Chloramphenicol Stimulation of Light Harvesting Chlorophyll Protein Complex Accumulation in a Chlorophyll b Deficient Wheat Mutant

Abstract

ABSTRAC1As compared with normal wheat leaves, the chlorina wheat mutant, designated CD3, has a high chlorophyll a/b ratio and a deficiency in the light harvesting chlorophyll protein (LHCP) complex. Applications of 200 micrograms per milliliter of D-threo-chloramphenicol to etiolated seedlings decreased the chlorophyll a/b ratio and increased the accumulation of the 27 kilodalton LHCP polypeptide and the LHCP complex in thylakoids of the mutant during greening. These data led to the suggestion that a protein encoded in chloroplast genes impaired either transcriptional, translational, or posttranslational events in CD3 wheat limiting the accumulation of the LHCP complex. The LHCP complex which accumulated in chloramphenicol treated wheat appeared functional even though chlorophyll protein complex accumulations were altered greatly in the wheat thylakoids. LHCP polypeptides were phosphorylated by action of a membrane protein kinase but yet photosystem II electron transport was impaired. The chloramphenicol treatment increased the photosystem 1/photosystem II ratio of electron transport and the fluorescence emission ratio at 740 to 686 nanometers relative to those of untreated wheat. Chloramphenicol prevented development of normal granal thylakoids in normal wheat chloroplasts but not in those of the CD3 mutant. Elongated stacked thylakoids were observed in normal wheat. Net-like membranes and vesicles were noted in the stroma of chloroplasts from treated mutant seedlings.

Light-Harvesting Chlorophyll a/b Complexes: Interdependent Pigment Synthesis and Protein Assembly.

“…Chloramphenicol-dependent accumulation of Chl b was demonstrated in a wheat mutant (Duysen et al, 1985). Falbel and Staehelin (1994) subsequently identified impaired formation of chlorophyll precursors as the basis for Chl b deficiency.…”

Severity of Mutant Phenotype in a Series of Chlorophyll-Deficient Wheat Mutants Depends on Light Intensity and the Severity of the Block in Chlorophyll Synthesis

“…Conversely, when the Chl b level in a Chl b-deficient mutant is experimentally increased, e.g. by applying chloramphenicol to inhibit the synthesis of RC proteins that bind only Chl a, the increase in Chl b is matched by an increase in LHCs (Duysen et al, 1985. Also, greening wildtype barley plants can be treated with the porphyrin precursor 5-aminolevulinic acid to increase the supply of Chl in the greening experiment.…”

Chloramphenicol‐induced stabilization of light‐harvesting complexes in thylakoids during development

“…The RC polypeptides having higher affinity for Chl than those of LHC bind on Chl (in ImL) or remove it from pre-existing LHC (in plants transferred to the dark after brief preexposure to CL); the LHC apoproteins in the absence of Chl binding are digested. In view of these findings the stimulation of LHCP accumulation by CAP treatment in the CD3 Chl deficient wheat mutant, normally deficient in LHCP [12], may be attributed to the inhibition of RC polypeptide synthesis by CAP.…”

“…The leaves with one cotyledon removed were either exposed to ImL [2 rain white light alternating with 98 rain dark in cycles], or to CL for 18 h and then transferred to the dark. In the first case, leaves were immersed for 3 min in CAP solution (200/~g/ml), 7 h before and immediately prior to ImL exposure, according to [12]. In the latter, leaves were immersed in CAP once just before transfer to the dark and once more after 7 h in darkness; the leaves were dried on filter paper and kept in darkness until the second CAP treatment.…”