TY - JOUR
T1 - Acclimation to darkness in the marine chlorophyte Koliella antarctica cultured under low salinity
T2 - Hypotheses on its origin in the polar environment
AU - Ferroni, Lorenzo
AU - Baldisserotto, Costanza
AU - Zennaro, Valentina
AU - Soldani, Cristiana
AU - Fasulo, Maria Palmira
AU - Pancaldi, Simonetta
PY - 2007/2
Y1 - 2007/2
N2 - In order to obtain new insights on the origin and physiology of the marine chlorophyte Koliella antarctica, the response of the microalga was studied at a salinity of 0.2 in the light and during a 60-day dark period. In light conditions, the alga grows and maintains a functional cell organization. In darkness, the chloroplast-to-chromoplast transition, previously described during dark-acclimation in K. antarctica under a salinity of 34 was only partially triggered; thylakoid lamellae became re-organized into short bundles, but storage substructures were almost completely missing. Microspectrofluorometry, pigment analyses, and morphological observations revealed dark-induced degradation of photosystem II (PSII) with relative stability in the light-harvesting complex (LHCII). Chromatin condensation, mitochondrion fragmentation and material digestion in vacuoles were similar to morphological hallmarks of programmed cell death (PCD), but only 30% of cells underwent cell death and, at the end of the experiment, only 1-2% of cells were TUNEL-positive. Rapid recovery in culture growth after exposure to light showed that the changes apparent in the rest of cells were reversible. Taking into account the response of the plastid and assuming an adaptive benefit of PCD, our results are consistent with the hypothesis that K. antarctica evolved from an Antarctic freshwater ancestor.
AB - In order to obtain new insights on the origin and physiology of the marine chlorophyte Koliella antarctica, the response of the microalga was studied at a salinity of 0.2 in the light and during a 60-day dark period. In light conditions, the alga grows and maintains a functional cell organization. In darkness, the chloroplast-to-chromoplast transition, previously described during dark-acclimation in K. antarctica under a salinity of 34 was only partially triggered; thylakoid lamellae became re-organized into short bundles, but storage substructures were almost completely missing. Microspectrofluorometry, pigment analyses, and morphological observations revealed dark-induced degradation of photosystem II (PSII) with relative stability in the light-harvesting complex (LHCII). Chromatin condensation, mitochondrion fragmentation and material digestion in vacuoles were similar to morphological hallmarks of programmed cell death (PCD), but only 30% of cells underwent cell death and, at the end of the experiment, only 1-2% of cells were TUNEL-positive. Rapid recovery in culture growth after exposure to light showed that the changes apparent in the rest of cells were reversible. Taking into account the response of the plastid and assuming an adaptive benefit of PCD, our results are consistent with the hypothesis that K. antarctica evolved from an Antarctic freshwater ancestor.
KW - Antarctica
KW - Chloroplast
KW - Darkness
KW - Koliella antarctica
KW - Mitochondrion
KW - Nucleus
KW - Photosystem II (PSII)
KW - Programmed cell death
KW - Salinity
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U2 - 10.1080/09670260600960850
DO - 10.1080/09670260600960850
M3 - Article
AN - SCOPUS:33847191752
VL - 42
SP - 91
EP - 104
JO - British Phycological Bulletin
JF - British Phycological Bulletin
SN - 0967-0262
IS - 1
ER -