Open Access
Algae 2010, 25(1): 11-15
DOI: 10.4490/algae.2010.25.1.011 pISSN: 1226-2617 eISSN: 2093-0860
Ultrastructural observations of vegetative cells of two new genera in the Erythropeltidales (Compsopogonophyceae, Rhodophyta):
Pseudoerythrocladia and Madagascaria
Joseph L. Scott
1, Evguenia Orlova
1and John A. West
2,*1Department of Biology, College of William and Mary, Williamsburg, VA 23187, USA
2School of Botany, University of Melbourne, Parkville, Victoria 3010, Australia
Received 15 November 2009, Accepted 5 February 2010
Two new genera of red algae, Madagascaria erythrocladioides West et Zuccarello and Pseudoerythrocladia kornmannii West et Kikuchi (Erythropeltidales, Compsopogonophyceae, Rhodophyta), were previously described using molecular analysis and confocal microscopy of isolates in laboratory culture. We examined the ultrastructure of both genera to compare with ultrastructure of other members of the class Compsopogonophyceae. Both genera had Golgi bodies not associated with mitochondria and chloroplasts with a peripheral encircling thylakoid similar to all other members of the class studied thus far. Confocal autofluorescence images showed that Madagascaria has a single round central pyrenoid while Pseudoerythrocladia has no pyrenoid. Our electron microscopic work confirms these initial observations. Tables and keys are presented that assist in interpreting cellular details of genera in the class Compsopogonophyceae.
Key Words: chloroplasts; Compsopogononophyceae; Erythropeltidales; Golgi; pyrenoids; ultrastructure
INTRODUCTION
Detailed molecular and culture studies coupled with ultrastructural observations enable us to discover significant new genera and species of microscopic and macroscopic red algae (e.g., West et al. 2007a, 2007b, Yokoyama et al. 2009). Recently two new genera in the Erythropeltidales (Compsopogonophyceae) were described from algae collected in France, Madagascar and Japan and maintained in unialgal culture before conducting molecular analyses (Zuccarello et al. in press). Very few members of the Compsopogonophyceae have been examined by transmission electron microscopy (Scott and Broadwater 1989, West et al. 2007b, Yang et al. in press). It is readily apparent that each genus studied thus far has two distinctive ultrastructural characters: the association of Golgi bodies with endoplasmic reticulum instead of mitochondria as is typical of almost all red algae
investigated with transmission electron microscopy (TEM) (Scott et al. 2008, Yokoyama et al. 2009), and the presence of a peripheral encircling thylakoid in the chloroplast. No other multicellular algae have the combination of these two characters except genera in the Stylonematophyceae. However, the unicellular algae Rhodosorus (Stylonematophyceae; Scott et al. 2008) and Corynoplastis (Rhodellophyceae; Yokoyama et al.
2009) also share these characteristics. The phylogenetic interrelationships of these classes of red algae are becoming more fully understood (Yang et al. in press).
Since we enthusiastically believe that all applicable
*Corresponding author E-mail: jwest@unimelb.edu.au
Tel: +1-706-296-5228, Fax: +1-706-296-5286
Figs 1-3.Madagascaria erythrocladioides cell structure. Fig. 1. The large chloroplast occupies most of the cell and has a large embedded pyrenoid (P). A nucleus (N), portion of a vacuole (V) and several starch grains (*) are visible. Cell wall, CW. Fig. 2. Transverse section of a cell showing chloroplast and pyrenoid, starch grains (*) and a thin layer of peripheral cytoplasm (arrows). A peripheral encircling thylakoid is visible in the chloroplast lobes (arrowheads). Fig. 3. Golgi body at cell periphery. The Golgi cis-region (arrow) is just beneath the cell membrane. Cell wall, CW;
Golgi vesicle, *. Figs 1 & 2, 1 μm; Fig. 3, 0.5 μm.
Figs 4-5. Pseudoerythrocladia kornmannii cell structure. Fig. 4. A single nucleus (N) is located in the cell center along with abundant starch (*) and a small vacuole (V). Chloroplasts (arrows) are parietal and lack pyrenoids. Cell wall, CW. Fig. 5. A rarely encountered Golgi body (arrow) is in the cell center near a nucleus (N). Peripheral encircling thylakoids are visible in the chloroplast lobes (arrowheads). Fig. 4, 2 μm; Fig. 5, 0.5 μm.
techniques should be utilized to identify new taxa, we have conducted an ultrastructural study on two new algae, Madagascaria erythrocladioides West et Zuccarello and Pseudoerythrocladia kornmannii West et Kikuchi (Zuccarello et al. in press).
MATERIALS AND METHODS
Methods for collection, isolation and maintenance of cultures are presented in Zuccarello et al. (in press).
