Analysis of the Light-harvesting Pigment-Protein Complex of Wild Type and a Chlorophyll-b-less Mutant of Barley

Abstract

We have compared chloroplast lamellae isolated from a chlorophyll-bless mutant and wild type barley (Hordeum vulgare). The results demonstrate that: (a) one of the two major polypeptides comprising the lightharvesting complex (LHC) is present in the chlorophyll-b-less mutant; (b) higher cation concentrations are required to maintain grana stacks in the mutant; and (c) cation effects on excitation energy distribution are present in the chlorophyll-b-less mutant but are reduced in amount and are 'dependent on higher concentrations of cations.We interpret these data to support the concept that the LHC mediates cation-induced grana stacking and cation regulation of excitation energy distribution between photosystems I and II in chioroplast lamellae. A partial LHC complement in the mutant alters the quantitative cation requirement for both phenomena, but not the over-all qualitative response.The involvement of cations in the regulation of grana formation and in mediating excitation energy distribution between the two photosystems has been extensively examined in recent years (7,9,24). In greening systems, the onset of cation control of energy distribution and the formation of grana stacks appear concomitantly with the synthesis of LHC3 (4, 6, 15). A correlation between the levels of LHC in chloroplast membranes, cation regulation of grana formation, and cation mediation of excitation energy distribution has been shown for almost all higher plant systems studied (1,2,8,29). This has led to the concept that the light-harvesting complex is the primary membrane constituent which is responsible for cation-mediated changes in these chloroplast membrane processes (1, 7).The one exception to the above mentioned rule comes from studies of a chlorina mutant of barley which lacks Chl b. This mutant has been shown to be missing the pigmented light-harvesting Chl a/b protein when examined by SDS-polyacrylamide gel electrophoresis (3,16,18,21,22,28). When examined by electron microscopy this mutant showed either partial or extensive grana stacking (17,22). In addition, cations have an effect on the fluorescence yield of isolated chloroplasts from this barley mutant (10), thus indicating cation-controlled energy distribution processes. Since these data pertaining to the barley mutant tend to invalidate the hypothesis that LHC plays a pivotal role in cationmediated structure-function events, we have reexamined the isolated chloroplasts of the Chl-b-less barley mutant. We will dem-

Functional Organization of Chlorophyll a and Carotenoids in the Alga, Nannochloropsis salina

“…The position in the gel after electrophoresis, absorption spectrum, and pigment content of the algal PSII complex are all properties similar to PSII from higher plants; but, like PSI, its relative proportion seems to be lower (7% compared to 15% for spinach, Table I (9), probably because these pigment-proteins without Chl b are extremely labile and more susceptible to both protease and detergent action (12). The procedure used to isolate a Chl a antenna complex from the Chlorina-f2 barley mutant was the same as that applied here to N. salina, and the gel pattern for the fastest running green bands (LHCII and FP) were similar ( Table I).…”

Analysis of Leaf Sectors in the NCS6 Mitochondrial Mutant of Maize.

“…This is expected if there is a nonuniform loss of CPI in the chloroplasts. If the reduction in chlorophyll were due to loss of the light harvesting complex, as in the well-documented barley chlorina f2 mutant (Burke et al, 1979), a shift in the 740-nm band to the 720-to 725-nm region would be expected. The decrease in the chlorophyll alb ratio as well as the reduction, rather than a shift of the 740-nm fluorescence band, argues for an effect on the PSllCPl thylakoid complex in the yellow sectors.…”

Consequences of spatial separation of photosystem 1 and 2 in thylakoid membranes of higher plant chloroplasts

“…. (i) Simpson [46] showed that the EFs particles of a chl b-less mutant barley which lacks one of the LHCP polypeptides [47] were only 12% smaller than those of wild type barley. Since there was a 50% decrease in the number of PFs particles in mutant barley, he concludes that some LHCP is located in PFs particles which are closely associated with EFs particles.…”