Regulation of the FT2 gene in European aspen

Abstract

A genomic region containing the PtFT2 gene has previously been shown to be involved in the adaptation of Populus tremula (European aspen) to different daylengths. In this study regulatory elements of the gene, which is responsible for growth maintenance and inhibition of bud set, was investigated. The phenotypic and genetic effects of deleting predicted enhancer regions (PER)s, located in the PtFT2 genomic region and hypothesized to be involved in regulation of PtFT2, were analyzed. Plants with one PER upstream of the PtFT2 deleted and plants with one PER downstream of the gene deleted were grown in long day conditions followed by short day conditions. Expression of PtFT2 and traits related to growth cessation and bud set were measured. Indications of a down regulated gene expression and changes in growth cessation and other phenotypic traits were observed. Furthermore, a bioinformatic analysis of the PERs, to find conserved binding sites for potential homologous TFs present in Arabidopsis thaliana, was carried out. Homologous binding sites were found and the TFs binding to them in A. thaliana were involved in flowering, flower development and phase transitions. Finally, an experiment investigating gibberellins (GA)s effect on growth in Populus tremula x tremuloides (hybrid aspen) was performed as it can affect growth cessation. GA treatment counteracted growth cessation, slowed growth and bud set in hybrid aspen plants with PtFT2 deleted. This implies that gibberellin can affect growth cessation independently of PtFT2.