Effects of “Candidatus Liberibacter solanacearum” (haplotype B) on Bactericera cockerelli fitness and vitellogenesis

Abstract

"Candidatus Liberibacter solanacearum" (Lso) are phloem-restricted and unculturable Gram-negative bacteria. Presently five haplotypes have been identified worldwide; but only haplotypes A and B are associated with the vector Bactericera cockerelli (Šulc.) in the Americas. Previous studies showed that Lso-infection reduces B. cockerelli reproductive output and that Lso haplotype B is more pathogenic than Lso haplotype A. To understand the interaction of Lso haplotype B and B. cockerelli, the fitness of Lso-free and Lso B-infected insects, and the expression of vitellogenin (BcVg1-like), a gene involved directly in the insect reproduction were analyzed. Statistical differences in the number of eggs oviposited, and the total number of progeny nymphs and adults were found among crosses of insects with or without Lso. Significant differences in sex proportions were found between Lso B-infected and Lso-free crosses: a higher proportion of F adult females were obtained from Lso B-infected mothers. A significant reduction of BcVg1-like was observed in crosses performed with Lso B-infected females compared to the Lso-free insects. In female cohorts of different age, a significant reduction of BcVg1-like expression was measured in 7-d-old Lso B-infected females (virgin and mated) compared with 7-d-old Lso-free females (virgin and mated), respectively. The reduction of BcVg1-like transcript was associated with a lower number of developing oocytes observed in female's reproductive systems. Overall, this study represents the first step to understand the interaction of Lso B with B. cockerelli, highlighting the effect of Lso B infection on egg production, BcVg1-like expression, and oocyte development.

Interactions between insect vectors and plant pathogens span the parasitism–mutualism continuum

“…These findings, contrary to our initial hypothesis, come with two caveats: the number of studies remains relatively small, and vectors typically acquire pathogens by feeding on infected plants, making it challenging to disentangle the direct and indirect effects of the pathogen on the insect vector. Some studies limited the contribution of indirect effects by infecting vectors in vitro [14,41,43,45,46,50,[53][54][55] or transferring them regularly onto unexposed plants [50]. For most other studies, whether effects were direct, indirect, likely both, or certainly both were inferred based on pathogen transmission mode and the experimentally infected party (electronic supplementary material, figure S2).…”

Concanavalin A Toxicity Towards Potato Psyllid and Apoptosis Induction in Midgut Cells

“…Interestingly, ConA caused greater mortality in LsoA-infected psyllids after two days of feeding when compared to the effects on Lso-free psyllids. It is most likely that ConA toxicity coupled with Lso infection pose a dual detrimental effect on psyllids because Lso has negative effects on the potato psyllid physiology; for example, Lso infection results in decreased psyllid oviposition and nymphal survival [28,43]. Recently, a study in the interaction of Asian citrus psyllid-'Ca.…”

Liberibacter, A Preemptive Bacterium: Apoptotic Response Repression in the Host Gut at the Early Infection to Facilitate Its Acquisition and Transmission

“…We noted that at 7-day infection, the caspase-3 gene was upregulated; however, we could not observe apoptosis in the psyllid gut. This may reflect the existence of a potato psyllid response to Lso since Lso, in particular LsoB, is detrimental to the vector fitness (Nachappa et al, 2012b;Yao et al, 2016;Frias et al, 2020). Although caspase-3 was upregulated at day 7 of the infection, it might not have reached or exceeded the threshold to trigger an intracellular apoptotic immune reaction (Maiuri et al, 2007).…”