Light-Harvesting System of the Red Alga Gracilaria tikvahiae

Abstract

ABSTRACIWild type Gracilaria tik'ahiae, a macrophytic red alga, and fourteen genetically characterized pigment mutants were analyzed for their biliprotein and chlorophyll contents. The same three biliproteins, phycoerythrin, phycocyanin, and allophycocyanin, which are found in the wild type are found in all the Mendelian and non-Mendelian mutants examined. Some mutants overproduce R-phycoerythrin while others possess only traces of phycobiliprotein; however, no phycoerythrin minus mutants were found. Two of the mutants are unique; one overproduces phycocyanin relative to allophycocyanin while the nuclear mutant obr synthesizes a phycoerythrin which is spectroscopically distinct from the R-phycoerythrin of the wild type. The phycoerythrin of obr lacks the typical absorption peak at 545 nanometers characteristic of R-phycoerythrin and possesses a phycoerythrobilin to phycourobilin chromophore ratio of 2.6 in contrast to a ratio of 4.2 found in the wild type. Such a lesion provides evidence for the role of nuclear genes in phycoerythrin synthesis. In addition, comparisons are made of the pigment compositions of the Gracilaria strains with those of Neoagardhiella bailyei, a macrophytic red alga which has a high phycoerythrin content, and Anacystis nidulans, a cyanobacterium which lacks phycoerythrin. The mutants described here should prove useful in the study of the genetic control of phycobiliprotein synthesis and phycobilisome structure and assembly.The functional photosynthetic unit of 02-evolving plants is composed of large arrays of light-harvesting pigment-proteins which are associated with the reaction centers and electron transport chains of PSI and PSII. While the reaction centers, electron transport chains, and dark reactions of photosynthesis are probably very similar in the major plant groups, the lightharvesting systems are quite diverse. For example, the antennae pigments fucoxanthin and Chl c are found in the photosynthetic unit of the diatoms and brown algae. In the red algae, Cryptomonads, and cyanobacteria, the phycobiliproteins serve this function while Chl b functions in the green plants (22). These pigments along with the proteins which bind them are major '

Seasonal changes in the pigment composition of natural population of Gracilaria domingensis (Gracilariales, Rhodophyta)

“…These strains also showed a slight difference in phycocyanin and chlorophyll-a concentrations in some months. These results corroborate those of earlier studies using color variants of other species of Rhodophyceae (Kursar et al, 1983;Dawes, 1992;Guimarães et al, 2003;Plastino et al, 2004;Yokoya et al, 2007).…”

Light Absorption in Coralline Algae (Rhodophyta): A Morphological and Functional Approach to Understanding Species Distribution in a Coral Reef Lagoon

“…Pigment extractions were analyzed in a conventional spectrophotometer (Elyptica, Ensenada, Mexico) after centrifuging samples maintained in darkness at 4 • C for 2 h. The residual carbonate pellet was re-suspended in 80% acetone for chlorophyll a extraction. Samples were maintained overnight in darkness, at 4 • C. Phycobilliprotein and chlorophyll a contents were calculated according to the equations of, respectively, Kursar et al (1983) and Lichtenthaler and Wellburn (1983).…”

Effects of Cadmium on Growth, Photosynthetic Pigments, Photosynthetic Performance, Biochemical Parameters and Structure of Chloroplasts in the Agarophyte <i>Gracilaria domingensis</i> (Rhodophyta, Gracilariales)

“…The homogenates were centrifuged at 2000 g for 20 min. Phycobiliprotein levels [allophycocyanin (APC), phycocyanin (PC), and phycoerythrin (PE)] were determined by UV-vis spectrophotometry, and calculations were performed using the equations of Kursar et al [31].…”