A novel gene that bears a DnaJ motif influences cyanobacterial cell division

Abstract

Transposon Tn5-692 mutagenizes Synechococcus sp. strain PCC 7942 efficiently. The predicted product of the gene mutated in the Tn5-692-derived cell division mutant FTN2 has an N-terminal DnaJ domain, as have its cyanobacterial and plant orthologs. Anabaena sp. strain PCC 7120, when mutated in genes orthologous to ftn2 and ftn6, forms akinete-like cells.

FIG. 1.

Morphology of wild-type PCC 7942 (A) and of mutants FTN2 (C) and FTN6 (B), grown in liquid medium and visualized by bright-field light microscopy. Scale bars represent 12.5 μm (A and B) or 25.6 μm (C).

FIG. 2.

Structures of wild-type PCC 7942 (A) and of mutants FTN2 (C; see box in panel B) and FTN6 (E; see box in panel D), negatively stained with uranyl acetate and examined by electron microscopy. The cells of both mutants divide infrequently. Scale bars represent 1 μm (A, C, and E) or 10 μm (B and D).

FIG. 3.

Morphology of Anabaena sp. strain PCC 7120 wild type (A and B) and mutants FTN2_A (C and D) and FTN6_A (E and F) grown in liquid medium free of combined nitrogen (AA/8 [20]) (A, C, and E) or supplemented with 5 mM nitrate (B, D, and F). Scale bars represent 12.5 μm. Akinete-like cells are indicated by arrows.