Transgenesis of Agrobacterium rhizogenes K599 orf3 into plant alters plant phenotype to dwarf and branch

Abstract

Virulent strains of Agrobacterium rhizogenes (A. rhizogenes) contain Ri plasmids responsible for hairy root development on susceptible plants. Ri plasmid possesses different gene segments. T-DNA region of Ri plasmid pRi2659 in A. rhizogenes strain K599 carries 11 functional genes/coding regions. In this study, we cloned a complete orf3-coding region in T-DNA of plasmid pRi2659, which is 1479 bp in length and encodes 492 amino acid residues. Then, we developed an orf3-containing expression vector named pRI101-AN-orf3 and generated the orf3-transgenic tobacco plants via A. tumefaciens-mediated method. The orf3-transgenic tobacco displayed altered morphological characters including shortened internodes, dwarfisms, more branches, shortened leaf blade length, early flowering, and weak roots. Compared to those of untransformed tobacco, the contents of two endogenous plant hormones, auxins (IAA) and abscisic acid, were decreased whereas the cytokinin content was increased but gibberellic acid content was not consistently obviously changed. Besides, we also transferred orf3 into Arabidopsis thaliana using floral-dip method and obtained orf3-transgenic Arabidopsis homozygous offspring. The orf3-transgenic Arabidopsis displayed morphological characters of dwarfism and more branches similar to those of the orf3-transgenic tobacco. Together, these results indicate that K599 orf3 possesses the functions of altering plant phenotypes and promotes plants to become dwarf and branch.