Chromosome evolution in Passiflora: from chromosome numbers to single-copy and repetitive DNA sequences

SADER M. A.1, DIAS Y.1, MUNHOZ C.2, PENHA H.3, AMORIM B. S.; COSTA L.1, VAIO M.5, CAUZ-SANTOS L. A.2, DORNELAS M.; BERGÈS H.7, MELO N. F.8, SOUZA G.1,; VIEIRA M. L.2, PEDROSA-HARAND A.1

Praga

Congreso; 22nd International Chromosome Conference; 2018

Passiflora L. has around 500 species mainly distributed in the Neotropics. The genus shows different basicchromosome numbers associated to different subgenus (x = 6, 9 and 12) and high variation in genome size. In orderto investigate karyotype evolution in this group, we generated a time-calibrated phylogeny including 102 taxa withknown chromosome number and tested the relative importance of polyploidy and dysploidy. We establishedcomparative cytogenetic maps using BACs (bacterial artificial chromosomes) and ribosomal DNA (rDNA) as probes influorescent in situ hybridization (FISH) to investigate conservation of synteny among species with n = 9. We alsogenerated low-coverage, whole-genome data from species with different genome sizes to investigate composition andabundance of its repetitive DNA with RepeatExplorer and Satminer. The ancestral basic chromosome number of thegenus was x = 6, and a recent diversification in the Passiflora subgenus (~25.94 Mya, Miocene) correlated to genomesize increase and chromosome change from n = 6 to n = 9 by ascending dysploidy. Single-copy BACs suggestconservation of synteny among species with n = 9 (P. edulis, P. alata and P. watsoniana), although an extra 35S DNArsite was detected in P. watsoniana. Repeat content differed markedly between P. quadrangularis (2n = 18; 2C = 2.680pg), P. cincinnata (2n = 18; 2.202 pg) and P. organensis (2n = 12; 0.404 pg). While P. quadrangularis and P.cincinnata (Passiflora subgenus) showed high proportions of Ty1-copia LTR-retrotransposons from the Angelalineage, it was not among the most abundant clusters in the small P. organensis genome (Decaloba subgenus). On theother hand, satellite DNA (satDNA) diversity and abundance was higher in P. organensis. Altogether, structuralrearrangements that caused dysploidy to n = 9 in the Passiflora subgenus did not further reshaped genomes duringits diversification, but some transposable elements have contributed to increased genome size.