Evidence for Dosage Compensation in Coccinia grandis, a Plant with a Highly Heteromorphic XY System

Here, we review the literature on sexual lability in dioecious angiosperm species with well-studied sex chromosomes. We distinguish three types of departures from strict dioecy, concerning either a minority of flowers in some individuals (leakiness) or the entire individual, which can constantly be bisexual or change sex. We found that for only four of the 22 species studied, reports of lability are lacking. The occurrence of lability is only weakly related to sex chromosome characteristics (number of sex-linked genes, age of the non-recombining region). These results contradict the naive idea that lability is an indication of the absence or the recent evolution of sex chromosomes, and thereby contribute to a growing consensus that sex chromosomes do not necessarily fix sex determination once and for all. We discuss some implications of these findings for the evolution of sex chromosomes, and suggest that more species with well-characterized lability should be studied with genomic data and tools. This article is part of the theme issue ‘Sex determination and sex chromosome evolution in land plants’.

Section: Resultsmentioning

confidence: 99%

Labile sex expression in angiosperm species with sex chromosomes

Käfer

Méndez

Mousset

2022

“…This species has strongly heteromorphic XY sex chromosomes with a larger Y that evolved approximately 3 Ma [89]. The decrease in Y expression was compensated by an increase in male X expression for X/Y genes [90]. However, a detailed analysis of X-hemizygous genes revealed that only half of them are dosage compensated (electronic supplementary material, table S2).…”

Section: Common Patterns Of Incomplete Dosage Compensation In Other P...mentioning

confidence: 99%

Dosage compensation evolution in plants: theories, controversies and mechanisms

Muyle

Marais

Bačovský

et al. 2022

Self Cite

In a minority of flowering plants, separate sexes are genetically determined by sex chromosomes. The Y chromosome has a non-recombining region that degenerates, causing a reduced expression of Y genes. In some species, the lower Y expression is accompanied by dosage compensation (DC), a mechanism that re-equalizes male and female expression and/or brings XY male expression back to its ancestral level. Here, we review work on DC in plants, which started as early as the late 1960s with cytological approaches. The use of transcriptomics fired a controversy as to whether DC existed in plants. Further work revealed that various plants exhibit partial DC, including a few species with young and homomorphic sex chromosomes. We are starting to understand the mechanisms responsible for DC in some plants, but in most species, we lack the data to differentiate between global and gene-by-gene DC. Also, it is unknown why some species evolve many dosage compensated genes while others do not. Finally, the forces that drive DC evolution remain mysterious, both in plants and animals. We review the multiple evolutionary theories that have been proposed to explain DC patterns in eukaryotes with XY or ZW sex chromosomes. This article is part of the theme issue ‘Sex determination and sex chromosome evolution in land plants’.

“…(c) Dosage compensation in plants Dosage compensation has been described in different plant species: S. latifolia [210][211][212][213], Silene otites [214], Coccinia grandis [215], Rumex rothschildianus [216] and Cannabis sativa [217]. It was inferred either (i) by using the ratio of male to female expression, which is close to one for dosage compensated sexlinked genes in spite of Y expression degeneration, or (ii) by studying the ratio of X expression in males to autosomal expression in an outgroup without sex chromosomes.…”

Section: (B) X Inactivation and Upregulation In Mammalsmentioning

confidence: 99%

Epigenetics drive the evolution of sex chromosomes in animals and plants

Muyle

Bachtrog

Marais

et al. 2021

Self Cite

We review how epigenetics affect sex chromosome evolution in animals and plants. In a few species, sex is determined epigenetically through the action of Y-encoded small RNAs. Epigenetics is also responsible for changing the sex of individuals through time, even in species that carry sex chromosomes, and could favour species adaptation through breeding system plasticity. The Y chromosome accumulates repeats that become epigenetically silenced which leads to an epigenetic conflict with the expression of Y genes and could accelerate Y degeneration. Y heterochromatin can be lost through ageing, which activates transposable elements and lowers male longevity. Y chromosome degeneration has led to the evolution of meiotic sex chromosome inactivation in eutherians (placentals) and marsupials, and dosage compensation mechanisms in animals and plants. X-inactivation convergently evolved in eutherians and marsupials via two independently evolved non-coding RNAs. In Drosophila , male X upregulation by the male specific lethal (MSL) complex can spread to neo-X chromosomes through the transposition of transposable elements that carry an MSL-binding motif. We discuss similarities and possible differences between plants and animals and suggest future directions for this dynamic field of research. This article is part of the theme issue ‘How does epigenetics influence the course of evolution?’