Increased vegetative development and sturdiness of storekeeper-transgenic tobacco

The STOREKEEPER (STK) family of DNA-binding proteins work as transcription factors and the ectopic expression of two stk-like genes from Arabidopsis thaliana, stk01 (At1g61730) and stk03 (At4g00238), in tobacco increased the number of vegetative internodes and promoted plant and leaf size, stem diameter and sturdiness. The development of these plants started with rosette formation while pronounced shoot elongation and flowering was delayed. Moreover, when the STK01 and STK03 proteins were fused to the Herpes Simplex Virus VP16 transcriptional activation domain and expressed in tobacco the vigorous storekeeper-phenotype did not appear indicating that transgenic STK-like proteins in part worked as repressors of tobacco reproductive development. Furthermore, Yeast Two-Hybrid screenings proved that STK01 and STK03 can form homodimers and heterodimers with further members of the STKlike family. Therefore, we assume that interactions between transgenic Arabidopsis STKs and resident tobacco STKs could have contributed to the observed developmental changes in transgenic tobacco. Our findings open up promising applications for overexpression of stk-like genes in crops that benefit from increased sturdiness and vegetative organ development, such as tobacco in molecular farming approaches, biomass-based energy crops and medicinal plants that produce bioactive compounds in leaves