Cyanobacterial alkaline/neutral invertases. Origin of sucrose hydrolysis in the plant cytosol?

W.A. VARGAS; A.C. CUMINO; G.L. SALERNO

PLANTA

Springer-Verlag

Lugar: Berlin-Heidelberg; Año: 2003 vol. 216 p. 951 - 960

0032-0935

The aim of this work was to investigate theoccurrence of invertase (Inv) in cyanobacteria. Wedescribe the first isolation and characterization ofprokaryotic alkaline/neutral Inv (A/N-Inv) genes. Twogenes (invA and invB) were identified in Anabaenasp. PCC 7120, which share about 50–56% identitywith plant A/N-Inv and encode proteins of about53–55 kDa. The identification of these proteins wasconfirmed by biochemical and immunological studieswith recombinant proteins and with the enzymes isolatedfrom Anabaena cells. Expression analysis supported theimportant role of A/N-Inv in nitrogen-fixing growthconditions. Nevertheless, A/N-Inv activities wereshown in all filamentous and unicellular cyanobacteriainvestigated, regardless of their capacity to fix dinitrogen.Searches in complete sequenced genomes showed thatA/N-Inv homologues are restricted to cyanobacterialspecies and plants. In particular, filamentous nitrogenfixingstrains display two A/N-Inv genes and unicellularstrains have only one. Phylogenetic analysis leads us tosuggest that modern plant A/N-Inv might have originatedfrom an orthologous ancestral gene after theendosymbiotic origin of chloroplasts