Nucleolytic enzymes and DNA degradation in aleurone layers of imbibed aged wheat seeds

During prolonged storage seeds progressively lose viability and as the rate of ageing is tightly linked to conditions of storage in this work wheat seeds stored for different periods at different temperatures were used. Seeds were categorised as viable, non-viable or of intermediate viability. The object was to determine whether ageing is associated with changes in the activity of RNases and nucleases in the aleurone of wheat seeds. The aleurone dies during post germination and this death appears to be programmed. As some plant nucleases are involved in PCD, these enzymes were studied to follow aleurone cell fate during the imbibition of seeds with different viability and stored at different temperatures. Worth noting was the appearance of a particular Zn2+- dependent nuclease (p40) and of a DNA ladder pattern on the second day of imbibition for all materials used, except for viable cold stored seeds, where Zn2+-dependent nuclease and DNA laddering appeared on the fourth day of imbibition. Results obtained support the correlation between induction of nuclease activities (p40) and DNA laddering. Ageing was characterised by the same pattern of changes with a more precocious degeneration in less viable seeds. Cold storage seems to delay the DNA ladder in viable material.