Interactions Between Heavy Metals and Glucosinolates as Defense Mechanisms in Brassicaceae

Due to their sessile nature, plants have to stay at the same place for their whole life span. Plants are always exposed to a variety of stress factors and attacks that threaten their survival and fitness. To overcome these attacks and to safeguarding themselves, plants have developed a plenty of defense mechanisms. Secondary metabolites are involved in chemical defense as organic compounds. Secondary metabolites, including terpenes, phenolics and nitrogen and sulphur containing compounds, defend plants against a variety of herbivores and pathogenic microorganisms as well as various kinds of abiotic stresses. Glucosinolates are important nitrogen-containing plant secondary metabolites which are involved in chemical defense. Most studies of plant defense chemicals have focused upon organic compounds. But, the most accepted hypothesis over the last few decades is the ‘elemental defence’ hypothesis, which states that high levels of metals defend the plant against herbivores. Secondary metabolites and heavy metals are known to play important role in protection of plant against biotic and abiotic stress conditions. The question to be answered is whether metal or glucosinolates act as the primary defense in plants. The answer of this question is very important in terms of understanding the molecular mechanisms of plant defense in future studies. In this review, interactions between heavy metals and glucosinolates as defense mechanisms in Brassicaceae and the recent advances in this regard are discussed.