Synthesis of low molecular weight thiols in response to Cd exposure in Thlaspi caerulescens

In this study, we investigated the accumulation of phytochelatins (PCs) and other low molecular weight (LMW) thiols in response to Cd exposure in two contrasting ecotypes differing in Cd accumulation. Using a root elongation test, we found that the highly accumulating ecotype Ganges was more tolerant to Cd than the low Cd-accumulation ecotype Prayon.L-buthionine-(S,R)-sulphoximine (BSO), a potent inhibitor of the gamma-glutamylcysteine synthetase (gamma-ECS) (an enzyme involved in the PC biosynthetic pathway), increased the Cd sensitivity of Prayon, but had no effect on Ganges. Although PC accumulation increased in response to Cd exposure, no significant differences were observed between the two ecotypes. Cd exposure induced a dose-dependent accumulation of both Cys and a still unidentified LMW thiol in roots of both ecotypes. Root accumulation of Cys and this thiol was higher in Ganges than in Prayon; the ecotypic differences were more pronounced when the plants were treated with BSO. These findings suggest that PCs do not contribute to the Cd hypertolerance displayed by the Ganges ecotype of Thlaspi caerulescens, whereas Cys and other LMW thiols might be involved

Phytoextraction: a review on enhanced metal availability and plant accumulation Fitoextração: uma revisão sobre disponibilidade induzida e acumulação de metais em plantas

Phytoextraction has emerged as a novel approach to clean up metal-polluted soils in which plants are used to transfer toxic metals from soils to shoots. This review provides a synthesis of current knowledge on phytoextraction of metals from soils and their accumulation in plants. The objective is to integrate soil-related (root exudates and chemical amendments) and biological advances to suggest research needs and future directions. As far as can be deduced from the literature, it will be some time before phytoextraction may be established as a commercial technology. For chemically-assisted phytoextraction, research has not shown easily biodegradable compounds to overcome the risks associated with the use of EDTA for poorly available metals in soils. On the other hand, significant progress has been made on the physiological and molecular aspects regarding tolerance and phytoaccumulation of metals in plants. A multidisciplinary approach is warranted to make phytoextraction a feasible commercial technology to remediate metal-polluted soils.<br>A fitoextração é uma tecnologia emergente para despoluição de solos contaminados por metais pesados que usa plantas para transferir metais do solo para a parte aérea, a qual pode ser removida da área poluída. Esta revisão apresenta uma síntese do atual conhecimento sobre fitoextração de metais pesados do solo e sua acumulação em plantas. O objetivo é integrar em uma mesma discussão os avanços relacionados à química do solo (exsudação radicular e adição de agentes quelantes para aumentar a absorção) e à biologia (tolerância a metais e melhoramento genético) visando sugerir futuras pesquisas na área. Embora promissor, o atual estado de desenvolvimento da fitoextração ainda não permite estabelecê-la como uma tecnologia comercial. A pesquisa ainda não encontrou agentes quelantes facilmente biodegradáveis que possam substituir o EDTA na solubilização de metais pouco disponíveis em solos. Entretanto, significativos progressos têm sido feitos no entendimento dos mecanismos fisiológicos e moleculares de tolerância e acumulação de metais em plantas. Uma abordagem multidisciplinar dos vários aspectos que envolvem a fitoextração poderá tornar essa tecnologia econômica e ambientalmente viável a médio prazo