Two phenylalanine ammonia-lyase genes (DcPAL2 and DcPAL3) are involved in the cut-induced stem-end wound reaction of carnation (Dianthus caryophyllus L.)

摘要

The cut stem-end wound reaction is potentially important during the physical blockage of water uptake in cut flowers. Phenylalanine ammonia-lyase (PAL; EC 4.3.1.24) is involved in plant wound reactions, being the key regulatory enzyme of phenylpropanoid metabolism. Two full-length PAL genes (DcPAL2 and DcPAL3) cDNAs were isolated from cut carnation (Dianthus caryophyllus L.) flower stem-ends and found to be transiently expressed following wounding. DcPAL2 was 2,439 bp-long with an open reading frame (ORF) encoding a putative protein of 718 amino acids. DcPAL3 was 2,453 bp-long with an ORF encoding a putative protein of 709 amino acids. An increase in PAL enzyme activity within the basal 2-cm stem-end of cut carnation flowers commenced 12 h after wounding and peaked at 48 h. However, DcPAL2 and DcPAL3 transcript levels increased earlier than PAL activity. DcPAL2 transcript levels increased gradually to a peak 12 h after wounding and remained relatively high thereafter. In contrast, DcPAL3 gene transcripts peaked 3 h after wounding, then decreased. A third PAL gene, DcPAL1, showed constitutively high levels of expression, with only a slight change after wounding. Collectively, these results suggest that expression of DcPAL2 and DcPAL3 leads to increased PAL activity during the wound reaction in cut carnation stems.