Abstract
This study reports the identification of splice variants for the calcium/calmodulin-dependent protein kinase II (CaMKII) gene from Nilaparvata lugens, Laodelphax striatellus, and Sogatella furcifera. CaMKII is a multifunctional serine/threonine protein kinase that transduces Ca2+ signals in cells to control a range of cellular processes in the nervous system and muscular tissue. Sequence analysis showed that CaMKII was 99.0% identical at the amino acid level among three rice planthoppers, with the exception of a variable region located in the association domain. Four kinds of 20–81 amino acid “inserts” were found in the variable region. The phylogenetic tree of the deduced amino acid sequences showed that the NlCaMKII isoforms were more closely related to the LsCaMKII isoforms and were slightly distinct from SfCaMKII. CaMKII-E was the dominant type among the five main isoforms. CaMKII genes were constitutively expressed in various nymphal and adult stages and in tested tissues with the predominant transcription occurring in the head. There was no major tissue specificity of isoform expression, but the expression pattern and relative abundance of isoforms varied when compared with the RT-PCR between tissues. In addition, RNAi in N. lugens with dsRNA at a concentration of 200 ng nymph−1 induced a mortality of 77.7% on the 10th day and a reduction in the mRNA expression level of 67.2%. Unlike the holometabolous insect Helicoverpa armigera, the knockdown of NlCaMKII did not suppress the expression of 20E response genes, such as ECR, USP1, and HR3, in N. lugens. These results indicate that the role of CaMKII in hemimetabolous insects may be different from that in holometabolous insects.
Highlights
Rice (Oryza sativa L.) is a major food crop in Asia
Based on the transcriptome data of three planthopper species, PCR primers were designed and used to clone the calmodulin-dependent protein kinase II (CaMKII) gene from RNA isolated from three planthopper species
About 50 positive clones were sequenced in both strands from N. lugens, S. furcifera, and L. striatellus, respectively
Summary
Rice (Oryza sativa L.) is a major food crop in Asia It serves as an important food source for insects and is attacked by around 800 species [1]. Of these insects, the brown planthopper (Nilaparvata lugens (Stål)), the white-backed planthopper (Sogatella furcifera (Horváth)), and the small brown planthopper (Laodelphax striatellus (Fallén)) are three major destructive pests in rice ecosystems. In Drosophila, it was demonstrated that increasing the level of constitutively active CaMKII decreased the initial courtship and enhanced the rate of the suppression of courtship in response to a mated female This effect could be mediated by cholinergic neurons that enhance training-dependent suppression [10,11]. The RNAi efficiency of NlCaMKII by injecting dsRNA into the insect body and the nymph lethality of the RNAi in N. lugens were analyzed
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