A novel kinase subverts aluminium resistance by boosting ornithine decarboxylase-dependent putrescine biosynthesis.

Rice, as one of the most aluminium (Al)-resistant cereal crops, has developed more complicated Al resistance mechanisms than others. By using forward genetic screening from a rice ethyl methanesulfonate mutant library, we obtained a mutant showing specifically high sensitivity to Al. Through MutMap analysis followed by a complementation test, we identified the causal gene, Al-related Protein Kinase (ArPK) for Al-sensitivity. ArPK expression was induced by a relatively longer exposure to high Al concentration in the roots. The result of RNA-sequencing indicated the functional disorder in arginine metabolism pathway with downregulation of N-acetylornithine deacetylase (NAOD) expression and upregulation of Ornithine decarboxylase1 (ODC1) expression in arpk mutant. Al specifically and rapidly upregulated ODC1 expression and causes overaccumulation of putrescine (Put), whereas the ODC inhibitor difluoromethylornithine reverted Al-sensitive phenotype of arpk, suggesting that overaccumulation of endogenous Put might be harmful for root growth, and that ArPK seems to act as an endogenous inhibitor of ODC1 action to maintain suitable endogenous Put level under Al treatment. Overall, we identified ArPK and its putative repressive role in controlling a novel ODC-dependent Put biosynthesis pathway specifically affecting rice Al resistance, thus enriching the fundamental understanding of plant Al resistance.

Water-Soluble Silicon Quantum Dots with Quasi-Blue Emission.

In this study, water-soluble silicon quantum dots have quasi-blue emission at 390 nm by being capped with 1-vinylimidazole in resese micelles. As-obtained silicon quantum dots have a diameter of 2~5 nm and high crystallinity. The quasi-blue emission of the silicon quantum dots is likely attributed to the polarity of the capping ligands. Moreover, the silicon quantum dots are water-soluble and have photoluminescence nanosecond decay time, suggesting their potential application in biological field.