Relationship between freezing tolerance of root-tip cells and cold stability of microtubules in rye (Secale cereale L. cv Puma)

• Published in: Plant physiology (Bethesda) 1990-05, Vol.93 (1), p.77-82
• Main Authors: Kerr, G.P. (University of Minnesota, St. Paul, MN), Carter, J.V
• Format: Article
• Language: English
• Subjects: Acclimatization; ADAPTACION FISIOLOGICA; ADAPTATION; Biological and medical sciences; CONGELACION; CONGELATION; CULTIVO DE CELULAS; CULTURE DE CELLULES; Depolymerization; Environmental and Stress Physiology; Freezing; FRIO; FROID; Fundamental and applied biological sciences. Psychology; Low temperature; Microtubules; Physical agents; Plant physiology and development; Plant roots; Plants; RACINE; RAICES; RESISTANCE A LA TEMPERATURE; RESISTENCIA A LA TEMPERATURA; Root tips; Rye; SECALE CEREALE; Seedlings; Vegetative apparatus, growth and morphogenesis. Senescence
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.93.1.77

The response of cortical microtubules to low temperature and freezing was assessed for root tips of cold-acclimated and nonacclimated winter rye (Secale cereale L. cv Puma) seedlings using indirect immunofluorescence microscopy with antitubulin antibodies. Roots cooled to 0 or -3 degrees C were fixed for immunofluorescence microscopy at these temperatures or after an additional hour at 4 degrees C. Typical arrays of cortical microtubules were present in root-tip cells of seedlings exposed to the cold-acclimation treatment of 4 degrees C for 2 days. Microtubules in these cold-acclimated cells were more easily depolymerized by a 0 degrees C treatment than microtubules in root-tip cells of nonacclimated, 22 degrees C-grown seedlings. Microtubules were still present in some cells of both nonacclimated and cold-acclimated roots at 0 and -3 degrees C; however, the number of microtubules in these cells was lower than in controls. Microtubules remaining during the -3 degrees C freeze were shorter than microtubules in unfrozen control cells. Repolymerization of microtubules after both the 0 and -3 degrees C treatments occurred within 1 h. Root tips of nonacclimated seedlings had an LT-50 of -9 degrees C. Cold acclimation lowered this value to -14 degrees C. Treatment of 22 degrees C-grown seedlings for 24 h with the microtubule-stabilizing drug taxol caused a decrease in the freezing tolerance of root tips, indicated by a LT-50 of -3 degrees C. Treatment with D-secotaxol, an analog of taxol that was less effective in stabilizing microtubules, did not alter the freezing tolerance. We interpret these data to indicate that a degree of depolymerization of microtubules is necessary for realization of maximum freezing tolerance in root-tip cells of rye