Abstract
AbstractPreviously, we isolated Chlorella sp. HS2 (referred hereupon as HS2) from a local tidal rock pool and demonstrated its halotolerance and high biomass productivity under different salinity conditions. To further understand acclimation responses of this alga under high salinity stress, we performed transcriptome analysis of triplicated culture samples grown in freshwater and marine conditions at both exponential and stationary growth phases. The results indicated that the transcripts involved in photosynthesis, TCA, and Calvin cycles were downregulated, whereas the upregulation of DNA repair mechanisms and an ABCB subfamily of eukaryotic type ABC transporter was observed at high salinity condition. In addition, while key enzymes associated with glycolysis pathway and triacylglycerol (TAG) synthesis were determined to be upregulated from early growth phase, salinity stress seemed to reduce the carbohydrate content of harvested biomass from 45.6 dw% to 14.7 dw% and nearly triple the total lipid content from 26.0 dw% to 62.0 dw%. These results suggest that the reallocation of storage carbon toward lipids played a significant role in conferring the viability of this alga under high salinity stress by remediating high level of cellular stress partially resulted from ROS generated in oxygen‐evolving thylakoids as observed in a direct measure of photosystem activities.
Highlights
Microalgae exhibit a greater biomass yield than most terrestrial crops and can be grown with excess nutrients in wastewater sources, prompting its industrial utilization as a biofeedstock for the production of nutraceuticals, pharmaceuticals, cosmetics, and biofuels (Hu et al, 2008; Quinn & Davis, 2015; Smith et al, 2010; Unkefer et al, 2017; Yun, Cho, Lee, Heo, et al, 2018)
While the results of HS2 cultivation in 1-L cylindrical PBRs were reported in our previous study (Yun et al, 2019), both autotrophic cultures grown in freshwater inorganic medium and in marine inorganic growth medium supplemented with 3% (w/v) sea salt were subjected to transcriptome analysis
To elucidate differentially expressed genes (DEGs), read normalization was first performed using SVCD normalization following standard DEGseq2 statistical test; a total of 9117 DEGs were subsequently obtained from 52,770 unigenes corresponding to 39,469 transcripts
Summary
Marine Biotechnology Program and Collaborative Genome Program funded by the Ministry of Oceans and Fisheries of the Republic of Korea, Grant/Award Number: 20150184 and 20180430; Ministry of Science and ICT of the Republic of Korea, Grant/Award Number: 2020M3H7A1098291 and 2016922286; Ministry of Oceans and Fisheries, Grant/ Award Number: 20150184 and 20180430; of the Republic of Korea, Grant/Award Number: 20150184 and 20180430; KRIBB Research Initiative Program; ANR [The copyright line for this article was changed on 8 January 2021, after original online publication]
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