Small RNAs from Bemisia tabaci Are Transferred to Solanum lycopersicum Phloem during Feeding

Abstract

The phloem-feeding whitefly Bemisia tabaci is a serious pest to a broad range of host plants, including many economically important crops such as tomato. These insects serve as a vector for various devastating plant viruses. It is known that whiteflies are capable of manipulating host-defense responses, potentially mediated by effector molecules in the whitefly saliva. We hypothesized that, beside putative effector proteins, small RNAs (sRNA) are delivered by B. tabaci into the phloem, where they may play a role in manipulating host plant defenses. There is already evidence to suggest that sRNAs can mediate the host-pathogen dialogue. It has been shown that Botrytis cinerea, the causal agent of gray mold disease, takes advantage of the plant sRNA machinery to selectively silence host genes involved in defense signaling. Here we identified sRNAs originating from B. tabaci in the phloem of tomato plants on which they are feeding. sRNAs were isolated and sequenced from tomato phloem of whitefly-infested and control plants as well as from the nymphs themselves, control leaflets, and from the infested leaflets. Using stem-loop RT-PCR, three whitefly sRNAs have been verified to be present in whitefly-infested leaflets that were also present in the whitefly-infested phloem sample. Our results show that whitefly sRNAs are indeed present in tomato tissues upon feeding, and they appear to be mobile in the phloem. Their role in the host-insect interaction can now be investigated.

Transient Expression of Whitefly Effectors in Nicotiana benthamiana Leaves Activates Systemic Immunity Against the Leaf Pathogen Pseudomonas syringae and Soil-Borne Pathogen Ralstonia solanacearum

“…It appears that the plant recognizes whitefly rRNA as a non-self-molecular pattern. Also, three small RNAs from whitefly were detected in tomato leaf tissue through sequencing tomato phloem RNA from whitefly-infested plants and the nymphs themselves, and the translocation of these RNAs was confirmed using stem-loop qRT-PCR (van Kleeff et al, 2016). The translocation of sRNA has also been observed during plant-fungus interactions.…”

“…Whitefly saliva is thought to contain proteins that modulate plant defense responses and facilitate feeding. Secreted whitefly laccase 1 (LAC1) and small RNAs have been identified and are thought to help the insect overcome plant immunity responses (van Kleeff et al, 2016;Yang et al, 2017). …”

Methylation analysis revealed salicylic acid affects pearl millet defense through external cytosine DNA demethylation

“…This inhibition of plant defense through increase of DNA methylation level could be from H. albipunctella infestation. In the class of Lepidoptera in which belong the headminer, some larvae have oral secretion contain suppressors acting as methylating agents or effectors that inhibit the host defense responses (van Kleeff et al 2016;Acevedo et al 2017). This strategy has been reported in Helicoverpa zea (Eichenseer et al 1999;Musser et al 2005), in Leptinotarsa decemlineata (Chung et al 2013), and mite species (Villarroel et al 2016).…”

Spotlight on the Roles of Whitefly Effectors in Insect–Plant Interactions

“…The gland lumens empty into primary or accessory salivary gland ducts, which are connected to each other (Ghanim et al, 2001). The primary salivary glands of all hemipterans investigated thus far contain multiple cell types that each have different kinds of electron-dense secretory vesicles (Sogawa, 1968;Wayadande et al, 1997;Ghanim et al, 2001;Reis et al, 2003;Ammar et al, 2017;Dai et al, 2019), and produce and secrete salivary components such as proteins (Sogawa, 1968;Mutti et al, 2008;Yang et al, 2017;Su et al, 2019;Xu et al, 2019;Huang et al, 2020), long non-coding RNAs (Chen et al, 2020), and small RNAs (Van Kleeff et al, 2016). Some of these secreted salivary component are effectors or elicitors, but some have other functions, such as structural roles in salivary sheaths (Cohen et al, 1998;Freeman et al, 2001;Will and Vilcinskas, 2015), and others may play a role in both (Shangguan et al, 2018).…”