Novel type of red-shifted chlorophyll a antenna complex from Chromera velia. I. Physiological relevance and functional connection to photosystems.

Chromera velia is an alveolate alga associated with scleractinian corals. Here we present detailed work on chromatic adaptation in C. velia cultured under either blue or red light. Growth of C. velia under red light induced the accumulation of a light harvesting antenna complex exhibiting unusual spectroscopic properties with red-shifted absorption and atypical 710nm fluorescence emission at room temperature. Due to these characteristic features the complex was designated "Red-shifted Chromera light harvesting complex" (Red-CLH complex). Its detailed biochemical survey is described in the accompanying paper (Bina et al. 2013, this issue). Here, we show that the accumulation of Red-CLH complex under red light represents a slow acclimation process (days) that is reversible with much faster kinetics (hours) under blue light. This chromatic adaptation allows C. velia to maintain all important parameters of photosynthesis constant under both light colors. We further demonstrated that the C. velia Red-CLH complex is assembled from a 17kDa antenna protein and is functionally connected to photosystem II as it shows variability of chlorophyll fluorescence. Red-CLH also serves as an additional locus for non-photochemical quenching. Although overall rates of oxygen evolution and carbon fixation were similar for both blue and red light conditions, the presence of Red-CLH in C. velia cells increases the light harvesting potential of photosystem II, which manifested as a doubled oxygen evolution rate at illumination above 695nm. This data demonstrates a remarkable long-term remodeling of C. velia light-harvesting system according to light quality and suggests physiological significance of 'red' antenna complexes.

Kardiovize Brno 2030, a prospective cardiovascular health study in Central Europe: Methods, baseline findings and future directions.

Background Atherosclerotic cardiovascular disease is highly prevalent in Eastern and Central Europe, where the incidence is the highest in the world. The Kardiovize Brno 2030 study was designed as a prospective cohort study to investigate the complex relationships of cardiovascular disease and outcomes with a range of biological, psychosocial, environmental, behavioral, and economic factors in an urban population of the Czech Republic. Methods We randomly selected a 1% sample of the city of Brno residents aged 25-64 years stratified by sex and age. The study assessed traditional and novel cardiovascular disease risk factors, including sociodemographic and smoking status, physical activity, diet, depression, stress, body fat, cardio-ankle vascular index, and intima media thickness, complemented by blood tests; biological samples were stored for future analyses. Results The study enrolled 2160 participants (54.8% women), with a mean age of 47 ± 11.3 years. They were mostly full-time employed (75.6%) and married (62.1%). Hyperlipidemia was highly prevalent (70.7% in men, and 67.1% in women, NS). Hypertension and diabetes mellitus were more prevalent in men than in women (54.3% vs. 38.7% and 7.1% vs. 3.5%, respectively, P < 0.001 for both). A total of 25.3% of men and 21.9% of women smoked, whereas 20.0% and 43.0% of men and 18.1% and 26.6% of women were obese and overweight, respectively. Conclusions Cardiovascular risk factors are highly prevalent in the city of Brno, an urban population from Central Europe. The Kardiovize Brno 2030 study will provide unique multidimensional and longitudinal cardiovascular health data from a region where epidemiological studies are scarce.

Photosynthesis in Chromera velia represents a simple system with high efficiency.

Chromera velia (Alveolata) is a close relative to apicomplexan parasites with a functional photosynthetic plastid. Even though C. velia has a primitive complement of pigments (lacks chlorophyll c) and uses an ancient type II form of RuBISCO, we found that its photosynthesis is very efficient with the ability to acclimate to a wide range of irradiances. C. velia maintain similar maximal photosynthetic rates when grown under continual light-limited (low light) or light-saturated (high light) conditions. This flexible acclimation to continuous light is provided by an increase of the chlorophyll content and photosystem II connectivity under light limited conditions and by an increase in the content of protective carotenoids together with stimulation of effective non-photochemical quenching under high light. C. velia is able to significantly increase photosynthetic rates when grown under a light-dark cycle with sinusoidal changes in light intensity. Photosynthetic activities were nonlinearly related to light intensity, with maximum performance measured at mid-morning. C. velia efficiently acclimates to changing irradiance by stimulation of photorespiration and non-photochemical quenching, thus avoiding any measurable photoinhibition. We suggest that the very high CO(2) assimilation rates under sinusoidal light regime are allowed by activation of the oxygen consuming process (possibly chlororespiration) that maintains high efficiency of RuBISCO (type II). Despite the overall simplicity of the C. velia photosynthetic system, it operates with great efficiency.

Non-photochemical fluorescence quenching in Chromera velia is enabled by fast violaxanthin de-epoxidation.

Non-photochemical quenching (NPQ) is a mechanism protecting photosynthetic organisms against excessive irradiation. Here, we analyze a unique NPQ mechanism in the alga Chromera velia, a recently discovered close relative of apicomplexan parasites. NPQ in C. velia is enabled by an operative and fast violaxanthin de-epoxidation to zeaxanthin without accumulation of antheraxanthin. In C. velia violaxanthin also serves as a main light-harvesting pigment. Therefore, in C. velia violaxanthin acts as a key factor in both light harvesting and photoprotection. This is in contrast to a similar alga, Nannochloropsis limnetica, where violaxanthin has only light-harvesting function.