B chromosomes and their repetitive DNA composition in Cestrum nocturnum (Solanaceae)

MALDONADO, L.; YI-TZU, K.; SADER, M.; URDAMPILLETA J.D.

Rio Cuarto

Congreso; LI Congreso Argentino de Genética; 2023

Sociedad Argentina de Genética

B chromosomes (Bs) are additional components of the genome found in more than 15% of plant species. They are made up mostly of non-coding repetitive DNA, and their presence can affect the phenotype, being unfavorable in high number. In Cestrum nocturnum L., the number of Bs varies from 0 to 13, between and within individuals, possibly due to meiotic and/ or mitotic instability. To understand the repetitive composition of Bs, the genome of two individuals of C. nocturnum were sequenced, one with Bs and other one without Bs. The results of the analysis showed that almost 60% of the genome is made up of repetitive DNA and those families of repetitive DNA with a proportion greater than 0,540% were considered enriched in the sample with Bs. The results of a comparative analysis between the two genomes showed that Bs of C. nocturnum are mostly enriched in satellite repeats, rDNA and Ty3-gypsy transposable elements, which are probably derived from A complement repeat sequences. Within the repetitive DNA enriched in the sample with Bs, we found transposable elements Ty3-gypsy/Tekay (CL283-0,558%) and Ty3-gypsy/ Retand (CL251-0,541%), satellite DNA (Cnoc_ sat01_32-0,550%, Cnoc_sat03_78-0,549%, Cnoc_ sat04_180-0,546%, Cnoc_sat07_51-0,547% and Cnoc_sat10_48-0,557%) and ribosomal DNA 35S (CL117-0.548% and CL216-0.544%) and 5S (CL218 0.571%). The distribution of the Bs-enriched repeats were compared in A and B chromosomes by FISH mapping, with probes labeled directly (FITC and TRICT). The neutral nature of Bs could be one of the basic principles of the accumulation of repetitive sequences in the genome.