Chloroplast Composition and Structure Differences in a Soybean Mutant

Abstract

A nuclear nmtutationl of Glycine nmax (soybean) segregates 1:2:1 in regard to chlorophyll conitent. The heterozygous (LG) leaf blade contains about onie-half the pigment content of the wild type (DG) other chlorophyll-depleted mutants, have limited or no lamellar stacking into grana. Weber and Weiss (30) described a soybean nuclear mutation in which seeds collected from heterozygous plants segregate 1:2:1 in regard to chlorophyll content. The heterozygous plants are a light green (LG) and the homozygous plants are either normal dark green (DG) or a lethal yellow (LY). The yellow plants do not mature under normal physiological conditions but die when the colyledonary food reserves are depleted (about 9-14 days after germination).Wolf (32) reported the pigment content of the aerial portions of these seedling types growing under 500 ft-c of fluorescent lighting at 24 C. The LG contained approximately one-half the pigment content of the DG, and the LY contained about 20 ( of the DG pigments. The rate of CO2 fixed per leaf area of the LG was not significantly different from that of the DG while that of the LY was reduced. Carbon dioxide fixation rates in the three types, however, were light-saturated at the same intensity, unlike the above mentioned mutants.Sun (27) reported reduced plastid size, limited grana stacking, and ultrastructural abnormalities in the later stages of LY plastid development.This soybean mutation is unusual in the 1:2:1 segregation of the phenotypes and because the heterozygotes light-saturate at the same intensity as the normally pigmented plant.This communication describes some pigment and nonpigment compositional differences and structural differences among the three phenotypes. A companion paper presents results of our studies concerning the comparative rates of electron and proton transport and photophosphorylation. METHODS AND MATERIALSMutations altering photosynthesis are found in many algae and higher plants (18). These mutations may be nuclear or nonnuclear and have been shown to affect pigments, electron transport chain components, and carbon cycle enzymes and structure (20).The majority of algal and higher plant mutants which are depleted in chlorophyll content are lethal or grow very slowly (18). Several mutants have been described which at high light intensities photosynthesize at rates comparable to the wild type (8,15,16,25 Insoluble residue was removed on a sintered glass filter, and extraction was continued with additional small portions of the same solvent mixture until the residue was free of chlorophyll. Chloroform was used as the final extractant in the amount necessary to bring the combined extracts to a 1 :1 (v/v) chloroform-methanol composition; 0.8 volume of cold water was then added to give a two-phase mixture. The upper (aqueous) layer was separated, washed with chloroform, and discarded. The combined chloroform-rich solutions were evaporated under nitrogen at room temperature or below and the residual lipid was taken up in chloroform-methanol (9:1, v/v) to...

Characterization of Chloroplasts Isolated from Triazine-Susceptible and Triazine-Resistant Biotypes of Brassica campestris L.

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Interactions of Lipoidal Materials and a Pyridazinone Inhibitor of Chloroplast Development

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