TY - JOUR
T1 - EVIDENCE THAT THE NUCLEOMORPHS OF CHLORARACHNION REPTANS (CHLORARACHNIOPHYCEAE) ARE VESTIGIAL NUCLEI
T2 - MORPHOLOGY, DIVISION AND DNA‐DAPI FLUORESCENCE
AU - Ludwig, Martha
AU - Gibbs, Sarah P.
PY - 1989/6
Y1 - 1989/6
N2 - Chlorarachnion reptans Geitler shows affinities to both the Chlorophyceae and the chloroplast endoplasmic reticulum‐containing chromophyte algae in possessing chlorophyll b and chloroplasts which are limited by four membranes, respectively. In the periplastidal compartment surrounding each of the four to eight chloroplasts of a C. reptans cell are putative eukaryotic‐sized ribosomes, scattered tubules and vesicles, and a small double‐membrane‐limited nucleus‐like organelle named the nucleomorph. The nucleomorphs display 4′‐6‐diamidino‐2‐phenylindole (DAPI)fluorescence which is sensitive to DNase digestion, but not to treatment with RNase. The nucleomorphs also contain a fibrillogranular body which resembles a nucleolus. Nucleomorph division occurs by the sequential infolding of the inner and outer envelope membranes and subsequent constriction in two, with no involvement of microtubules. In all these characteristics, the nucleomorphs of C. reptans are similar to the cryptomonad nucleomorph which has been hypothesized to be the vestigial nucleus of an ancestral red alga which gave rise to the chloroplasts of the Cryptophyceae. The presence of chlorophyll b and the contents and morphology of C. reptans chloroplast compartments suggest a green algal origin for the chloroplasts of these cells. The discovery of a second organism with a DNA‐containing, nucleus‐like organelle in its chloroplast compartment lends strong support to the hypothesis that the chloroplasts of many algae have evolved from eukaryotic endosymbionts.
AB - Chlorarachnion reptans Geitler shows affinities to both the Chlorophyceae and the chloroplast endoplasmic reticulum‐containing chromophyte algae in possessing chlorophyll b and chloroplasts which are limited by four membranes, respectively. In the periplastidal compartment surrounding each of the four to eight chloroplasts of a C. reptans cell are putative eukaryotic‐sized ribosomes, scattered tubules and vesicles, and a small double‐membrane‐limited nucleus‐like organelle named the nucleomorph. The nucleomorphs display 4′‐6‐diamidino‐2‐phenylindole (DAPI)fluorescence which is sensitive to DNase digestion, but not to treatment with RNase. The nucleomorphs also contain a fibrillogranular body which resembles a nucleolus. Nucleomorph division occurs by the sequential infolding of the inner and outer envelope membranes and subsequent constriction in two, with no involvement of microtubules. In all these characteristics, the nucleomorphs of C. reptans are similar to the cryptomonad nucleomorph which has been hypothesized to be the vestigial nucleus of an ancestral red alga which gave rise to the chloroplasts of the Cryptophyceae. The presence of chlorophyll b and the contents and morphology of C. reptans chloroplast compartments suggest a green algal origin for the chloroplasts of these cells. The discovery of a second organism with a DNA‐containing, nucleus‐like organelle in its chloroplast compartment lends strong support to the hypothesis that the chloroplasts of many algae have evolved from eukaryotic endosymbionts.
KW - Chlorarachnion reptans
KW - chloroplast evolution
KW - DNA‐DAPI fluorescence
KW - nucleomorph
UR - http://www.scopus.com/inward/record.url?scp=84986870277&partnerID=8YFLogxK
U2 - 10.1111/j.1529-8817.1989.tb00135.x
DO - 10.1111/j.1529-8817.1989.tb00135.x
M3 - Article
AN - SCOPUS:84986870277
VL - 25
SP - 385
EP - 394
JO - Journal of Phycology - an International journal of algal research
JF - Journal of Phycology - an International journal of algal research
SN - 0022-3646
IS - 2
ER -