VviFSK and VviFTK, Two Novel Genes Encoding Putative Non-RD Receptor Kinases Associated with Reproductive Development in Grapevine

Although several genes homologous to those involved in the modulation of reproductive development in the model plant Arabidopsis thaliana have been identified in the Vitis vinifera genome, the regulatory network associated with pollen development, pollen tube elongation, and fecundation in grapevine is largely unknown. In Arabidopsis, receptor kinases play essential roles in pollen tube growth and guidance, leading to proper fertilization and fruit initiation. Comparing the transcriptomic profiles of flowers and early developing berries, two grapevine genes encoding proteins with structural domains corresponding to non-RD receptor kinases were identified. The first of them, VviFTK (Vitis vinifera Flower and Tendril Kinase), is transcribed in flowers at pre-anthesis and in tendrils and shares high sequence homology with At3g03770 gene from Arabidopsis which encodes a putative phloem-specific receptor kinase of unknown function. The second gene, VviFSK (Vitis vinifera Flower and Seed Kinase), is mainly expressed in flowers at anthesis stage and in immature seeds and codes for a protein with high similarity to ScORK17, a receptor kinase involved in the ovule and seed development regulation in Solanum chacoense. VviFSK shows different expression patterns in two cultivars with opposite tendency to parthenocarpic fruit development (PFD) and its transcription is induced in response to exogenously added sucrose. In concordance with the expression mode of VviFSK, the in silico analysis of its promoter region indicates the presence of cis regulatory sequences recognized by floral homeotic transcription factors as well as elements associated with seed-specific expression and sugar induction of gene transcription. These results suggest that VviFSK protein plays a role in the seed development process in grapevine.