Figure 1.

Developmental variations in M. angicava zygotes produce multicellular sporophytes. (a) Unicellular/multicellular developmental variation of genetically identical zygotes. Arrow: a multicellular body. Arrowheads: unicellular cysts. (b–h) Differential development of zygotes. (b) Zygotes usually develop into spherical unicellular cysts (c,d). (e) Some zygotes develop into filamentous multicellular bodies (f), which then grow into disc-like (g) and saccate forms (h). (i) Sex markers reveal that multicellular sporophytes have both male- and female-specific genomic regions; ‘m’: male marker. ‘f’: female marker. Side bar: 500 bp. (j) Zoospores develop into filamentous multicellular bodies (k), which then grow into disc-like (l) and saccate forms (m). Insets in (h) and (m) show male (green, arrowheads) and female (red, arrow) FISH signals on nuclei of a diploid sporophyte and haploid gametophyte, respectively. Scale bars: 1 µm. 1N: haploid; 2N: diploid.