Knockout of a rice K5.2 gene increases Ca accumulation in the grain

Rice is a staple food for half of the world’s population,but it is a poor dietary source of calcium(Ca)due to the low concentration.It is an important issue to boost Ca concentration in this grain to improve Ca deficiency risk,but the mechanisms underlying Ca accumulation are poorly understood.Here,we obtained a rice(Oryza sativa)mutant with high shoot Ca accumulation.The mutant exhibited 26%-53% higher Ca in shoots than did wild-type rice(WT)at different Ca supplies.Ca concentration in the xylem sap was 36% higher in the mutant than in the WT.There was no difference in agronomic traits between the WT and mutant,but the mutant showed 25% higher Ca in the polished grain compared with the WT.Map-based cloning combined with a complementation test revealed that the mutant phenotype was caused by an 18-bp deletion of a gene,OsK5.2,belonging to the Shaker-like K+channel family.OsK5.2 was highly expressed in the mature region of the roots and its expression in the roots was not affected by Ca levels,but upregulated by low K.Immunostaining showed that OsK5.2 was mainly expressed in the pericycle of the roots.Taken together,our results revealed a novel role for OsK5.2 in Ca translocation in rice,and will be a good target for Ca biofortification in rice.

Knockout of a gene encoding a Gγ protein boosts alkaline tolerance in cereal crops

Sorghum is highly tolerant to alkaline stress,but the underlying mechanisms are not well understood.Here,based on genotypic difference in alkaline tolerance of sorghum,it was found that AT1(Alkaline tolerance 1)encoding a G protein is involved in alkaline tolerance through negatively modulating the phosphorylation level of PIP2,an aquaporin with transport activity for H_(2)O_(2).Knockout of AT1 releases its inhibition of PIP2,thereby resulting in an increased transport of H_(2)O_(2)from the cytosol into the apoplast,subsequently boosting alkaline tolerance.

Plant Nutrition for Human Nutrition:Hints from Rice Research and Future Perspectives

Both plants and humans require mineral elements for their healthy growth and development.Mineral elements in the soil are taken up by the plant roots and transported to the edible parts for human consumption through various different transporters.An ideal future crop for human health should be rich in essential mineral elements but with less toxic elements in the edible parts.However,due to the great difference in the numbers and amounts of mineral elements required between plants and humans,it is a challenge to balance plant growth and nutrient requirement for humans.In this article,we mainly focus on the transport system of mineral elements from soil to grain in rice,a staple food for half of the world's population,and discuss recent progress on the underlying genetic and physiological mechanisms.Examples are given for silicon,zinc,and iron essential/beneficial for both plants and humans,selenium and iodine only essential for humans,and toxic cadmium and arsenic for all organisms.Manipulation of some transporters for these elements,especially those localized in the node for allocation of mineral elements to the grain,has been successful in generating rice with higher density and bioavailability of essential elements but with less accumulation of toxic elements.We provide our perspectives toward breeding future crops for human health.