miRNA alterations are important mechanism in maize adaptations to low-phosphate environments

Maize is a globally important crop, and a low phosphate (LP) supply frequently limits maize yields in many areas. microRNAs (miRNAs) play important roles in plant development and environmental adaptation. In this study, spatio-temporal miRNA transcript profiling and some of the target genes in the roots and leaves of the maize inbred line Q319 were analyzed in response to LP. Complex small RNA populations were detected after LP culture, and they displayed different patterns in the roots and leaves. Differentially expressed miRNAs can be grouped into 'early' miRNAs, which respond rapidly and are often non-specific to phosphate deficiency, and 'late' miRNAs, which alter the morphology, physiology or metabolism of plants upon prolonged phosphate deficiency. miR827 and miR399-mediated posttranscriptional pathway responses to phosphate availability were conserved and species-specific in maize. Abiotic stress-related miRNAs were engaged in interactions with different signaling and/or metabolic pathways. Auxin-related miRNAs and their targets' expression may be involved in root architecture modification and upland growth retardation in maize when subjected to LP. The changes that were found in the expression of miRNAs and their target genes suggested that miRNA regulation/alterations are pivotal mechanisms in maize adaptations to LP environments. A complex regulatory mechanism involving miRNAs in response to the LP environment is present in maize.