Variation of gene expression of fatty acid acyl CoA reductase associated with wax secretion of a scale insect, Ericerus pela, and identification of its regulation factors through the accessible chromatin analyses and yeast one-hybrid

The Chinese white wax scale insect (CWWSI), Ericerus pela, can secret an amount of wax equivalent to their body weight. Previous studies demonstrated the fatty acyl-CoA reductase (far3) plays a pivotal role in wax secretion of CWWSI. The high expression of far3 is crucial for the massive wax secretion. However, the transcription regulation of far3 was not clear. To identify regulatory factors that control the expression of far3, the assay for transposase-accessible chromatin (ATAC) and yeast one-hybrid (Y1H) were carried out in this study. The ATAC sequencing of the CWWSI at the early wax-secretion stage ATAC-seq resulted in 22.75 GB raw data, generated 75,827,225 clean reads and revealed 142,771 peaks. There was one significant peak in the 3 kb upstream regulation regions. The peak sequence is located between −1000 and −670 bp upstream of the far3 transcription start site, spanning a length of 331 bp. This peak sequence served as bait for creating the pAbAi-peak recombinant vector, used in Y1H screenings to identify proteins interacting with far3 gene. The results indicate a successful CWWSI cDNA library construction with a capacity of 1.2 × 10⁷ colony forming unit, a 95.8% recombination rate, and insert sizes between 1,000 and 2,000 bp. Self-activation tests established that 100 ng/mL of AbA effectively inhibited bait vector self-activation. Finally, a total of 88 positive clones were selected. After sequencing and removal of duplication, 63 unique clones were obtained from these screened colonies. By aligning the clone sequences with full-length transcriptome and genome of CWWSI, the full-length coding sequences of these clones were obtained. BlastX analysis identified a transcription factor, nuclear transcription factor Y beta, and two co-activators, cAMP-response-element-binding-protein-binding protein and WW domain binding protein 2. Reverse transcription quantitative polymerase chain reaction analysis confirmed that their expression patterns were consistent with the developmental stages preceding wax secretion and matched the wax secretion characteristics during ovulation periods. These results are beneficial for further research into the regulatory mechanisms of wax secretion of CWWSI.