Dynamic changes of miR166s at both the transcriptional and post-transcriptional levels during somatic embryogenesis in Lilium

Abstract

miR166s are involved in fundamentally important biological processes in plants and exhibit functional redundancy and specificity. However, the regulatory role of miR166-mediated somatic embryogenesis (SE) in plants remains unclear. Our previous results preliminarily identified four miR166 family members that have diverse expression profiles during SE in Lilium pumilum DC. Fisch. and in Lilium davidii var. unicolor. In the present study, phylogenetic inference indicated that pre-miR166s are relatively diverse within a species but are closely related among different Lilium species, suggesting that plant miRNA precursors are complex. The predicted targets of LMBR1, IDD1 and PHB were identified by RNA ligase-mediated rapid amplification of cDNA ends (RLM-RACE), and we dynamically monitored miR166s at both the transcriptional and post-transcriptional levels via qRT-PCR. The results indicated that the expression of miR166 precursors and targets was negatively regulated by miR166 s. Moreover, the expression profiles of miR166 family members differed between the two lily species, and the expression levels of miR166 family members also varied among different members of the same species. Lpu-miR166a was expressed at low levels in the embryonic callus and embryo maturation stages, but lpu-miR166b, lda-miR166a and lda-miR166b were expressed at high levels in the torpedo and cotyledon stages. The first gene studied in plant SE, LMBR1, was expressed at high levels during the embryonic callus and late SE stages, suggesting that this gene may be crucial for embryonic cell formation and embryo germination.