Aberrant light sensing and motility in the green alga Chlamydomonas priscuii from the ice-covered Antarctic Lake Bonney

Light quality affects chlorophyll biosynthesis and photosynthetic performance in Antarctic Chlamydomonas

“…Up to this point, our results suggest that the two psychrophiles acclimated to different light conditions respond more strongly to light intensity rather than light quality, possibly related to decreased ability to sense and respond to spectral wavelengths (Poirier et al 2023). These results contrast with those reported by Morgan-Kiss et al (2005), where a sudden shift from white to red light caused a complete growth inhibition and led to re-arrangement in the stoichiometry of the two photosystems in C. priscuii.…”

“…While phytohormones have been detected in algae, their physiological roles remain unknown (Lu and Xu 2015). Phytochrome and cryptochrome photoreceptors are important regulators of LPOR expression in angiosperms, but C. priscuii lacks phytochromes (like all Chlorophytes; Li et al 2015) and encodes for a significantly reduced complement of cryptochrome genes compared to its relatives (Poirier et al 2023). The coordination of LPOR and DPOR expression in species that have both (such as ICE-MDV) is also poorly understood, although complementation of LPOR downregulation by DPOR has been reported in the cyanobacterium Fremyella diplosiphon (Shui et al 2009).…”

“…C. priscuii has a 'locked' physiology and largely lacks the capacity to respond to short-term environmental challenges. This alga has an attenuated heat stress response at non-permissive temperatures (Cvetkovska et al 2022b), minimal PSI restructuring under iron stress (Cook et al 2019), has lost the ability to balance PSI and PSII light excitation through state transitions (Morgan-Kiss et al 2002;Szyszka-Mroz et al 2015) and has a very weak phototactic response (Poirier et al 2023). Curiously, C. priscuii lacks the genes that encode for DPOR and thus relies solely on LPOR to synthesize chlorophyll (Cvetkovska et al 2018a).…”

“…In contrast, ICE-MDV displays a more flexible physiology and a photosynthetic apparatus similar to its non-extremophilic relatives. ICE-MDV has retained the capacity for state transitions, PSI restructuring and phototaxis (Cook et al 2019;Kalra et al 2023;Poirier et al 2023), and can induce protective mechanisms under temperature stress (Cvetkovska et al 2022b). Its plastid genome does encode for DPOR, giving this alga the flexibility of both light dependent and independent chlorophyll biosynthesis (Smith et al 2019).…”

“…and PSII light excitation through state transitions(Kalra et al 2023) and responds phototactically to light signals(Poirier et al 2023) suggesting a photosynthetic apparatus similar to the mesophile C. reinhardtii. ICE-MDV is naturally adapted to a wider range of light conditions in Lake Bonney(Li and Morgan-Kiss 2019;Sherwell et al 2022) compared to C. priscuii, which is reflected in its ability to maintain photosynthetic efficiencies under both red and blue light.…”