Effects of short-term high-temperature conditions on oviposition and differential gene expression of <i>Bactrocera cucurbitae</i> (Coquillett) (Diptera: Tephritidae)

Abstract

Bactrocera cucurbitae is a major pest of fruit and its reproductive capacity is greatly affected by high temperature. Utilizing ovarian dissection and transcriptome to examine the reproductive biology, we determined that the reproductive capacity of this species is enhanced after exposure for 1 h to 45 °C. The total number of eggs, daily number of eggs, preoviposition period and egg-hatching rate of flies exposed to the high temperature treatment were 693 eggs, 20.4 eggs/d, 6 d and 63.5% versus 666 eggs, 9.6 eggs/d, 11.7d and 96.3%, respectively, in control held at 25 °C for 1 h. The egg-hatching rate was lower than in control, but their ovaries matured in only 6 d versus 12 d in the control. Transcriptome sequencing revealed that after exposure for 1 h to 45 °C, 37 °C, 25 °C, a sequence of 14,492,121,840 nucleotide and 46,826 uniques were screened, and six target genes were involved in oviposition. As temperatures increased, expression levels of Vg-1, Vg-2 and JH-epoxide hydrolase-2 initially increased and subsequently decreased, but the expression of Vg-3 continued to increase there-after. The Vg-receptor which first decreased but then increased.