Detection of telomeric sequences and ribosomal RNA genes in holokinetic chromosomes of five jumping plant-lice species: First data on the superfamily Psylloidea (Hemiptera: Sternorrhyncha)

Abstract

Fluorescence in situ hybridization (FISH) is a technique used to determine the chromosomal position of DNA and RNA probes. The present study contributes to knowledge on jumping plant-lice genomes by using FISH with 18S rDNA and telomeric (TTAGG)n probes on meiotic chromosomes of Psylla alni (2n = 24 + X), Cacopsylla mali (2n = 22 + neo-XY and 20 + neo-X1X2Y), C. sorbi (2n = 20 + neo-XY), Baeopelma foersteri (2n = 14 + X), and Rhinocola aceris (2n = 10 + X). This is the first study that has used FISH on the hemipteran superfamily Psylloidea. We found that the chromosomes of all studied species contain the insect-type telomere motif, (TTAGG)n. In C. mali and C. sorbi, the neo-sex chromosomes originating from autosome-sex chromosome fusions showed no interstitially located clusters of TTAGG repeats, suggesting their loss or inactivation. Similarly, no interstitial (TTAGG)n clusters were detected in an extremely large autosome pair of B. foersteri that most likely originated from a fusion of at least five ancestral chromosome pairs. Clusters of 18S rDNA were detected on the fused and second largest autosome pairs of B. foersteri and on one of the large autosome pairs of the remaining species. In C. mali and B. foersteri, the rDNA clusters were shown to coincide with the NORs as detected by the AgNOR method. Finally, we speculate, based on the obtained FISH markers, on the mechanisms of karyotype evolution of psylloid species differing in chromosome numbers and sex chromosome systems.

Keywords

• hemiptera
• sternorrhyncha
• psylloidea
• psyllidae
• aphalaridae
• telomeric repeats
• 18s rdna
• fish
• nor