What Is the Role of Auxin?
The auxin inhibition of bud outgrowth in decapitated plants appears to require the long-distance signal regulated by RMS1 (Fig. 2A). Decapitated rms1 mutant shoots can only respond to exogenous auxin when grafted to WT rootstocks (Beveridge et al., 2000). Moreover, RMS1 may be auxin regulated because RMS1 expression drops after decapitation and is restored by exogenous auxin (E. Foo, C. Beveridge, and C. Rameau, unpublished data). The possibility that other phytohormones or environmental cues may directly or indirectly regulate RMS1 expression, RMS1 protein stability, precursor availability, or product degradation and therefore affect levels of the shoot-to-root signal regulated by RMS1, should be investigated. This could reveal how bud outgrowth may be regulated via long-distance signals that do not cause auxin-related pleiotropic effects. In pea, the bushy mutant and several late flowering mutants under certain conditions (Fig. 1B and see below) have a pleiotropic highly branched and
