An unusually high heterochromatin content and large genome size in the palm tree Trithrinax campestris (Arecaceae)
2012
Gaiero, P. | Mazzella, C. | Vaio, M. | Barros e Silva, A. E. | Santiñaque, F. F. | López-Carro, B. | Folle, G. A. | Guerra, M.
Trithrinax campestris (Burmeist.) Drude & Griseb., a neotropical member of tribe Cryosophileae, subfamily Coryphoideae (Arecaceae), forms small populations in the southern most extreme of the distribution for the tribe. To provide genetic information to assist its conservation, we performed detailed karyotype analysis in samples from Uruguay. The species displayed a karyotype with 2n=36, a genome size (2C=17.15±0.07pg) exceptionally high for a palm tree, and an elevated heterochromatin amount, represented by eight Chromomycin A3 (CMA) bands and numerous 4′,6-diamidino-2-phenylindole (DAPI) bands. 45S rDNA sites were found co-localising with CMA+ bands on Chromosome pairs 6, 9, 13 and 18, whereas a single pair of 5S rDNA sites was found on the proximal region of Chromosome pair 7. Its complex CMA and/or DAPI banding, together with the position of rDNA sites, allowed the identification of each chromosome pair and provided a useful tool to evaluate cytogenetic variations among populations and closely related species. Although this species maintains several karyotype similarities with its close relative T. brasiliensis, it can be promptly recognised by its DNA amount and DAPI bands. The large genome size in T. campestris is probably associated with its large blocks of heterochromatin, which represent 39% of its total chromosome length. Excluding the heterochromatin fraction, its chromosome size and 2C value become similar to those reported for most other diploid species in the family, suggesting that amplification of satellite DNA played an important role in its karyotype evolution.
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