Inhibition of protein synthesis by cycloheximide does not prevent adaptive responses triggered by heavy metal salts in Vicia faba

Copper sulfate, lead nitrate, and cadmium nitrate conditioning treatments of Vicia faba root tip meristem cells result in adaptive responses to triethylenemelamine (TEM)- and maleic hydrazide (MH)-induced genotoxic effects, i.e., they significantly reduce the yield of metaphases with chromatid aberrations. Contrary to adaptive responses triggered by low clastogen concentrations or heat shock, protective effects induced by heavy metals cannot be prevented by inhibition of protein synthesis and last for a much longer time span (up to at least 48 h). These and other data support the conclusion that the cells can react to the impact of external factors by various inducible functions which eventually protect their DNA from damage.

Combined application of MH and TEM for conditioning treatment simultaneously triggers two protective functions against induction of chromatid aberrations in Vicia faba root tip meristem cells

Conditioning pre-exposure of Vicia faba root tip meristem cells to triethylenemelamine (TEM) does not trigger an adaptive response to maleic hydrazide (MH) and vice versa. Since TEM conditioning treatment can induce protective effects (as evident from the yield of metaphases with chromatid aberrations) against TEM challenging treatment and MH conditioning can trigger an adaptive response to MH challenging treatment, two different protective functions are apparently triggered in dependence on the agent used for conditioning pre-exposure. When a mixture of TEM and MH is being used for conditioning treatment, adaptive responses to both TEM and MH can simultaneously be induced and significantly reduce the yield of metaphases with chromatid aberrations observed after challenge treatment with TEM or MH.

Low temperature between conditioning and challenge treatment prevents the 'adaptive response' of Vicia faba root tip meristem cells

When the temperature during intertreatment time (2 h) between conditioning and challenge treatment of Vicia faba root tip meristems with either triethylenemelamine or maleic hydrazide was reduced from 24 degrees C to 12 degrees C no adaptive response occurred any more. The yield of metaphases with chromatid aberrations under these circumstances was similar to that observed after challenge treatment alone, i.e., no reduction occurred. This indicates that the metabolic state of the cells is of critical importance for the presence or absence of adaptive responses.

Involvement of phytochelatins in NiCl2-triggered protection against induction of chromatid aberrations by TEM and MH in Vicia faba root tip meristems?

Conditioning treatment of Vicia faba root tip meristem cells with NiCl2 prior to challenge treatment with triethylenemelamine (TEM) or maleic hydrazide (MH) triggered protective functions against both these clastogens, i.e., resulted in a significantly reduced yield of metaphases with chromatid aberrations. Protection was prevented by pretreatment with buthionine sulfoximine (BSI), an inhibitor of the synthesis of plant phytochelatins (PCs), indicating that the NiCl2-triggered PC synthesis may be involved in the protective functions induced by NiCl2 conditioning treatment. BSI (instead of NiCl2) conditioning treatment triggered protection against MH but not against TEM.