Identification And Functional Characterization Of Terpene Synthase Genes Induced By Helicoverpa Armigera Feeding In Different Cotton Cultivars

Plants infested by insect release large amounts of pest volatiles,which play a crucial role in both direct and indirect plant defenses.In recent years,chemical ecological control technology based on pest-induced volatiles is a key direction for green control of agricultural pests.Volatile profiles and transcriptome changes of Gossypium barbadense after cotton bollworm feeding were investigated.A sesquiterpene synthase gene Gb TPS1 was cloned.In vitro enzyme activity assays were performed,and the effects of two enzymic products on the feeding behavior and growth of cotton bollworm were investigated.The results are summarized as follows.1.Comparison of the volatile collection showed that cotton bollworm feeding induced the production of a large number of volatiles in cotton,which were mainly divided into three major categories: terpene volatiles,fatty acid derivatives,and shikimic acid derivatives.Qualitative and quantitative changes of volatiles in G.barbadense were the highest,and solid phase microextraction the terpene volatiles such as α-pinene,β-myrcene,and(R)-limonene were differentially increased in Helicoverpa armigera-induced cotton plants.2.Transcriptome analysis showed that H.armigera feeding on resulted in differential expression of5629 genes in G.barbadense,of which 2460 were significantly up-regulated.Cotton bollworm feeding activated the phytohormone signaling network,mainly the JA signaling pathway,and biosynthesis pathway of defense-related secondary metabolite,while inhibited growth-related photosynthesis.3.A terpene synthase gene,Gb TPS1 from G.barbadense was cloned,which contains an open reading frame of 1653 bp,encodes 551 amino acids,and belongs to the TPSa family.Gb TPS1 was up-regulated in in G.barbadense after H.armigera feeding.In vitro enzymatic assays showed that Gb TPS1 protein was able to catalyze farnesyl pyrophosphate(FPP)to produce celerythrene(48.20%),gurunene(32.65%)and β-elemene(19.15%),and catalyze neryl diphosphate to produce(R)-limonene.4.Behavioral assays of cotton bollworm larvae showed that 0.1 mg/m L,1 mg/m L,10 mg/m L of β-elemene and(R)-limonene had a significant repellent effect.Feeding bioassays showed that both β-elemene(2 ng/g,20 ng/g and 200 ng/g)and limonene(4.5 ng/g,45 ng/g and 450 ng/g)significantly increased mortality of H.armigera larvae.Our findings will help to mine novel insect-resistant genes from excellent germplasm resources,but also to develop novel strategies for sustainable management of cotton pests.