Differential gene expression during intra-puparial period of Lucilia sericata (Diptera: Calliphoridae) for improving minimum postmortem interval estimation

Abstract

One of the main objectives of forensic entomology is to estimate the minimum postmortem interval (PMImin) by analyzing the size and duration of the immature stages of insects colonizing a cadaver. However, this estimation becomes difficult during the intra-puparial period due to the absence of significant visible morphological changes. This study explores the differential gene expression of Lucilia sericata (Calliphoridae) pupae as a molecular tool for PMImin estimation. Pupae were collected daily under controlled conditions at 23 °C, and RNA was extracted for gene expression analysis. Six target genes (ecdysone receptor, Hsp90, actin, regucalcin, wingless, and fat body protein 1) were identified and correlated with distinct different stages of intra-puparial development. Our results suggests that the combination of the expression levels of at least three genes, such as ecdysone receptor, regucalcin and wingless, is sufficient to infer the percentage of development throughout the entire intra-puparial period. Additionally, graphical tools were developed to facilitate the use of individual and grouped genes as markers for L. sericata age estimation. Since the intra-puparial period comprises approximately half of the Calliphoridae developmental cycle, these findings are particularly valuable when these stages represent the most advanced evidence recovered from a crime scene or autopsy.