Holocentric chromosomes have been reported in at least 768 species both in animal and plant kingdoms and appeared 12 times during evolution. The spread of the centromere on the whole length of chromosome arms has several consequences on functional organization of the genome in term of evolution rate, distribution of transposable elements (TE) and of chromatin domains, the need for adaptations during meiosis. From the analysis of the nematode C. elegans, the best characterized holocentric model, kinetochore protein composition seemed conserved between monocentrics and holocentrics. However, recent studies highlighted the absence of the ubiquitous histone H3 like CENP-A in several orders of holocentric insects including Lepidoptera as shown in the silkworm, showing diversity in kinetochore composition of holocentric species. In this talk, I will present our attempts to understand the functional organization of a major pest of agriculture, Spodoptera frugiperda through i) characterization of centromeric protein homologs by RNA interference in a cell line ii) annotation of TE elements in various genome assemblies as well as piRNAs, their non-coding RNA regulators iii) analysis of heterochromatin domains in vitro and in vivo.