Characterization of physiological and molecular processes associated with potato response to Zebra chip disease

Authors: NWUGO, CHIKA - Former ARS Employee; SENGODA, VENKATESAN - California Seed And Plant Labs; TIAN, LI - University Of California; Lin, Hong

Submitted to: Horticulture Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2017
Publication Date: 12/6/2017
Citation: Nwugo, C., Sengoda, V.G., Tian, L., Lin, H. 2017. Characterization of physiological and molecular processes associated with potato response to Zebra chip disease. Horticulture Research. 4:1-10. https://doi.org/10.1038/hortres.2017.69.
DOI: https://doi.org/10.1038/hortres.2017.69

Interpretive Summary: Potato is the most important non-grain crop in the world, and its production is threatened by zebra chip (ZC) disease caused by the insect-transmissible bacterium ‘Candidatus Liberibacter solanacearum’ (Lso). In this study molecular and physiological analyses were applied to identify molecular processes associated with host plant responses to Lso infection. To achieve this, gene expression and nutrient concentrations in above ground (AG) and below ground (BG) tissues of healthy and Lso-infected potato plants were investigated. In general, results suggest that ZC disease development involves a reprogramming of the gene regulatory processes in AG tissues into acting like BG tissues as well as poor utilization of energy resources characteristic of a broad indiscriminate increase in gene and protein expression and nutrient accumulation despite limiting photosynthesis. Results from this study revealed novel insights into molecular and physiological aspects associated with potatoes to Lso infection.

Technical Abstract: Transcriptional analyses were applied to identify molecular mechanisms associated with the response of leaf and root potato tissues to ‘Ca. Liberibacter solanacearum’ (Lso) infection, causal agent of zebra chip disease (ZC). Lso infection affected several host processes including defense response-, regulation-, starch metabolism-, and energy production-related processes. Interestingly, while proteinase inhibitors were strongly up-regulated in leaf tissues, a concerted down-regulation was observed in root tissues. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis suggests that alternative splicing might play a role. Furthermore, the transcriptional expression of redox homeostasis-related genes, including superoxide dismutase, showed that the most responses to Lso are tissue specific, highlighting potential targets of Lso susceptibility. Additionally, observation of a net increase in gene expression in Lso-infected tissues despite the concerted down-regulation of photosynthesis-related processes, suggests an Lso-mediated low resource-use-efficiency. Subsequent nutritional analysis revealed an Lso-mediated increase in certain nutrient accumulation, particularly a 210% and 108% increase in the potassium concentration of Lso-infected leaf and root tissues, respectively, suggesting an important role for potassium in ZC pathophysiology. Taken together, this study highlights insights of above and below ground tissues in molecular and physiological aspects associated with potato response to Lso infection.