Regulatory control of the triphasic life cycle in a model red alga

• Applicant: Dr. Michael Borg
• Subject Area: Plant Genetics and Genomics ; Evolution and Systematics of Plants and Fungi ; Plant Cell and Developmental Biology
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 573935254

Red algae (or Rhodophyta) are a highly diverse phylum of marine organisms in the Archaeplastida kingdom that were one of the first eukaryotic lineages to evolve multicellularity. Although most red macroalgae (or seaweeds) exhibit remarkably complex reproductive processes that rival the sophistication found in land plants, very little is known about red algal development at a molecular level. One of the defining features of most of the Florideophyceae – where the largest and most advanced orders of red seaweeds are classified - is an enigmatic reproductive strategy called the triphasic life cycle. Like the biphasic life cycle of plants and other algae, the triphasic life cycle also involves transitions between multicellular haploid and diploid generations, but differs in that these transitions are bridged by an additional diploid generation called the carposporophyte. The carposporophyte evolved to undergo a unique process in biology by amplifying the zygote into an abundant mass of diploid spores, thereby maximising reproductive outcomes from a single fertilisation event. Precisely why the the Florideophyceae evolved the triphasic life cycle is still debated, but its prevalence and developmental elaboration in the most dominant orders of red seaweeds suggests a profound impact on their evolutionary and ecological success. This DFG proposal seeks to uncover the regulatory frameworks underlying the triphasic life cycle in Bostrychia mortiziana, a complex red seaweed that we have established as a model system to investigate red algal development. Our first objective will use bulk and single-cell transcriptomics to dissect gene regulatory networks across the triphasic life cycle. The goal is to uncover the genetic programs underlying the triphasic life cycle and help provide insight into its molecular control and evolutionary origins. The second objective is to profile chromatin landscapes across each major stage in the triphasic life cycle using microscopy and epigenomic approaches. This goal is to understand how chromatin landscapes are shaped in red seaweeds, how these are modulated across the triphasic life cycle, and ultimately help provide much-needed insights into how chromatin has evolved to function in the red algal lineage. Collectively, these interdisciplinary approaches promise to deliver new molecular and evolutionary perspectives of a unique reproductive strategy that has cemented the evolutionary success of these essential aquatic organisms, and in turn open up new avenues to further explore the molecular and developmental biology of red seaweeds.

• DFG Programme: Research Grants