Ectopic expression of the apple Md-miRNA156h gene regulates flower and fruit development in Arabidopsis

Abstract

The microRNA miR156 is involved in the regulation of plant growth and development by specifically restricting the transcripts of target genes. In this study, the Md-miR156h gene and its target cDNA fragments, specifically, MdSPL2a-b, MdSPL4, MdSPL6a-g, MdSPL9a-b, MdSPL13a-e and MdSPL15, were isolated from the apple cultivar ‘Gala’. Phylogenetic analysis showed that 18 MdSPL genes were putative targets of miR156. Subsequently, the expression construct p35S:Md-miR156h was created and transformed into Arabidopsis plants. Expression analysis showed that Md-miR156h transcripts and mature miR156 accumulation increased, while its target transcripts AtSPL9 and AtSPL15 were downregulated in transgenic Arabidopsis plants. As a result, the transgenic plants exhibited an extended juvenile phase, increased numbers of leaves, short siliques and the partial abortion of seeds compared with the WT control plants. These results demonstrate that miR156 and its target SPL genes are involved in various developmental processes, especially flower development, and miR156 mediates a conserved post-transcriptional regulation pathway in the apple and Arabidopsis.