Quantitative isotope-labeled cross-linker proteomics reveals developmental variation in protein interactions and post-translational modifications in diaphorina citri, the citrus greening insect vector

Authors: Ramsey, John - John; ZHONG, XUEFEI - University Of Washington; SAHA, SURYA - Boyce Thompson Institute; CHAVEZ, JUAN - University Of Washington; JOHNSON, RICHARD - University Of Washington; MAHONEY, JACLYN - Boyce Thompson Institute; KELLER, ANDREW - University Of Washington; MOULTON, KATHY - Boyce Thompson Institute; MUELLER, LUKAS - Boyce Thompson Institute; Hall, David; MACCOSS, MICHAEL - University Of Washington; BRUCE, JAMES - University Of Washington; Heck, Michelle

Submitted to: ACS Agricultural Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2022
Publication Date: 4/25/2022
Citation: Ramsey, J.S., Zhong, X., Saha, S., Chavez, J., Johnson, R., Mahoney, J., Keller, A., Moulton, K., Mueller, L., Hall, D.G., Maccoss, M., Bruce, J., Heck, M.L. 2022. Quantitative isotope-labeled cross-linker proteomics reveals developmental variation in protein interactions and post-translational modifications in diaphorina citri, the citrus greening insect vector. ACS Agricultural Science and Technology. 2(3):486-500. https://doi.org/10.1021/acsagscitech.1c00264.
DOI: https://doi.org/10.1021/acsagscitech.1c00264

Interpretive Summary: The bacterium ‘Candidatus Liberibacter asiaticus’ (CLas) is associated with citrus greening disease and is transmitted by the Asian citrus psyllid. The bacterial infection attacks all citrus varieties worldwide, causing reduced fruit marketability and tree death, with no cure available. In this work, we used proteomics analysis, which is the large-scale study of the proteins in an organism, to understand molecular details about the psyllid's development. By analyzing fractions that are enriched with the bacteria and methods to measure how proteins interact within cells, we showed that proteins involved in DNA structure are master regulators of insect development and interactions between the Asian citrus psyllid and the CLas bacterium. Several protein interactions have been found between proteins within human cells, suggesting these protein interactions are important for basic functions within all animal cells across the tree of life. These protein interactions may serve as novel targets for the development of therapies that can block insect spread of citrus greening disease.

Technical Abstract: Acquisition of the citrus greening bacterial pathogen, “Candidatus Liberibacter asiaticus” by Asian citrus psyllid (Diaphorina citri) nymphs is required for efficient tree-to-tree transmission during the adult stage. Quantitative isotope-labeled protein interaction reporter cross-linkers were used in parallel with protein quantification using spectral counting to quantify protein interactions within microbe-enriched cellular fractions of nymph and adult D. citri. Over 100 unique cross-links were found between five insect histone proteins, and over 30% of these were more abundant in nymphs compared to adult insects. Strikingly, some crosslinks detected in D. citri proteins were conserved in cross-linking studies on human cells, suggesting that these protein interaction topologies were present in the common ancestor prior to divergence of the arthropods or are subject to convergent evolution. Analysis of post-translational modifications (PTMs) of cross-linked histones revealed the presence of acetylated and methylated lysine residues, which may impact the psyllid chromatin structure and gene expression. Histone H3 peptides acetylated in the N terminal tail region were found to be more abundant in nymphs compared to adult insects in two orthogonal proteomics methods. The insect life stage-specific histone PTMs and protein interactions represent physical evidence that metamorphosis is associated with changes in chromatin structure that regulate genome-wide transcriptional reprograming.