Two putative fatty acid synthetic genes of BgFas3 and BgElo1 are responsible for respiratory waterproofing in Blattella germanica. (5th February 2021)

• Record Type: Journal Article
• Authors: Pei, Xiao‐Jin; Bai, Tian‐Tian; Zhang, Zhan‐Feng; Chen, Nan; Li, Sheng; Fan, Yong‐Liang; Liu, Tong‐Xian
• Is Part Of: Insect science. Volume 29:Number 1(2022)
• Page Start: 33
• Page End: 50
• Publication Date: 2021-02-05
• Subjects: elongase -- fatty acid synthase -- German cockroach -- respiratory water loss -- very long chain fatty acid -- water retention; Insects -- Periodicals; Entomology -- Periodicals; 595.705
• DOI: 10.1111/1744-7917.12900
• Languages: English
• ISSNs: 1672-9609

Abstract

Abstract: Water retention is critical for physiological homeostasis and survival in terrestrial insects. While deposition of hydrocarbons on insect cuticles as a key measure for water conservation has been extensively investigated, we know little about other mechanisms for preventing water loss in insects. Here, we report two fatty acid synthetic genes that are independent of hydrocarbon production but crucial for water retention in the German cockroach Blattella germanica (L.). First, an integument enriched fatty acid elongase gene ( BgElo1 ) was identified as a critical gene for desiccation resistance in B. germanica ; however, knockdown of BgElo1 surprisingly failed to cause a decline in cuticular lipids. In addition, RNA interference (RNAi)‐knockdown of an upstream fatty acid synthase gene ( BgFas3 ) showed a similar phenotype, and transmission electron microscopy analysis revealed that BgFas3 ‐ or BgElo1 ‐RNAi did not affect cuticle architecture. Bodyweight loss test showed that repression of BgFas3 and BgElo1 significantly increased the weight loss rate, but the difference disappeared when the respiration was closed by freeze killing the cockroaches. A water immersion test was performed, and we found that BgFas3 ‐ and BgElo1 ‐RNAi made it difficult for cockroaches to recover from drowning, which was supported by the upregulation of hypoxia‐related genes after a 10‐h recovery from drowning. Moreover, a dyeing assay with water‐soluble Eosin Y showed that this was caused by the entry of water into the respiratory system. Our research suggests that BgFas3 and BgElo1 are required for both inward and outward waterproofing of the respiratory system. This study benefits the understanding of water retention mechanisms in insects. Abstract : In this study, we identified a fatty acid synthase gene ( BgFas3 ) and a fatty acid elongase gene ( BgElo1 ) which are predicted to belong to the very long chain fatty acid (VLCFA) biosynthesis pathway. The putative VLCFA‐based pathway maintains both inward and outward waterproofing of the respiratory system in the German cockroach Blattella germanica (L.). RNA interference knockdown of BgFas3 or BgElo1 not only increased water loss via the spiracular respiratory system, but also allowed exogenous water‐soluble substances (like Eosin Y) to penetrate the respiratory system.