Accumulation Of Secondary Carotenoids Research Articles

Carotenoid content in growing cells of Haematococcus pluvialis during a sunlight cycle

Under certain culture conditions, cells of the chlorophyte Haematococcus pluvialis accumulate significant amounts of astaxanthin. This study describes biomass and carotenoid production during a sunlight cycle in a continuous culture of growing cells of H. pluvialis and shows that these two parameters are under the control of irradiance. The hourly carotenoid production increases with light intensity and, in our culture conditions, carotenoid accumulation occurs in a few hours and without any morphological change in the algae. These carotenoids seem to be efficient in protecting algal cells against photoinhibition damage if their content is greater than 1% dry biomass. Below this concentration, that is to say in the early hours of high light intensity, dry biomass decreases due to cell lysis. The results demonstrate that secondary carotenoid accumulation in H. pluvialis may occur in the active growth phase and is stimulated from the first hours of sunlight illumination.

Pigment and Structural Changes in Chlorella zofingiensis upon Light and Nitrogen Stress

Summary The green alga Chlorella zofingiensis was found to respond very rapidly to exposure to combined conditions of high light intensity and nitrogen deficiency by accumulation of secondary carotenoids. Accumulation of secondary carotenoids was detected as early as 60 min after induction to light stress (300 μmol·m−2. s−1) in a nitrogen-free medium. Canthaxanthin and astaxanthin (free and monoesters) were detected 2–3 h later, and after an additional 12 h an astaxanthin diester also appeared. The accumulation of total secondary carotenoids was linear in relation to time. After 24 h the main secondary carotenoids were the monoester of astaxanthin (about 50% of total secondary carotenoids) and canthaxanthin (20–25%). During the first 8 h of stress the content of the primary carotenoids β-carotene and lutein increased but subsequently the content of both chlorophyll and the primary carotenoids was reduced. The reduction in the content of the photosynthetic pigments was followed by a degradation of the thylakoids and a reduction of the potential rate of photosynthesis (α), but not of Pmax. After 3 days under light stress the chloroplast was modified to a chromoplast-like organelle, full of secondary carotenoids and free of thylakoid membranes. Twelve hours after the induction of stress, lipid bodies containing secondary carotenoids appeared around the chloroplast and accumulated at the periphery of the cell. The profile of the secondary carotenoids in the lipid bodies was similar to that in the chromoplast, both containing double the amount of astaxanthin diester and half the amount of free astaxanthin as compared with total cell carotenoids. After 3 days under stress, a hydrophobic layer rich in secondary carotenoids formed inside the cell wall. Our results suggested that the lipid layer functions as a light filter to reduce irradiation of the cell components, to prevent photooxidative damage and to reduce water losses.

FUNCTIONAL ASPECTS OF SECONDARY CAROTENOIDS IN HAEMATOCOCCUS LACUSTRIS (VOLVOCALES). III. ACTION AS A “SUNSHADE”1

ABSTRACTWe investigated the protection from photoinhibition by different developmental stages of Haematococcus lacustris [Girod] Rostafinski using chlorophyll fluorescence measurements of single cells and suspensions. An overall correlation between higher cellular content of secondary carotenoids and the capacity to withstand excessive irradiation was observed in flagellated cells and aplanospores of H. lacustris. Low‐light‐reversible spreading of extra‐chloroplastic secondary carotenoids occurred in the periphery of the cell during strong irradiation. This process resulted in increased shading of the cup‐shaped chloroplast as demonstrated by a decrease in chlorophyll fluorescence. Extrachloroplastic accumulation of secondary carotenoids in H. lacustris can be interpreted as a specific adaptation to habitats that exhibit strong insolation.

Functional aspects of secondary carotenoids in Haematococcus lacustris (Girod) Rostafinski (Volvocales): I. The accumulation period as an active metabolic process.

Alterations of photosynthetic activity were investigated during accumulation of secondary carotenoids in Haematococcus lacustris (Girod) Rostafinski. Using several methods regarding (i) pigment pattern and pigment content (cytophotometry, computer-aided microscopic image analysis, in vivo absorption spectroscopy, high-performance liquid chromatrography) and (ii) photosynthesis (microfluorometry, modulated chlorophyll fluorescence and luminescence detection, O2 evolution and consumption measurement, 77 K fluorescence spectroscopy) we examined single cells and cell suspensions of the green alga. The results indicate decrease of both the photosystem II activity and the linear electron transport accompanying synthesis of secondary carotenoids. On the other hand, activation of those processes leading to an increased transthylakoid proton gradient could be established during early accumulation period. This is assumed to be an active adaptation of the photosynthetic apparatus to energetic requirements given by secondary carotenoid biosynthesis in H. lacustris.

EVIDENCE A PHOTOPROTECTIVE FOR SECONDARY CAROTENOIDS OF SNOW ALGAE1

ABSTRACTSnow algae occupy a unique habitat in high altitude and polar environments. These algae are often subject to extremes in nutrient availability, acidity, solar irradiance, desiccation, and ambient temperature. This report documents the accumulation of secondary carotenoids by snow algae in response to the availability of nitrogenous nutrients. Unusually large accumulations of astaxanthin esters in extra‐chloroplastic lipid globules produce the characteristics red pigmentation typical of some snow algae (e.g. Chlamydomonas nivalis (Bauer) Wille). Consequently these compounds greatly reduce the amount of light available for absorption by the light‐harvesting pigment‐protein complexes, thus potentially limiting photoinhibition and photodamage caused by intense solar radiation. The esterification of astaxnthin with fatty acids represents a possible mechanism by which this chromophore can be concentrated within cytoplasmic globules to maximize its photoprotective efficiency.

Ultrastructural study of Haematococcus lacustris (Girod.) Rostafinski (Volvocales). I. Some aspects of carotenogenesis.

The process of accumulation of secondary carotenoids (astaxanthin) in Haematococcus lacustris was analysed in the optical and electron microscopes. The more relevant results of this cytological study are the following: a. In motile cells, the lipochromes are spherical inclusions, initially of small size, and located in the perinuclear cytoplasm apparently in preferential correlation with E. R. Although without a true limiting biomembrane, these sudanophilic and osmiophilic inclusions do not easily fuse when contacting. b. In the cysts, the pigment deposits, although being identical to the ones of the motile cells in what concerns their location and affinity for lipids “stains”, show a variety of shapes, including “long filaments”, rods and more or less complex reticulate forms. c. Cells of the older cultures (11-20 days) appear almost uniformly “stained” deep red. This process is reversible, i.e., these cultures again turn green when successively subcultured to fresh media. d. Apart from the stigma globules, the haematochrome is always localized outside the chloroplast, the photosynthetic apparatus of which remains practically intact through this process. Then, no sign of plastidal transformation, (chloroplast in chromoplast) comparable to the changes which take place in various organs of higher plants was observed.