The -miR399 Regulatory Module Is Important for Low Phosphate Tolerance in Maize.

The regulation of adaptive responses to phosphorus (P) deficiency by the ()/ () pathway has been well studied in Arabidopsis () but not in maize (). Here, we show that miR399 transcripts are strongly induced in maize by phosphate (Pi) deficiency. Transgenic maize plants that overexpressed accumulated excessive amounts of P in their shoots and displayed typical Pi-toxicity phenotypes. We reannotated with an additional 1,165 bp of the 5' untranslated region. miR399-guided posttranscriptional repression of was mainly observed in the P-efficient lines. We identified Pi-deficiency-induced long-noncoding RNA1 () from our strand-specific RNA libraries. Transient expression assays in and maize leaf protoplasts demonstrated that inhibits ZmmiR399-guided cleavage of The abundance of was significantly higher in P-inefficient lines than in P-efficient lines, which is consistent with the abundance of ZmmiR399 transcripts. These results indicate that the interaction between and miR399 is important for tolerance to low Pi in maize.