Functional aspects of solanaceae trichomes in heavy metal detoxification

Abstract

Solanaceous plants are ubiquitous and are able to colonize degraded, abandoned and metal polluted habitats. Members of the family have evolved interesting extrinsic and intrinsic traits to combat the metal toxicity in multiple ways. Indumentum constituted mostly of trichome layer provides structural defense for both biotic stress (herbivory, oviposition, microbial pathogenesis) and abiotic stress (like drought, heat, freezing, photooxidation and UV radiation). Plants with heavy metal tolerance can accumulate toxic heavy metals in their trichomes as a part of their elemental defense detoxification strategy. Apart from the canonical functions, trichomes support ion and metal homeostasis, including the sequestration, compartmentalization, accumulation and excretion of heavy metals in many ways. The trichomes in Solanaceae are known to have a key role in the detoxification of Cd, Ni, Pb and Zn. Expressed sequence tag (EST)‐based large‐scale gene analysis in tobacco has indicated that trichomes are biologically active and stress–responsive structures. Trichome secretions and exudates also play an active role in metal detoxification process. Given that trichomes provide chemical defense from heavy metal stresses in the form of sequestration and extrusion, the plants having trichomes have potential role in remediation of contaminated soils. Solanaceae trichomes can serve as important model tissues that can be modified to attenuate metal toxicity, serve as environmental indicators and enhance phytoremediation potential of the family.