Metals can accumulate inside plants when absorbed through the roots. Excess
metals in plants can lead to increased ethylene production. Ann Cuypers,
from Hasselt University in Belgium, and her team studied the effects of
cadmium (Cd) on ethylene and its precursor 1-aminocyclopropane-1-carboxylic
acid (ACC). The expression of the ethylene responsive genes, were also
examined in Arabidopsis thaliana.

Increased ethylene, enhanced levels of ACC as well as higher mRNA levels of
ethylene responsive genes indicate increased ethylene production in
Arabidopsis. Researchers found that expression levels of ACS2 and ACS4,
genes that initiate ACC production, significantly increased after Cd
exposure. This increase in ACC led to higher ethylene production.

Cadmium induced increased expression of ACS2 and ACS6, which led to the
increase of ACC and ethylene in Arabidopsis plants. This was confirmed when
mutant plants not expressing the genes showed decreased ethylene production
given the same cadmium levels between wild-types and mutant plants.

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