Unzipped assemblies of polyploid root-knot nematode genomes reveal new kinds of unilateral composite telomeric repeats

Abstract

AbstractTelomeres play central roles in senescence, aging and chromosome integrity. Using ONT long read sequencing we have assembled the genomes ofMeloidogyne incognita,M. javanicaandM. arenaria, the three most devastating plant-parasitic nematodes at unparalleled contiguity. The telomeric repeat (TTAGGC)n, evolutionarily conserved in nematodes, was not found in these genomes. Furthermore, no evidence for a telomerase enzyme or for orthologs ofC. eleganstelomere-associated proteins could be found. Instead, we identified species-specific composite repeats mostly present at one end of contigs. These repeats were G-rich, oriented and transcribed, similarly to known telomeric repeats. Using FISH we confirmed these repeats were present at one single end ofM. incognitachromosomes. The discovery of a new kind of telomeric repeat in these species highlights the evolutionary diversity of chromosome protection systems despite their central roles and opens new perspectives towards the development of more specific control methods against these pests.