Date Published: July 12, 2017
Publisher: Public Library of Science
Author(s): Jia Wang, Huan Fan, Ke-Cai Xiong, Ying-Hong Liu, J. Joe Hull.
The Chinese citrus fly, Bactrocera minax (Enderlein), is a devastating citrus pest in Asia. This univoltine insect enters obligatory pupal diapause in each generation, while little is known about the course and the molecular mechanisms of diapause. In this study, the course of diapause was determined by measuring the respiratory rate throughout the pupal stage. In addition, the variation of transcriptomic and metabolomic profiles of pupae at five developmental stages (pre-, early-, middle-, late-, and post-diapause) were evaluated by next-generation sequencing technology and 1H nuclear magnetic resonance spectroscopy (NMR), respectively. A total of 4,808 genes were significantly altered in ten pairwise comparisons, representing major shifts in metabolism and signal transduction as well as endocrine system and digestive system. Gene expression profiles were validated by qRT-PCR analysis. In addition, 48 metabolites were identified and quantified by 1H NMR. Nine of which significantly contributed to the variation in the metabolomic profiles, especially proline and trehalose. Moreover, the samples collected within diapause maintenance (early-, middle-, and late-diapause) only exhibited marginal transcriptomic and metabolomic variation with each other. These findings greatly improve our understanding of B. minax diapause and lay the foundation for further pertinent studies.
The Chinese citrus fly, Bactrocera minax (Enderlein), is a devastating oligophagous pest of citrus plants in the temperate areas of Asia, especially in China [1–3]. Larval feeding can cause serious yield losses [4–6], as such this pest has become a focus of interest in citrus-growing regions in China. Given the economic importance of B. minax, a number of prior studies have been carried out [7–13]. However, the long-lasting pupal stage in which diapause occurs has severely hindered the laboratory-rearing of this pest and restricted further scientific research.
In this study, transcriptomic and metabolomic analyses were performed to discover differentially expressed genes and significantly altered metabolites that coincided with pupal development. The findings provide insights into the diapause programming of B. minax. All DEGs and significantly altered metabolites identified may collectively play roles in stress resistance and survival of B.minax during diapause. However, the functions of most of the genes and metabolites remain unknown. To elucidate the mechanisms underlying pupal diapause of B. minax and comprehensively understand this pest, further investigations will focus on the specific aspects of biological variation along with pupal development or between diapausing and non-diapausing pupae.