Crop Biotech Update

Rice Proteins Involved in Arsenite Permeability and Tolerance in Plants

March 2, 2012

Arsenic contamination of groundwater is a problem that affects millions of people across the world. Compared to other cereal species, rice accumulates higher concentrations of Arsenic, thus play an important part in the transfer of Arsenic in the food chain. Kareem Mosa from the University of Massachusetts and colleagues identified proteins called rice plasma membrane intrinsic proteins (PIPs) that are involved in Arsenic tolerance and transport. They searched for sequences in the rice genome that are similar with the known Arsenic transporters in mammals and yeast, and found five candidate genes (OsPIP1;2, OsPIP1;3, OsPIP2,4; OsPIP2;6; and OsPIP2;7). They cloned the genes and expressed them in the oocytes of African clawed frog (Xenopus laevis). Results of the assay showed that there was an increase in the oocyte's uptake of Arsenic.

On the other hand, the team also overexpressed the genes in Arabidopsis. The transgenic plants exhibited improved arsenite tolerance and higher biomass accumulation. However, long term uptake assays revealed that Arsenic failed to accumulate in shoot and root tissues.

These results imply that there is a biodirectional arsenite permeability of rice PIPs in plants. The rice PIPs could be used for development of biofuel crops with enhanced productivity on contaminated soils without increasing the uptake of Arsenic in the biomass or edible plant parts.

Read the abstract at http://www.springerlink.com/content/p201680425661m44/.