Cadmium accumulation in plants: Insights from physiological/molecular
mechanisms to evolutionary biology
Abstract
Cadmium (Cd) contamination in the environment has becoming a hot issue
worldwide, as it has posed a great risk to human health through food
chain. Cd accumulation in the edible parts of crops are involved in four
processes: uptake, translocation, sequestration and (re)distribution,
which are all controlled by membrane transporters. In this review, the
advance in studies on physiological and molecular mechanisms of Cd
accumulation in plants was summarized, and then the functional evolution
was discussed based on oneKP database. Cd accumulation in plants is a
derived and polyphyletic trait that has evolved convergently by several
times. During their evolution, the membrane transporter families, such
as NRAMPs, HMAs, ABCCs, ZIPs, CDFs, CAXs and OPTs, have undergone the
lineage specific expansion due to gene duplication. The orthologues of
OsHMA2 in higher plants are stepwisely evolved from monophyletic
evolutionary lineage with one common ancestor; whereas the orthologues
of OsNRAMP5 from a polyphyletic evolutionary lineage with several
ancestors. In addition, phylogenetic clusters of the orthologues of
OsNRAMP5 have occurred rampant intermixing, suggesting horizontal gene
transfer. It may be concluded that evolution of Cd accumulation in
plants could provide an adaptive advantage for colonization of plants to
the new habitats like metalliferous soil.