The putative miR172 target gene InAPETALA2-like is involved in the photoperiodic flower induction of Ipomoea nil

The miR172 gene is involved in the regulation of flowering time and floral organ identity in Arabidopsis thaliana through regulation of APETALA2 (AP2)-like genes’ activity. AP2 plays critical roles in establishing meristem and organ identity during floral development. Additionally, the AP2-like genes including TARGET OF EAT1 (TOE1), TOE2, SMZ, SNZ are involved in the timing of flowering in Arabidopsis thaliana. In our study, a full-length cDNA encoding InAP2-like transcription factor was isolated from cotyledons of morning glory (Ipomoea nil named also Pharbitis nil), a model short day plant. The identified sequence shows significant similarity to the cDNA of TOE1 from Arabidopsis thaliana and contains nucleotides complementary to miR172. Semi-quantitative RT-PCR analysis and in situ hybridization showed that the accumulation of InAP2-like transcripts was high, especially in cotyledons of 5-d-old seedlings. During the 16 h-long inductive night, an increase in the expression of InAP2-like and a decrease in the accumulation of miR172 were observed. Auxin and ethylene treatment, as well as a “night-break”, which completely eliminated flowering induction of Ipomoea nil, caused a decrease in the InAP2-like mRNAs levels in cotyledons of Ipomoea nil. These results suggest the potential involvement of miR172 and InAP2-like in the mechanism of flowering induction in Ipomoea nil.