Project description:Although N2 fixation can occur in free-living cyanobacteria, the unicellular endosymbiotic cyanobacterium Candidatus Atelocyanobacterium thalassa (UCYN-A) is considered to be a dominant N2-fixing species in marine ecosystems. Four UCYN-A sublineages are known from partial nitrogenase (nifH) gene sequences. However, few studies have investigated their habitat preferences and regulation by their respective hosts in open-ocean versus coastal environments. Here, we compared UCYN-A transcriptomes from oligotrophic open-ocean versus nutrient-rich coastal waters. UCYN-A1 metabolism was more impacted by habitat changes than UCYN-A2. However, across habitats and sublineages genes for nitrogen fixation and energy production were highly transcribed. Curiously these genes, critical to the symbiosis for the exchange of fixed nitrogen for fixed carbon, maintained the same schedule of diel expression across habitats and UCYN-A sublineages, including UCYN-A3 in the open-ocean transcriptomes. Our results undersore the importance of nitrogen fixation in UCYN-A symbioses across habitats, with consequences for community interaction and global biogeochemical cycles.
Project description:Here, we showed that a long non-coding RNA (lncRNA), ncRNA-a3 that is transcribed from TAL1 erythroid +51kb enhancer, is required for TAL1 activation during EPO-induced lineage commitment and formation of erythroblasts. ncRNA-a3 regulates long-range chromatin interactions between +51 enhancer, promoter and other regulatory elements in the TAL1 locus to maintain the erythroid interaction hub. By binding and recruiting p300/BRG1 to the TAL1 locus ncRNA-a3 facilitates chromatin accessibility in the TAL1 locus and activates TAL1 transcription program, including subsequent epigenetic and transcriptional activation of erythroid specific TAL1 target genes.
