Insights into life cycle patterns, spore formation, induction of reproduction, biochemical and molecular aspects of sporulation in green algal genus Ulva: implications for commercial cultivation

The green algal genus Ulva (Ulvophyceae) has been recently perceived as a model organism, due to its tractability for genetic analyses. This biomass is drawing considerable attention as a potential feedstock for energy security, including emerging applications in functional foods, bio-fuels and energy, pharmaceutical, biotechnological industries, etc. Nevertheless, unlike other commercially farmed seaweeds where clonal propagation is practiced, this genus solely relies on motile reproductive cells (zoospores or gametes) for seeding or seedling production. The culture practices encompass photobioreactor, land-based and open sea farming. The knowledge of reproduction is pivotal for efficient seeding technologies, selecting and domesticating fast growing varieties as well as genetic improvement. The successful induction of reproduction in Ulva spp. is being achieved through external environmental stimuli as well as by manipulating sporulation and swarming inhibitor concentration. However, comprehensive biochemical and molecular evidences are underdeveloped and further knowledge is imperative to improve aquaculture practice. This mini-review provides comprehensive insights into life cycle, spore formation, mechanisms for the induction of reproduction, biochemical and molecular aspects of sporulation besides advances in the farming of Ulva spp. with future prospective. The existing commercial trade of Japan about 1500 t dry annum−1 is poised to become the leading industry with focus on niche, high-value products in the coming decade.