Molecular characterization and gene silencing
of Laccase 1 in the grain aphid, Sitobion avenae
State KeyLaboratory of Plant Diseases and
Insect Pests, Institute of Plant Protection,
Chinese Academy of Agricultural Sciences, Bei-
jing, P.R. China
Functional and Evolutionary Entomology, Gem-
bloux Agro-Bio Tech, University of Liège, Liege,
Julian Chen, State Key Laboratory of Plant Dis-
eases and Insect Pests, Institute of Plant Protec-
tion, Chinese Academy of Agricultural Sciences,
Beijing 100193, P.R. China.
Laccase 1 (Lac1), a polyphenol oxidase, has been proposed to be
involved in insect iron metabolism and immunity responses. How-
ever, little information is available on the roles of Lac 1 in insect–
plant interactions. The grain aphid Sitobion avenae is one of the most
destructive pests of cereal, directly drawing phloem sap and trans-
mitting viruses. In the present study, we first cloned the open read-
ing frame (ORF) of Lac 1 from S. avenae, and the putative protein
sequence was predicted to have a carboxyl-terminal transmembrane
domain. We found that SaLac1 had higher expression levels in the
fourth and adult stages using reverse transcription real-time quan-
titative PCR (RT-qPCR). SaLac 1 was highly expressed in the sali-
vary gland and midgut and also in wingless compared with winged
morphs. After feeding on aphid-resistant wheat with a high total phe-
nol content, the expression level of SaLac 1 increased significantly.
RNA interference (RNAi) by oral feeding successfully inhibited the
transcript levels of SaLac 1, and the knockdown of Lac 1 significantly
decreased the survival rate of S. avenae on aphid-resistant wheat.
Our study demonstrated that S. avenae Lac1 was involved in the
detoxification of phenolic compounds in wheat and was essential for
the aphid to adapt to resistant plants.
aphid–wheat interactions, laccase 1, RNAi, RT-qPCR, Sitobion avenae
Laccases, members of the multicopper oxidase (MCO) family, are polyphenol oxidases found in plants, fungi, bacteria,
and insects (Alexandre & Zhulin, 2000; Bao, O'Malley, Whetten, & Sederoff, 1993; Pezet, Pont, & Hoangvan, 1991).
Laccases can oxidize a wide range of compounds, including diphenols, monolignols, isoflavonoids, and tannins (Mayer
& Staples, 2002). Two types of laccase genes, laccase 1 (Lac 1)andlaccase 2 (Lac 2), are identified in many insect species
(Dittmer et al., 2004; Parkinson et al., 2003). Several studies demonstrate that Lac 2 encodes an enzyme that is prin-
cipally involved in insect cuticular pigmentation and hardening (Futahashi, 2011; Niu et al., 2008 ). Lac 2 is highly
expressed in insect cuticles and levels of expression correlate temporally and spatially with cuticle sclerotization.
Arch. Insect Biochem. Physiol. 2018;97:e21446. wileyonlinelibrary.com/journal/arch
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