NIP aquaporins: New tools to reduce rice arsenic accumulation

Lead Research Organisation: Rothamsted Research
Department Name: Unlisted


Among major food crops, rice is especially efficient at the accumulation of the toxic and carcinogenic metalloid arsenic (As), thereby posing a significant risk to human health. We have recently discovered that arsenite, the predominant form of arsenic in flooded paddy soil, is taken up by rice roots through the silicon (Si) uptake pathway, with the Nodulin 26-like Intrinsic Protein NIP2;1aquaporin mediating the influx of both Si and arsenite. Other members of nodulin 26-like intrinsic proteins (NIP) are likely to be permeable to arsenite, but their roles in arsenic distribution to rice grain remain unknown. The overall aim of this proposal is to elucidate the roles of NIP channels in the transport of arsenite and methylated As towards rice grain.

Specific objectives are:
1. To quantify expression levels of different NIP genes in rice leaf and grain tissues of rice lines with high and low As accumulation in grain, especially during the grain development stage. This will provide information about the candidate NIP genes that may be involved in As distribution to grain. Furthermore, the promoters of these candidate genes will be used to identify their expression pattern.
2. To investigate the in planta function in terms of As distribution of rice NIP genes that are expressed in leaf and grain tissues using knockout mutants.
3. To determine arsenite transport activity and substrate (arsenite, methylated As, Si) specificity of different rice NIP channel proteins, and to evaluate their relationships with the amino acid composition of the aromatic/arginine (ar/R) filter. To further determine the structure-function relationship by site-directed mutagenesis of the ar/R filter of selected rice NIP genes that are expressed in leaf and grain tissues.
4. To alter the expression of relevant NIP genes in leaf and grain tissues using specific promoters with the aim of decreasing As accumulation.


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