Calmodulin Levels Are Not Responsible for Aluminium Tolerance in Wheat

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Abstract
Circumstantial evidence has suggested that the protein calmodulin may be the primary target of aluminium toxicity in plants. Experiments were carried out to test the hypothesis that genetic differences in aluminium tolerance in wheat (Triticum aestivum L.) are the consequence of different levels of calmodulin. The tolerant wheat, selection Waalt, differed from cv. Warigal by a single dominant gene for aluminium tolerance as indicated by analysis of the F2. The tolerance of cv. Carazinho also is reported to be genetically simple. Crosses between the two tolerant wheats, Carazinho and Waalt, showed that they have linked or allelic genes for aluminium tolerance. Calmodulin was extracted from the whole roots and from root tips alone, either after 3 days exposure to aluminium, or without aluminium treatment. Calmodulin levels were measured using a radioimmunoassay. No significant differences were observed between Carazinho (tolerant) and Sunstar (sensitive). Additionally the four genotypes (Waalt, Carazinho, Warigal and Sunstar) showed no consistent differences in sensitivity, as measured by seedling root growth, to three calmodulin antagonists, trifluoperazine, chlorpromazine and calmidizolium. Thus it appears that the different aluminium tolerances in these wheats are not due to different calmodulin levels.