Figure 1

Azolla filiculoides, the cyanobacterial symbiont (NoAz) and the NoAz genome. A. The water-fern Azolla filiculoides growing in the greenhouse. B. Close-up of Azolla leaves. Each leaf contains a specialized cavity (marked with dotted circle) where a colony of ‘Nostoc azollae’ 0708 resides. C. ‘Nostoc azollae’ 0708 filaments. Arrows indicate the differentiated nitrogen-fixing heterocysts. Bar is 10 μm. D. Repeat sequences and pseudogenes in the NoAz genome (5.35 Mbps). Red ticks indicate positions of pseudogenes among the black-ticked non-affected functional genes, while green ticks indicate the positions of IS elements within the genome.