Yoon, J.-T. | bioRxiv Science

bioRxiv2026

A climate-resilient microalga, Desmodesmus ecotolerans sp. nov., for biophotovoltaic applications

Microalgae are promising biological platforms for sustainable energy production because they can convert photosynthetic activity into electricity in biophotovoltaic (BPV) systems. Identifying strains that grow well at elevated temperatures and under reduced irradiance is an important step toward BPV applications in seasonally variable environments. Microalgae were isolated from Seondong Lake (Seoul, Republic of Korea) during three sampling periods and screened for growth at different temperatures. Among 45 isolates, KHUC-11 showed the highest weighted growth index based on growth rates at 25, 30, and 35 under dark conditions and was selected for further characterization. Phylogenetic reconstruction of the 45S rRNA gene cluster, internal transcribed spacer 2 (ITS2) secondary-structure comparison, and morphological characterization supported the description of KHUC-11 as Desmodesmus ecotolerans sp. nov. D. ecotolerans produced more biomass than Chlamydomonas reinhardtii CC-125 under both moderate- and low-light conditions. Under low light, its final dry biomass concentrations were 1.81 and 1.58 times those of CC-125 under mixotrophic and photoautotrophic conditions, respectively. Despite its smaller cell size, D. ecotolerans showed higher photosynthetic performance than CC-125, and screen-printed electrode (SPE)-based electrochemical assays demonstrated enhanced anodic current generation and CV-derived estimated power output. Taken together, these findings identify D. ecotolerans as a novel climate-resilient Desmodesmus species with bioelectrochemical properties that support further evaluation for BPV applications.

microbiology↗

bioRxiv2026

The Impact of TOR-S6K-eIF5A Signaling on Translational Control is Key to Plant Root Development

Nutrient-responsive Target of Rapamycin (TOR)-S6 kinase (S6K) signaling coordinates plant growth with protein synthesis, but how it interfaces with translation elongation to produce specific developmental outputs remains unclear. Here, we identify eukaryotic translation factor 5A (eIF5A) as an S6K-associated phosphoprotein in Arabidopsis thaliana. S6K1 and S6K2 associate with all three eIF5A isoforms and phosphorylate them in vitro, with Ser2 emerging as the major S6K1-responsive site in eIF5A-2. The corresponding N-terminal serine is invariant across the analyzed Archaeplastida eIF5A proteins. Conditional depletion of TOR, S6K1/2, or eIF5A produces overlapping reductions in primary root length and root hair coverage. eIF5A depletion leaves bulk protein synthesis and polysome profiles largely unchanged while selectively decreasing output from deca-proline reporters. Reporter activity is restored by amiRNA-resistant wild-type and phosphomimetic S2D eIF5A-2, whereas S2A does not restore activity, demonstrating the functional importance of the Ser2 state. Proteomic profiling identifies a restricted set of eIF5A-responsive proteins, and five of six tested insertion mutants display altered primary root growth, root hair coverage, or both. Together, these findings uncover a regulatory connection between S6K and eIF5A and establish eIF5A-dependent selective translation as a mechanism contributing to root development in A. thaliana.

molecular biology↗