Abstract

Fragaria chiloensis is an endemic berry, characterized for a white-pink color and a pleasant taste and aroma, however it can stand only a short post-harvest period as it softens very fast. Softening is due to cell wall disassembling mediated by cell Wall degrading enzymes. Transcription factors (TF) are regulators of developing processes such as fruit ripening. A new NAC gene named FcNAC2 was isolated from F. chiloensis fruit; the sequence codifies a protein of 346 amino acid residues and displays the characteristic NAC domain at the N-terminal, sub-divided into five sub-domains. Phylogenetic analyses evidences that FcNAC2 shares the group with NAC members related to senescence. The expression of FcNAC2 displays an increase in its transcription during fruit ripening; it is also expressed in roots, stems and runners. Hormonal treatments of fruits evidence that FcNAC2 transcripts are induced by auxins and repressed by abscisic acid. Functional assays evidence that FcNAC2 can trans-activate the promoters of FcEXP2, a cell wall remodeling gene. Thehomology model of FcNAC2 protein was built, and it is composed of two α-helices, one α-helix 310, 4 β-sheets and 7 loops. In addition, FcNAC2 formed stable homodimers. The conserved zone at the Nterminal (sub-domain A) contains the residues involved in dimerization; Arg24 and Glu31 residues are crucial for homodimer formation. FcNAC2 homodimer interacts with DNA through a β-sheet core (β2), which contains the conserved WKATGTD domain that interacts with the major DNA groove, forming a DNA-FcNAC2 complex. The results suggest the participation of FcNAC2 during development of Chilean strawberry fruit.