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Guanchochroma wildpretii gen. et spec. nov. (Ochrophyta) Provides New Insights into the Diversification and Evolution of the Algal Class Synchromophyceae.

Schmidt M, Horn S, Ehlers K, Wilhelm C, Schnetter R - PLoS ONE (2015)

Bottom Line: A new relative of the chrysophyte genus Chrysopodocystis was found in Tenerife and termed Guanchochroma wildpretii.Yet, neither Chrysopodocystis nor Guanchochroma showed this feature in ultrastructure analyses.Evidence for the sequence of events leading to the formation of the plastid complex of Synchromophyceae still remains ambiguous because of the apparently short timeframe in which they occurred.

View Article: PubMed Central - PubMed

Affiliation: Universität Leipzig, Department of Plant Physiology, Johannisallee 21-23, 04103 Leipzig, Germany.

ABSTRACT
A new relative of the chrysophyte genus Chrysopodocystis was found in Tenerife and termed Guanchochroma wildpretii. This unicellular alga was most noticeably discernible from Chrysopodocystis socialis (the only species of this genus) by the presence of a cyst-like stage with a multilayered lorica, which also functions as a dispersal unit and shows secondary wall growth. Secondary expansion of loricae (cell casings not involved in cell division, usually with a more or less pronounced opening) has never been observed previously and marks a unique feature of the new taxon. Plastids are non-randomly distributed within cells of G. wildpretii. 18S rRNA gene analyses identified the two species as sister lineages and placed them in a monophyletic group with the Synchromophyceae, a heterokont algal (Ochrophyta) class characterized by the presence of chloroplast complexes. Yet, neither Chrysopodocystis nor Guanchochroma showed this feature in ultrastructure analyses. Additionally, their 18S rRNA genes possessed distinct inserts, the highest GC-content known for Ochrophyta and exceptionally long branches on the Ochrophyta 18S rDNA phylogenetic tree, suggesting substantially increased substitution rates along their branch compared to Synchromophyceae. Plastid marker data (rbcL) recovered a monophyletic clade of Chrysopodocystis, Guanchochroma and Synchromophyceae as well, yet with lower supports for internal split order due to limited resolution of the marker. Evidence for the sequence of events leading to the formation of the plastid complex of Synchromophyceae still remains ambiguous because of the apparently short timeframe in which they occurred.

No MeSH data available.


Related in: MedlinePlus

Arrangement of plastids in Guanchochroma wildpretii.(A) TEM of two amoebae in one multilayered lorica after binary division. The nucleolus is distinct within the nucleus. Vacuoles, mostly roundish, are present in different sizes. The plastids show no pyrenoids and are not interconnected. (B) TEM of an amoeba within a multilayered lorica. Vacuoles are present, yet with highly variable outline. Some plastids show terminal elongations without thylakoids (arrowhead). No Nucleus is visible in this section plane. (C) TEM of an amoeba within a multilayered lorica, showing four plastids and a nucleus without nucleolus in the section plane. Plastids possess tubular to globular shaped protrusions (white arrowhead) that group in the cell center (black arrowhead). The cytoplasm appears highly granular with variably shaped, non-globular vesicles. V—vesicle, N—nucleus, L—lorica, C chloroplast. Scale bars 5 μm.
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pone.0131821.g002: Arrangement of plastids in Guanchochroma wildpretii.(A) TEM of two amoebae in one multilayered lorica after binary division. The nucleolus is distinct within the nucleus. Vacuoles, mostly roundish, are present in different sizes. The plastids show no pyrenoids and are not interconnected. (B) TEM of an amoeba within a multilayered lorica. Vacuoles are present, yet with highly variable outline. Some plastids show terminal elongations without thylakoids (arrowhead). No Nucleus is visible in this section plane. (C) TEM of an amoeba within a multilayered lorica, showing four plastids and a nucleus without nucleolus in the section plane. Plastids possess tubular to globular shaped protrusions (white arrowhead) that group in the cell center (black arrowhead). The cytoplasm appears highly granular with variably shaped, non-globular vesicles. V—vesicle, N—nucleus, L—lorica, C chloroplast. Scale bars 5 μm.

Mentions: Guanchochroma wildpretii was identified as a unicellular, amoeboid eukaryote with a close resemblance to Chrysopodocystis socialis. Most cells of G. wildpretii are sessile amoebae, whose MCBs are encased in globular, hyaline loricae. The reticulopodium of the cell can exit the lorica via usually one ostiole with a short rim, which is located laterally, pointing slightly towards the surface (Fig 1A, 1H and 1I). Reticulopodia of different cells may fuse, creating a so called meroplasmodium, in which particles such as food vacuoles are transported to the MCBs (see Fig 1D and 1E for an overview and close-up of a meroplasmodium). Asexual reproduction of cells occurs by binary division inside the lorica (Fig 2A), after which one cell leaves the lorica of the mother cell as a migrating amoeba by hatching through the ostiole. Optionally, the second amoeba can also hatch. Migrating amoebae of G. wildpretii can take various shapes depending on the direction and speed of their movement. The shape ranges from almost spherical cells with various axopodia-like filopodia to fusiform cells, with a leading and a trailing filopodium. This description is similar to the conditions found in C. socialis and, apart from the lorica shape, also for the Synchroma species.