In addition, several cultures were grown in 30 psu von Stosch enriched seawater (von Stosch 1964) in Pyrex No.
3250 dishes in front of north-facing windows (37o 27′N, 76o 71W ). Filaments from cultures grown in window light at 20oC were prepared for TEM as described in Scott et al. (2008).
RESULTS AND DISCUSSION
Mature thalli of both Madagascarensis erythroclad- ioides and Pseudoerythrocladia kornmannii are mono- stromatic to distromatic crusts approximately 0.1-2 mm in diameter, depending upon age. In M. erythrocladioides cells are rectangular, approximately 6-12 μm in length and 5-6 μm in width. Figure 1 shows a transverse section through a peripheral crust cell of M. erythrocladioides. A thick fibrillar cell wall surrounds each cell and pit plugs were never seen. The parietal chloroplast occupies most of the cell and contains a large embedded pyrenoid, 1.5-2.0 μm in diameter. Using confocal microscopy Zuccarello et al. (in press) clearly showed large, circular non-fluorescent regions which they interpreted as being pyrenoids in M. erythrocladioides from both Madagascar and Japan. Our TEM images confirm their confocal work. The pyrenoid matrix is moderately electron dense, containing numerous thylakoids derived from thylakoids that delimit the pyrenoid periphery (Figs 1 &
2). Phycobilisomes are present on chloroplast thylakoids but appear absent from those in the pyrenoid matrix. A peripheral encircling thylakoid is present (Fig. 2). The cell contains a small peripheral nucleus, several starch grains lining the chloroplast, a small vacuole containing membranous debris (Fig. 1), and a thin layer of cytoplasm at the cell periphery (Figs 1 & 2). Surprisingly, conspicuous mitochondria were not seen in any of our preparations. Figure 3 shows one of several Golgi bodies detected. Mitochondria were never seen in close association with Golgi bodies, which are usually located at the cell periphery with the cis-region adjacent to the
cell membrane.
Figure 4 is a glancing section through several cells of P. kornmannii. Cells are rectangular, approximately 6-20 μm in length and 4-8 μm in width. Over 200 cells were examined by TEM. The cell wall consists of several moderately electron dense fibrous layers along with an inner electron transparent layer that most likely represents an artifact of fixation (Figs 4 & 5). Our results confirm the absence of pyrenoids (Figs 4 & 5) reported by Zuccarello et al. (in press) based on confocal microscopic images. One or more parietal chloroplasts are located at the cell periphery and peripheral encircling thylakoids are apparent (Fig. 5). A single nucleus is found in the cell center along with abundant starch, an occasional mitochondrion (not shown), and Golgi bodies not associated with mitochondria (Fig. 5).
Very few Golgi bodies were found, even after intensive searches, and more than one Golgi body was never detected in the same cell, although several hundred cells from several preparations were examined. Each cell appeared to have one or more small vacuoles (Fig. 4).
Our results have shown that, as expected, both M. erythrocladioides and P. kornmannii conform to previous TEM work that shows that cells of all members of the Compsopogonophyceae possess Golgi not associated with mitochondrion as well as a peripheral encircling thylakoid in the chloroplasts (Tables 1 & 3 ). What was not well established prior to this work was an awareness of pyrenoid distribution among the genera in this class. Table 2 lists pyrenoid presence and absence in genera of the three orders comprising class Compsopogonophyceae. Pyrenoids are absent in all genera of the Compsopogonales and the Rhodochaetales but present in eight of the ten genera of the Erythropeltidales. Pseudoerythrocladia and Porphyropsis are the only algae lacking pyrenoids.
Ultrastructural studies are remarkably consistent with the most recent red algal supraordinal classification schemes based largely on molecular technology (Saunders and Hommersand 2004, Yoon et al. 2006).
Appendix is a dichotomous key based mainly on ultrastructural characters along with algal morphology type (i.e., unicellular vs. multicellular) and life history stage. It is apparent from this table that an unknown macro-stage of a multicellular red alga could readily be assigned to one of three “groups” of classes by examining ultrastructural character states of its Golgi bodies and chloroplasts. 1) If the Golgi is associated with a mitochondrion and a peripheral encircling thylakoid is present, the alga is in class Florideophyceae.
2) If the Golgi is associated with a mitochondrion and a peripheral encircling thylakoid is absent, the alga is in
class Bangiophyceae. 3) But if the Golgi is not associated with a mitochondrion and a peripheral encircling
thylakoid is present, the alga could be a member of either class Compsopogonophyceae or Stylonematophyceae.
We are not suggesting use of this key as a diagnostic guide to solving red algal phylogenetic questions and instead, present it as continued evidence that when molecules speak, cells listen!
