Transcriptome analysis reveals functional diversity in salivary glands of plant virus vector, Graminella nigrifrons

Authors: RAJARAPU,, SWAPNA - The Ohio State University; Bansal, Raman; MITTAPELLY, PRIYANKA - The Ohio State University; MICHEL, ANDREW - The Ohio State University

Submitted to: Gene
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2020
Publication Date: 10/29/2020
Citation: Rajarapu,, S.P., Bansal, R., Mittapelly, P., Michel, A. 2020. Transcriptome analysis reveals functional diversity in salivary glands of plant virus vector, Graminella nigrifrons. Gene. 11(11):1289. https://doi.org/10.3390/genes11111289.
DOI: https://doi.org/10.3390/genes11111289

Interpretive Summary: In North-America, maize viruses cause severe damage to maize yield and quality. Two of these viruses, maize chlorotic dwarf virus, and maize fine streak virus are severe pathogens transmitted by the black-faced leafhopper (BFL, Graminella nigrifrons). During feeding, the BFL injects saliva into the plant host which not only contains the viral disease particles but also the effector proteins. These salivary effectors perform various functions including the suppression of plant defenses which is imperative for successful colonization and virus transmission by BFL. Using transcriptomic sequencing approach, here, we identified 58 BFL genes encoding for candidate salivary effectors. Several of these salivary effector genes have significantly higher expression in the salivary glands compared to rest of the insect body and are involved in antioxidation, detoxification, calcium binding, and carbohydrate metabolizing functions. The availability of these candidate effector genes presents testable hypothesis that will lead to the determination of function of BFL proteins in mediating its interaction with maize which further can potentially lead to development of novel disease management tools.

Technical Abstract: Salivary glands of phloem feeding insects are important for host adaptation since they release proteins such as effectors that modify or suppress host defenses. Studying the salivary gland transcriptome can improve our understanding of plant-insect interactions. The black-faced leafhopper, Graminella nigrifrons, vectors several agronomically important plant viruses. To identify effectors and other important salivary genes in the black-faced leafhopper, we generated a salivary gland (SG) specific transcriptome and used RNA-Sequencing to identify differentially expressed genes compared to the black-faced leafhopper carcass. Overall, the SG transcriptome is represented by functions such as ‘oxidoreduction’, ‘membrane transport’ and ‘ATP-binding’ which might be important for the fundamental physiology of black-faced leafhopper. SGs contain more transcripts related to the extracellular region and membrane compared to the carcass. Additional SG transcripts with higher expression encoded potential effectors with antioxidant, detoxification, calcium binding and carbohydrate metabolizing functions, and were evaluated using RTq-PCR. Three transcripts, GnP19, GnP75 and GnE63, were significantly upregulated in maize fed adults relative to starved adults. Our results indicate that SG of the black-faced leafhopper expresses transcripts related to other phloem feeders that facilitate plant-insect interactions.