Novel sporophyte-like plants are regenerated from protoplasts fused between sporophytic and gametophytic protoplasts of Bryopsis plumosa

Abstract

Protoplasts of the marine coenocytic macrophyte Bryopsis plumosa (Hudson) C. Agardh. [Caulerpales] can easily be obtained by cutting gametophytes or sporophytes with sharp scissors. When a protoplast isolated from a gametophyte was fused with a protoplast isolated from a sporophyte of this alga, it germinated and developed into either one of two completely different forms. One plant form, named Type G, appeared quite similar to a gametophyte, and the other, named Type S, looked similar to a sporophyte. While the Type G plant contained many small nuclei of gametophyte origin together with a single giant nucleus of sporophyte origin, the Type S plant contained many large nuclei of uniform size. These large nuclei in the Type S plant had metamorphosed from the gametophytic nuclei, and were not formed through division of the giant nucleus of sporophyte origin. Fragments of the Type S plant, each having such a large nucleus, developed into creeping filaments that look very similar to sporophytes. While cell walls of gametophytes and Type G plants were stained by Congo-red, those of the thalli of regenerated Type S plants and sporophytes were not stained by the dye. This indicated that the large nuclei of the Type S plant did not express genes for xylan synthesis, which are characteristic of gametophytes. Two-dimensional gel electrophoretic analysis revealed that most of the proteins synthesized in the Type S plant were identical to those of sporophytes. These results strongly suggest that in the Type S plant, the gametophytic nuclei are transformed into sporophyte-like nuclei by an unknown factor(s) produced by the giant nucleus of sporophyte origin and that the transformed nuclei express the set of genes characteristic of sporophytes. Despite morphological similarity, however, the regenerated Type S plant could not produce zoospores, because its large nuclei did not divide normally. The transformed large nuclei of gametophyte origin still seemed to be in the haploid state.

OUROBOROS is a master regulator of the gametophyte to sporophyte life cycle transition in the brown alga Ectocarpus

“…The carbohydrate binding dye Congo red, which is used to stain xylan fibers in algal cell walls (19), stained the gametophyte, but not the sporophyte, of wild-type Ectocarpus ( Fig. 1 L and M).…”

Plant protoplast technology: Current status

“…Physcomitrella patens; Hohe and Reski 2002) and al gae (e.g. Bryopsis plumosa; Yamagishi et al 2004). Inter est ingly, the re lease of proto plasts from Bryopsis in volved a me chan i cal pro ce dure by cut ting of game tophyte or sporophyte tis sues with sharp scissors.…”

CELL‐WALL POLYMER MAPPING IN THE COENOCYTIC MACROALGA CODIUM VERMILARA (BRYOPSIDALES, CHLOROPHYTA)1

“…1979), a hybrid protoplast with both gametophytic and sporophytic nucleus synthesizes only β‐(1→4)‐ d ‐mannans. The gametophytic nucleus seems to repress the genes coded in the coexisting sporophytic one that are involved in xylan synthesis (Yamagishi et al. 2004).…”