Isolation of cDNA clones for genes that are expressed during leaf senescence in Brassica napus. Identification of a gene encoding a senescence-specific metallothionein-like protein.

cDNA clones representing genes that are expressed during leaf senescence in Brassica napus were identified by differential screening of a cDNA library made from RNA isolated from leaves at different stages of senescence. The expression of these genes at different stages of leaf development was examined by northern blot analysis, and several different patterns of expression were observed. One of the clones, LSC54, represented a gene that is expressed at high levels during leaf senescence. Analysis of this gene indicated strong expression in flowers as well as in senescing leaves. DNA sequence analysis of the LSC54 cDNA indicated a similarity between the deduced amino acid sequence and several metallothionein-like proteins previously identified in plants.