Regulation and Localization of Key Enzymes during the Induction of Kranz-Less, C4-Type Photosynthesis in Hydrilla verticillata - PubMed (original) (raw)

Regulation and Localization of Key Enzymes during the Induction of Kranz-Less, C4-Type Photosynthesis in Hydrilla verticillata

N. C. Magnin et al. Plant Physiol. 1997 Dec.

Abstract

Kranz-less, C4-type photosynthesis was induced in the submersed monocot Hydrilla verticillata (L.f.) Royle. During a 12-d induction period the CO2 compensation point and O2 inhibition of photosynthesis declined linearly. Phosphoenolpyruvate carboxylase (PEPC) activity increased 16-fold, with the major increase occurring within 3 d. Asparagine and alanine aminotransferases were also induced rapidly. Pyruvate orthophosphate dikinase (PPDK) and NADP-malic enzyme (ME) activities increased 10-fold but slowly over 15 d. Total ribulose-1,5-bisphosphate carboxylase/oxygenase activity did not increase, and its activation declined from 82 to 50%. Western blots for PEPC, PPDK, and NADP-ME indicated that increased protein levels were involved in their induction. The H. verticillata NADP-ME polypeptide was larger (90 kD) than the maize C4 enzyme (62 kD). PEPC and PPDK exhibited up-regulation in the light. Subcellular fractionation of C4-type leaves showed that PEPC was cytosolic, whereas PPDK and NADP-ME were located in the chloroplasts. The O2 inhibition of photosynthesis was doubled when C4-type but not C3-type leaves were exposed to diethyl oxalacetate, a PEPC inhibitor. The data are consistent with a C4-cycle concentrating CO2 in H. verticillata chloroplasts and indicate that Kranz anatomy is not obligatory for C4-type photosynthesis. H. verticillata predates modern terrestrial C4 monocots; therefore, this inducible CO2-concentrating mechanism may represent an ancient form of C4 photosynthesis.

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References

    1. Plant Physiol. 1983 Nov;73(3):729-34 - PubMed
    1. Plant Physiol. 1949 Jan;24(1):1-15 - PubMed
    1. Plant Physiol. 1983 Oct;73(2):488-96 - PubMed
    1. Proc Natl Acad Sci U S A. 1991 Apr 1;88(7):2883-7 - PubMed
    1. Arch Biochem Biophys. 1977 Mar;179(2):361-9 - PubMed

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