Molecular mechanisms to reduce Arsenic in Rice

Food security is under pressure all over the globe. Abiotic stress is one of the
largest threats to crop production and amongst these, crop contamination
with arsenic (As) is prevalent in many areas of the world. Arsenic is an
extremely toxic metalloid and human exposure to As is common in many
areas of the world, occurring via drinking water and crop consumption,
particularly rice. To reduce the danger of diet contamination, it is imperative
to reduce As in crops, especially in the edible parts such as grain and seed.

This PhD project will continue studies into the role of membrane
transporters in uptake, distribution and seed deposition of As in plants. We,
and other labs, showed that specific aquaporins (from the NIP subfamily),
are responsible for arsenite uptake in plants. Recently, we showed that
some of these (such as AtNIP7;1 in Arabidopsis) play an important role in
delivering As to the grain. Other studies showed that specific sugar
transporters (AtINT2 and AtINT4) are also involved in this process. These
exciting results suggest that specific NIPs and INTs are important
determinants of As deposition in seeds and that loss of function in these
proteins may help generate a healthier crop!

Another part of the project is concerned with aquaporin structure-function:
Several studies have shown that mutating plant aquaporins to reduce As
permeability also reduces uptake of beneficial nutrients such as silicon and
boron. However, a recent report demonstrated that a, as yet unique Killifish
aquaporin did not conduct AsIII and yet may have a high silicon
permeability. We will test this hypothesis in heterologous expression
systems (Xenopus embryos), measuring As and Si transport in wildtype and
mutated forms of Killifish and plant aquaporins.