Alternative relay regulates the adenosine triphosphatase activity of Locusta migratoria striated muscle myosin

Locust(Locusta migratoria)has a single striated muscle myosin heavy chain(Mhc)gene,which contains 5 clusters of alternative exclusive exons and 1 differently included penultimate exon.The alternative exons of Mhc gene encode 4 distinct regions in the myosin motor domain,that is,the N-terminal SH3-like domain,one lip of the nucleotide-binding pocket,the relay,and the converter.Here,we investigated the role of the alternative regions on the motor function of locust muscle myosin.Using Sf9-baculovirus protein expression system,we expressed and purified 5 isoforms of the locust muscle myosin heavy meromyosin(HMM),including the major isoform in the thorax dorsal longitudinal flight muscle(FL1)and 4 isoforms expressed in the abdominal intersegmental muscle(AB1 to AB4).Among these 5 HMMs,FL1-HMM displayed the highest level of actin-activated adenosine triphosphatase(ATPase)activity(hereafter referred as ATPase activity).To identify the alternative region(s)responsible for the elevated ATPase activity of FL1-HMM,we produced a number of chimeras of FL1-HMM and AB4-HMM.Substitution with the relay of AB4-HMM(encoded by exon-14c)substantially decreased the ATPase activity of FL1-HMM,and conversely,the relay of FL1-HMM(encoded by exon-14a)enhanced the ATPase activity of AB4-HMM.Mutagenesis showed that the exon-14a-encoded residues Gly474 and Asn509 are responsible for the elevated ATPase activity of FL1-HMM.Those results indicate that the alternative relay encoded by exon-14a/c play a key role in regulating the ATPase activity of FL1-HMM and AB4-HMM.

BIOINSECTICIDES AS FUTURE MAINSTREAM PEST CONTROL AGENTS: OPPORTUNITIES AND CHALLENGES

Bioinsecticides are naturally-occurring substances from different sources that control insect pests.Ideal bioinsecticides should have low toxicity to non-target organisms.They should also be easily degraded in sewage treatment works and natural environments,highly effective in small quantities and affect target pests only.Public concerns about possible side-effects of synthetic pesticides have accelerated bioinsecticide research and development.However,to develop bioinsecticides into mainstream products,their high production costs,short shelf-life and often uncertain modes of action need to be considered.This review summarizes current progress on bioinsecticides which are categorized as biochemical insecticides and their derivatives,plant-incorporated protectants,and microbial bioinsecticides.The current constraints that prevent bioinsecticides from being widely used are discussed and future research directions are proposed.