Q000737:chemistry; D018515:Plant Leaves / Q000737:chemistry; D018521:Plant Physiological Phenomena; D010940:Plant Proteins / Q000737:chemistry; D018087:Plastids / Q000737:chemistry; D011521:Protochlorophyllide / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
D010860:Pigments, Biological; D010940:Plant Proteins; D000096:Acetone; D002734:Chlorophyll; D011521:Protochlorophyllide; C037184:chlorophyll b; D004047:Diethyl Pyrocarbonate