Two Bombyx mori acetylcholinesterase genes influence motor control and development in different ways

Authors: YE, XINHAI - Zheijiang University; YANG, LIWEN - Nanjing Agricultural University; Stanley, David; FANG, QI - Zheijiang University; LI, FEI - Zheijiang University

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/26/2017
Publication Date: 7/10/2017
Citation: Ye, X., Yang, L., Stanley, D.W., Fang, Q., Li, F. 2017. Two Bombyx mori acetylcholinesterase genes influence motor control and development in different ways. Scientific Reports. https://doi.org/10.1038/s41598-017-05360-7.
DOI: https://doi.org/10.1038/s41598-017-05360-7

Interpretive Summary: Humans interact with a very small proportion of the roughly million insect species on Earth. Some are serious pest species and others are valuable beneficials, such as honey bees and silk moths, among others. Silk textiles were first developed in China, the earliest forms dating to about 5,000 years ago and, though silk is now produced in many countries, China remains the top silk producer. The problem, however, is silk production systems are not yet thoroughly optimized in a way that leads to high quality silk with minimal environmental impact. This situation stems, in part, from lack of information, at the molecular level, on silkworm growth and development. Here, we report on the identification of two silkworm genes that encode proteins necessary for proper nerve functions. Further study showed that these two genes act in several areas of silkworm biology, beyond nerve functions. Silencing each of the genes, separately, led to reduced activities of their corresponding proteins, reduced motor control, slowed development, increased mortality and, surprisingly, substantially reduced the sizes of their cocoons, from which silk thread and fabrics are produced. The silencing experiments also showed that the two genes contribute to different areas of silkworm biology, gene 1 having greater influence on motor control and development and gene 2 acting in sensory physiology. The significance of our finding is the identification of specific genes operating in silk production. These new research results will be directly useful to scientists working to improve silk quality and efficiency of silk production.

Technical Abstract: Among its other biological roles, acetylcholinesterase (AChE, EC 3.1.1.7), encoded by two ace genes in most insects, catalyses the breakdown of acetylcholine, thereby terminating synaptic transmission. ace1 encodes the synaptic enzyme and ace2 has other essential actions in many insect species, such as Chilo suppressalis and Plutella xylostella. The silkworm, Bombyx mori, has been domesticated for more than two thousand years and its aces have no history of pesticide exposure. Here, we investigated the function difference of two ace genes, BmAce1 and BmAce2, in the silkworm. qPCR analysis indicated that BmAce1 is highly expressed in muscle and BmAce2 is more ubiquitously expressed among tissues and enriched in the head. Both genes were separately suppressed using chemically synthesized siRNAs. The mRNA abundance of the two ace genes was significantly reduced to about 13% – 75% of the control levels after siRNA injection. The AChE activities were decreased to 32% to 85% of control levels. Silencing BmAce2 resulted in about 26% mortality, faster and higher than the 20% recorded in the siBmAce1-treated group. Silencing BmAce1 impacted motor control and development to a greater extent than silencing BmAce2, although both treatment groups suffered motor disability, slowed development and reduced cocoons. Both genes have essential, differing biological significance.