Silicon supplementation induces expression of a histidine-rich defensin gene family in Nicotiana tabacum

Authors: MUHINDI, STEPHEN - University Of Toledo; ZELLNER, WENDY - University Of Toledo; FLORA, CHRISTOPHER - University Of Toledo; Boldt, Jennifer; LEISNER, SCOTT - University Of Toledo

Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2022
Publication Date: 8/15/2022
Citation: Muhindi, S., Zellner, W., Flora, C., Boldt, J.K., Leisner, S. 2022. Silicon supplementation induces expression of a histidine-rich defensin gene family in Nicotiana tabacum. Journal of Plant Nutrition. https://doi.org/10.1080/01904167.2022.2108446.
DOI: https://doi.org/10.1080/01904167.2022.2108446

Interpretive Summary: Silicon can help plants tolerate stresses and lessen the negative impacts to growth and yield. However, the molecular mechanisms involved in generating these positive responses are not fully understood. Defensins are small proteins that help plants and animals defend against microbes. A novel subgroup in plants called histidine-rich defensins was recently described. We have identified 14 histidine-rich defensins in tobacco, a model research plant. Gene expression increased in plants that were given supplemental silicon, primarily in the roots and upper leaves. The discovery that histidine-rich defensins are upregulated by silicon, in location-specific responses, suggests they may play a role in silicon-induced stress mitigation. This information will help researchers better understand the role of this gene family and how silicon elicits the beneficial responses observed in plants.

Technical Abstract: Silicon (Si) is known to protect plants from a variety of environmental and biological stressors. The mode of action for these Si responses is unclear. In this study, a family of 14 histidine-rich defensin genes (HRDs) in Nicotiana tabacum, previously described as Defensin 19-like, were identified and induced following Si treatment. These genes formed two subclades within the NtHRD1 family. All but one of the NtHRD1 genes were induced in roots with Si treatment, with members of the two subclades showing differential regulation in upper and lower roots. More than 60% of the NtHRD1 genes showed induced expression with Si treatment in leaves from the upper portion of the plant, while only two genes showed induced expression in lower leaves. Histidine-rich defensins are a newly described group of plant cis-defensins that may play roles in both antimicrobial activity and metal binding. Induction of these genes in N. tabacum following Si treatment could explain some of the beneficial properties of this nutrient.