Differentiation of Nolana and Sclerophylax (Solanaceae) by means of heterochromatin and rDNA patterns

CHIARINI F.; LUJEA N.

New Zealand Journal of Botany

RSNZ PUBLISHING

Año: 2017 vol. 55 p. 163 - 177

0028-825X

Within Solanaceae, Nolana L. f. and Sclerophylax Miers aretwo genera that have deserved special attention because of theirrare anatomical characteristics. However, they are poorly knownfrom the cytogenetic perspective. In order to discuss theirchromosome features in an evolutionary context, classicalstaining, chromomycin A3/4′-6-diamidino-2-phenylindole (CMA/DAPI) fluorescent banding and in situ hybridisation (FISH) withprobes for the 18-5.8-26S and the 5S rDNA loci were applied toroot tips of germinating seeds. All the species presented thechromosome number 2n = 24. Karyotypes were highly symmetric,with most chromosomes being metacentric and with a maximumof three submetacentric pairs in N. divaricata. The CMA/DAPIbanding technique, assayed for the first time in Sclerophylax,showed CMA+/DAPI− bands associated with nucleolar organiserregions (NORs) in the first metacentric chromosome pair in eachspecies. The FISH technique (applied to four species ofSclerophylax and, for the first time, in one species of Nolana)showed that the 18-5.8-26S loci coincide with CMA+/DAPI− bands.Three Sclerophylax species presented two pairs of 5S signals,whereas S. adnatifolia showed three. The rDNA loci resulted asasyntenic in Sclerophylax, but were localised in the samechromosome in N. divaricata. Despite the morphologicalpeculiarities of Nolana and Sclerophylax, the chromosome numberand karyotype features are consistent with the position of the twogenera within the ?x = 12 clade?, while the number and position ofrDNA loci established the chromosome rearrangements,suggesting different evolutionary pathways with respect to theirclosest relatives, Lycium and Jaborosa.