Hormonal Regulation of Lateral Root Development in Arabidopsis Modulated byMIZ1and Requirement of GNOM Activity forMIZ1Function    

Abstract

Plant organ development is important for adaptation to a changing environment. Genetic and physiological studies have revealed that plant hormones play key roles in lateral root formation. In this study, we show that MIZU-KUSSEI1 (MIZ1), which was identified originally as a regulator of hydrotropism, functions as a novel regulator of hormonally mediated lateral root development. Overexpression of MIZ1 (MIZ1OE) in roots resulted in a reduced number of lateral roots being formed; however, this defect could be recovered with the application of auxin. Indole-3-acetic acid quantification analyses showed that free indole-3-acetic acid levels decreased in MIZ1OE roots, which indicates that alteration of auxin level is critical for the inhibition of lateral root formation in MIZ1OE plants. In addition, MIZ1 negatively regulates cytokinin sensitivity on root development. Application of cytokinin strongly induced the localization of MIZ1-green fluorescent protein to lateral root primordia, which suggests that the inhibition of lateral root development by MIZ1 occurs downstream of cytokinin signaling. Surprisingly, miz2, a weak allele of gnom, suppressed developmental defects in MIZ1OE plants. Taken together, these results suggest that MIZ1 plays a role in lateral root development by maintaining auxin levels and that its function requires GNOM activity. These data provide a molecular framework for auxin-dependent organ development in Arabidopsis (Arabidopsis thaliana).

An altered hydrotropic response (ahr1) mutant of Arabidopsis recovers root hydrotropism with cytokinin

“…However, at 3 μM and 10 μM kinetin, the root growth of all mutants and that of wt seedlings was strongly inhibited. The slight resistant phenotype to exogenous cytokinins of miz1 was recently reported by Moriwaki et al (2011). Interestingly, kinetin significantly repressed the orthogravitropic growth in all five genotypes tested, although ahr1 , wt, and nhr1 roots were the most affected since these moved ∼75 ° away from the vertical compared with miz1 and miz2 roots, which deviated to a lesser extent (∼30 °) (Supplementary Fig.…”

Root phenotypic characterization of lesquerella genetic resources

“…Nine accessions had more lateral roots at 21/13 • C, while the remaining accessions had more at 30/21 • C. The initiation of lateral root branching in pea and Arabidopsis is highly regulated by temperature and other environmental signals (Moriwaki et al, 2011;Malamy and Ryan, 2001;Gladish and Rost, 1993). However, we did not find an overall effect of temperature in lesquerella on this study (p = 0.84, see Table 2).…”

The dynamics of plant plasma membrane proteins: PINs and beyond

“…auxin transport and of hormone gradient formation (Geldner et al, 2004;Moriwaki et al, 2011;Wolters et al, 2011;Okumura et al, 2013). However, even in very severe gnom alleles, a substantial fraction of PIN proteins is still sorted to the plasma membrane, contrasting with the intracellular protein retention observed upon BFA treatment (Steinmann et al, 1999) and highlighting redundant BFA-sensitive sorting activities acting in addition to GNOM.…”