Abstract
BackgroundHydrogen photoproduction from green microalgae is regarded as a promising alternative solution for energy problems. However, the simultaneous oxygen evolution from microalgae can prevent continuous hydrogen production due to the hypersensitivity of hydrogenases to oxygen. Sulfur deprivation can extend the duration of algal hydrogen production, but it is uneconomical to alternately culture algal cells in sulfur-sufficient and sulfur-deprived media.ResultsIn this study, we developed a novel way to simulate sulfur-deprivation treatment while constantly maintaining microalgal cells in sulfur-sufficient culture medium by overexpressing an endogenous microRNA (miR1166.1). Based on our previous RNA-seq analysis in the model green alga Chlamydomonas reinhardtii, three endogenous miRNAs responsive to sulfur deprivation (cre-miR1166.1, cre-miR1150.3, and cre-miR1158) were selected. Heat-inducible expression vectors containing the selected miRNAs were constructed and transformed into C. reinhardtii. Comparison of H2 production following heat induction in the three transgenic strains and untransformed control group identified miR1166.1 as the best candidate for H2 production regulation. Moreover, enhanced photobio-H2 production was observed with repeated induction of miR1166.1 expression.ConclusionsThis study is the first to identify a physiological function of endogenous miR1166.1 and to show that a natural miRNA can regulate hydrogen photoproduction in the unicellular model organism C. reinhardtii.
Highlights
Hydrogen photoproduction from green microalgae is regarded as a promising alternative solution for energy problems
The precursor of cre-miR1162, a highly expressed endogenous miRNA of C. reinhardtii, was used as the expression backbone [36], and the mature sequence of cre-miR1162 was replaced fragments per kilobase of transcript sequence per million mapped reads) of miR1166.1 was up-regulated from 0.70 to 2.72 after sulfur deprivation (Fig. 1), which suggested a close relationship of this endogenous miRNA with sulfurdeprivation metabolism pathways in C. reinhardtii
Our result shows that endogenous miRNA1166.1 significantly affects H2 production in C. reinhardtii
Summary
Hydrogen photoproduction from green microalgae is regarded as a promising alternative solution for energy problems. Hydrogen gas (H2) is a clean energy source, and hydrogen production from green algae is regarded as a promising alternative solution for energy problems, since green algae have iron hydrogenases with high enzyme activity and can rely on solar energy for growth [1,2,3,4,5,6,7,8]. Algal cell respiration exhausts oxygen and causes anaerobiosis in the culture. This two-stage method separates hydrogen production from oxygen evolution and carbon accumulation, and sulfur deprivation makes sustained hydrogen production possible [11]. The replacement of normal medium with sulfur-deprived medium requires the centrifugation of algal cells, which may affect cell activity and is difficult to apply in large-scale production
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