Functional Characterization of the Nuclear Receptor Gene SaE75 in the Grain Aphid, Sitobion avenae

Abstract

Ecdysteroid hormones are key regulators of insect development and metamorphosis. Ecdysone-inducible E75, a major component of insect ecdysone signaling pathway, has been well characterized in holometabolous insects, however, barely in hemimetabolous species. In this study, a total of four full-length E75 cDNAs from the English grain aphid, Sitobion avenae, were identified, cloned, and characterized. The four SaE75 cDNAs contained 3048, 2625, 2505, and 2179 bp open reading frames (ORF), encoding 1015, 874, 856, and 835 amino acids, respectively. Temporal expression profiles showed that SaE75 expression was low in adult stages, while high in pseudo embryo and nymphal stages. SaE75 was differentially expressed between winged and wingless morphs. RNAi-mediated suppression of SaE75 led to substantial biological impacts, including mortality and molting defects. As for the pleiotropic effects on downstream ecdysone pathway genes, SaHr3 (hormone receptor like in 46) was significantly up-regulated, while Sabr-c (broad-complex core protein gene) and Saftz-f1 (transcription factor 1) were significantly down-regulated. These combined results not only shed light on the regulatory role of E75 in the ecdysone signaling pathway, but also provide a potential novel target for the long-term sustainable management of S. avenae, a devastating global grain pest.

Full-length transcriptome-referenced analysis reveals developmental and olfactory regulatory genes in Dermestes frischii

“…In Drosophila, mutations in E74A and E74B are lethal during prepupal and pupal development, which is consistent with the critical role their gene products play in metamorphosis (Fletcher et al 1995). In Sitobion avenae (Fabricius, 1775) (Hemiptera: Aphididae), as a major component of the insect ecdysone signaling pathway, the expression of ecdysone-inducible E75 was low in the adult stage, but high in the pseudo embryo and nymphal stages (Zheng et al 2023). In this study, we speculate that the strong up-regulation of these ecdysoneinducible genes (E74, E75, E78, and E93) is because of a rapidly increasing 20E pulse, leading to undergoing extensive metamorphic remodeling in the pupae.…”