Silicon modulates expression of pathogen defense-related genes during alleviation of copper toxicity in Nicotiana tabacum

Authors: FLORA, CHRISTOPHER - University Of Toledo; KHANDEKAR, SUSHANT - University Of Toledo; Boldt, Jennifer; LEISNER, SCOTT - University Of Toledo

Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2020
Publication Date: 11/23/2020
Citation: Flora, C., Khandekar, S., Boldt, J.K., Leisner, S. 2020. Silicon modulates expression of pathogen defense-related genes during alleviation of copper toxicity in Nicotiana tabacum. Journal of Plant Nutrition. 44(5):723-733. https://doi.org/10.1080/01904167.2020.1849296.
DOI: https://doi.org/10.1080/01904167.2020.1849296

Interpretive Summary: Plants are exposed to a variety of stresses which limit growth and productivity. Treating with the element silicon (Si) helps plants to better handle stress. For example, treating tobacco with elevated copper (Cu) results in poor plant growth, but this can be reversed by concurrently providing the plants with Si. However, the mechanisms underlying the benefits conferred by Si are unclear. A better understanding of how Si benefits plants will provide new strategies for stress alleviation and increase crop productivity. Treating plants with excessive amounts of Cu activated the expression of genes involved in plant disease defense. The expression of disease defense genes was induced in tobacco roots after one week of Cu treatment, and the addition of Si increased them even higher. However, the Si enhancement of disease defense gene expression in plants supplied excess Cu was reduced after three weeks of treatment. Therefore, when examining Si effects in plants in order to understand them, it is critical that researchers pay attention to the length of time after treatment that plants are examined. These data also lead to new hypotheses that researchers can test to further elucidate how Si confers its benefits to plants.

Technical Abstract: Plants treated with metals appear to better fend off infection by pathogens. This activity is mediated, at least in part, by the activation of the salicylic acid (SA) signaling pathway. Previous work in our laboratory demonstrated that silicon (Si) could alleviate copper (Cu) toxicity stress in Nicotiana tabacum. However, how Si affected expression of genes involved in SA biosynthesis and signaling in N. tabacum under Cu stress was unclear. Therefore, we investigated this at two time points. Roots of plants treated with Cu toxicity for one week exhibited increased transcript levels for Isochorismate Synthase, a key gene involved in SA biosynthesis, and the addition of Si further enhanced expression. Microarray analysis identified a number of disease defense-associated genes up-regulated in N. tabacum roots after one week of Cu toxicity treatment and further increased when plants were also supplemented with Si. However, the effect of Si was lost after three weeks of treatment, indicating these effects are dynamic.