Biology subjects

Piulachs, M.-D.

Publications and source records attributed to Piulachs, M.-D..

6 recordsLinked to original sources

bioRxiv2026

The dynamics of piRNA expression in Blattella germanica ovaries

The cockroach Blattella germanica possesses panoistic ovaries, in which oocytes lack nurse cells and therefore need to rely on their own transcriptional activity to support embryogenesis. Ovarian development in this species involves the development of a single basal ovarian follicle (BOF) per gonadotropic cycle, a process strictly regulated by endocrine signals, primarily juvenile hormone and ecdysone, which act at both the transcriptional and translational levels. In addition, transcriptional activity in these ovaries is necessary for both regulating and genome protection, and at this level, PIWI-interacting RNAs (piRNAs) play an essential role. Although insect ovaries are known to be particularly rich in piRNAs, their function in ovary maturation is still not well defined. For this purpose, we characterize the piRNA expression dynamics across seven key developmental and reproductive stages, ranging from late nymphal instars to post-vitellogenic adults. piRNA expression in B. germanica shows coordinated fluctuations. Expression remains stable in previtellogenic ovaries, whereas vitellogenic ovaries show pronounced changes. Moreover, vitellogenic ovaries exhibit reduced piRNA diversity due to strong enrichment of a subset of highly expressed piRNAs. Our data show that although piRNAs predominantly map to transposable elements, particularly LINEs, there is a notable increase in gene-derived piRNAs toward the end of the cycle. Our results suggest regulatory roles of piRNAs in modulating both TEs and mRNAs during BOF maturation, likely related to changes in the follicular cell program.

developmental biology↗

bioRxiv2024

Capicua maintains anterior-posterior axis in Blattella germanica ovaries

The establishment of the symmetry axis is crucial for the development of all organisms. In insects, this process begins early in oogenesis with the correct distribution of the mRNAs and proteins in the oocyte. One protein that plays a role in organizing this distribution is the transcription factor Capicua (Cic). Cic has been studied in the context of oogenesis and embryonic development in Drosophila melanogaster. It is maternally expressed, begins essential for establishing the dorsoventral axis, and functions as a transcriptional repressor. Although the Cic sequences are conserved across species, their function in other types of insect ovaries is still little known. We wondered whether the function of Cic in insects has been maintained through evolution despite the ovary type or if it has been modified in parallel to the ovary evolution. To address this, we studied the Cic function in a phylogenetically basal insect, the cockroach Blattella germanica, a species with panoistic ovaries. Our findings show that B. germanica Cic is essential for oocyte development and the maturation of ovarian follicles. A loss of Cic function leads to disrupted cytoskeletal organization, defects in anterior-posterior polarity, and compromised follicle integrity. The conservation and functional divergence of Cic across different species suggest evolutionary adaptations in the mechanisms of insect oogenesis.

developmental biology↗

bioRxiv2024

A piRNA regulating oogenesis and embryo development in cockroaches

PIWI-interacting RNAs (piRNAs) are small non-coding RNAs, typically 26 to 31 nucleotides long, originally known for silencing transposable elements (TEs), thus maintaining genomic stability. However, recent research has revealed additional regulatory roles. In this study, we investigate piRNA-305221, which is highly expressed in the ovaries of the German cockroach, Blattella germanica, to understand its involvement in oogenesis and reproduction. piRNA-305221 is found in germinal and somatic cells during the gonadotropic cycle, and is maternally provided to the egg. Its expression correlates with critical ovarian events, such as endoreplication and follicular cell differentiation, suggesting regulatory functions beyond TE silencing. Functional knockdown using antisense oligonucleotides (ASOs) resulted in delayed oviposition, malformed oothecae, and reduced offspring viability. Gene expression analysis revealed that the reduction of piRNA-305221 decreased shade mRNA levels, impairing the conversion of ecdysone to its active form, 20-hydroxyecdysone, and a concomitant increase in expression of upstream steroidogenic genes (spook, phantom, disembodied). These results indicate that piRNA-305221 may regulate steroidogenesis through direct or indirect control of mRNA targets. This study highlights the broader regulatory functions of piRNAs and demonstrates the utility of ASO-mediated knockdown in functional studies of non-coding RNAs.

