Kr-h1 is vital for vitellogenesis in two ladybird beetle species

Krüppel homolog1 (Kr-h1), a transcription factor with a DNA-binding motif of eight C₂H₂ zinc fingers, exerts species-specific functions by mediating juvenile hormone (JH) signal in certain physiological processes during female reproduction in insects. Nevertheless, the regulatory role of Kr-h1 on vitellogenesis deserves further exploration. Here, we found that Kr-h1 was actively expressed from 0- to 12-day-old females and among detected tissues including fat body and ovary in two potato-defoliating beetles, Henosepilachna vigintioctopunctata and H. vigintioctomaculata. RNA interference (RNAi) for Kr-h1 significantly lengthened the preoviposition period, dramatically impaired ovarian development, and decreased oviposition. Weaker yolk accumulation occurred in the Kr-h1 RNAi oocytes, in contrast to a larger quantity of yolk granules in controls. Correspondingly, Vg transcript levels in the fat bodies and ovaries and of VgR amounts in the ovarian tissues were substantially reduced in the Kr-h1 knockdown samples. In H. vigintioctomaculata, RNAi for the other two JH signal genes, HvmHairy and HvmGroucho, was also performed. Silencing either or both genes affected neither female reproduction nor the mRNA levels of Vg and VgR. Therefore, our findings suggest Kr-h1, rather than Hairy/Groucho, regulates vitellogenesis in the two Henosepilachna species. Moreover, targeting Kr-h1 could potentially be a new way to control potato pests.