Characteristics of mitosis in the gametophyte cells of the marine green alga Monostroma angicava

Yusuke Horinouchi,Tatsuya Togashi

doi:10.1186/s40529-019-0256-z

Abstract

BackgroundSome marine algae exhibit several characteristics of mitosis (e.g., the timing of mitosis such as diurnal periodicity) that are unique from those of land plants. Not only the timing but also other characteristics of mitosis, including the process itself and the number of chromosomes involved, are largely unknown in ulvophycean marine green algae. Effective mitotic inhibitors are useful for observing mitosis and identifying the number of chromosomes. However, few such inhibitors are available for ulvophycean algae. Here, we examined the timing and process of mitosis and the number of chromosomes with several mitotic inhibitors in the haploid gametophyte cells of the Ulvophyceae alga Monostroma angicava.ResultsMitosis did not occur during the light period but began immediately after the onset of the dark period. The typical process of mitosis was observed. The mitotic inhibitors colchicine and 8-hydroxyquinoline, which generally arrest mitosis in land plants, were ineffective in M. angicava. We found that three other mitotic inhibitors, amiprophos methyl, griseofulvin and oryzalin, are effective to arrest mitosis. With three-dimensional fluorescence microscopy, we demonstrated that there were nine chromosomes in each cell.ConclusionsIn the gametophyte cells of M. angicava, mitosis occurs diurnally. It is triggered by the onset of the dark period. We identified the number of chromosomes as N = 9. Our study shows effective inhibitors to observe mitosis in ulvophycean algae.

Highlights

Some marine algae exhibit several characteristics of mitosis that are unique from those of land plants
Timing of mitosis no dividing cells were observed during the light period, we found dividing cells with condensed chromosomes during the dark period (Fig. 1)
Some dividing cells at different phases of mitosis were always observed during the dark period

Summary

Introduction

Some marine algae exhibit several characteristics of mitosis (e.g., the timing of mitosis such as diurnal periodicity) that are unique from those of land plants. Effective mitotic inhibitors are useful for observing mitosis and identifying the number of chromosomes. Few such inhibitors are available for ulvophycean algae. We examined the timing and process of mitosis and the number of chromosomes with several mitotic inhibitors in the haploid gametophyte cells of the Ulvophyceae alga Monostroma angicava. Some mitotic inhibitors that arrest mitosis in land plants, such as colchicine and 8-hydroxyquinoline (Evans et al 1957; Wanner et al 1991; Komaki and Schnittger 2016), might not take effect in algal species (e.g., McNaughton and Goff 1990). Mitotic inhibitors are useful for examining the details of the process of mitosis and counting the number of chromosomes

Methods

Results

Conclusion