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.
Highlights
The Psylloidea, or jumping plant-lice (Sternorrhyncha), are small sap-sucking hemipteran insects distributed worldwide
The present paper provides the first cytogenetic knowledge on holokinetic chromosomes of Psylloidea studied with Fluorescence in situ hybridization (FISH) technology
The male karyotype 2n = 24 + X of Psylla alni is known to be a conserved pattern found in most species and is considered to be evolutionarily ancestral for Psylloidea (MaryańskaNadachowska, 2002)
Summary
The Psylloidea, or jumping plant-lice (Sternorrhyncha), are small sap-sucking hemipteran insects distributed worldwide. They feed on the phloem of vascular plants, with most species developing exclusively on dicotyledonous plants. Approximately 175 psylloid species belonging to 55 genera of all families, except for the small family Phacopteronidae, have been analyzed cytogenetically (MaryańskaNadachowska & Głowacka, 2005; Labina et al, 2007; Nokkala et al, 2008, 2013, 2017; for other references see Maryańska-Nadachowska, 2002). Jumping plant-lice are characterized by fairly uniform karyotypes with regard to both chromosome number, which is predominantly 25/26 (male/female), and sex chromosome system, which is of an X(0)/XX (male/female) type in more than 95% of species.
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