Chromatic adaptation and the events involved in phycobilisome biosynthesis

Abstract

Abstract. The major light‐harvesting complex in cyanobacteria and red algae is the phycobilisome, a macromolecular complex that is attached to the surface of the photosynthetic membranes. The phycobilisome is composed of a number of different chromophoric polypeptides called phycobiliproteins and nonchromophoric polypeptides called linker proteins. Several environmental parameters modulate the synthesis, assembly and degradation of phycobilisome components. In many cyanobacteria, the composition of the phycobilisome can change to accommodate the prevalent wavelengths of light in the environment. This phenomenon is called complementary chromatic adaptation. Organisms that exhibit complementary chromatic adaptation must perceive the wavelengths of light in the environment and transduce the light signals into a sequence of biochemical events that result in altering the activities of genes encoding specific phycobiliprotein and linker polypeptides. Other environmental parameters such as light intensity and nutrient status can also have marked effects on both the number and composition of the phycobilisomes. The major concern of this article is the molecular events involved in chromatic adaptation. Most of the information concerning this process has been gained from studies involving the filamentous cyanobacterium Fremyella diplosiphon. However, also briefly considered are some of the complexities involved in phycobilisome biosynthesis and degradation; they include post‐translational modification of phycobilisome polypeptides, the coordinate expression of chromophore and apobiliprotein, the specific degradation of phycobilisomes when cyanobacteria are deprived of macronutrients such as nitrogen, sulphur and phosphorus, and the assembly of the individual phycobilisome components into substructures of the light harvesting complex.

Complementary chromatic adaptation alters photosynthetic strategies in the cyanobacterium Calothrix

“…This acclimation process is termed complementary chromatic adaptation (CCA). The molecular mechanism for the red/green light regulation of CCA receives considerable attention (reviewed by Grossman, 1990; Grossman e t al., 1994;Tandeau de Marsac e t al., 1988;Tandeau de Marsac & Houmard, 1993), particularly in the strain Calothrix sp. PCC 7601 (Calotbrix 7601, syn.…”

A role for cpeYZ in cyanobacterial phycoerythrin biosynthesis

“…Conversely, in green light, the rods contain high levels of PE and very little PC 2 ; cells are pigmented red in green light. The change in rod phycobiliprotein composition is mediated primarily through differential expression of genes encoding the PC 2 and PE apoproteins (17) and presumably provides the cells an adaptive advantage, since PC 2 efficiently absorbs red light and PE efficiently absorbs green light.…”

“…strain PCC 7601) is one of several strains that respond to changes in spectral light quality by altering the phycobiliprotein composition of the phycobilisome (5,17,31). This acclimation, termed complementary chromatic adaptation, allows the cells to modulate the phycobiliprotein composition of the rods for maximum absorbance of incident light.…”

DNA-Binding Properties of the Fremyella diplosiphon RpbA Repressor

“…Green-enriched light promotes synthesis of rods composed of three distal hexamers of PE linked to the core by a PC 1 hexamer, whereas red light promotes synthesis of rods composed of two distal hexamers of PC 2 linked to the core by a PC 1 hexamer. Complementary chromatic adaptation is mediated through differential transcription of the gene sets encoding PE and PC 2 (7) and provides cells an adaptive advantage, as PE absorbs green light and PC absorbs red light. Under sulfate-limiting conditions, cells cease expression of PC 1 , PC 2 , and PE and initiate expression of PC 3 (17).…”