Dissecting the contribution of microtubule behaviour in adventitious root induction.

Mohamad Abu-Abied,Inna Mordehaev,Geoffrey O Wasteneys,Einat Sadot,Rivka Elbaum,Oksana Rogovoy (Stelmakh),Marina Grumberg

doi:10.1093/jxb/erv097

Abstract

Induction of adventitious roots (ARs) in recalcitrant plants often culminates in cell division and callus formation rather than root differentiation. Evidence is provided here to suggest that microtubules (MTs) play a role in the shift from cell division to cell differentiation during AR induction. First, it was found that fewer ARs form in the temperature-sensitive mutant mor1-1, in which the MT-associated protein MOR1 is mutated, and in bot1-1, in which the MT-severing protein katanin is mutated. In the two latter mutants, MT dynamics and form are perturbed. By contrast, the number of ARs increased in RIC1-OX3 plants, in which MT bundling is enhanced and katanin is activated. In addition, any1 plants in which cell walls are perturbed made more ARs than wild-type plants. MT perturbations during AR induction in mor1-1 or in wild-type hypocotyls treated with oryzalin led to the formation of amorphous clusters of cells reminiscent of callus. In these cells a specific pattern of polarized light retardation by the cell walls was lost. PIN1 polarization and auxin maxima were hampered and differentiation of the epidermis was inhibited. It is concluded that a fine-tuned crosstalk between MTs, cell walls, and auxin transport is required for proper AR induction.

Highlights

Adventitious root (AR) formation helps plants respond to environmental stresses such as water logging
The mutant rid5 was isolated in a screen for temperature-sensitive mutants with aberrations in AR formation (Konishi and Sugiyama, 2003), whereas mor1-1 was identified in a screen for temperature-dependent disruption of MT organization (Whittington et al, 2001)
In 1978 Oppenoorth noticed that colchicine, an MT-disrupting drug, inhibited cell de-differentiation and differentiation during AR formation in herbaceous cuttings of Phaseolus vulgaris (Oppenoorth, 1978)

Summary

Introduction

Adventitious root (AR) formation helps plants respond to environmental stresses such as water logging. It is exploited for the propagation of cuttings in agriculture and forestry, so there is intense interest in understanding the mechanisms that drive this complex process of root differentiation and regeneration from non-root tissues (Riov et al, 2013). In many difficult-to-root plants the transition from step II to step III is inhibited and, instead of root primordia, clusters of cells or callus are formed (Ballester et al, 1999; Greenwood et al, 2001; Levy et al, 2014; Vidal et al, 2003). Microtubules (MTs) are assembled into the spindle apparatus and the phragmoplast to allow plant cells to execute mitosis, meiosis and cytokinesis

Methods

Results

Conclusion