Guanchochroma wildpretii gen. et spec. nov. (Ochrophyta) Provides New Insights into the Diversification and Evolution of the Algal Class Synchromophyceae.

Schmidt M, Horn S, Ehlers K, Wilhelm C, Schnetter R - PLoS ONE (2015)

Arrangement of plastids in Guanchochroma wildpretii.(A) TEM of two amoebae in one multilayered lorica after binary division. The nucleolus is distinct within the nucleus. Vacuoles, mostly roundish, are present in different sizes. The plastids show no pyrenoids and are not interconnected. (B) TEM of an amoeba within a multilayered lorica. Vacuoles are present, yet with highly variable outline. Some plastids show terminal elongations without thylakoids (arrowhead). No Nucleus is visible in this section plane. (C) TEM of an amoeba within a multilayered lorica, showing four plastids and a nucleus without nucleolus in the section plane. Plastids possess tubular to globular shaped protrusions (white arrowhead) that group in the cell center (black arrowhead). The cytoplasm appears highly granular with variably shaped, non-globular vesicles. V—vesicle, N—nucleus, L—lorica, C chloroplast. Scale bars 5 μm.
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Related In: Results  -  Collection

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pone.0131821.g002: Arrangement of plastids in Guanchochroma wildpretii.(A) TEM of two amoebae in one multilayered lorica after binary division. The nucleolus is distinct within the nucleus. Vacuoles, mostly roundish, are present in different sizes. The plastids show no pyrenoids and are not interconnected. (B) TEM of an amoeba within a multilayered lorica. Vacuoles are present, yet with highly variable outline. Some plastids show terminal elongations without thylakoids (arrowhead). No Nucleus is visible in this section plane. (C) TEM of an amoeba within a multilayered lorica, showing four plastids and a nucleus without nucleolus in the section plane. Plastids possess tubular to globular shaped protrusions (white arrowhead) that group in the cell center (black arrowhead). The cytoplasm appears highly granular with variably shaped, non-globular vesicles. V—vesicle, N—nucleus, L—lorica, C chloroplast. Scale bars 5 μm.
Mentions: Guanchochroma wildpretii was identified as a unicellular, amoeboid eukaryote with a close resemblance to Chrysopodocystis socialis. Most cells of G. wildpretii are sessile amoebae, whose MCBs are encased in globular, hyaline loricae. The reticulopodium of the cell can exit the lorica via usually one ostiole with a short rim, which is located laterally, pointing slightly towards the surface (Fig 1A, 1H and 1I). Reticulopodia of different cells may fuse, creating a so called meroplasmodium, in which particles such as food vacuoles are transported to the MCBs (see Fig 1D and 1E for an overview and close-up of a meroplasmodium). Asexual reproduction of cells occurs by binary division inside the lorica (Fig 2A), after which one cell leaves the lorica of the mother cell as a migrating amoeba by hatching through the ostiole. Optionally, the second amoeba can also hatch. Migrating amoebae of G. wildpretii can take various shapes depending on the direction and speed of their movement. The shape ranges from almost spherical cells with various axopodia-like filopodia to fusiform cells, with a leading and a trailing filopodium. This description is similar to the conditions found in C. socialis and, apart from the lorica shape, also for the Synchroma species.

Bottom Line: A new relative of the chrysophyte genus Chrysopodocystis was found in Tenerife and termed Guanchochroma wildpretii.Yet, neither Chrysopodocystis nor Guanchochroma showed this feature in ultrastructure analyses.Evidence for the sequence of events leading to the formation of the plastid complex of Synchromophyceae still remains ambiguous because of the apparently short timeframe in which they occurred.

View Article: PubMed Central - PubMed

Affiliation: Universität Leipzig, Department of Plant Physiology, Johannisallee 21-23, 04103 Leipzig, Germany.

ABSTRACT
A new relative of the chrysophyte genus Chrysopodocystis was found in Tenerife and termed Guanchochroma wildpretii. This unicellular alga was most noticeably discernible from Chrysopodocystis socialis (the only species of this genus) by the presence of a cyst-like stage with a multilayered lorica, which also functions as a dispersal unit and shows secondary wall growth. Secondary expansion of loricae (cell casings not involved in cell division, usually with a more or less pronounced opening) has never been observed previously and marks a unique feature of the new taxon. Plastids are non-randomly distributed within cells of G. wildpretii. 18S rRNA gene analyses identified the two species as sister lineages and placed them in a monophyletic group with the Synchromophyceae, a heterokont algal (Ochrophyta) class characterized by the presence of chloroplast complexes. Yet, neither Chrysopodocystis nor Guanchochroma showed this feature in ultrastructure analyses. Additionally, their 18S rRNA genes possessed distinct inserts, the highest GC-content known for Ochrophyta and exceptionally long branches on the Ochrophyta 18S rDNA phylogenetic tree, suggesting substantially increased substitution rates along their branch compared to Synchromophyceae. Plastid marker data (rbcL) recovered a monophyletic clade of Chrysopodocystis, Guanchochroma and Synchromophyceae as well, yet with lower supports for internal split order due to limited resolution of the marker. Evidence for the sequence of events leading to the formation of the plastid complex of Synchromophyceae still remains ambiguous because of the apparently short timeframe in which they occurred.

No MeSH data available.


Related in: MedlinePlus