developmental biology↗

bioRxiv2021

siRNA enrichment in Argonaute 2-depleted Blattella germanica

BackgroundRNA interference (RNAi) is a cellular mechanism used to fight various threats, including transposons, aberrant RNA, and some types of viruses. It relies on dsRNA detection and, through a mechanism involving Dicer-2 (Dcr-2) and Argonaute 2 (AGO2), together with a small RNA fragment (siRNA) as a complementary guide, binds to an RNA and cleaves it. MethodsUsing the cockroach Blattella germanica as a model, we examined AGO2 activity by depleting its mRNA levels using RNAi and analyzing the phenotypes produced. ResultsSilencing AGO2 expression had no remarkable effect on nymphal development or reproduction. dsRNA treatment triggered an immediate and transitory increase in AGO2 expression, independently of Dcr-2 action. In addition, we analyzed the siRNAs generated after injecting a heterologous dsRNA in control and AGO2-depleted animals. The results revealed that siRNAs were distributed non-uniformly along the dsRNA sequence. In AGO2-depleted animals, the proportion of 22 nucleotide reads was higher and accumulations of reads appeared in areas less well-represented in the controls. We also detected a slight preference for cytosine as the first nucleotide in controls to be lost in AGO2-depleted individuals. Conclusions/General significanceThe siRNAs produced from a dsRNA are heterogeneously distributed along the length of the dsRNA and this arrangement depends on the sequence. AGO2 exerts its role as nuclease on the siRNA duplexes independently of its action on the homologous mRNA. This study sheds light on an extremely useful process for reverse genetics in laboratories, in addition to the design of more effective, specific, and eco-friendly pest-control strategies. Highlights- RNA interference is used to fight cellular threats including transposons and viruses - Silencing AGO2 in Blattella germanica does not affect development or reproduction - siRNA distribution along the dsRNA sequence is non-uniform and sequence dependent - AGO2 depletion increased the proportion of 22 nt reads in certain areas

physiology↗

bioRxiv2019

Different roles of eye absent in the basal ovarian follicle and germarium of developing cockroach ovaries

Eyes absent (Eya), is a protein structurally conserved from hydrozoans to humans, for which two basic roles have been reported: it can act as a transcription cofactor and as a protein tyrosine phosphatase. Eya was discovered in the fly Drosophila melanogaster in relation to its function in eye development, and the same function was later reported in other insects. Eya is also involved in insect oogenesis, although studies in this sense are limited to D. melanogaster, which has meroistic ovaries, and where eya mutations abolish gonad formation. In the present work we studied the function of eya in the panoistic ovary of the cockroach Blattella germanica. We show that eya is essential for correct development of panoistic ovaries. In B. germanica, eya acts at different level and in a distinct way in the germarium and the vitellarium. In the germarium, eya contributes to maintain the correct number of somatic and germinal cells by regulating the expression of steroidogenic genes in the ovary. In the vitellarium, eya facilitates follicle cells proliferation and contributes to regulate the cell program, in the context of basal ovarian follicle maturation. Thus, eya-depleted females of B. germanica arrest the growth and maturation of basal ovarian follicles and become sterile.

developmental biology↗

bioRxiv2017

Hemimetabolous genomes reveal molecular basis of termite eusociality

Around 150 million years ago, eusocial termites evolved from within the cockroaches, 50 million years before eusocial Hymenoptera, such as bees and ants, appeared. Here, we report the first, 2GB genome of a cockroach, Blattella germanica, and the 1.3GB genome of the drywood termite, Cryptotermes secundus. We show evolutionary signatures of termite eusociality by comparing the genomes and transcriptomes of three termites and the cockroach against the background of 16 other eusocial and non-eusocial insects. Dramatic adaptive changes in genes underlying the production and perception of pheromones confirm the importance of chemical communication in the termites. These are accompanied by major changes in gene regulation and the molecular evolution of caste determination. Many of these results parallel molecular mechanisms of eusocial evolution in Hymenoptera. However, the specific solutions are remarkably different, thus revealing a striking case of convergence in one of the major evolutionary transitions in biological complexity.

evolutionary biology↗