@article{han_rotenberg_2021, title={Integration of transcriptomics and network analysis reveals co-expressed genes in Frankliniella occidentalis larval guts that respond to tomato spotted wilt virus infection}, volume={22}, ISSN={["1471-2164"]}, DOI={10.1186/s12864-021-08100-4}, abstractNote={The gut is the first barrier to infection by viruses that are internally borne and transmitted persistently by arthropod vectors to plant and animal hosts. Tomato spotted wilt virus (TSWV), a plant-pathogenic virus, is transmitted exclusively by thrips vectors in a circulative-propagative manner. Frankliniella occidentalis (western flower thrips), the principal thrips vector of TSWV, is transmission-competent only if the virus is acquired by young larvae. To begin to understand the larval gut response to TSWV infection and accumulation, a genome-assisted, transcriptomic analysis of F. occidentalis gut tissues of first (early L1) and second (early L2 and late L2) instar larvae was conducted using RNA-Seq to identify differentially-expressed transcripts (DETs) in response to TSWV compared to non-exposed cohorts.The larval gut responded in a developmental stage-dependent manner, with the majority of DETs (71%) associated with the early L1 stage at a time when virus infection is limited to the midgut epithelium. Provisional annotations of these DETs inferred roles in digestion and absorption, insect innate immunity, and detoxification. Weighted gene co-expression network analysis using all assembled transcripts of the gut transcriptome revealed eight gene modules that distinguish larval development. Intra-module interaction network analysis of the three most DET-enriched modules revealed ten central hub genes. Droplet digital PCR-expression analyses of select network hub and connecting genes revealed temporal changes in gut expression during and post exposure to TSWV.These findings expand our understanding of the developmentally-mediated interaction between thrips vectors and orthotospoviruses, and provide opportunities for probing pathways for biomarkers of thrips vector competence.}, number={1}, journal={BMC GENOMICS}, author={Han, Jinlong and Rotenberg, Dorith}, year={2021}, month={Nov} }
 @article{nalam_han_pitt_acharya_nachappa_2021, title={Location, location, location: Feeding site affects aphid performance by altering access and quality of nutrients}, volume={16}, ISBN={1932-6203}, DOI={10.1371/journal.pone.0245380}, abstractNote={Feeding location on a plant can affect aphid reproduction and survival, however little is known about factors that influence aphid performance on specific plant parts. We determined performance and feeding behavior of soybean aphid (Aphis glycines) on stem, adaxial (upper) and abaxial (lower) leaf surfaces during early vegetative growth of soybean plants and analyzed the associated phloem sap composition. Stems harbored greater aphid populations and aphids had shorter development time on stems compared to adaxial and abaxial leaf surfaces. While aphids feeding on the stem took the longest time to begin probing, potentially due to higher density and length of trichomes, this did not impact aphid population growth. Once aphids began probing, the sieve elements were more conducive to feeding as evidenced by less salivation from the stem as compared to either leaf surface. Moreover, vascular sap-enriched exudates from stems had higher sugars and amino acids, which supported higher aphid populations in artificial diet feeding assays. The high quality of stems as a food source may in part explain the shorter development time and overall greater population of aphids observed on stems. In summary, our findings suggest that the choice of feeding location and performance of aphids on a specific plant is driven largely by accessibility to and the quality of nutrients rather than morphological factors.}, number={2}, journal={PLOS ONE}, author={Nalam, Vamsi J. and Han, Jinlong and Pitt, William Jacob and Acharya, Shailesh Raj and Nachappa, Punya}, year={2021} }
