Nitrosative stress triggers microtubule reorganization in Arabidopsis thaliana

Microtubules (MTs) are essential components of the cytoskeleton and fulfil multiple cellular functions in developmental processes, readily responding to intrinsic and external cues. Nitric oxide signalling is well established in plants, and the MT cytoskeleton is one of its potential targets. To mimic low level nitrosative stress, growth medium was supplemented with 3-nitro-l-tyrosine (NO(2)-Tyr), a nitrated form of the amino acid tyrosine, and concentration-dependent changes in root growth rate and a reduction in cell division frequencies in Arabidopsis thaliana were observed. In addition, it is reported that exposure to low NO(2)-Tyr concentrations was not detrimental to plant health and caused subtle and reversible defects. In contrast, growth defects caused by high NO(2)-Tyr concentrations could not be reversed. Live cell imaging of an MT reporter line revealed that treatment with a low concentration of NO(2)-Tyr correlated with disorganized cortical MT arrays and associated non-polar cell expansion in the elongation zone. NO(2)-Tyr treatment antagonized the effects of taxol and oryzalin, further supporting the association of NO(2)-Tyr with MTs. Furthermore, oblique division plane orientations were observed which were probably induced prior to cytokinesis.