Details

Autor(en) / Beteiligte

• Rao, Srinath K.
• Magnin, Noël C.
• Reiskind, Julia B.
• Bowes, George

Titel

Photosynthetic and Other Phosphoenolpyruvate Carboxylase Isoforms in the Single-Cell, Facultative C4 System of Hydrilla verticillata1

Ist Teil von

• Plant physiology (Bethesda), 2002-10, Vol.130 (2), p.876-886

Ort / Verlag

Oxford University Press

Erscheinungsjahr

2002

Quelle

EZB Free E-Journals

Beschreibungen/Notizen

• The submersed monocot Hydrilla verticillata (L.f.) Royle is a facultative C 4 plant. It typically exhibits C 3 photosynthetic characteristics, but exposure to low [CO 2 ] induces a C 4 system in which the C 4 and Calvin cycles co-exist in the same cell and the initial fixation in the light is catalyzed by phospho enol pyruvate carboxylase (PEPC). Three full-length cDNAs encoding PEPC were isolated from H. verticillata , two from leaves and one from root. The sequences were 95% to 99% identical and shared a 75% to 85% similarity with other plant PEPCs. Transcript studies revealed that one isoform, Hvpepc4 , was exclusively expressed in leaves during C 4 induction. This and enzyme kinetic data were consistent with it being the C 4 photosynthesis isoform. However, the C 4 signature serine of terrestrial plant C 4 isoforms was absent in this and the other H. verticillata sequences. Instead, alanine, typical of C 3 sequences, was present. Western analyses of C 3 and C 4 leaf extracts after anion-exchange chromatography showed similar dominant PEPC-specific bands at 110 kD. In phylogenetic analyses, the sequences grouped with C 3 , non-graminaceous C 4 , and Crassulacean acid metabolism PEPCs but not with the graminaceous C 4 , and formed a clade with a gymnosperm, which is consistent with H. verticillata PEPC predating that of other C 4 angiosperms.