The sex‐linked region in Populus tremuloides Turesson 141 corresponds to a pericentromeric region of about two million base pairs on P. trichocarpa chromosome 19

Abstract

In the dioecious genus Populus, sex determination has been located to chromosome 19. However, despite a high degree of genome collinearity, various Populus species seem to differ with regard to the location of the sex-determining region on the respective chromosome and the apparent heterogametic sex. In this study, the boundaries of the recombination-suppressed, sex-linked region of the male P. tremuloides clone Turesson 141 were localised by genetic mapping using new SNP and InDel markers. The respective region seems to be located in a pericentromeric position. The corresponding P. trichocarpa genome region spans about two million bp and comprises 65 gene loci, which were bioinformatically evaluated for their potential as candidate genes for sex determination. Three putative transcription factor genes and four genes that are potentially involved in flower development processes, e.g. meristem transition from the vegetative to the reproductive phase, were identified. Populus tremuloides sequence data of the sex-linked region is required for a final search for candidate genes.

Sex‐biased gene expression in flowers, but not leaves, reveals secondary sexual dimorphism in Populus balsamifera

“…tremula common ancestor to P. trichocarpa (hereafter P. trichocarpa lineage), and for the lineage from P. trichocarpa to P. tremula . These two species harbor different SDRs (Kersten et al ., ; Geraldes et al ., ). First, we compared the median values of dN/dS for sex‐biased and sex‐limited genes with a random sample of unbiased genes, using a non‐parametric Kruskal–Wallis test (function kruskal.test in R, post hoc tests were conducted using dunn.test).…”

Patterns of genetic diversity and differentiation in resistance gene clusters of two hybridizing European Populus species

“…This chromosomal region is not only particular regarding its genetic diversity but also regarding its genomic architecture. Despite high levels of synteny among Populus genomes, the location of the gender determination locus appears to be variable in position along chromosome XIX in different sections of the Populus genus (Gaudet et al 2008;Yin et al 2008;Pakull et al 2011;Kersten et al 2014). In P. alba and P. tremula, sex determination appears to have a centromeric localization rather than the peritelomeric localization described for Populus trichocarpa (Tuskan et al 2012).…”

“…Although genetic maps show that sex determination in European Populus species is located further towards the centromere (Paolucci et al 2010;Tuskan et al 2012;Kersten et al 2014) and ongoing genomic work in P. trichocarpa continues to discover novel aspects of the sex determination system (Hou et al 2015;Geraldes et al 2015), this chromosome block was shown to present segregation distortion and reduced recombination in P. alba and P. tremula, as expected for an incipient sex chromosome (Macaya-Sanz et al 2011). The presence of a large NBS-LRR gene cluster may explain the evolution of this particular chromosome.…”

“…Recent studies of this chromosome have revealed different aspects of its complex history: different genomic architectures of sex determination depending on species (Geraldes et al 2015;Kersten et al 2014) but also a chromosome that is younger than the rest of the Populus genome with turnover events in the recent past (Geraldes et al 2015;Hou et al 2015). We discuss the potential roles of both R-genes and sex determination in shaping the genomic architecture of this chromosome.…”

A System for Dosage-Based Functional Genomics in Poplar

“…It can be used to assist in identifying genes underlying previously identified QTLs (Dillen et al, 2009;Novaes et al, 2009;Marron et al, 2010;Rohde et al, 2011;Induri et al, 2012). For example, sex determinants have been mapped to chromosome 19 in several different species of poplar, although the exact location seems to vary between species Kersten et al, 2014;Geraldes et al, 2015) and the exact molecular mechanisms leading to sex determination in poplar remain unclear. Chromosome 19 is particularly well covered by indel mutations (Figure 5), which can be used to further our understanding of the sex determination mechanisms in poplar.…”