Figure 1.
Rough outline of phylogenetic relationships in volvocine green algae [9], [10], [15].
Figure 2.
Time course of synchronous culture of Tetrabaena socialis NIES-571.
Light-dark cycle (light:dark = 12 h:12 h) were indicated on the horizontal axis, percentages of cells during cytokinesis were indicated on a vertical line of left side with a pink line, and number of cells were indicated on a right side with a green line. Each error bars shows standard deviation (n = 3).
Figure 3.
Images and diagrams of microtubular rootlet (MTR) and basal bodies (BB)/pro-basal bodies (pBB).
(A–I) Immunofluorescence microscopy. (A–C) Double stained fluorescence of acetylated tubulin and CrSAS-6 showing MTR and BB/pBB, respectively. Each scale bar represents 5 µm. (A) Chlamydomonas reinhardtii. (B) Tetrabaena socialis. (C) Gonium pectorale. (D–F) Fluorescence of acetylated tubulin. Each white arrowhead or asterisk indicates distal end of MTR or flagellum, respectively. Each scale bar represents 1 µm. Upper sides of panels E and F represent the directions of center in the flattened colonies. (D) C. reinhardtii. (E) T. socialis. (F) G. pectorale. (G–I) Fluorescence of CrSAS-6. Each arrow or arrowhead indicates BB or pBB, respectively. Each scale bar represents 1 µm. Upper sides of panels H and I represent the directions of center in the flattened colonies. (G) C. reinhardtii. (H) T. socialis. (I) G. pectorale. (J–L) Diagrams of MTR and BB/pBB arrangements. Upper sides of panels K and L represent the directions of center in the flattened colonies. (J) C. reinhardtii. (K) T. socialis. (L) G. pectorale. (M, N) Transmission electron microscopy of T. socialis. ECM, extracellular matrix; cm, cell membrane; df, distal fiber; pf, proximal fiber; asterisk, flagellar proper. (M) Longitudinal section of anterior end of cell showing BB and distal fiber. Note proximal ends of the two BB (white arrows) are separated from each other. (N) Longitudinal section of anterior end of cell showing BB with proximal fiber.
Figure 4.
Time-lapse analysis for cytokinesis of Tetrabaena socialis NIES-571.
(A) Parental colony of T. socialis, shown at the same magnification throughout. Scale bar represents 5 µm. (B) Enlarged image in frame in (A), shown at the same magnification throughout. Scale bar represents 5 µm. Note possible connections between daughter protoplasts (arrowheads).
Figure 5.
Transmission electron microscopy of cytokinesis of four-celled embryos of Tetrabaena socialis NIES-571.
(A) Transverse section of almost central part of four daughter protoplasts before formation of new flagella. Note a daughter protoplast connected to two neighbors by cytoplasmic bridges (arrowheads). (B) Semi-longitudinal section of daughter protoplasts after formation of new flagella (large frame) within parental extracellular matrix (ECM) (asterisks). Note two protoplast connected to each other by cytoplasmic bridges (small frame). (C, D) Enlarged images of two frames in (B). (C) New flagella (arrows) within parental ECM (asterisks). (D) Cytoplasmic bridges (arrowhead) connecting two daughter protoplasts.
Figure 6.
Light and transmission electron microscopy of vegetative colonies of Tetrabaena socialis NIES-571.
(A–C) Three light microscopic views of four-celled vegetative colony, showing positions of flagella and eyespots. Note that flagella (asterisks) and eyespots (arrowheads) are arranged in symmetric pattern in the whole colony. (D, E) Transmission electron microscopy. ECM, extracellular matrix; ce, chloroplast envelope; ch, chloroplast; cm, cell membrane; n, nucleus; p, pyrenoid. (D) Longitudinal section of vegetative colony. (E) Eyespot composed three layers of globules.
Table 1.
List of three volvocine algae used in this study.