ISOLATION OF MIR156 AND ITS TARGET GENE FROM STRAWBERRY AND THEIR EXPRESSION IN DIFFERENT STAGE PLANTS

Plant miRNAs negatively regulate their target genes, which function in a range of developmental processes. A growing body of evidence suggests that miR156 and its targeted SPL gene are important controllers in vegetative phase changes. In this study, the miR156-targeted SPL9 gene was isolated from strawberry by RACE and the expressions of miR156 and SPL9 were analyzed by qRT-PCR in different growth stages of strawberry. The full-length cDNA of SPL9 was cloned from strawberry cultivar 'Allstar' and was named FaSPL9. The CDS length of FaSPL9 was 1,143 bp and encoded a predicted protein of 381 amino acid residues. About 521 bp fragments of the FaSPL9 gene were isolated from other strawberry cultivars, including 'Toyonoka', 'Tudla' and selection 08-4-1. These fragments shared 99.18% nucleotide and 98.73% amino acid identities. The expressions of miR156 and FaSPL9 in strawberry leaves were compared at six different stages of micropropagated plants, including in vitro plants, micropropagated plants transplanted into soil for one, two, three, four and five months. The qRT-PCR result showed that relative quantifications of miR156 in six stages were 1.000, 0.588, 0.161, 0.253, 0.195 and 0.130, respectively. The expression of FaSPL9 gene was strikingly inversely proportional to the expression of miR156. So we deduce that miR156 may play an important role in growth phases of strawberry.