Molecular cloning, characterization and mRNA expression of a ryanodine receptor gene from diamondback moth, Plutella xylostella

Abstract

Diamondback moth, Plutella xylostella (L.), is one of the most destructive insect pests of cruciferous vegetables around the world. Diamide insecticides provide a new option for control of P. xylostella populations resistant to other chemicals. Insect ryanodine receptors are the target sites of the diamide insecticides. The full-length cDNA of a ryanodine receptor gene (PxRyR) was cloned and characterized from P. xylostella. The cDNAs of PxRyR contain a 15,495-bp open reading frame, 267-bp 5′ untranslated region (UTR) and a 3′-UTR of 351-bp. The predicted mature protein consists of 5164 amino acids with a predicted molecular weight of 583.7-kDa. PxRyR shares common structural features with known RyRs: the well-conserved COOH-terminal domain, which forms a functional Ca2+ channel, and a large hydrophilic NH2-terminal domain. PxRyR shows a high level of amino acid sequence identity (78–80%) to the insect RyR isoforms. Ten deletion polymorphism sites were detected in PxRyR cDNAs, suggesting a single PxRyR can produce many polymorphic transcripts. Although the highest mRNA expression level was observed in larva and the lowest in pupa, there was a relatively stable expression during the developmental period from egg to adult. The relative mRNA expression levels of PxRyR were similar among the head, thorax, and abdomen of the fourth-instar larva body. These results can serve as an important basis for the functional expression of PxRyR and for investigating the involvement of target site gene mutations in resistance to the diamide insecticides in P. xylostella.