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Harmful algal blooms: mechanisms, monitoring, and prevention in a rapidly changing world
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Cyanate Utilization and Identification of Cyanase Gene in Toxic Dinoflagellate Alexandrium pacificum
Wednesday 9th @ 1430-1450, Multifunction Hall
Xuewei Mao* , College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
Yunyun Zhuang, College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
Huan Zhang, Department of Marine Science, University of Connecticut, Groton, CT 06340, USA
Guangxing Liu, College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
Presenter Email: maoxuewei_ouc@163.com |
| Cyanate is a potential nitrogen source in marine environment, which is the by-product of urea decomposition. The acquisition and utilization of cyanate have been characterized in cyanobacteria, but remain elusive in eukaryotic phytoplankton. In this study, we integrated the physiological and transcriptional data to explore the cyanate utilization in a toxic dinoflagellate Alexandrium pacificum, a HABs causative species. We monitored the growth, photosystem II Fv/Fm and cell diameter of A. pacificum grown on five concentrations of cyanate, nitrate and under N-depleted condition. At the concentration of 50, 100 and 200¦ÌM, cyanate promoted the growth of A. pacificum, while at the concentration of 400 and 800 ¦ÌM, cyanate significantly depressed growth and caused irreversible damage to the cells. No significant difference was detected between the growth rate, Fv/Fm, cell diameter of cyanate- and nitrate-grown cells at the concentration of 100¦ÌM N during the early logarithmic phase. Transcriptome profiling revealed a gene encoding cyanase in A. pacificum (ApcynS), the enzyme hydrolyzes cyanate to ammonium and CO2. We isolated the full-length cDNA of ApcynS (653bp). The deduced protein was 173 amino acids with a predicted molecular mass of 18.7 kDa, which is in the range of most documented cyanase. By screening the existing datasets, we found cyanase-encoding genes in a variety of eukaryotic phytoplankton and phylogenetic analyses support the transfer of cynS between cyanobacteria and dinoflagellates. However, unlike that in cyanobacteria, the expression of ApcynS was not regulated by N sources. Transcriptome profiling also revealed that cyanate induced the up-regulation of several ATP-binding cassette transporters, potentially related to cyanate uptake or permeation. Our results showed that the growth of A. pacificum could be supported by cyanate as the sole source of external N, which might provide competitive advantage for this species in HABs formation and maintenance. |
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