Candidatus Liberibacter solanacerum (CLso), transmitted by Bactericera trigonica in a persistent and propagative mode causes carrot yellows disease, inflicting hefty economic losses. Understanding the process of transmission of CLso by psyllids is fundamental to devise sustainable management strategies. Persistent transmission involves critical steps of adhesion, cell invasion, and replication before passage through the midgut barrier. This study uses a transcriptomic approach for the identification of differentially expressed genes with CLso infection in the midguts, adults, and nymphs of B. trigonica and their putative involvement in CLso transmission. Several genes related to focal adhesion and cellular invasion were upregulated after CLso infection. Interestingly, genes involved with proper functionality of the endoplasmic reticulum (ER) were upregulated in CLso infected samples. Notably, genes from the endoplasmic reticulum associated degradation (ERAD) and the unfolded protein response (UPR) pathway were overexpressed after CLso infection. Marker genes of the ERAD and UPR pathways were also upregulated in Diaphorina citri when infected with Candidatus Liberibacter asiaticus (CLas). Upregulation of the ERAD and UPR pathways indicate induction of ER stress by CLso/CLas in their psyllid vector. The role of ER in bacteria–host interactions is well-documented; however, the ER role following pathogenesis of CLso/CLas is unknown and requires further functional validation.

Begomoviruses are whitefly-transmitted ss-DNA viruses infecting dicotyledonous plants and contribute to major economic losses to global crop production. Invasion and establishment of an aggressive species of B. tabaci , known as the B cryptic species, has severely constrained vegetable production in the southeastern and southwestern United States. Disruption of genes/pathways critical for whitefly mediated transmission can be effective for the management of begomoviruses. In this study, yeast two hybrid (Y2H)-based screening of B. tabaci cDNA library identified a cyclic adenosine monophosphate (cAMP)-specific phosphodiesterase (PDE4) of the whitefly as an interacting partner with capsid proteins (CPs) of old- and new-world begomoviruses. Interactions of PDE4 with begomovirus CPs were validated by GST-pull-down assays, co-immunoprecipitation, and co-immunolocalization in whitefly midgut. The PDE4 family of enzymes hydrolyze cAMP and regulate intracellular cAMP levels. This study revealed that elevation of cAMP within whitefly by chemically inhibiting or gene (PDE4) silencing resulted in increased retention and transmission of begomoviruses. Similarly, decreased cAMP levels resulted in reduced begomovirus retention. The results of this study demonstrate that whitefly mediated transmission of begomoviruses is regulated by intracellular cAMP by unknown mechanisms. Importance: Begomoviruses, transmitted by the sweetpotato whitefly, ( Bemisa tabaci Gennadius ), are the causal agents of many economically important plant virus diseases. Lack of host plant resistance against begomoviruses, high whitefly abundance, and whitefly’s ability to develop insecticide resistance rapidly often renders commonly used management practice ineffective. This study demonstrates how begomovirus retention within whitefly and its transmission can be modulated by altering cAMP expression of its insect vector. Naturally occurring bio-pesticides that target insect cAMPs are known. Our findings can lead to alternative strategies for the management of begomoviruses by targeting whitefly cAMP using chemicals, botanicals, or RNAi-based insecticides.