Open AccessPhotosynthetic carbon reduction pathway is absent in chloroplasts of Vicia faba guard cells
Author(s) -
William H. Outlaw,
Jill K. Manchester,
Cynthia A. Dicamelli,
Douglas D. Randall,
Barbara J. Rapp,
G Veith
Publication year - 1979
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.76.12.6371
Subject(s) - guard cell , vicia faba , chloroplast , biochemistry , biology , photosynthesis , ribulose , rubisco , microbiology and biotechnology , botany , gene
Four cell types fromVicia faba Linnaeus “Long Pod” leaflets were assayed for three enzymes unique to the photosynthetic carbon reduction pathway. The enzymes were ribulosebisphosphate carboxylase [3-phospho-D-glycerate carboxy-lyase (dimerizing), EC 4.1.1.39], phosphoribulokinase (ATP:D-ribulose-5-phosphate 1-phosphotransferase, EC 2.7.1.19), and glyceraldehyde-phosphate dehydrogenase (NADP+ ) (phosphorylating) [D-glyceraldehyde-3-phosphate:NADP+ oxidoreductase (phosphorylating), EC 1.2.1.13]. On a dry weight basis, these enzyme activities were about twice as high in palisade as in spongy parenchyma. Two of the enzymes were not detected in epidermal cells and the other was present in only a trace amount. In guard cells, these enzyme activities were absent or present at les than 1% of the amount in palisade cells. Immunoelectrophoresis showed that ribulosebisphosphate carboxylase was absent in extracts of guard cell protoplasts. Microscopy confirmed the abundance of typical guard cell chloroplasts. These results demonstrate the absence of the photosynthetic carbon reduction pathway in guard cell chloroplasts. This is the only chloroplast type known to be deficient in this pathway in plants whose primary CO2 acceptor is ribulose bisphosphate. Possible reasons for the absence of this pathway in guard cells are discussed.