Male Meiotic Recombination in the Steppe Agama, <b><i>Trapelus sanguinolentus</i></b> (Agamidae, Iguania, Reptilia)

Abstract

Meiotic recombination rates and patterns of crossover distributions along the chromosomes vary considerably even between closely related species. The adaptive significance of these differences is still unclear due to the paucity of empirical data. Most data on recombination come from mammalian species, while other vertebrate clades are poorly explored. Using immunolocalization of the protein of the lateral element of the synaptonemal complex (SYCP3) and the mismatch-repair protein MLH1, which marks mature recombination nodules, we analyzed recombination rates and crossover distribution in meiotic prophase chromosomes of the steppe agama (Trapelus sanguinolentus, Agamidae, Acrodonta, Iguania) and compared them with data obtained for the genus Anolis (Dactyloidae, Pleurodonta, Iguania). We found that, despite a smaller genome size, the total SC length and the MLH1 focus number per cell are much higher in the agama than in the anoles. The distributions of the MLH1 foci in the agama are multimodal in larger chromosomes and bimodal in smaller chromosomes without a significant centromere effect, resembling the patterns known for birds. A possible relationship between karyotype remodeling and the evolution of recombination in Iguania is discussed.

Identification of sex chromosomes in Eremias velox (Lacertidae, Reptilia) using lampbrush chromosome analysis

“…In particular, the occurrence of two chiasmata, like those observed in bivalent XIX (Fig. 2), is extremely rare in the microchromosomes of male lizards (Lisachov et al 2017, 2019). This suggests the occurrence of more crossovers in female than male meiosis in lacertids (heterochiasmy).…”

Comparative Cytogenetics of Four Sea Turtle Species (Cheloniidae): G-Banding Pattern and in situ Localization of Repetitive DNA Units

“…Nevertheless, reptiles have proven to be excellent models for understanding chromosomal evolution in cytogenetic studies [Valenzuela and Adams, 2011;Deakin and Ezaz, 2019]. This is because their karyotypes are highly diverse in terms of (i) chromosome number and morphology [Olmo, 2008;Valenzuela and Adams, 2011;Montiel et al, 2016;Deakin and Ezaz, 2019]; (ii) the absence or presence of microchromosomes (mc) [Burt, 2002;Mezzasalma et al, 2016]; (iii) macrochromosome breaks and rearrangements, which result in loss of synteny, in conflict with the hypothesis that turtle chromosomes are highly conserved [Badenhorst et al, 2015;Deakin and Ezaz, 2019;Lee et al, 2019], and (iv) sex-determining mechanisms [Valenzuela and Adams, 2011;Valenzuela et al, 2014;Rovatsos et al, 2017;Lee et al, 2019] and types of sex chromosome systems [Pokorná et al, 2011;Gamble et al, 2015;Iannucci et al, 2019;Lisachov et al, 2019;Mazzoleni et al, 2019;Nielsen et al, 2019].…”

“…Usually, studies applying repetitive DNAs in turtles involve chromosomal localization of multigene families [Badenhorst et al, 2015;Cavalcante et al, 2018Cavalcante et al, , 2020aMatsubara et al, 2019] and in situ localization of satellite DNA sequences or transposable elements, restricted to a few groups [Badenhorst et al, 2015;Boissinot et al, 2019;Cavalcante et al, 2020b]. However, chromosomal painting and BAC-FISH for detecting single-copy genes has proven useful for identifying chromosomal rearrangements in reptiles in cytogenetic studies [Young et al, 2013;Badenhorst et al, 2015;Iannucci et al, 2019;Lee et al, 2019;Lisachov et al, 2019].…”

Whole-chromosome fusions in the karyotype evolution ofSceloporus(Iguania, Reptilia) are more intense in sex chromosomes than autosomes

“…We did not confirm the hypothesis that S. malachiticus could have lower crossing over rates than the related bimodal species. On the contrary, both species of Sceloporus show similar intra-chromosomal components of r , which are higher than in two previously studied bimodal Anolis species [23]. Thus, at least in the studied species of Pleurodonta, the crossover patterns depend on the phylogenetic position of the species, and not on the structure of its karyotype.…”

“…The SC spreads of S. malachiticus and S. variabilis were prepared and immunostained as described previously, using the antibodies to SYCP3, the protein of the lateral element of the SC; to MLH1, the mismatch-repair protein which marks mature recombination nodules; and to CENP, the centromere proteins [23].…”