The effect of arsenic (As) exposure on genome-wide expression was examined in rice
(Oryza sativa L., ssp. Indica). A group of defense and stress-responsive genes, transporters,
heat-shock proteins, metallothioneins, sulfate-metabolizing proteins, and regulatory
genes showed differential expression in rice seedlings challenged with arsenate (AsV)
and arsenite (AsIII). AsV stress led to upregulation or downregulation of an additional
set of genes in comparison to AsIII. Differential expression of several genes that
showed the highest contrast in a microarray analysis was validated by following the
quantitative changes in the levels of individual transcripts following challenge with
AsV, AsIII, Cd, Cr, and Pb. Most of the selected genes responded to challenge by heavy
metals such as arsenic. However, expression of one of the cytochrome P450 genes (Os01g43740)
in rice root was induced by AsV but not by other heavy metals. Similarly, one glutaredoxin
(Os01g26912) is expressed specifically in the AsIII-treated shoot.