Cloning and characterization of three chemosensory proteins from Spodoptera exigua and effects of gene silencing on female survival and reproduction

Abstract

Insect chemosensory proteins (CSPs) are supposed to transport hydrophobic chemicals to receptors on sensory neurons. However, CSPs are broadly expressed in various insect tissues, suggesting their involvement in the physiological processes beyond chemoreception. So, the exact physiological roles of CSPs in insects still need to be unraveled. In this study, three full-length of CSP genes from Spodoptera exigua have been cloned and characterized. The deduced amino acid sequences of SexiCSP1, SexiCSP2 and SexiCSP3 revealed open reading frames of 128, 128 and 126 amino acids, respectively, with four conserved cysteine residues. The expression patterns of the three SexiCSPs were further investigated by real-time PCR. Three SexiCSPs were expressed in antennae, heads, legs, wings, thoraxes, abdomens, testes and ovaries, with the highest expression level in female and male antennae. Furthermore, all three SexiCSPs mRNA were distributed extensively in the tested development stages with the highest expression level in pupae. RNAi-based gene silencing study resulted in a dramatic reduction of corresponding mRNA in female S. exigua after injection with dsRNA of all three SexiCSPs. Consequentially, 42.5% of mortalities, 68.3% (compare to DEPC water injected control) and 71.4% (compare to uninjected control) oviposition inhibition, and significantly effected egg hatching were observed in the female S. exigua injected with dsSexiCSP3 as compared to control treatments. On the other hand, dsSexiCSP1 and dsSexiCSP2 injected female adults did not show effects on survival and reproduction. Our study confirms the utility of RNAi approach to functional characterization of CSP genes in S. exigua and provides a starting point for further studies on female survival and reproduction in this insect. It also reveals the potential pest controlling method, as insect behavior regulation agent that disrupts the expression of chemosensory proteins.

Establishment and analysis of a reference transcriptome for Spodoptera frugiperda

“…Interestingly, while most of the OBPs expression was not visible when entire animals were used for RNA extraction (transcript “dilution”), many CSP transcripts could still be highly visible in different samples, suggesting that their expression is not restricted to the olfactory organs. This correlates well with some evidences that CSP function would not be restricted to olfaction [38, 39] and that these proteins would act in fact as general carriers of hydrophobic molecules throughout the insect body. Interestingly, the expression of some ORs was not restricted to the olfactory organs and several could be observed as expressed in the fat body or the midgut (Figure 6A).…”

Molecular identification and expression patterns of odorant binding protein and chemosensory protein genes inAthetis lepigone(Lepidoptera: Noctuidae)

“…Compared to the AlOBP genes highly expressed in the antennae, only three AlCSP s had antennae-biased expression, indicating that these three genes may be involved in the recognition and transmission of sex pheromones, host volatiles, and other odorants. On the other hand, many insect CSPs are broadly expressed in non-chemosensory tissues and have non-chemosensory functions, such as SexiCSP3, which has been shown to have effects on the survival and reproduction of S. exigua (Gong et al, 2012), and AmelCSP5, which is involved in embryonic integument formation in A. mellifera (Foret, Wanner & Maleszka, 2007). In this study, many AlCSP s were found in various tissues and were highly expressed in non-chemosensory tissues suggesting that these AlCSPs (especially AlCSP14, which had the highest expression) may be involved in other physiological functions apart from chemosensory ones.…”

“…Unlike OBPs, CSPs are smaller and more conserved in distinct insects, which only have four conserved cysteines that form two interlocking disulphide bridges (Bohbot et al, 1998; Lartigue et al, 2002; Maleszka & Stange, 1997; Pelosi, Calvello & Ban, 2005; Zhang et al, 2014). Furthermore, OBPs are usually specifically or predominately expressed in the antennae, whereas many CSPs are expressed in the antennae and other tissues (Pelosi, Calvello & Ban, 2005; Vogt, 2005; Zhang et al, 2016a; Zhang et al, 2013), suggesting insect CSPs have both chemosensation and non-chemosensation functions as is illustrated by their association with chemosensation in moths (Jacquin-Joly et al, 2001; Sun et al, 2015; Zhang et al, 2014), limb regeneration in Periplaneta eparate (Nomura et al, 1992), embryo development in Apis mellifera (Maleszka et al, 2007), behavioral phase change in Locusta migratoria (Guo et al, 2011), and female moth survival and reproduction in Spodoptera exigua (Gong et al, 2012). …”

RNA Interference in Moths: Mechanisms, Applications, and Progress

“…A number of other genes in moths have also been studied by using RNAi techniques, such as the chemosensory protein from S. exigua [121], the CO 2 gustatory receptor from H. armigera [122], the delta 6-desaturase which is the rate-limiting factor in the biosynthesis of polyunsaturated fatty acids in B. mori [123], the serotonin receptor B that relates to diapause initiation in A. pernyi [46], and the aspartate decarboxylase which is required for normal pupa pigmentation in B. mori [124]. …”