RNAi-Mediated Knock-Down of transformer and transformer 2 to Generate Male-Only Progeny in the Oriental Fruit Fly, Bactrocera dorsalis (Hendel)

Abstract

The transformer (tra) gene appears to act as the genetic switch that promotes female development by interaction with the transformer2 (tra-2) gene in several dipteran species including the Medfly, housefly and Drosophila melanogaster. In this study, we describe the isolation, expression and function of tra and tra-2 in the economically important agricultural pest, the oriental fruit fly, Bactrocera dorsalis (Hendel). Bdtra and Bdtra-2 are similar to their homologs from other tephritid species. Bdtra demonstrated sex-specific transcripts: one transcript in females and two transcripts in males. In contrast, Bdtra-2 only had one transcript that was common to males and females, which was transcribed continuously in different adult tissues and developmental stages. Bdtra-2 and the female form of Bdtra were maternally inherited in eggs, whereas the male form of Bdtra was not detectable until embryos of 1 and 2 h after egg laying. Function analyses of Bdtra and Bdtra-2 indicated that both were indispensable for female development, as nearly 100% males were obtained with embryonic RNAi against either Bdtra or Bdtra-2. The fertility of these RNAi-generated males was subsequently tested. More than 80% of RNAi-generated males could mate and the mated females could lay eggs, but only 40-48.6% males gave rise to progeny. In XX-reversed males and intersex individuals, no clear female gonadal morphology was observed after dissection. These results shed light on the development of a genetic sexing system with male-only release for this agricultural pest.

The transformer2 gene of the pumpkin fruit fly, Bactrocera tau (Walker), functions in sex determination, male fertility and testis development

“…In this study, the Btau‐tra2 gene was identified and we found that the structure of this gene was similar to those of other tephritid insects (Pane et al, ; Lagos et al, ; Ruiz et al, ; Schetelig & Handler, ; Morrow et al, ; Liu et al, ; Peng et al, ). On the contrary, Btau‐tra2 was multi‐transcribed into three transcript variants instead of only one transcript as occurs with the tra2 genes of other tephritids and M. domestica (Salvemini et al, ; Sarno et al, ; Schetelig & Handler, ; Liu et al, ). To date, tra2 genes that are transcribed into multi‐transcripts have been found in other insect groups; for example, three transcripts were found to be produced in T. castaneum (Shukla & Palli, ), four in D. melanogaster , Aedes aegypti (Amrein et al, ; Liu et al, ) and N. vitripennis (Geuverink et al, ), six in Ap.…”

“…Moreover, in the embryonic RNAi experiment, the surviving flies developing from Ba. tau embryos injected with Btau ‐ tra2 dsRNA showed a strong male‐biased sex ratio (70%), similar to those of previous reports (90% male‐biased sex ratio) about other insects (Burghardt et al, ; Salvemini et al, ; Sarno et al, ; Schetelig & Handler, ; Liu et al, ). The strong male sex bias may be due to the requirement of Btau‐tra2 for female sexual development or to this gene causing female lethality.…”

Efeitos do silenciamento gênico de transformer-2 a partir da aplicação de RNAi parental em Anastrepha sp.1 affinis fraterculus (Diptera, Tephritidae)

“…Existe a possibilidade de a aplicação de dsRNA de tra-2 junto com dsRNA de tra levar a produção de uma progênie com uma frequência ainda maior de machos, como já testado em outras moscasdas-frutas através de injeção no embrião LIU et al, 2015), sendo que nesses casos a frequência de machos chegou próxima a 100%.…”

“…Outro efeito comum relatado nesses trabalhos foi o fato de esses pseudomachos apresentarem as estruturas sexuais internas com alterações, como alterações no grau de desenvolvimento das gônadas de um mesmo indivíduo (SARNO et al, 2010;LIU et al, 2015), podendo inclusive ser assimétricas, e a presença de estruturas sexuais internas de machos e de fêmeas em mosaico (SARNO et al, 2010). Além disso, detectou-se que em…”

“…Anastrepha suspensa (SACCONE et al, 2007;SALVEMINI et al, 2009;SARNO et al, 2010;LIU et al, 2015), sua utilização é bastante improvável. Isso por que a técnica de injeção de dsRNA diretamente nos embriões desses tefritídeos além de consistir em uma metodologia trabalhosa resulta em uma altíssima mortalidade ao procedimento:…”