Cold acclimation in Helleborus niger and accompanying ultrastructural adaptations of the chloroplast

Beschreibung

Cold acclimation, leading to frost tolerance, is an adaptive process in evergreen plants such as Helleborus niger, a frost-tolerant herbaceous perennial mesophyte, whereby in aerial vegetative structures temperature-insensitive photochemical processes and temperature-sensitive biochemical reactions are balanced to prevent photooxidative damage [1]. Thus, the threefold stressors: freezing, dehydration and high light exposure, during the winter are heralded by low temperature, and these nonfreezing temperatures induce cold acclimation and thus, frost tolerance. Currently, there are three structural changes in chloroplasts known to be associated with cold temperatures compared to chloroplasts from warm adapted leaves. 1. Chloroplasts from frozen plants appear swollen. 2. They show a segregation in thylakoid-containing and thylakoid-free zones. 3. Different varieties of thylakoid-free chloroplast extensions were described before. Cold acclimation activates an innate program, that involves volume regulation of the thylakoid system and reorganization of ribosomes along thylakoid membranes, which may facilitate repair mechanisms for photodamaged PSII proteins. Intraorganellar repair mechanisms, structural and biochemical preadaptation to frost are expected to repair photodamaged PSII proteins when the temperature constraints are relieved at least for short period of time. A major repair mechanism in the chloroplasts to remove and replace photodamaged proteins within the PSII supercomplex includes changes in the thylakoid volume. Our study shows that similar ultrastructural phenomena as mentioned above are observed in the chloroplast during cold acclimatization in Helleborus niger.

Zeitraum	4 Apr. 2024
Ereignistitel	14th ASEM Workshop 2024: Advanced Electron Microscopy
Veranstaltungstyp	Workshop
Ort	Graz, ÖsterreichAuf Karte anzeigen
Bekanntheitsgrad	International