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Intergenerational Pathogen-Induced Diapause in Caenorhabditis elegans Is Modulated by mir-243.
The interaction and communication between bacteria and their hosts modulate many aspects of animal physiology and behavior. Dauer entry as a response to chronic exposure to pathogenic bacteria in Caenorhabditis elegans is an example of a dramatic survival response. This response is dependent on the RNA interference (RNAi) machinery, suggesting the involvement of small RNAs (sRNAs) as effectors. Interestingly, dauer formation occurs after two generations of interaction with two unrelated moderately pathogenic bacteria. Therefore, we sought to discover the identity of C. elegans RNAs involved in pathogen-induced diapause. Using transcriptomics and differential expression analysis of coding and long and small noncoding RNAs, we found that mir-243-3p (the mature form of mir-243) is the only transcript continuously upregulated in animals exposed to both Pseudomonas aeruginosa and Salmonella enterica for two generations. Phenotypic analysis of mutants showed that mir-243 is required for dauer formation under pathogenesis but not under starvation. Moreover, DAF-16, a master regulator of defensive responses in the animal and required for dauer formation was found to be necessary for mir-243 expression. This work highlights the role of a small noncoding RNA in the intergenerational defensive response against pathogenic bacteria and interkingdom communication.IMPORTANCE Persistent infection of the bacterivore nematode C. elegans with bacteria such as P. aeruginosa and S. enterica makes the worm diapause or hibernate. By doing this, the worm closes its mouth, avoiding infection. This response takes two generations to be implemented. In this work, we looked for genes expressed upon infection that could mediate the worm diapause triggered by pathogens. We identify mir-243-3p as the only transcript commonly upregulated when animals feed on P. aeruginosa and S. enterica for two consecutive generations. Moreover, we demonstrate that mir-243-3p is required for pathogen-induced dauer formation, a new function that has not been previously described for this microRNA (miRNA). We also find that the transcriptional activators DAF-16, PQM-1, and CRH-2 are necessary for the expression of mir-243 under pathogenesis. Here we establish a relationship between a small RNA and a developmental change that ensures the survival of a percentage of the progeny
Taxonomy, phylogeny and distribution of the genus Steromapedaliodes sensu novo in the Cordillera de M茅rida, Venezuela (Lepidoptera: Nymphalidae: Satyrinae: Satyrini)
International audienceWe revise the taxonomy and phylogeny of the genera Steromapedaliodes Forster, 1964 and Redonda Adams & Bernard, 1981, both subparamo and paramo endemics of the Cordillera de M茅rida (Venezuela). Redonda is hereby synonymized with Steromapedaliodes, a decision supported by a comparative study evidencing several synapomorphies of both genera in external characters and genitalia, and the lack of salient synapomorphies specific to each genus in morphological, biogeographical and ecological traits. Also, Steromapedaliodes mavarezi sp.n. presents several intermediate characters in relation to the species traditionally assigned to Redonda and Steromapedali odes. Furthermore, a molecular phylogenetic analysis with the use of one nuclear and three mitochondrial markers shows no support for reciprocal monophyly between Redonda and Steromapedaliodes but provides strong support for the monophyly of Steromapedaliodes sensu novo, with low levels of genetic divergence among species. Two new species of Steromapedaliodes are described, S. kahlua sp.n. and S. mavarezi sp.n. We describe five new subspecies of S. albonotata (Godman, 1905), two of S. albarregas (Adams & Bernard, 1981), and the females of S. empetrus empetrus (Thieme, 1905) comb.n. and S. lathraia Viloria & Camacho, 2015 comb.n. Several new status and synonymies are also established. Accordingly, Steromapedaliodes contains nine species, including four that are highly polytypic. Adult Seromapedaliodes share several striking morphological and genital similarities with another north Andean paramo genus, Dangond Adams & Bernard, 1979 from the Sierra de Perij谩. However, our phylogenetic analysis shows that the two are not sister taxa and that they originated in separate clades of the speciose Pedaliodes complex. This shows that convergence in butterflies affects not only external morphology traits directly correlated with habitat selection but also genitalia. Steromapedaliodes has undergone an adaptive radiation in geographically isolated paramos resulting in unusual morphological and behavioural characters such as brachyptery and flightlessness of the females of S. bordoni Viloria & Pyrcz, 2003 comb.n. and S. empetrus (Thieme, 1905) comb.n., a unique adaptation among the world's butterflies