Chloroplast Division and Differentially Regulated Expression of <i>FtsZ1</i> and <i>FtsZ2</i> in the Synchronous Culture of <i>Nannochloris bacillaris</i> (Chlorophyta, Trebouxiophyceae)
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In plants, the prokaryote-derived chloroplast division protein FtsZ is divided into the FtsZ1 and FtsZ2 families. To clarify the relationship between <i>FtsZ1</i> and <i>FtsZ2</i> expression and chloroplast division in the unicellular green alga <i>Nannochloris bacillaris</i>, we compared <i>FtsZ1</i> and <i>FtsZ2</i> expression in alga cultured in 2 nutritionally different media. Cells grown in a rich medium had 1 FtsZ ring throughout the cell division cycle, whereas cells in an inorganic medium showed only 1 FtsZ ring during the chloroplast division phase. Both <i>FtsZ1</i> and <i>FtsZ2</i> mRNA levels in the rich medium were higher than those in the inorganic medium. However, a much larger difference in the amount of transcripts between cells cultured in the rich and in the inorganic media was observed in <i>FtsZ2</i> than that in <i>FtsZ1</i>, suggesting different gene regulatory mechanisms between the <i>FtsZ</i> genes. <i>N. bacillaris</i> cells cultured in inorganic medium showed cell division photoperiodicity, whereas cells cultured in organic media proliferated continuously under a light/dark cycle. Although <i>FtsZ1</i> was expressed constantly throughout the chloroplast division cycle in the rich medium, the increase in <i>FtsZ1</i> mRNA level was simultaneous with chloroplast division under a light/dark cycle in the inorganic medium. <i>FtsZ2</i> was expressed constantly in both media. The control of chloroplast division by regulating FtsZ ring formation is discussed.
CYTOLOGIA 77(1), 59-66, 2012
Japan Mendel Society, International Society of Cytology