Cytomolecular analysis of species in the Peltophorum clade (Caesalpinioideae, Leguminosae)

Abstract

The Peltophorum clade (Caesalpinioideae, Leguminosae) comprises 16 genera and approximately 105 species with overall pantropical distributions. The genera Peltophorum (Vogel) Benth. (9 spp.) and Delonix Raf. (11 spp.) are notable for having arboreal habits, ornamental uses, and karyotypes of 2n = 26 and 2n = 28, respectively. The present work sought to characterize the patterns of heterochromatin distribution and rDNA sites, as well as the genome sizes of three representatives of the Peltophorum clade. We analyzed P. pterocarpum (DC.) Backer ex K. Heyne, P. dubium (Spreng.) Taub., and D. regia (Bojer ex 121 Hook.) Raf. using double staining with the fluorochromes CMA and DAPI, fluorescent in situ hybridization (FISH) to detect rDNA sites, as well as flow cytometry to determine their DNA contents. The two species of Peltophorum have a chromosome number of 2n = 26, with meta/submetacentric chromosomes measuring on average 2.33 lm. On the other hand, D. regia has a number of 2n = 28, with larger chromosomes. Genome sizes varied from 1C = 0.90 pg in the two Peltophorum species to 1C = 1.55 pg in D. regia. CMA/DAPI staining showed CMA ? /DAPIbands predominantly in the terminal regions of the chromosomes, with six, four, and three pairs being observed in P. pterocarpum, P. dubium, and D. regia, respectively. FISH revealed the presence of a chromosome pair with 5S rDNA sites in each of the two species of Peltophorum, and on two chromosome pairs in D. regia. The numbers of 35S sites varied from 6 to 24, with synteny being observed with 5S rDNA sites in a pair of chromosomes of P. pterocarpum and in two pairs in D. regia. Our data suggest that cytomolecular analysis could be useful tool for differentiating the species within the Peltophorum clade and that comparative analyses with other species could provide new insights into the karyotypic diversification of the subfamily Caesalpinioideae.

Heterochromatin and numeric chromosome evolution in Bignoniaceae, with emphasis on the Neotropical clade Tabebuia alliance

“…(Figueredo et al, 2016), however, the heterochromatin pattern appears to be quite conserved and demonstrate only small variability among the different species. In most plant groups, however, heterochromatin patterns tend to be random and quite distinct, even among closely related species (Berjano et al, 2009;Scaldaferro et al, 2012;Grabiele et al, 2018;Van-Lume and Souza, 2018). For Bignoniaceae as a whole, three heterochromatin patterns can be seen, with the occurrence of a specific pattern for Jacarandeae (terminal CMA + blocks), conserved patterns for the diploid species of the Tabebuia alliance (two terminal CMA + blocks and 0-2 pericentromeric CMA + blocks), and a pattern of random attributions in relation to the numbers and positions of CMA + blocks in the tribe Binonieae (Cordeiro et al, 2017).…”