Unravelling the secret life of MultiAnnual delayed gametophytes in the order of the Laminariales

Summary

Research within the Laminariales in nature has predominantly focused on the sporophyte phase, often overlooking the other half of a bi-phasic life cycle; the gametophytes which can grow and propagate independently. This study examines the potential function that gametophytes might have within the Laminariales, focussing primarily on the understudied MultiAnnual Delayed (MAD) gametophyte, and comparing it with the typically researched newly formed single celled or delayed gametophyte. MAD gametophytes, characterized by extended vegetative growth before reproduction, display notable morphological and functional differences compared to their single-celled or younger multicellular counterparts. Key fundamental questions arise when discussing the evolutionary pressures that result in the formation of these older gametophytes. Why do MAD gametophytes actually exist? Why can MAD gametophytes seemingly live forever? Why do MAD gametophytes grow vegetatively and seemingly without limits? We posit an updated life cycle model for Laminariales, hypothesizing two phenotypically different gametophyte types, each with unique morphologies, functionalities, and reproductive behaviors. This life cycle model puts more focus on the understudied MAD gametophytes and their role in nature, thereby aiming to push for more research and thus comprehensive understanding of the in-culture selection pressures and in vivo life cycle dynamics that affect MAD gametophytes. An understanding that is pertinent since unravelling the secret life of MAD gametophytes is fundamental to the success of future kelp domestication and large scale rewilding efforts.