Loss of the Chloroplast Transit Peptide from an Ancestral C3Carbonic Anhydrase Is Associated with C4Evolution in the Grass GenusNeurachne.
Neurachneis the only known grass lineage containing closely related C3, C3-C4intermediate, and C4species, making it an ideal taxon with which to study the evolution of C4photosynthesis in the grasses. To begin dissecting the molecular changes that led to the evolution of C4photosynthesis in this group, the complementary DNAs encoding four distinct β-carbonic anhydrase (CA) isoforms were characterized from leaf tissue ofNeurachne munroi(C4),Neurachne minor(C3-C4), andNeurachne alopecuroidea(C3). Two genes (CA1andCA2) each encode two different isoforms: CA1a/CA1b and CA2a/CA2b. Transcript analyses found thatCA1messenger RNAs were significantly more abundant than transcripts from theCA2gene in the leaves of each species examined, constituting ∼99% of all β-CA transcripts measured. Localization experiments using green fluorescent protein fusion constructs showed that, while CA1b is a cytosolic CA in all three species, the CA1a proteins are differentially localized. TheN. alopecuroideaandN. minorCA1a isoforms were imported into chloroplasts ofNicotiana benthamianaleaf cells, whereasN. munroiCA1a localized to the cytosol. Sequence analysis indicated an 11-amino acid deletion in the amino terminus ofN. munroiCA1a relative to the C3and C3-C4proteins, suggesting that chloroplast targeting of CA1a is the ancestral state and that loss of a functional chloroplast transit peptide inN. munroiCA1a is associated with the evolution of C4photosynthesis inNeurachnespp. Remarkably, this mechanism is homoplastic with the evolution of the C4-associated CA in the dicotyledonous genusFlaveria, although the actual mutations in the two lineages differ.
School of Molecular Sciences, University of Western Australia, Perth, Western Australia 6009, Australia (H.C., M.S., M.L.).|Australian Research Council Centre for Translational Photosynthesis, Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia (V.R., R.S.); and.|Western Australian Herbarium, Science and Conservation Division, Department of Parks and Wildlife, Perth, Western Australia 6152, Australia (T.M.).
Harmony
H
Clayton
School of Molecular Sciences, University of Western Australia, Perth, Western Australia 6009, Australia (H.C., M.S., M.L.).|Australian Research Council Centre for Translational Photosynthesis, Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia (V.R., R.S.); and.|Western Australian Herbarium, Science and Conservation Division, Department of Parks and Wildlife, Perth, Western Australia 6152, Australia (T.M.).
Montserrat
M
Saladié
School of Molecular Sciences, University of Western Australia, Perth, Western Australia 6009, Australia (H.C., M.S., M.L.).|Australian Research Council Centre for Translational Photosynthesis, Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia (V.R., R.S.); and.|Western Australian Herbarium, Science and Conservation Division, Department of Parks and Wildlife, Perth, Western Australia 6152, Australia (T.M.).
Vivien
0000-0002-9232-1287
V
Rolland
School of Molecular Sciences, University of Western Australia, Perth, Western Australia 6009, Australia (H.C., M.S., M.L.).|Australian Research Council Centre for Translational Photosynthesis, Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia (V.R., R.S.); and.|Western Australian Herbarium, Science and Conservation Division, Department of Parks and Wildlife, Perth, Western Australia 6152, Australia (T.M.).
Robert
R
Sharwood
School of Molecular Sciences, University of Western Australia, Perth, Western Australia 6009, Australia (H.C., M.S., M.L.).|Australian Research Council Centre for Translational Photosynthesis, Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia (V.R., R.S.); and.|Western Australian Herbarium, Science and Conservation Division, Department of Parks and Wildlife, Perth, Western Australia 6152, Australia (T.M.).
Terry
T
Macfarlane
School of Molecular Sciences, University of Western Australia, Perth, Western Australia 6009, Australia (H.C., M.S., M.L.); martha.ludwig@uwa.edu.au.|Australian Research Council Centre for Translational Photosynthesis, Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia (V.R., R.S.); and martha.ludwig@uwa.edu.au.|Western Australian Herbarium, Science and Conservation Division, Department of Parks and Wildlife, Perth, Western Australia 6152, Australia (T.M.) martha.ludwig@uwa.edu.au.
Martha
0000-0002-0324-7602
M
Ludwig
D000595:Amino Acid Sequence; D024401:Carbonic Anhydrase I / Q000235:genetics; D024402:Carbonic Anhydrase II / Q000235:genetics; D002256:Carbonic Anhydrases / Q000235:genetics*; D060365:Chloroplast Proteins / Q000235:genetics*; D003593:Cytoplasm / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D019143:Evolution, Molecular; D017353:Gene Deletion; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D007527:Isoenzymes / Q000235:genetics; D018613:Microscopy, Confocal; D010788:Photosynthesis / Q000235:genetics*; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics; D006109:Poaceae / Q000145:classification / Q000201:enzymology / Q000235:genetics*; D021382:Protein Sorting Signals / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D060365:Chloroplast Proteins; D007527:Isoenzymes; D021382:Protein Sorting Signals; C078737:chloroplast transit peptides; D024401:Carbonic Anhydrase I; D024402:Carbonic Anhydrase II; D002256:Carbonic Anhydrases