A partially sex-reversed giant kelp sheds light into the mechanisms of sexual differentiation in UV sexual system

ABSTRACT: In UV sexual systems, sex is determined during the haploid phase of the life cycle and males have a V chromosome whereas females have a U chromosome. Previous work in the model Ectocarpus revealed that the V chromosome has a dominant role in male sex determination and the female developmental program being a ‘default’ program, triggered in the absence of the male master sex determination gene(s). Here, we describe the identification of a genetically male giant kelp strain presenting phenotypic features typical of a female, despite lacking the U-specific region. The conversion to the female developmental program is however incomplete, because gametes of this feminised male are unable to produce the sperm-attracting pheromone lamoxiren. We identify the transcriptomic pathways underlying the male and female specific developmental programs and show that the phenotypic feminisation of the variant strain is associated with both feminisation and de-masculinisation of gene expression patterns. Importantly, the feminisation phenotype was associated with the dramatic downregulation of two V-specific genes including a candidate sex-determining gene on the V-specific region. Our results reveal the transcriptional changes associated with sexual differentiation in a UV system with extensive sexual dimorphism, disentangling the role of sex-linked genes and autosomal gene expression in the initiation of the male and female developmental programs. Overall, the data presented here imply that the U-specific region in the giant kelp is not required to initiate the female developmental program, but is critical to produce fully functional eggs, arguing against the idea that female is the ‘default’ sex in this species.

ORGANISM(S): Macrocystis pyrifera

PROVIDER: GSE165423 | GEO | 2022/04/28

REPOSITORIES: GEO