A photosystem I mutant in barley (Hordeum vulgare L.)

Abstract

The nuclear gene mutant viridis-n 34 in barley has been characterized as a photosystem I mutant. The slow component of the light dependent absorption change at 518 nm and the photooxidation of cytochrome f were greatly reduced in mutant leaves compared with wild-type leaves. The oxidation of cytochrome f in mutant leaves irradiated with far-red light was only 7 % of the value obtained with wild-type. The fast component of the 518 nm absorbance change was similar in wild-type and mutant leaves. The rate of photosystem I electron transport in the mutant is approximately 10% of the rate observed with wild-type thylakoids whereas photosystem II electron transport appears normal. Little or no P700 was detected in the mutant. The levels of cytochromes and ferredoxin-NADP § oxidoreductase were normal. Mutant thylakoids were unable to generate a proton gradient upon illumination. Analysis of the polypeptide composition of thylakoids of viridis-n 34 revealed that these are depleted in chlorophyll a-protein 1 and three polypeptides believed to be iron-sulfur proteins. These four polypeptides are components of photosystem I particles isolated from wild-type barley.Abbreviations: Asc = ascorbic acid, Chl = chlorophyll, Cyt = cytochrome, DBMIB = dibromothymoquinone, DCIP = 2,6-dichlorophenolindophenol, DCMU = 3-(3,4-dichlorophenyl)--l,l-dimethylurea, DTT = dithiothreitol, FeCN = potassium ferricyanide, GD --Gramicidin D, MeV = methylviologen, NADP § = {~-nicotinamide adenine dinucleotide phosphate, PD --p-phenylenediamine, PS = photosystem, SDS-PAGE --sodium dodecyl sulfate polyacrylamide gel electrophoresis, TMPD = N,N,N',N'-tetramethylphenylenediamine, Tricine --N-(tris-(hydroxymethyl)-methyl)glycine, Tris = tris-(hydroxymethyl)aminomethane.

Low temperature absorption spectroscopy of barley mutants. Guassian deconvolution and fourth derivative analysis

“…This mutant, which completely lacks the reaction centre chlorophyll-protein of PSI (20,27), produced the absorption spectrum shown in Figure 6a. There was a marked reduction in the amplitude of the chlorophyll b peak at 650 nm, as confirmed by the fourth derivative, which also lacked the component at 691 nm (Fig.…”

Chlorophyll fluorescence photography to detect mutants, chilling injury and heat stress

“…The mutant viridis-n 34 contains 75-80% of the amount of chlorophyll present in the wild type but is blocked at photosystem I (17). Consequently, the fluorescence rises to a higher level than in the wild type and this high level is maintained since re-oxidation of Q in the light is Figure 4.…”

“…This series shows that the chlorophyll fluorescence at room temperature of the two mutants and wild type in this experiment recording fluorescence at wavelengths below 700 nm was in the order viridise 64 > viridis-M 4 > wild type. While viridis-n 34 is defective in photosystem I activity (17), viridis-e 64 is low in both photosystems (30). The two mutants can be distinguished by studying the variable fluorescence, viridis-e 64 lacking variable fluorescence while viridis-n 34 has variable fluorescence due to a normally functioning photosystem II (26).…”

Freeze-fracture studies on barley plastid membranes V.viridis-n 34, a photosystem I mutant

“…x 54,000. (4,5,9). In comparison with wild-type, there is a partial deficiency in the amount of the P700-chlorophyll a-protein 1 which contains the reaction centre of photosystem I.…”

“…Using the chlorophyll b-less mutant, chlorina-f2, it has recently been shown that the light-harvesting chlorophyll a/b-protein 2 is localised in the majority of particles on the PFs face (13). This paper describes the ultrastructure of rotary shadowed freeze-fractured thylakoids from the well-characterised barley mutant viridis-n 34, which is partially deficient in photosystem I activity (4,5,9,16,17).…”