An analysis of temperature and light sensitivity intigrina mutants of barley

Abstract

Quantitative determinations of chlorophylls, carotenes and xanthophylls were carried out by high pressure liquid chromatography on the nuclear gene mutanttigrina-o 34. In the dark the mutant accumulates lycopene and protochlorophyllide at 23°C but almost none at 30°C, while xanthophylls are deficient only at 23°C. In the light, lycopene accumulation and β-carotene as well as xanthophyll deficiency is severe at 23°C, whereas an improved content of β-carotene and xanthophyll is observed at 30°C. An improved content can also be achieved by growing mutant seedlings in red light of wavelengths longer than 650nm at 23°C. Under conditions where lycopene accumulates in the dark the presence of abnormal membrane structures is correlated with a deficiency in certain membrane polypeptides, e.g. the α, β subunits of coupling factor. Under conditions of severe β-carotene deficiency in light grown seedlings, photodynamic destruction of chloroplast ribosomes and preferential accumulation of light harvesting chlorophylla/b-protein is observed. Eventually, the chloroplast structure disintegrates. Under conditions of simultaneous lycopene accumulation and β-carotene as well as lutein deficiency the chlorophyll aggregates into a non-fluorescing form absorbing at 743nm. This form is part of a complex insoluble in 2% SDS and containing lycopene, chlorophylla and protein. Tigrina mutants at other loci have been characterized as to their temperature and light sensitivity.