A role for gibberellic acid in orienting microtubules and regulating cell growth polarity in the maize root cortex

Abstract

Abstract. The role of gibberellins and cortical microtubules in determining the polarity of cell growth in the root cortex of maize (Zea mays L.) was examined. Inhibition of gibberellin biosynthesis, either naturally through mutation (d5 mutant) or by means of chemicals such as 2S,3S paclobutrazol, caused thickening of root apices and increased their starch content. Immunofluorescence microscopy of cortical microtubules, coupled with a comparison of cell widhts, lengths and shapes, indicated that the meristem and immediate post-mitotic zone were the targets of gibberellin deficiency. Cortical cells in these regions were impaired in their ability to develop highly ordered transversal arrays of cortical microtubules. Consequently, the cells became wider and shorter. Application of gibberellic acid re-established the arrangements of cortical microtubules and the polarity of cell growth characteristic for roots having normal levels of gibberellins, it also decreased the starch content. These results indicate that gibberellins are morphogenetically active substances, not only in shoots but also in roots of maize.

Impacts of Aluminum on the Cytoskeleton of the Maize Root Apex. Short-Term Effects on the Distal Part of the Transition Zone1

“…In contrast, cells within the meristem and elongation region retained their characteristic MT arrays, which appeared even more abundant and extensively bundled. Similar tissue-specific disintegration of MTs in maize root apices was also reported after high ethylene treatment when cells of the inner cortex lost their MTs, whereas outer cortex cells were rather resistant to ethylene (Baluška et al, 1993b). However, high auxin treatment temporarily depolymerized the MTs in all of the root cells (Baluška et al, 1996a).…”

“…Recent findings on the cell wall-PM-cytoskeleton continuum (Wyatt and Carpita, 1993;Miller et al, 1997) call for a reassessment of this debate. In maize (Zea mays L.), detailed information on the arrangement of CMTs and actin MFs was presented for growing and developing cells of intact roots under diverse experimental conditions (Baluška et al, 1992(Baluška et al, , 1993a(Baluška et al, , 1993b(Baluška et al, , 1995(Baluška et al, , 1996a(Baluška et al, , 1996cBlancaflor and Hasenstein, 1993, 1995a, 1995bBaluška and Hasenstein, 1997).…”

Microtubule arrays in maize root cells. Interplay between the cytoskeleton, nuclear organization and post‐mitotic cellular growth patterns

“…Excised root tips were fixed in EPA (Jensen, 1962), embedded in paraffin wax, and then handled and evaluated as described by Baluska, Parker & Barlow, 1993 a. Briefly, after dewaxing in xylene and rehydration through an ethanol series, median longitudinal sections were stained by the PAS (periodic acid-Schiff's) reaction (Jensen, 1962).…”

TheArabidopsis lue1mutant defines a katanin p60 ortholog involved in hormonal control of microtubule orientation during cell growth

“…By contrast, ethylene (ET) and abscisic acid, an antagonist of GA, promote an oblique orientation. In the GAdeficient maize d5 dwarf, CMTs exhibit an oblique orientation that can be restored to the wild-type transverse orientation upon GA application, which results in normal growth (Baluska et al, 1993). Moreover, the use of a GA biosynthesis inhibitor leads to a CMT misorientation in wild-type root cells that is similar to that in d5.…”

“…For example, auxin, gibberellin (GA) and brassinosteroid treatments lead to a modification of cortical MT (CMT) orientation into a transverse array (Ishida and Katsumi, 1992;Baluska et al, 1993;Zandomeni and Schopfer, 1993). By contrast, ethylene (ET) and abscisic acid, an antagonist of GA, promote an oblique orientation.…”