Evidences for a role of two Y-specific genes in sex determination in Populus deltoides

Abstract

Almost all plants in the genus Populus are dioecious (i.e. trees are either male or female), but it is unknown whether dioecy evolved in a common ancestor or independently in different subgenera. Here, we sequence the small peritelomeric X- and Y-linked regions of P. deltoides chromosome XIX. Two genes are present only in the Y-linked region. One is a duplication of a non-Y-linked, female-specifically expressed response regulator, which produces siRNAs that block this gene’s expression, repressing femaleness. The other is an LTR/Gypsy transposable element family member, which generates long non-coding RNAs. Overexpression of this gene in A. thaliana promotes androecium development. We also find both genes in the sex-determining region of P. simonii, a different poplar subgenus, which suggests that they are both stable components of poplar sex-determining systems. By contrast, only the duplicated response regulator gene is present in the sex-linked regions of P. davidiana and P. tremula. Therefore, findings in our study suggest dioecy may have evolved independently in different poplar subgenera.

Nanopore RNA Sequencing Revealed Long Non-Coding and LTR Retrotransposon-Related RNAs Expressed at Early Stages of Triticale SEED Development

“…A similar trend was demonstrated in some plant species, including maize, where 65% of lncRNAs had similarities to TEs [ 18 ]. More intriguingly, the TE-derived sequences may trigger the origin of new lncRNAs, providing a positive feedback loop with the evolution of lncRNAs [ 11 , 19 ]. TE-derived lncRNAs can have important and conserved biological functions [ 20 ].…”

When and how do sex‐linked regions become sex chromosomes?

“…2). Turnovers have been detected in many animals (Vicoso 2019), and are starting to be discovered in plants (Tennessen et al 2018;Xue et al 2020;Yang et al 2020). Finally, genetic maps are increasingly being used to separate the two haplotypes of the sex-linked region, by genotyping progeny individuals and a parent of the heterozygous sex (Zhou et al 2020).…”

“…If the Y-linked region includes genes not present on the X chromosome, such referencebased assembly will either leave these sequences unmapped or incorrectly map them to the most similar autosomal sequences. Reference-quality genome sequences of both sexes are therefore needed (Wei and Bachtrog 2019;Xue et al 2020).…”

“…5) might directly prevent pairing in the regions flanking the insertion, causing a few neighboring genes to also become fully Y-or X-linked (pink). Single-gene systems in poplar species appear to involve a male-determining gene that, like that in the persimmon, arose as a duplication that silenced a female-promoting gene (Müller et al 2020;Xue et al 2020). Small genome regions carrying multiple male-specific genes have been detected in two other plants, Asparagus officinalis (Harkess et al 2020) and the date palm (Tor-res et al 2018).…”

Deborah Charlesworth, winner of the society for the study of evolution's inaugural lifetime achievement award: Evolutionary biology for the genomics era

“…Recent molecular genetic characterization of sex determination in several systems has provided support for the presence of two linked loci controlling sex determination in plants predicted by the Charlesworth model, including asparagus (Harkess et al 2017, Harkess et al 2020, papaya (Min et al 2012), and Silene (Kazama et al 2016), whereas other systems have single-locus control that may be explained by the fixation of a previous polymorphism at the locus conferring male sterility (Charlesworth 2019;Akagi et al 2020;Xue et al 2020). Furthermore, work by Akagi and Charlesworth (2019) using identified female sterility genes from both kiwifruit and persimmon transformed into hermaphroditic species has recently provided the first evidence, suggesting that the female sterility mutation directly confers pleiotropic benefits on male function, a key prediction of Darwin's (Darwin 1877) and Charlesworths' models (Charlesworth and Charlesworth 1978).…”