ACKNOWLEDGEMENTS
We thank Chris O’Brien for assistance with the Photoshop program. Laboratory investigations have been partially supported by grants to JAW from the Australian Research Council, Australian Biological Resources Study and Hermon Slade Foundation.
REFERENCES
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Phycologia 11:181-191.
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West, J. A., Zuccarello, G. C., Scott, J. L., West, K. A. & de Table 2. Pyrenoid presence or absence in the Compsopogonophyceaea
Pyrenoid Compsopogonales
Compsopogon -
Compsopogonopsis -
Boldia -
Pulvinaster -
Erythropeldidales
Chlidophyllonb +
Erythrocladia +
Erythrotrichia +
Madagascaria +
Porphyropsis -
Porphyrostromium +
Pseudoerythrocladia -
Pyrophyllonb +
Sahlingia +
Smithora +
Rhodochaetales
Rhodochaete -
aInformation gathered from numerous references.
bAssumed to have pyrenoids since this genus was previously placed in Porphyra.
Table 1.Ultrastructural characters of genera in the Compsopogonophyceae
Genus Chloroplast
peripheral thylakoid
Golgi association Boldia
(West et al. 2007a, b) Present ER
Compsopogon
(Scott & Broadwater 1989) Present ER
Erythrocladia
(Scott, unpublished observation) Present ER Madagascaria
(current work) Present ER
Pseudoerythrocladia
(current work) Present ER
Pulvinaster
(West et al. 2007a, b) Present ER
Rhodochaete
(Pueschel & Magne 1987) Present ER
Smithora
(McBride & Cole 1969, 1971, 1972) Present ER ER, Endoplasmic reticulum.
Goër, S. L. 2007b. Pulvinus veneticus gen. et sp. nov.
(Compsopogonales, Rhodophyta) from Vanuatu.
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West, J. A., Zuccarello, G. C., Scott, J. L., West, K. A. &
Karsten, U. 2007c. Rhodaphanes brevistipitata gen. et sp. nov., a new member of the Stylonematophyceae (Rhodophyta). Phycologia 46:440-449.
West, J. A., Scott, J. L., West, K. A., Karsten, U., Clayden, S. L.
& Saunders, G. W. 2008. Rhodachlya madagascarensis gen. et sp. nov.: a distinct acrochaetioid repesents a new order and family (Rhodachlyales ord. nov., Rhodachlyaceae fam. nov.) of the Florideophyceae (Rhodophyta). Phycologia 47:203-212.
Yang, E. C., Scott, J., West, J. A., Orlova, E., Gauthier, D., Kupper, F. C. & Karsten, U. New taxa of the Porphyridiophyceae (Rhodophyta): Timspurckia oligopyrenoides gen. et sp. nov. and Erythrolobus madagascarensis sp. nov. Phycologia (in press) .
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et sp. nov. and Dixonialles ord. nov. (Rhodellophyceae, Rhodophyta) based on morphological and molecular evidence. Phycol. Res. 57:278-289.
Yoon, H. S., Muller, K. M., Sheath, R. G., Ott, F. D. &
Bhattacharya, D. 2006. Defining the major lineages of red algae (Rhodophyta). J. Phycol. 42:482-492.
Zuccarello, G. C., Kikuchi, N. & West J. A. Molecular phylogeny of the cr ustose members of the Er ythropeltidales (Compsopogonophyceae, Rhodophyta): new genera Pseudoerythrocladia and Madagascaria and the evolution of the upright habit. J. Phycol. (in press).
Appendix
Key to red algal classes utilizing ultrastructural and specific morphological characters
1. Golgi bodies associated with mitochondrion ... 2 1. Golgi bodies not associated with mitochondrion...4
2. All genera are unicellular, chloroplasts lack a peripheral encircling thylakoid ……… Porphyridiophyceae 2. All genera are multicellular ... 3
3. Chloroplasts of all life history stages have a peripheral encircling thylakoida ……….. Florideophyceae 3. Chloroplasts of gametophyte stages lack a peripheral encircling thylakoid ………. Bangiophyceae
4. All genera are unicellular, Golgi bodies either associated with endoplasmic reticulum (ER) or the nuclear envelope, chloroplasts of some genera have a peripheral encircling thylakoid ……… Rhodellophyceae 4. Genera are either unicellular or multicellular, Golgi- bodies associated with ER and all life history stages have chloroplasts with a peripheral encircling thylakoidb ...5
5. Genera are either unicellular or multicellular...Stylone- matophyceae
5. Genera are multicellular ………..Compsopogonophyceae
a One exception, Rhodachlya, West et al. 2008
b One exception, Rhodaphanes, West et al. 2007c
