Tomatinase gene

The tomatinase gene from F. oxysporum f. sp. lycopersici has been cloned recently [34]. This gene encodes a protein that has no sequence homology to any previously described saponinase but which is highly similar to xylanases (family 10 of glycosyl hydrolases) [84, 85, 93-95]. Although F. oxysporum tomatinase does not have any detectable xylanase activity, it remains to be determined whether any of the xylanases listed in this family possesses activity against a-tomatine. In any case, it is... 

One of the isolates used by Quidde et al., was unable to metabolize tomatine and was more sensitive to the glycoalkaloid. In addition, this isolate was not able to induce disease symptoms on detached tomato leaves, but could pathogenize bean leaves, indicating that the ability to degrade tomatine may be required for pathogenicity of B. cinerea on tomato [36]. It would be very interesting to transformed this strain with one tomatinase gene to confirm this hypothesis. 

The structural relationship of tomatinase from B. cinerea to other tomatinases is unknown, but its molecular mass (70 kDa) is different from the other two enzymes mentioned before, 50 kDa from F. oxysporum [35, 38] and 110 kDa from S. lycopersici [33]. Moreover, when Quidde et al., attempted cloning of the tomatinase gene from B. cinerea using the tomatinase from S. lycopersici as a probe, they isolated a gene with high sequence homology, whose product had not tomatinase activity but was able to detoxify avenacin A-l [97], the saponin from oats related to some extent to tomatine. 

Effects of targeted replacement of the tomatinase gene on the interaction of Septoria lycopersici with tomato plants. Mol. Plant-Microbe Interact. 13, 1301-1311... 

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