ISSN:
1432-2048
Keywords:
Key words:Amaranthus (mutant)
;
C4 photosynthesis
;
Mutant (Amaranthus) NAD malic enzyme
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract. A mutant of Amaranthus edulis (Speg.) lacking activity of the C4 leaf form of NAD-malic enzyme (ME; EC 1.1.1.39) has been isolated. Homozygous mutant (5% wild-type ME activity) and heterozygous (50% wild-type ME activity) F2 plants were shown to contain both the α and β NAD-ME subunits in similar amounts to those detected in the wild-type leaves. The rate of photosynthetic CO2 assimilation was reduced in the homozygous mutant to 5% of that observed for the wild-type leaves. Other C4 enzymes were not down-regulated in the mutant plants. There was little difference in photosynthetic rate of the heterozygous plants compared to the wild-type, suggesting that NAD-ME exerts little control over the rate of C4 photosynthesis, and that in the wild-type the enzyme has a very low control coefficient. The activity loss in the heterozygote may therefore be compensated by regulatory mechanisms that increase the activity of the enzyme in vivo. Data for bundle-sheath strands indicated that although the homozygous mutants were able to oxidise malate via the Krebs cycle, they were unable to convert malate to pyruvate and alanine via NAD-ME.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004250050443
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