Whole-transcriptome sequence analysis of pumpkin ovules in response to heat shock during unfertilized ovary culture

Abstract

Unfertilized ovary culture is one of the most effective approaches to induce haploids in Cucurbitaceae. Previous studies have greatly contributed to inducing more and better haploids, but there has been less contribution to the mechanism involved. Our previous research established efficient haploid regeneration protocol of unfertilized ovary culture and found that heat shock can effectively promote ELSs’ induction. In this study, firstly, we accurately calculated the contribution of heat shock to ELSs’ induction via unfertilized ovary culture of pumpkin, and then performed whole-transcriptome sequence using “Yi-Chuan-Ling 4″, which is more sensitive to heat shock and has a higher induction rate. The results show that heat shock treatment was obviously beneficial to the unfertilized ovary culture of pumpkin, and the average induction rate in the treatment group (35°C,5d) was 26.6 times higher than in the control group (25°C,5d) . Through whole-transcriptome sequencing, we obtained 4579 differentially expressed (DE) RNAs, including 3133 mRNAs, 120 lncRNAs, 814 circRNAs, and 512 miRNAs. GO annotation analysis showed that DEmRNAs were associated with cellular processes, metabolic processes, biological regulation, response to stimulus, and so on. The ceRNA network was constructed using differential expressed RNAs. It captured the gene MSTRG.28850.1, which was related to embryogenesis and regulated by miRNA Nov-m0336–5 p. In conclusion, these findings might provide an important reference for mechanism research regarding embryogenesis induction and accelerate the application of unfertilized ovary/ovule culture in Cucurbita breeding.