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Nuclear behavior and roles indicate that Codiolum phase is a sporophyte in <i>Monostroma angicava</i> (Ulotrichales, Ulvophyceae)
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- Yusuke Horinouchi
- Marine Biosystems Research Center Chiba University Kamogawa 299‐5502 Japan
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- Masashi Yamaguchi
- Medical Mycology Research Center Chiba University Chiba 260‐8673 Japan
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- Hiroji Chibana
- Medical Mycology Research Center Chiba University Chiba 260‐8673 Japan
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- Tatsuya Togashi
- Marine Biosystems Research Center Chiba University Kamogawa 299‐5502 Japan
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- M. Roleda
- editor
Bibliographic Information
- Published
- 2019-03-28
- Resource Type
- journal article
- Rights Information
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- http://onlinelibrary.wiley.com/termsAndConditions#vor
- DOI
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- 10.1111/jpy.12841
- Publisher
- Wiley
Search this article
Description
<jats:p>The life‐cycle system of Ulotrichales, a major order of Ulvophyceae, remains controversial because it is unclear whether the Codiolum phase, a characteristic unicellular diploid generation in ulotrichalean algae, is a zygote or a sporophyte. This controversy inhibits the understanding of the diversified life cycles in Ulvophyceae. To distinguish between zygotes and sporophytes, we have to examine not only whether diploid generations function as sporophytes, but also whether mitosis occurs before meiosis in diploid generations. However, the nuclear behavior in the Codiolum phases is largely unknown, probably because no suitable methods are available. Using fluorescent microscopy with ethidium bromide and transmission electron microscopy of cell‐wall‐dissected specimens, we report the nuclear behavior in the Codiolum phases of an ulotrichalean alga with a representative life cycle, <jats:italic>Monostroma angicava</jats:italic>. Each vegetative Codiolum phase had a single polyploid nucleus due to endoreduplication, a type of mitosis without nuclear division. During zoosporogenesis, the nucleus had a structure that would be a meiosis‐specific complex. We quantitatively showed that Codiolum phases grew extremely large and produced numerous zoospores. Our results suggest that an event comparable to mitosis occurs before meiosis in the Codiolum phase of <jats:italic>M. angicava</jats:italic>. This nuclear behavior and the functions (growth and zoospore production abilities) correspond to those of sporophytes. Therefore, the life‐cycle system of <jats:italic>M. angicava</jats:italic> is a heteromorphic haplo‐diplontic cycle. This system appears to be widely adopted among other ulotrichalean algae.</jats:p>
Journal
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- Journal of Phycology
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Journal of Phycology 55 (3), 534-542, 2019-03-28
Wiley
