Complementation of wild strawberry (Fragaria vesca L.) SPATULA (FvSPT) and SPIRAL (FvSPR) genes in Arabidopsis thaliana

Abstract

This study assessed the function of genes involved in wild strawberry (Fragaria vesca L.) fruit development and maturation to better understand the mechanism of non-climacteric fruit ripening. SPATULA (FvSPT) and SPIRAL (FvSPR) genes of Fragaria vesca displayed differential expression between the green and red ripening stages. SPT, which encodes a bHLH transcription factor, was characterized in Arabidopsis thaliana L. where its recessive mutation caused degenerative carpel and fruit development. The spt mutant of A. thaliana had shorter, smaller, and wider spatula-shaped siliques than the wild type. SPT was expressed throughout the development of marginal and transmission tract tissues, confirming its role in regulating the growth of these tissues. Two A. thaliana SPIRAL genes, SPR1 and SPR2, are required for directional control of cell elongation. Recessive mutations in either of these genes decreased anisotropic growth of endodermal and cortical root cells and etiolated hypocotyls and caused right-handed helical growth in epidermal cells. The strawberry SPATULA (FvSPT) and SPIRAL (FvSPR) genes were amplified and spt and spr mutant A. thaliana plants were transformed with FvSPT::pGWB401, FvSPR1-1::pGWB401 and FvSPR1-2::pGWB401 vector constructs. Silique length and seed number/silique in the A. thaliana spt mutant were effectively complemented by FvSPT whereas spr was almost fully complemented by FvSPR1-2, but not by FvSPR1-1.