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.

BackgroundPhosphorus (P) stress is a global problem in maize production. Although macro/microarray technologies have greatly increased our general knowledge of maize responses to P stress, a greater understanding of the diversity of responses in maize genotypes is still needed.ResultsIn this study, we first evaluated the tolerance to low P of 560 accessions under field conditions, and selected the low P-tolerant line CCM454 and the low P-sensitive line 31778 for further research. We then generated 24 strand-specific RNA libraries from shoots and roots of CCM454 and 31778 that had been subjected to P stress for 2 and 8 days. The P deficiency-responsive genes common to CCM454 and 31778 were involved in various metabolic processes, including acid phosphatase (APase) activity. Determination of root-secretory APase activities showed that the induction of APase by P stress occurred much earlier in CCM454 than that in 31778. Gene Ontology analysis of differentially expressed genes (DEGs) and CAT/POD activities between CCM454 and 31778 under P-sufficient and -deficient conditions demonstrated that CCM454 has a greater ability to eliminate reactive oxygen species (ROS) than 31778. In addition, 16 miRNAs in roots and 12 miRNAs in shoots, including miRNA399s, were identified as DEGs between CCM454 and 31778.ConclusionsThe results indicate that the tolerance to low P of CCM454 is mainly due to the rapid responsiveness to P stress and efficient elimination of ROS. Our findings increase the understanding of the molecular events involved in the diversity of responses to P stress among maize accessions.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0903-4) contains supplementary material, which is available to authorized users.

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