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Mariner-like elements (MLEs) are widespread Class II transposable elements in insects that are subdivided into several subfamilies. In the current study, we carried out in silico analysis and in vitro experiments to identify MLEs belonging to the irritans subfamily in two cecidomyiid flies, Mayetiola destructor and M. hordei. In silico investigation of M. destructor genome allowed the identification of 25 irritans-like elements, which were mostly defective due to several mutations. These defective forms might be the remnants of active elements that ancestrally invaded the host genome. Structural analyses, including signature motifs and transposase-encoding ORFs, revealed structural heterogeneity and the presence of two full length copies. Five consensuses, reflecting the probable evolutionary groups of these elements, were constructed, based on a similarity matrix. The first consensus (Maymarcons1) belonged to Himar1-like elements reported in other insects, while the remaining four (Maymarcons2 to 5) seemed to be more specific to Cecidomyiidae. Moreover, the presence of elements belonging to the Maymarcons4 group was ascertained by PCR amplification, in both Mayetiola species, and was further identified in the Transcriptome Shotgun Assembly (TSA) of the orange fly, Sitodiplosis mosellana (Cecidomyiidae), suggesting the existence of irritans elements within the Cecidomyiidae, which were derived from an ancestral species by vertical transmission during speciation. On the other hand, consensuses that are specific to M. destructor could be derived from a more recent invasion. This study suggests that both M. destructor and M. hordei genomes have been invaded by irritans elements many times with at least two different evolutionary histories.

In several parts of the world, important yield losses are caused to Faba bean due to attack by the black bean aphid Aphis fabae Scopoli. Although resistance could be a good alternative to chemical control, its genetic basis is still largely unknown; and its phenotypic expression is still poorly described, making crucial the permanent evaluation of genetic resources available in different countries; together with using adequate agronomic parameters and statistical inference. In this study, two Faba bean collections provided by Faba bean breeding programs of Tunisia and Spain were evaluated for resistance to A. fabae during two consecutive years in the field, based on infestation rates and three yield parameters: number of grains (NG), weight of grains (WG) and weight of pods (WP). Principal components analysis (PCA) showed that the most effective parameters contributing to response variation were the weight of pods (WP) and the number of grains (NG). Genotypes were grouped based on clustering patterns inferred from PCA and UPGMA, both showing the existence of two distinct groups: a resistant group characterized by high WP; and in most cases high NG values; and a susceptible group characterized by a low WP; and in most cases a low NG + WG. Furthermore, tolerance to infestation was identified in one genotype from the Spanish collection. Our results demonstrate that WP is the most reliable parameter for resistance selection; and that the genotypes V1, V9 and V16 from the Tunisian collection and V2e and V7e from the Spanish one should be exploited for their resistance potential.

Proteins containing nucleotide binding sites (NBS) encoded by plant resistance genes play an important role in the response of plants to a wide array of pathogens. In this paper, an in silico search was conducted in order to identify and characterize members of NBS-encoding gene family in the tribe of Triticeae. A final dataset of 199 sequences was obtained by four search methods. Motif analysis confirmed the general structural organization of the NBS domain in cereals, characterized by the presence of the six commonly conserved motifs: P-loop, RNBS-A, Kinase-2, Kinase-3a, RNBS-C and GLPL. We revealed the existence of 11 distinct distribution patterns of these motifs along the NBS domain. Four additional conserved motifs were shown to be significantly present in all 199 sequences. Phylogenetic analyses, based on genetic distance and parsimony, revealed a significant overlap between Triticeae sequences and Coiled coil-Nucleotide binding site-Leucine rich repeat (CNL)-type functional genes from monocotyledons. Furthermore, several Triticeae sequences belonged to clades containing functional homologs from non Triticeae species, which has allowed for these sequences to be functionally assigned. The findings reported, in this study, will provide a strong groundwork for the isolation of candidate R-genes in Triticeae crops and the understanding of their evolution.