How diverse is heterochromatin in the Caesalpinia group? Cytogenomic characterization of Erythrostemon hughesii Gagnon &
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ORIGINAL ARTICLE
How diverse is heterochromatin in the Caesalpinia group? Cytogenomic characterization of Erythrostemon hughesii Gagnon & G.P. Lewis (Leguminosae: Caesalpinioideae) Yennifer Mata‑Sucre1 · Mariela Sader1 · Brena Van‑Lume1 · Edeline Gagnon2 · Andrea Pedrosa‑Harand1 · Ilia J. Leitch3 · Gwilym P. Lewis3 · Gustavo Souza1 Received: 21 May 2020 / Accepted: 27 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Main conclusion Cytogenomic characterization of Erythrostemon hughesii reveals a heterogeneity of repeats in its subtelomeric heterochromatin. Comparative analyses with other Caesalpinia group species reveal a significant reduction in the abundance of Ty3-gypsy/Chromovirus Tekay retrotransposons during its evolution. In numerically stable karyotypes, repetitive DNA variability is one of the main causes of genome and chromosome variation and evolution. Species from the Caesalpinia group (Leguminosae) are karyotypically characterized by 2n = 24, with small chromosomes and highly variable CMA+ heterochromatin banding patterns that correlate with environmental variables. Erythrostemon hughesii differs from other species of the group examined to date for having subtelomeric C MA+ bands; this contrasts with most species in the group which have proximal bands. Here we analyse the repeatome of E. hughesii using genome skimming and chromosomal mapping approaches to characterize the identity of the most abundant repetitive elements and their physical location. The repetitive fraction of E. hughesii comprises 28.73% of the genome. The most abundant elements were retrotransposons (RT) with long terminal repeats (LTR-RT; 9.76%) and satellite DNAs (7.83%). Within the LTR-RTs, the most abundant lineages were: Ty1/copia-Ale (1%), Ty3/gypsy CRM (0.88%) and Ty3/gypsy Athila (0.75%). Using fluorescent in situ hybridization four satellite DNAs and several LTR-RT elements were shown to be present in most subtelomeric CMA+ bands. These results highlight how the repeatome in E. hughesii, a species from Oaxaca state in Mexico, is clearly distinct from Northeast Brazilian species of the Caesalpinia group, mainly due to its high diversity of repeats in its subtelomeric heterochromatic bands and low amount of LTR-RT Ty3/gypsy-Tekay elements. Comparative sequence analysis of Tekay elements from different species is congruent with a clade-specific origin of this LTR-RT after the divergence of the Caesalpinia group. We hypothesize that repeat-rich heterochromatin may play a role in leading to faster genomic divergence between individuals, increasing speciation and diversification. Keywords Cytogenetics · Genome evolution · Mobile elements · Repetitive sequences · Satellite DNA
Communicated by Anastasios Melis. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00425-020-03453-8) contains supplementary material, which is available to authorized users. * Gustavo Souza [email protected] 1
Laboratory of Plant Cytogenetics and Evoluti
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