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Plant Physiology 96:227-231 (1991) © 1991 American Society of Plant Biologists Characterization of Cytoplasmic and Nuclear Mutations Affecting Chlorophyll and Chlorophyll-Binding Proteins during Senescence in Soybean 1Biology Department, University of Michigan, Ann Arbor, Michigan 48109-1048
Soybean plants (Glycine max [L.] Merr. cv Clark) carrying nuclear and cytoplasmic "stay-green" mutations, which affect senescence, were examined. Normally, the levels of chlorophyll (Chl) a and b decline during seedfill and the Chl a/b ratio decreases during late pod development in cv Clark. Plants homozygous for both the d1 and d2 recessive alleles, at two different nuclear loci, respectively, retained most (64%) of their Chl a and b and exhibited no change in their Chl a/b ratio. Combination of G (a dominant nuclear allele in a third locus causing only the seed coat to stay green during senescence) with d1d2 further inhibited the loss of Chl in the leaf. Whereas the thylakoid proteins seem to be degraded in normal Clark leaves during late pod development, they were not substantially diminished in d1d2 and Gd1d2 leaves. In plants carrying a cytoplasmic mutation, cytG, Chl declined in parallel with normal cv Clark; however, the cytG leaves had a much higher level of Chl b, and somewhat more Chl a, remaining at abscission, enough to color the leaves green. In cytG, most thylakoid proteins were degraded, but the Chl a/b-binding polypeptides of the light-harvesting complex in photosystem II (LHCII), and their associated Chl a and b molecules, were not. Thus, the combination of d1 and d2 causes broad preservation of the thylakoid proteins, whereas cytG appears to selectively preserve LHCII. The cytG mutation may be useful in elucidating the sequence of events involved in the degradation of LHCII proteins and their associated pigments during senescence.
2 J. J. G. is a researcher at C.I.C., Pcia de Buenos Aires, Argentina. 1 Supported in part by U. S. Department of Agriculture grant 88-37262-3878 to E. P., by a grant from the University of Michigan Office of the Vice President for Research to L. D. N., and by a fellowship from Consenjo Nacional Investigaciones Cientificas y Técnicas, Republica Argentina to J. J. G. This article has been cited by other articles:
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