Senescence-induced expression of a homologue of Δ9 desaturase in rose petals

cDNAs for senescence-inducible genes were isolated by differential hybridization from a cDNA library derived from mRNAs from the petals of rose flowers. The amino acid sequence deduced from these cDNAs exhibited significant homology to those of Δ9 acyl-lipid desaturases of cyanobacteria and of Δ9 acyl-CoA desaturases of a yeast and mammals. There was no amino-terminal sequence indicative of a leader peptide for targeting to the chloroplasts or to mitochondria. Northern blot analysis indicated that the transcripts of the cDNAs were expressed specifically in petals at late developmental stages and during senescence. It is proposed that a Δ9 desaturase in the senescing petals play an important role in the degradation of saturated fatty acids of membrane lipids.