Maternal provision of non‐sex‐specific transformer messenger RNA in sex determination of the wasp Asobara tabida

In many insect species maternal provision of sex‐specifically spliced messenger RNA (mRNA) of sex determination genes is an essential component of the sex determination mechanism. In haplodiploid Hymenoptera, maternal provision in combination with genomic imprinting has been shown for the parasitoid Nasonia vitripennis, known as maternal effect genomic imprinting sex determination (MEGISD). Here, we characterize the sex determination cascade of Asobara tabida, another hymenopteran parasitoid. We show the presence of the conserved sex determination genes doublesex (dsx), transformer (tra) and transformer‐2 (tra2) orthologues in As. tabida. Of these, At‐dsx and At‐tra are sex‐specifically spliced, indicating a conserved function in sex determination. At‐tra and At‐tra2 mRNA is maternally provided to embryos but, in contrast to most studied insects, As. tabida females transmit a non‐sex‐specific splice form of At‐tra mRNA to the eggs. In this respect, As. tabida sex determination differs from the MEGISD mechanism. How the paternal genome can induce female development in the absence of maternal provision of sex‐specifically spliced mRNA remains an open question. Our study reports a hitherto unknown variant of maternal effect sex determination and accentuates the diversity of insect sex determination mechanisms.     

Expression patterns and colocalization of two sensory neurone membrane proteins in Ectropis obliqua Prout,a geometrid moth pest that uses Type‐II sex pheromones

Sensory neurone membrane proteins (SNMPs) function as essential cofactors for insect sex pheromone detection. In this study, we report two SNMPs in Ectropis obliqua Prout, a serious geometrid pest that produces typical Type‐II sex pheromones. Sequence alignments and phylogenetic analyses showed that EoblSNMP1 and EoblSNMP2 belong to two distinct SNMP subfamilies. Quantitative real‐time PCR suggested that EoblSNMP1 was male antennae‐biased, whereas EoblSNMP2 was highly expressed on male antennae but was also expressed on female antennae and other chemosensory tissues. Additionally, EoblSNMP1 and EoblSNMP2 differed in their developmental expression profiles. In situ hybridization revealed that EoblSNMP1 was sensilla trichodea I specific, whereas EoblSNMP2 was expressed in sensilla trichodea I and the sensilla basiconica; furthermore, EoblSNMP1 and EoblSNMP2 were co‐expressed in sensilla trichodea I but in different cells. This study suggests that EoblSNMP1 is functionally distinct from EoblSNMP2 in E. obliqua; EoblSNMP1 may specifically contribute to the recognition of sex pheromones, whereas EoblSNMP2 exhibits multiple olfactory roles. Our findings comprehensively reveal the expression patterns of SNMPs in a lepidopteran species that uses Type‐II sex pheromones, providing new insights into the functional evolution of SNMPs from lepidopteran moths with Type‐I sex pheromones to those with Type‐II sex pheromones.