Tergal and pleural structures contribute to the formation of ectopic prothoracic wings in cockroaches

Wings were a fundamental morphological innovation for the adaptive radiation of insects, the most diversified group among all animals. Pterygote insects have two pairs of wings, the mesothoracic (T2) forewings and the metathoracic (T3) hindwings, whereas the prothorax (T1) is wingless. Using RNA interference approaches, we have found that the gene Sex combs reduced (Scr) determines the wingless identity of T1 in the cockroach Blattella germanica. Interference of Scr triggers the formation of ectopic wing structures in T1, which are formed from the expansion of the latero-posterior region of the pronotum, along with a contribution of the epimeron, a pleurite of T1. These data support the theory of a dual origin for insect wings, from pronotal (tergal origin theory) and pleural (pleural origin theory) structures and genes.Support for this research was provided to X.B. by the Spanish Ministry of Science and Innovation (grant no. CGL2008-03517/BOS) and Ministry of Economy and Competitiveness (grant CGL2012-36251 and CGL2015-64727- P, including FEDER funds) and by the Catalan Government, AGAUR (2014 SGR 619). M.E.N. was awarded a post-doctoral fellowship by the Fundação de Amparo à Pesquisa do Estado de São Paulo, Brazil (FAPESP 2012/15397-0)

Dignoptinus, a new genus for fossil Dignomus regiomontanus Alekseev from Eocene Baltic amber, and new status for Bruchoptinus Reitter and Pseudoptinus Reitter (Coleoptera: Ptinidae)

The holotype of Dignomus regiomontanus Alekseev, 2014, from the Eocene Baltic amber (Tertiary, Paleogene), is re-examined and re-described. Dignoptinus gen. nov. is proposed to place this species. Bruchoptinus Reitter, 1884, and Pseudoptinus Reitter, 1884, described as subgenera of Ptinus Linnaeus, 1767, are the closest relatives of the new fossil genus. These two subgenera are proposed as independent genera: Bruchoptinus Reitter, 1884 stat. nov. and Pseudoptinus Reitter, 1884 stat. nov. Forty-four new combinations for the species of these genera are proposed

Chorion formation in panoistic ovaries requires windei and trimethylation of histone 3 lysine 9

Epigenetic modifications play key roles in transcriptional regulation. Trimethylation of histone 3 lysine 9 (H3K9me3) is one of the most widely studied histone post-translational modifications, and has been linked to transcriptional repression. In Drosophila melanogaster, Windei is needed for H3K9me3 in female germ line cells. Here, we report the occurrence of a D. melanogaster Windei (Wde) ortholog in the ovary of the hemimetabolous insect Blattella germanica, which we named BgWde. Depletion of BgWde by RNAi reduced H3K9me3 in follicular cells, which triggered changes in transcriptional regulation that led to the prevention of chorion gene expression. In turn, this impaired oviposition (and the formation of the ootheca) and, therefore, prevented reproduction. Windei and H3K9me3 have already been reported in follicular cells of D. melanogaster, but this is the first time that the function of these modifications has been demonstrated in the said cells. This is also the first time that an epigenetic marker is reported as having a key role in choriogenesis.Support for this research was provided by the Spanish Ministry of Science and Innovation (Grant nos. BFU2011-22404 to MDP and CGL2008-03517/BOS to XB), by the CSIC (Grant no. 2010TW0019, Formosa program) and from FEDER funds to XB. Support from Generalitat de Catalunya (Grant no. 2005 SGR 00053) and LINC-Global is also gratefully acknowledged. AH received a pre-doctoral research grant (JAE-LINCG program) from the CSIC, and The European Social Fund (ESF)

Chorion formation in panoistic ovaries requires windei and trimethylation of histone 3 lysine 9

Epigenetic modifications play key roles in transcriptional regulation. Trimethylation of histone 3 lysine 9 (H3K9me3) is one of the most widely studied histone post-translational modifications, and has been linked to transcriptional repression. In Drosophila melanogaster, Windei is needed for H3K9me3 in female germ line cells. Here, we report the occurrence of a D. melanogaster Windei (Wde) ortholog in the ovary of the hemimetabolous insect Blattella germanica, which we named BgWde. Depletion of BgWde by RNAi reduced H3K9me3 in follicular cells, which triggered changes in transcriptional regulation that led to the prevention of chorion gene expression. In turn, this impaired oviposition (and the formation of the ootheca) and, therefore, prevented reproduction. Windei and H3K9me3 have already been reported in follicular cells of D. melanogaster, but this is the first time that the function of these modifications has been demonstrated in the said cells. This is also the first time that an epigenetic marker is reported as having a key role in choriogenesis.Support for this research was provided by the Spanish Ministry of Science and Innovation (Grant nos. BFU2011-22404 to MDP and CGL2008-03517/BOS to XB), by the CSIC (Grant no. 2010TW0019, Formosa program) and from FEDER funds to XB. Support from Generalitat de Catalunya (Grant no. 2005 SGR 00053) and LINC-Global is also gratefully acknowledged. AH received a pre-doctoral research grant (JAE-LINCG program) from the CSIC, and The European Social Fund (ESF)

Comparative analysis of miRNA expression during the development of insects of different metamorphosis modes and germband types

BACKGROUND: Do miRNAs contribute to specify the germ-band type and the body structure in the insect embryo? Our goal was to address that issue by studying the changes in miRNA expression along the ontogeny of the German cockroach Blattella germanica, which is a short germ-band and hemimetabolan species. RESULTS: We sequenced small RNA libraries representing 11 developmental stages of B. germanica ontogeny (with especial emphasis on embryogenesis) and the changes in miRNA expression were examined. Data were compared with equivalent data for two long germ-band holometabolan species Drosophila melanogaster and Drosophila virilis, and the short germ-band holometabolan species Tribolium castaneum. The identification of B. germanica embryo small RNA sequences unveiled miRNAs not detected in previous studies, such as those of the MIR-309 family and 54 novel miRNAs. Four main waves of miRNA expression were recognized (with most miRNA changes occurring during the embryonic stages): the first from day 0 to day 1 of embryogenesis, the second during mid-embryogenesis (days 0-6), the third (with an acute expression peak) on day 2 of embryonic development, and the fourth during post-embryonic development. The second wave defined the boundaries of maternal-to-zygotic transition, with maternal mRNAs being cleared, presumably by Mir-309 and associated scavenger miRNAs. CONCLUSION: miRNAs follow well-defined patterns of expression over hemimetabolan ontogeny, patterns that are more diverse during embryonic development than during the nymphal stages. The results suggest that miRNAs play important roles in the developmental transitions between the embryonic stages of development (starting with maternal loading), during which they might influence the germ-band type and metamorphosis mode.This work was supported by the Spanish Ministry of Economy and Competitiveness (grants CGL2012–36251 and CGL2015–64727-P to X.B.), the Spanish Ministry of Science and Innovation (grants BFU2011–22404 and CGL2016–76011-R to M.D.P.) and the Catalan Government (2014 SGR 619). It also received financial assistance from the European Fund for Economic and Regional Development (FEDER funds to X.B. and M.D.P.