Evolutionary analysis of MIR156/157 family during floral induction in walnut (Juglans regia L.)

Abstract

ABSTRACT The miR156/157 family is widely identified in various plant species and plays important regulatory roles in floral induction and stress response. However, information regarding evolution of miR156/157s and their functions during floral induction in walnut (Juglans regia) remains unknown. In this study, four precursors and four mature miR156/157s were identified in J. regia via small RNA sequencing. We constructed phylogenetic trees for precursor sequences of miR156/157s from different plants, as well as J. regia. The upstream promoter sequences of four jre-MIR156/157s contained the core cis-regulatory elements (TATA-box and CAAT-box) and many additional cis-regulatory elements including elements for light, low temperature etc. The RT-qPCR showed expression of jre-miR156j, jre-miR157a-5p and jre-miR157d was up-regulated in female flower buds before floral induction (F_1) relative to female flower buds during floral induction (F_2), and down-regulated in female flower buds during floral induction (F_2) relative to leaf buds during the same period (JRL), which showed an opposite tendency with their target genes, Cluster-14,922.24187, Cluster-14,922.29571, Cluster-14,922.56749, Cluster-14,922.51135, Cluster-14,922.65142 and Cluster-14,922.32383. The results suggest jre-miR156/157s play important roles during floral induction in J. regia.