Unzipped genome assemblies of polyploid root-knot nematodes reveal new kinds of unilateral composite telomeric repeats

Abstract

Using long read sequencing we have assembled and unzipped the genomes of Meloidogyne incognita, M. javanica and M. 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 of C. elegans telomere-associated proteins could be found. Instead, we identified species-specific composite repeats enriched at one extremity of contigs. These repeats were G-rich, oriented and transcribed, similarly to known telomeric repeats. Using fluorescent in situ hybridization, we confirmed these repeats had telomeric location at one single end of M. incognita chromosomes. The discovery of a new kind of telomeric repeat in these species highlights the evolutionary diversity of chromosome protection systems despite their central roles in senescence, aging and chromosome integrity and opens new perspectives towards the development of more specific control methods against these pests.