Silencing the expression of the salivary sheath protein causes transgenerational feeding suppression in the aphid Sitobion avenae

Abstract

Aphids produce gel saliva during feeding which forms a sheath around the stylet as it penetrates through the apoplast. The sheath is required for the sustained ingestion of phloem sap from sieve elements and is thought to form when the structural sheath protein (SHP) is cross-linked by intermolecular disulphide bridges. We investigated the possibility of controlling aphid infestation by host-induced gene silencing (HIGS) targeting shp expression in the grain aphid Sitobion avenae. When aphids were fed on transgenic barley expressing shp double-stranded RNA (shp-dsRNA), they produced significantly lower levels of shp mRNA compared to aphids feeding on wild-type plants, suggesting that the transfer of inhibitory RNA from the plant to the insect was successful. shp expression remained low when aphids were transferred from transgenic plants and fed for 1 or 2 weeks, respectively, on wild-type plants, confirming that silencing had a prolonged impact. Reduced shp expression correlated with a decline in growth, reproduction and survival rates. Remarkably, morphological and physiological aberrations such as winged adults and delayed maturation were maintained over seven aphid generations feeding on wild-type plants. Targeting shp expression therefore appears to cause strong transgenerational effects on feeding, development and survival in S. avenae, suggesting that the HIGS technology has a realistic potential for the control of aphid pests in agriculture.

Functional Evaluation of Proteins in Watery and Gel Saliva of Aphids

“…Reduced sheath hardening weakened the capability of aphids to withdraw nutrition from sieve elements (Will and Vilcinskas, 2015). S. avenae individuals feeding on barley plants containing a similar dsRNA sequence suffered from decreased reproduction and reduced survival rates in comparison to aphids on control plants (Abdellatef et al, 2015). A necessity of salivary sheath proteins for the interaction between sucking insects and plants was also demonstrated for the brown plant hopper on rice plants (Huang et al, 2015).…”

A Salivary Endo-β-1,4-Glucanase Acts as an Effector That Enables the Brown Planthopper to Feed on Rice

“…Expressing C002 from the green peach aphid Myzus persicae in Nicotiana benthamiana increased aphid reproduction on these plants, whereas reducing C002 expression in aphids by plant-mediated RNA interference (RNAi) reduced aphid fecundity (Bos et al, 2010;Pitino et al, 2011). Other salivary proteins, such as Glc oxidase from the corn earworm Helicoverpa zea (Musser et al, 2002), calcium-binding proteins from the vetch aphid Megoura viciae (Will et al, 2007), Mp10 and Mp55 from the green peach aphid (Bos et al, 2010;Elzinga et al, 2014), structural sheath proteins from the grain aphid Sitobion avenae (Abdellatef et al, 2015), Me10 and Me23 from the potato aphid Macrosiphum euphorbiae (Atamian et al, 2013), and Armet from the pea aphid (Wang et al, 2015), also have been found to increase herbivore performance. Thus, herbivore effectors play a central role in overcoming plant defenses and helping the herbivore establish a population on host plants.…”

“…As a piercing-sucking insect, BPH secretes two primary kinds of saliva during feeding: coagulable and watery. Coagulable saliva forms salivary sheaths around the insect's stylets that help to stabilize and protect the stylets and may suppress plant defense responses to components of the watery saliva (Miles, 1999;Abdellatef et al, 2015). Watery saliva, which contains a mixture of amino acids, proteins, and digestive enzymes, assists in the digestion of plant material and helps suppress plant defense responses (Miles, 1968(Miles, , 1999Harmel et al, 2008;Carolan et al, 2009;Hogenhout and Bos, 2011;Nicholson et al, 2012;Elzinga and Jander, 2013).…”

Comparative Analysis of RNAi-Based Methods to Down-Regulate Expression of Two Genes Expressed at Different Levels in Myzus persicae

“…This strategy has already been validated in numerous studies with aphids [29,31,32,33,34,38,51,52,53]. The fragment of 249 bp from the Eph coding sequence was introduced in sense and antisense orientations into the pFGC5941 vector.…”