Cestrum strigilatum (Ruiz & Pavón, 1799) B chromosome shares repetitive DNA sequences with A chromosomes of different Cestrum (Linnaeus, 1753) species

Abstract

Species of Cestrum (Linnaeus, 1753) have shown large diversity in the accumulation and distribution of repetitive DNA families, and B chromosomes have been described in seven species. Some types of repetitive DNA were identified in A and B chromosomes in species of this plant group, such as AT-rich SSR, 35S and 5S rDNA, C-Giemsa and C-CMA/DAPI bands and retrotransposons. To increase our understanding of the relationships of A and B chromosomes, the B of C. strigilatum Ruiz & Pavón, 1799 was microdissected, amplified and hybridized in situ against chromosomes of this species, and in six other species of this genus. FISH signals were observed in whole the B of C. strigilatum, including stretches of A chromosomes, as well as in some A chromosomes of all tested species. A strong FISH signal was seen adjacent to the 5S rDNA in the proximal region of pair 8 of all species and, due to this, we have searched for 5S rDNA fragments in the microdissected B chromosome. PCR and sequencing data evidenced 5S rDNA deletion along evolutionary pathways of the B of C. strigilatum. Although A and B chromosomes displayed redundancy in the repetitive DNA families in different species, the B of C. strigilatum seemed to differ from those Bs of other Cestrum species by the loss of rDNA fractions. A possible origin of Bs in Cestrum was discussed.

Evolution of Plant B Chromosome Enriched Sequences

“…In C. intermedium and C. strigilatum , besides C-Giemsa+/CMA+/DAPI+ bands [ 73 ], the Bs also display hybridization signals with the Gypsy-like retrotransposon probe but not with rDNA probes [ 73 ]. Some types of repetitive DNA were identified in A and B chromosomes in C. strigilatum and in species of this plant group, such as AT-rich SSR, 35S and 5S rDNA, C-Giemsa and C-CMA/DAPI bands and retrotransposons [ 77 ].…”

Comprehending the dynamism of B chromosomes in their journey towards becoming unselfish

“…Chromosome painting of seven B chromosomes in two fish species belonging to the genus Astyanax with 18S ribosomal DNA (rDNA), H1 histone genes and As51 satellite DNA (AC) 15 microsatellite-based probes has shown that all Bs shared homologous DNA sequences not only amongst them but also with a variable number of A chromosomes in each species indicating a common origin for all seven Bs analysed ( Duílio et al, 2016 ). The B chromosome in Cestrum strigilatum differs from the B chromosome of the other six species as it lacks the 5S rDNA sequence, which either might have been lost during B chromosome differentiation in this species or the B chromosome has evolved independently in this species ( Vanzela et al, 2017 ).…”

Evolution of Plant B Chromosome Enriched Sequences

“…In C. intermedium and C. strigilatum, besides C-Giemsa+/CMA+/DAPI+ bands [66], the Bs also display hybridization signals with the Gypsy-like retrotransposon probe but not with rDNA probes [66]. Some types of repetitive DNA were identified in A and B chromosomes in C. strigilatum and in species of this plant group, such as AT-rich SSR, 35S and 5S rDNA, C-Giemsa and C-CMA/DAPI bands and retrotransposons [70].…”