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Klebsormidium flaccidum , a charophycean green alga, exhibits cold acclimation that is closely associated with compatible solute accumulation and ultrastructural changes
Author(s) -
NAGAO MANABU,
MATSUI KENJI,
UEMURA MATSUO
Publication year - 2008
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2008.01804.x
Subject(s) - chloroplast , abscisic acid , acclimatization , freezing tolerance , sucrose , botany , biology , cold tolerance , supercooling , chemistry , biochemistry , physics , gene , thermodynamics
To elucidate the fundamental mechanisms and subsequent evolutionary aspects of plant cold acclimation, we examined the effect of cold acclimation on freezing tolerance in Klebsormidium flaccidum , a green alga belonging to Charophyceae, a sister group of land plants. Freezing tolerance of K. flaccidum was significantly enhanced by cold treatment: survival increased from 15% at −10 °C when grown at 18 °C to 55 and 85% after exposure at 2 °C for 2 and 7 d, respectively. Accompanying the development of freezing tolerance, soluble sugars (glucose and sucrose), a putative glycoside and amino acids, including γ ‐aminobutyric acid (GABA), accumulated to high levels in the alga, suggesting that these solutes play a crucial role in the cold acclimation of K. flaccidum . Interestingly, the application of abscisic acid (ABA) did not change the freezing tolerance of the alga. We also observed changes in cell structure, including increased numbers and sizes of starch grains in chloroplasts, chloroplast enlargement, vacuole size reduction and cytoplasmic volume increase. These results suggest that K. flaccidum responds well to cold treatment and develops freezing tolerance in a process comparable to that of land plants.