show Abstracthide AbstractChondrus crispus is a red macroalga with a haploid-diploid life cycle, alternating between male and female gametophytes (n) and tetrasporophytes (2n). The gametophyte and tetrasporophyte life stages are isomorphic yet they display different physiological properties, including cell wall composition. We carried out transcriptomic studies on confirmed Chondrus male and female gametophytes and tetrasporophytes in order to identify genes differentially regulated between life cycle stages as well as candidates predicted or shown to be implicated in carrageenan biosynthesis.