Two Phytoplasmas Elicit Different Responses in the Insect Vector Euscelidius variegatus Kirschbaum

Abstract

Phytoplasmas are plant-pathogenic bacteria transmitted by hemipteran insects. The leafhopper is a natural vector of chrysanthemum yellows phytoplasma (CYp) and a laboratory vector of flavescence dorée phytoplasma (FDp). The two phytoplasmas induce different effects on this species: CYp slightly improves whereas FDp negatively affects insect fitness. To investigate the molecular bases of these different responses, transcriptome sequencing (RNA-seq) analysis of infected with either CYp or FDp was performed. The sequencing provided the first transcriptome assembly for a phytoplasma vector and a starting point for further analyses on differentially regulated genes, mainly related to immune system and energy metabolism. Insect phenoloxidase activity, immunocompetence, and body pigmentation were measured to investigate the immune response, while respiration and movement rates were quantified to confirm the effects on energy metabolism. The activation of the insect immune response upon infection with FDp, which is not naturally transmitted by, confirmed that this bacterium is mostly perceived as a potential pathogen. Conversely, the acquisition of CYp, which is naturally transmitted by , seems to increase the insect fitness by inducing a prompt response to stress. This long-term relationship is likely to improve survival and dispersal of the infected insect, thus enhancing the opportunity of phytoplasma transmission.

Pre-symptomatic modified phytohormone profile is associated with lower phytoplasma titres in an Arabidopsis seor1ko line

“…2A). The very high transmission efficiency of E. variegatus under natural and experimental conditions [34][35][36][37] is confirmed in our experimental system (transmission rate 100%, p = 1 27 ). Moreover, the higher vector survival rates on mutant lines (Fig.…”

RNA interference of muscle actin and ATP synthase beta increases mortality of the phytoplasma vector Euscelidius variegatus

“…During RNA‐seq analysis of E. variegatus transcriptome, a fragment of the cytoplasmic actin transcript was identified. Alignment of the muscle actin fragment used as a dsRNA template with the known sequence of the cytoplasmic actin revealed that the two sequences share 82.5% identity over a 321‐bp region (Fig.…”

“…To our knowledge, RNAi assays have not been attempted on a phytoplasma vector before the current investigation. As a first step, we took advantage of the recently published E. variegatus transcriptome assembly to perform an in silico identification of the genes coding for the major components of RNAi machinery, including Dicers, Argonauts, R2D2 and ribonuclease III enzymes. Nevertheless, the presence of all the RNAi core genes is not a guarantee of successful suppression of gene expression, because many elements strongly affect the efficiency of gene silencing in Hemiptera (reviewed by Li and colleagues).…”

Comparative genomics and transcriptomics of host–pathogen interactions in insects: evolutionary insights and future directions

“…In general, this wide range of studies has focused on annotating immune pathways in species (often of agriculture importance) without high quality genomes (e.g., [62,63]), elucidation of hostpathogen interactions of ecological interest (e.g., [38,[64][65][66]), and characterization of pathogen-vector interactions of medical relevance (e.g., [67,68]). There has been relatively less focus on explicitly comparative studies, either comparing multiple pathogens in the same species, or comparative studies across species, albeit with a few exceptions (e.g., [38,55,[69][70][71][72][73][74]).…”