Investigation of the Thallusin induced morphogenesis of Ulva mutabilis by integrated metabolomic and transcriptomic analysis

The green macroalga Ulva compressa serves as a valuable model for investigating algal development, particularly due to its dependence on symbiotic marine bacteria such as Roseovarius sp. MS2 and Maribacter sp. MS6 [1]. These bacteria secrete algal growth- and morphogenesis-promoting factors (AGMPFs) that are essential for normal algal development [2,3]. While Roseovarius sp. primarily stimulates cell division, Maribacter sp. induces morphogenesis and proper cell wall formation in axenic gametes. The AGMPF produced by Maribacter sp. has been identified as (−)-thallusin [4] and successfully synthesized [5,6], whereas the corresponding factor from Roseovarius sp. remains unknown. We demonstrated that axenic calli derived from Ulva gametes represent a suitable model system to investigate the metabolic effects of AGMPFs [7]. After two weeks of exposure, treated calli exhibited clear signs of regeneration accompanied by pronounced metabolic shifts compared to untreated controls, as revealed by metabolomics analyses. Targeted fatty acid profiling further showed substantial alterations, particularly affecting ω-3 and ω-6 fatty acids [7]. In addition, monosaccharide profiling of Ulva cultivated with bacteria for three months revealed distinct differences in carbohydrate composition compared to axenic controls, especially in treatments involving Maribacter sp. Ongoing transcriptomic and metabolomic analyses aim to elucidate the signaling pathways and molecular mechanisms triggered by (−)-thallusin. Differential gene expression patterns indicate significant effects on cell division, recovery processes, and overall metabolic activity. Together, these findings highlight the central role of bacterial-derived compounds in regulating metabolic and developmental processes in Ulva, with broader implications for aquaculture and developmental biology.

PhD start: 09/01/2022