Bicarbonate enhances synchronous division of the giant nuclei of sporophytes in Bryopsis plumosa

Abstract

A mature sporophyte of Bryopsis plumosa (Hudson) C. Agardh forms a huge number of zoospores in its cell continuum. Zoospore formation starts with the division of a single giant nucleus and subsequent repeated mitosis. We found that an elevation of photosynthetic activity triggered the division of a mature giant nucleus. Transfer to short-day conditions was not necessary. Giant nuclei did not divide in darkness or in the presence of 1 micro M DCMU. Giant nuclei of as many as 90% of sporophtyes started to divide following the addition of 5 microM NaHCO3 to the growth medium under continuous white light (6-12 W m(-2)). Frequency of nuclear division increased with increased light intensity. By combining those parameters that promoted the division of giant nuclei, we developed the "two-step culture method" which is composed of preliminary and main cultures. This new method guarantees that giant nuclei of more than 90% of all sporophytes synchronously divide between 72 and 96 h after the transfer to the main culture (continuous white light of 12 W m(-2) in PES medium supplemented with 5 mM NaHCO3).

Bacteria in Himalayan glacial ice and its relationship to dust

“…Treatment of samples by SYBR Green-II (Molecular Probes, Inc.) was modified from Yamagishi et al (2003). Fifty milliliters of each sample were fixed in 2% (vol/vol) glutaraldehyde buffered with phosphate-buffered saline (PBS) and then filtered onto 25mm, 0.2 µm black track-etch membrane filters (Whatman).…”

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

“…Sexual reproduction of gametophytes was induced by aeration, as previously described (Yamagishi et al 2003). Liberated male and female gametes were collected and fertilized by mixing them in a Petri dish, which was filled with PES medium.…”

“…were collected from the habitat at Murohama, Miyagi, Japan in July 1998. A unialgal culture of gametophytes was achieved according to a previously described method (Yamagishi et al 2003). Gametophytes were cultured in Provasoli's enriched seawater medium (PES; Provasoli 1966) at 23°C under continuous white light until use.…”

“…The body of the gametophyte is composed of a large cylindrical coenocytic thallus with beautiful pinnae. In laboratory conditions, however, such a pinnate gametophyte can only be obtained when it is cultured with gentle aeration (Yamagishi et al 2003). The dioecious gametophyte of B. plumosa contains many small haploid nuclei.…”

“…By contrast, a sporophyte is composed of a small, creeping, sparsely branched cell, which contains a single, large diploid nucleus. When maturation of the sporophyte is induced either spontaneously or experimentally, the giant nucleus undergoes meiosis, produces many small nuclei by the following mitosis, and finally forms a number of zoospores (Yamagishi et al 2003).…”