 @article{nalam_han_nachappa_szczepaniec_2020, title={Drought stress and pathogen infection alter feeding behavior of a phytopathogen vector}, volume={168}, ISSN={["1570-7458"]}, DOI={10.1111/eea.12937}, abstractNote={The impact of drought stress on tripartite plant‐pathogen‐vector interactions constitutes a complex and largely understudied field of plant‐insect interaction. A number of studies explored these topics using aphid vectors of plant pathogens, but few have considered the interactions between drought‐stressed plants and pathogen‐transmitting psyllids. The potato psyllid, Bactericera cockerelli (Šulc) (Hemiptera: Triozidae), is one of the key pests of solanaceous crops in the USA that causes direct injury as well as indirect injury through transmission of a bacterial pathogen, Candidatus Liberibacter solanacearum (Lso), the causal agent of zebra chip. Previous studies explored the impact of Lso infection and drought stress on B. cockerelli development and reproductive rate separately, but no research to date has evaluated whether drought stress and Lso infection alter feeding behavior of the insects. We explored this using the electrical penetration graph (EPG) technique and monitored feeding behavior of Lso‐infected and uninfected potato psyllids on well‐watered and drought‐stressed tomato (Solanum lycopersicum L., Solanaceae). We found that drought stress had a significant effect on feeding behavior associated with salivation into the phloem and phloem ingestion, both linked to Lso transmission. Furthermore, infected potato psyllids in particular produced a higher number of events associated with these feeding behaviors and remained in these phases longer in well‐watered plants than in plants that were under drought stress. We also reported a new and previously undescribed waveform H of unknown biological function that was produced by the psyllids. This is the first study that considered the impact of bacterial infection and concomitant drought stress on feeding behavior of an insect quantified using EPG.}, number={8}, journal={ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA}, author={Nalam, Vamsi J. and Han, Jinlong and Nachappa, Punya and Szczepaniec, Adrianna}, year={2020}, month={Aug}, pages={588–598} }
 @article{han_nalam_yu_nachappa_2019, title={Vector Competence of Thrips Species to Transmit Soybean Vein Necrosis Virus}, volume={10}, ISSN={["1664-302X"]}, DOI={10.3389/fmicb.2019.00431}, abstractNote={Soybean vein necrosis virus (SVNV) is a newly discovered species of tospovirus infecting soybean plants that is transmitted by the primary vector, soybean thrips (Neohydatothrips variabilis), and two additional secondary vectors, tobacco thrips (Frankliniella fusca) and eastern flower thrips (F. tritici). This study was undertaken to elucidate the association between virus acquisition [6, 12, 24, and 48 h acquisition access period (AAP)] and transmission efficiency [12, 24, and 48 h inoculation access period (IAP)] in the primary vector, N. variabilis, and to examine the mechanisms of vector competence by analyzing the effect of AAP (6, 12, and 24 h) on virus infection in various tissues. In addition, we examined virus infection in tissues of the two secondary vectors. We found a significant effect of virus acquisition on transmission efficiency, transmission rate post 6 and 48 h AAP was significantly lower than 12 and 24 h AAP. Our analysis did not reveal a correlation between virus transmission rate and virus RNA in corresponding N. variabilis adults. On the contrary, N. variabilis adults harboring higher accumulation of the virus (>104) resulted in lower transmission rates. Analysis of SVNV infection in the tissues revealed the presence of the virus in the foregut, midgut (region 1, 2, and 3), tubular salivary glands and principal salivary glands (PSG) of adults of all three vector species, however, the frequency of infected tissues was highest in N. variabilis followed by F. fusca and F. tritici. The frequency of SVNV infection in individual tissues specifically the salivary glands was lowest after 6 h AAP compared to 12 and 24 h AAP. This finding is in agreement with the transmission assays, where significantly lower virus transmission rate was observed post 6 h AAP. In addition, N. variabilis adults with high PSG infection (12 and 24 h AAP) were likely to have high percentage of foregut and midgut region 2 infection. Overall, results from the transmission assays and immunolabeling experiments suggest that shorter AAP results in reduced virus infection in the various tissues especially PSG, which are important determinants of vector competence in SVNV-thrips interaction.}, journal={FRONTIERS IN MICROBIOLOGY}, author={Han, Jinlong and Nalam, Vamsi J. and Yu, I-Chen and Nachappa, Punya}, year={2019}, month={Mar} }