Impacts of aluminum on the cytoskeleton of the maize root apex. Short-termeffects on the distal part of the transition zone

Using monoclonal tubulin and actin antibodies, AI-mediated alterations to m icrotubules (MTs) and actin microfilaments (MFs) were shown to be most prom inent in cells of the distal part of the transition zone (DTZ) of an Al-sen sitive maize (Zea mays L.) cultivar. An early response to Al (1 h, 90 mu M) was the depletion of MTs in cells of the DTZ, specifically in the outermos t cortical cell file. However, no prominent changes to the MT cytoskeleton were found in elongating cells treated with Al for 1 h in spite of severe i nhibition of root elongation. Al-induced early alterations to actin MFs wer e less dramatic and consisted of increased actin fluorescence of partially disintegrated MF arrays in cells of the DTZ. These tissue- and development- specific alterations to the cytoskeleton were preceded by and/or coincided with Al-induced depolarization of the plasma membrane and with callose form ation, particularly in the outer cortex cells of the DTZ. Longer Al supplie s (> 6 h) led to progressive enhancements of lesions to the MT cytoskeleton in the epidermis and two to three outer cortex cell files. Our data show t hat the cytoskeleton in the cells of the DTZ is especially sensitive to Al, consistent with the recently proposed specific Al sensitivity of this uniq ue, apical maize root zone.