The characterization of LeNUC1, a nuclease associated with leaf senescence of tomato.

Induction of nuclease and RNase activities, together with decreases in nucleic acid content are considered to be characteristics of senescence in higher plants. However, little is known about the specific identities or functions of the enzymes involved or the mechanisms controlling their activation. Here we report the identification of a 41-kDa-tomato nuclease, LeNUC1, which is specifically induced during tomato leaf senescence but not in ripening fruits.

The expression of a grapefruit gene encoding an isoflavone reductase-like protein is induced in response to UV irradiation.

Exposure of harvested grapefruit to UV-C (254 nm) irradiation was previously found to induce resistance against the green mold decay caused by Penicillium digitatum. In order to gain insight into the mechanism of this UV-induced resistance we initiated a study for isolation of genes induced during this process. Using the differential display method we cloned cDNA representing an mRNA which is accumulated in grapefruit peel upon UV irradiation.

Senescence-induced RNases in tomato.

A main feature of leaf senescence is the hydrolysis of macromolecules by hydrolases of various types, and redistribution of released materials. We have initiated a study for the characterization of RNases involved in nucleic acid catabolism during senescence. Using a PCR-based cloning approach we isolated from tomato two senescence-induced RNase cDNA clones.