microRNA expression profiles associated with phosphorus deficiency in white lupin (Lupinus albus L.)

Phosphate (P) deficiency is one of the major factors limiting crop growth and production. Although physiological and molecular identification of P deficiency in plants has been the focus for many years, little is known about the regulation of P-deficiency responsive genes and signal networks. In this study, we analyzed the global expression of miRNAs in white lupin (Lupinus albus) under phosphate deficiency. Total RNAs extracted from P-deficient or P-sufficient tissues was hybridized to an array containing 771 conserved plant miRNA sequences. An induction ratio of greater than 2.0 in all tissues was obtained for 167 miRNAs belonging to 35 miRNA families. Analyses of the data revealed that 35 white lupin miRNA families show differential expression under P deficiency, of which, 17, 9 and 10 were found to be up-regulated, while 7, 6 and 12 were down-regulated in roots, stems and leaves, respectively. These miRNAs were confirmed by RT-PCR-based assay. Within the 35 miRNAs, 30 were successfully validated. Our study provided the evidence that a set of miRNAs are involved in the regulation of adaptive response to P deficiency and that miRNAs coordinately regulate the network of downstream genes controlling morphological and metabolic processes in P-deficient plants.