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Two low phytic acid ( lpa) mutants have been developed previously with the aim to improve the nutritional value of rice ( Oryza sativa) grains. In the present study, the impacts of lpa mutations on grain composition and underlying molecular mechanisms were investigated., Comparative compositional analyses and metabolite profiling demonstrated that concentrations of both phytic acid ( PA) and total phosphorus (P) were significantly reduced in lpa brown rice, accompanied by changes in other metabolites and increased concentrations of nutritionally relevant compounds. The lpa mutations modified the expression of a number of genes involved in PA metabolism, as well as in sulfate and phosphate homeostasis and metabolism., Map-based cloning and complementation identified the underlying lpa gene to be Os SULTR3;3. The promoter of Os SULTR3;3 is highly active in the vascular bundles of leaves, stems and seeds, and its protein is localized in the endoplasmic reticulum. No activity of Os SULTR3;3 was revealed for the transport of phosphate, sulfate, inositol or inositol 1,4,5 triphosphate by heterologous expression in either yeast or Xenopus oocytes., The findings reveal that Os SULTR3;3 plays an important role in grain metabolism, pointing to a new route to generate value-added grains in rice and other cereal crops. [ABSTRACT FROM AUTHOR]

cis -natural antisense transcripts (cis -NATs) are widespread in plants and are often associated with downregulation of their associated sense genes. We found that a cis -NAT positively regulates the level of a protein critical for phosphate homeostasis in rice (Oryza sativa). PHOSPHATE1;2 (PHO1;2), a gene involved in phosphate loading into the xylem in rice, and its associated cis -NAT PHO1;2 are both controlled by promoters active in the vascular cylinder of roots and leaves. While the PHO1; 2 promoter is unresponsive to the plant phosphate status, the cis -NAT PHO1;2 promoter is strongly upregulated under phosphate deficiency. Expression of both cis -NAT PHO1;2 and the PHO1;2 protein increased in phosphate-deficient plants, while the PHO1;2 mRNA level remained stable. Downregulation of cis -NAT PHO1;2 expression by RNA interference resulted in a decrease in PHO1;2 protein, impaired the transfer of phosphate from root to shoot, and decreased seed yield. Constitutive overexpression of NAT PHO1;2 in trans led to a strong increase of PHO1;2, even under phosphate-sufficient conditions. Under all conditions, no changes occurred in the level of expression, sequence, or nuclear export of PHO1;2 mRNA. However, expression of cis -NAT PHO1;2 was associated with a shift of both PHO1;2 and cis -NAT PHO1;2 toward the polysomes. These findings reveal an unexpected role for cis -NAT PHO1;2 in promoting PHO1;2 translation and affecting phosphate homeostasis and plant fitness. [ABSTRACT FROM AUTHOR]

Two low phytic acid (lpa) mutants have been developed previously with the aim to improve the nutritional value of rice (Oryza sativa) grains. In the present study, the impacts of lpa mutations on grain composition and underlying molecular mechanisms were investigated. Comparative compositional analyses and metabolite profiling demonstrated that concentrations of both phytic acid (PA) and total phosphorus (P) were significantly reduced in lpa brown rice, accompanied by changes in other metabolites and increased concentrations of nutritionally relevant compounds. The lpa mutations modified the expression of a number of genes involved in PA metabolism, as well as in sulfate and phosphate homeostasis and metabolism. Map-based cloning and complementation identified the underlying lpa gene to be OsSULTR3;3. The promoter of OsSULTR3;3 is highly active in the vascular bundles of leaves, stems and seeds, and its protein is localized in the endoplasmic reticulum. No activity of OsSULTR3;3 was revealed for the transport of phosphate, sulfate, inositol or inositol 1,4,5 triphosphate by heterologous expression in either yeast or Xenopus oocytes. The findings reveal that OsSULTR3;3 plays an important role in grain metabolism, pointing to a new route to generate value-added grains in rice and other cereal crops., (© 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.)