Precocious Downregulation of Krüppel-Homolog 1 in the Migratory Locust, Locusta migratoria, Gives Rise to An Adultoid Phenotype with Accelerated Ovarian Development but Disturbed Mating and Oviposition

Abstract

Krüppel-homolog 1 (Kr-h1) is a zinc finger transcription factor maintaining the status quo in immature insect stages and promoting reproduction in adult insects through the transduction of the Juvenile Hormone (JH) signal. Knockdown studies have shown that precocious silencing of Kr-h1 in the immature stages results in the premature development of adult features. However, the molecular characteristics and reproductive potential of these premature adult insect stages are still poorly understood. Here we report on an adult-like or ‘adultoid’ phenotype of the migratory locust, Locusta migratoria, obtained after a premature metamorphosis induced by the silencing of LmKr-h1 in the penultimate instar. The freshly molted adultoid shows precocious development of adult features, corresponding with increased transcript levels of the adult specifier gene LmE93. Furthermore, accelerated ovarian maturation and vitellogenesis were observed in female adultoids, coinciding with elevated expression of LmCYP15A1 in corpora allata (CA) and LmKr-h1 and vitellogenin genes (LmVg) in fat body, whereas LmE93 and Methoprene-tolerant (LmMet) transcript levels decreased in fat body. In adultoid ovaries, expression of the Halloween genes, Spook (LmSpo) and Phantom (LmPhm), was elevated as well. In addition, the processes of mating and oviposition were severely disturbed in these females. L. migratoria is a well-known, swarm-forming pest insect that can destroy crops and harvests in some of the world’s poorest countries. As such, a better understanding of factors that are capable of significantly reducing the reproductive potential of this pest may be of crucial importance for the development of novel locust control strategies.

RNAi-Mediated Knockdown of Transcription Factor E93 in Nymphs of the Desert Locust (Schistocerca gregaria) Inhibits Adult Morphogenesis and Results in Supernumerary Juvenile Stages

“…The resulting JH-Met-Tai complex induces the expression of JH response genes, including the gene coding for Krüppel-homolog 1 (Kr-h1), a Zn-finger containing transcription factor [5,6]. RNA interference (RNAi) studies have demonstrated the importance of the JH receptor Met, as well as the downstream-acting transcription factor Kr-h1, in mediating the anti-metamorphic effects of JH in the red flour beetle Tribolium castaneum, the German cockroach Blattella germanica, the kissing bug Rhodnius prolixus, the two-spotted cricket Gryllus bimaculatus, the brown planthopper Nilaparvata lugens, the common bed bug Cimex lectularius, the migratory locust Locusta migratoria and the fire bug Pyrrhocoris apterus [7][8][9][10][11][12][13][14][15][16][17].…”

Ecdysteroid Biosynthesis Halloween Gene Spook Plays an Important Role in the Oviposition Process of Spider Mite, Tetranychus urticae

“…In the soft tick, Ornithodoros moubata, Spook expression was determined in the ovary from both final instar nymphs and adult females, and shade expression was frequently surged after engorgement and copulation in adult females, suggesting Spook and shade are involved in ovary development [30]. Similar expression was also detected in the Varroa mite, Varroa destructor [31], and in the migratory locust, Locusta migratoria [32]. In the rice planthopper, Nilaparvata lugens, silencing the expression of the Spookier led to less oviposition [8].…”

Molecular Characterization and RNA Interference Analysis of SLC26A10 From Nilaparvata lugens (Stål)

“…Because the synthesis of insect Vg is generally regulated by juvenile hormones (JH; Song et al, 2014 ; Lyu et al, 2019 ; Gijbels et al, 2020 ), and JH plays major roles in development, ovary maturation, and reproduction in insects ( Riddiford et al, 2003 ), genes related to JH synthesis and degradation were examined, including JHAMT (juvenile hormone acid methyltransferase), FAMET (farnesoic acid O-methyltransferase), and JHE (juvenile hormone esterase). After ds NlSLC26A10 treatment, the expression level of JHAMT decreased at 2 d.p.i., and significantly decreased at 3 and 5 d.p.i., compared with the ds GFP treatment ( Figure 9C ).…”