Plant Physiol, August 2000, Vol. 123, pp. 1415-1426
Kinetics of Photoacclimation in Response to a Shift to High Light
of the Red Alga Rhodella violacea Adapted to Low
Irradiance
Mathilde
Ritz,
Jean-Claude
Thomas,
Agnès
Spilar, and
Anne-Lise
Etienne*
Laboratoire Dynamique des Membranes Végétales-Complexes
Proteines-Pigments, Unité de Recherche Associée 1810 Centre
National de la Recherche Scientifique, Ecole Normale Supérieure,
46 rue d'Ulm, 75230 Paris cedex 05, France
The unicellular rhodophyte Rhodella violacea can
adapt to a wide range of irradiances. To create a light stress, cells
acclimated to low light were transferred to higher irradiance and the
kinetics of various changes produced by the light shift were analyzed. The proton gradient generated by excess light led to a
non-photochemical quenching of the chlorophyll fluorescence and some
photoinhibition of photosystem II centers was also produced by the
light stress. After the shift to higher irradiance, the mRNA levels of
three chloroplast genes that encode phycoerythrin and phycocyanin
apoproteins and heme oxygenase (the first enzyme specific to the bilin
synthesis) were negatively regulated. A change in the amount of
thylakoids and in the total pigment content of the cells occurred
during light acclimation after a light stress. The change in the size of the phycobilisome was limited to dissapearance of the terminal phycoerythrin hexamers in some of the rods. The ability of R. violacea to photoacclimate depends both on large changes in
thylakoid number and pigment content and on smaller changes in the
antenna size of photosystem II.
*
Corresponding author; e-mail etienne{at}wotan.ens.fr; fax
331-44-32-39-35.
© 2000 American Society of Plant Physiologists
