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Characterization of Cytoplasmic and Nuclear Mutations Affecting Chlorophyll and Chlorophyll-Binding Proteins during Senescence in Soybean

J. J. Guiamét, E. Schwartz, E. Pichersky and L. D. Noodén
Plant Physiology
Vol. 96, No. 1 (May, 1991), pp. 227-231
Stable URL: http://www.jstor.org/stable/4273581
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Characterization of Cytoplasmic and Nuclear Mutations Affecting Chlorophyll and Chlorophyll-Binding Proteins during Senescence in Soybean
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Abstract

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 $\text{d}_{1}\text{d}_{2}$ 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 $\text{d}_{1}\text{d}_{2}$ and $\text{Gd}_{1}\text{d}_{2}$ 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.

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