Microtubule associated protein END BINDING 1b: functional domain deletions and root responses to mechanical stimuli

The microtubule-associated protein EB1b inhibits root responses to mechanical stimulation. The goal of this study was to understand more clearly how EB1b regulates these responses. Loss of EB1b did not alter root elongation rates in response to mechanical cues. However, overexpressing EB1b had an inhibitory effect on root elongation. Mutant eb1b-1 Arabidopsis plants expressing truncated EB1b proteins, with and without GFP fusions, were generated. Truncations included both N-terminal (microtubule-binding) and C-terminal (protein-interaction) domains. Transgenic mutants expressing a truncated version of EB1b missing part of the C-terminal domain were analyzed. The responses of these mutant roots to mechanical stimulation was similar to untransformed eb1b-1 mutants. Since previous analyses have shown that responses of mutants expressing full-length EB1b are equivalent to wild type, this result indicates that the EB1b C-terminus is required for normal regulation of root responses to mechanical cues and that interactions between EB1b and other, non-tubulin proteins is involved.