Visualization of multiple FtsZ rings in actively dividing proplastids of cultured Bright Yellow-2 tobacco cells

The transfer of stationary-phase cultured tobacco (Nicotiana tabacum L.) Bright Yellow-2 (BY-2) cells into new medium induces active proplastid division. To examine the relationship between ftsZ gene expression and proplastid division, the transcript and protein levels of the ftsZ gene in stationary-phase cells and in 12-h-old cells after medium renewal were compared. RNA-gel blot analysis revealed that transcript levels for both types of ftsZ genes, ftsZ1 and ftsZ2, increased markedly following medium renewal. Similarly, immunoblot analysis using antibodies to lily FtsZ protein showed a remarkable increase in FtsZ protein following medium renewal. Furthermore, immuno-fluorescence microscopic observation revealed that FtsZ proteins appeared as multiple rings transversely aligned in elongated proplastids, which will be fragmented by multiple divisions during culture. These results suggest that FtsZ proteins may have a role in multiple division of proplastids.