Epigenetic regulation at the FTa1 flowering time locus in Medicago

J Putterill, L Zhang, G Thomson, C Che and M Jaudal

School of Biological Sciences, University of Auckland, Private Bag 12019, Auckland,New Zealand

A conserved function amongst many FT genes from different plants is to promote the transition to flowering. In the reference legume Medicago the FTa1 gene, a FT-like gene, strongly promotes flowering and functions as an important integrator of major environmental signals that promote flowering. Thus FTa1 transcript levels are strongly elevated in the leaves after extended exposure to cold (vernalisation) followed by long day (LD) growth at warm temperatures. Although Arabidopsis FT is also induced by these signals, the mechanisms that regulate FTa1 differ, because Medicago lacks a CO-like function and the FLC/MAF clade that are pivotal to Arabidopsis FT regulation by LD and vernalisation. We are studying the regulation of gene expression at the FTa1 locus using gene expression profiling, ChIP and Medicago flowering time mutants. These include the dominant early flowering spring mutants with retroelement transposon insertions at the FTa1 locus and the recessive Mtvrn2 mutants predicted to have defective Polycomb PRC2 function. Both types of mutants have precocious elevated FTa1 expression, bypass vernalisation and early flowering. We will present results indicating that epigenetic controls regulate important aspects of the developmental and environmental control of FTa1 expression. In addition, an adjacent gene encoding a long non-coding RNA (lnc RNA) which is elevated during cold exposure in multiple Medicago accessions will be described.