Characterization of the FaVRT-2 gene encoding a MADS-box transcription factor responsive to vernalization in tall fescue (Festucaarundinacea)

Abstract

Delay of floral transition is a valuable trait in commercially important turfgrass species. It has been reported that short vegetative phase (SVP)-like proteins, potential repressors of the floral inductive pathway, control the transition from vegetative to reproductive phase. A homolog of SVP-like genes was isolated from tall fescue (Festuca arundinacea) by 5′-rapid amplification of cDNA ends (RACE) and 3′-RACE and designated as F. arundinacea VEGETATIVE TO REPRODUCTIVE TRANSITION gene-2 (FaVRT-2). It encodes a putative protein of 226 amino acids with a conserved MADS (M) domain, a Keratin-like (K) domain, and a C-terminal (C) domain. Phylogenetic analysis showed that FaVRT-2 is most closely related to VRT-2 proteins from ryegrass, barley, and wheat and belongs to the StMADS11 subfamily of MADS-box transcription factors. Subcellular localization showed that the FaVRT-2 protein accumulates in the nucleus suggesting a role as trans acting factor. FaVRT-2 transcripts accumulate abundantly in roots and stems and is moderately present in leaves under normal conditions (without non-vernalization treatment). Real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) showed similar transcriptional patterns of FaVRT-2 under both vernalization and non-vernalization conditions. However, the peak of FaVRT-2 transcripts under vernalization condition occurred 14 days earlier than that found under non-vernalization condition. These results support the hypothesis that FaVRT-2, a putative repressor of floral transition, is regulated by vernalization in tall fescue.