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 the Nicotiana
tabacum histidine-rich defensin 1 (NtHRD1) family. All but one of the
NtHRD1 genes were induced in roots with Si treatment, with different
members 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.
