Transcriptome analysis reveals mechanisms of geroprotective effects of fucoxanthin in Drosophila.

BACKGROUND: We have previously showed that the carotenoid fucoxanthin can increase the lifespan in Drosophila melanogaster and Caenorhabditis elegans. However, the molecular mechanisms of the geroprotective effect of fucoxanthin have not been studied so far. RESULTS: Here, we studied the effects of fucoxanthin on the Drosophila aging process at the molecular and the whole organism levels. At the organismal level, fucoxanthin increased the median lifespan and had a positive effect on fecundity, fertility, intestinal barrier function, and nighttime sleep. Transcriptome analysis revealed 57 differentially expressed genes involved in 17 KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways. Among the most represented molecular pathways induced by fucoxanthin, a significant portion is related to longevity, including MAPK, mTOR, Wnt, Notch, and Hippo signaling pathways, autophagy, translation, glycolysis, oxidative phosphorylation, apoptosis, immune response, neurogenesis, sleep, and response to DNA damage. CONCLUSIONS: Life-extending effects of fucoxanthin are associated with differential expression of longevity-associated genes.

Nitrogen fixation activity in biological soil crusts dominated by cyanobacteria in the Subpolar Urals (European North-East Russia).

The nitrogen fixation by biological soil crusts with a dominance of cyanobacteria was studied using the acetylene reduction assay in the territory of the Subpolar Urals (65°11' N, 60°18' E), Russia. The field measurements of nitrogen fixation activity were conducted in situ for two different types of soil crusts dominated by Stigonema (V1 type) and Nostoc with Scytonema (V2 type). The nitrogen fixation process had similar dynamics in both crusts but nitrogen fixation rates were different. The crusts of the V2 type showed a significantly higher acetylene reduction activity, with ethylene production rate of 1.76 ± 0.49 g C2H4 m(-2) h(-1) at 15°C, compared with V1-type soil crusts, with a rate of 0.53 ± 0.21 mg C2H4 m(-2) h(-1) at 15°C. The daily value of acetylene reduction activity in V2-type soil crusts was 32.7 ± 6.2 mg C2H4 m(-2) d(-1) and in V1-type crusts, 12.3 ± 1.8 mg C2H4 m(-2) d(-1) After recalculation for N, the daily values of nitrogen fixation were in the range 3.3-22.3 mg N m(-2) d(-1), which is a few times higher than the values of N input from the precipitation to the soil in the studied regions. The dependence of nitrogen-fixation activity on temperature and light intensity of biological soil crusts was investigated. On the basis of temperature models obtained from the dependence, the nitrogen balance was calculated for the growing season (approximately 120 days). The crusts dominated by Stigonema species were fixing 0.3 g N m(-2) (ethylene production rate, 1.10 g C2H4 m(-2)) and crusts dominated by Nostoc and Scytonema were fixing 1.3 g N m(-2) (4.10 g C2H4 m(-2)).