Plant & Animal Genomes XIV Conference Plant & Animal Genomes XIV ConferenceJanuary 14-18, 2006
Town & Country Convention Center
San Diego, CA
Iryna Sanders , Fares Najar , Bruce A Roe
Medicago truncatula flavonoid genes exist in families that occur as single, duplicated or clustered genes. The flavonoid genes within a family share a high level of homology, both at the sequence and exon structure levels, implying homologous functions of duplicated genes. However even when flavonoid genes occur in clusters, all members are not necessarily expressed at the same time and place as a response to the same environmental condition. In majority of instances, the phylogenetically related members of a cluster or other genes from a particular family have different time and spatial expression profiles. Furthermore, not all members of a cluster or other genes from the same family are overexpressed as a result of stress. Although flavonoid genes often are expressed as a result of pathogenic attack or extreme environmental conditions (starvation, irradiation, etc.), our analysis of EST-based expression profiling reveals that phenylalanine ammonia-lyase (PAL), 4-coumarate:CoA ligase (4CL), chalcone synthase (CHS), and isoflavone reductase (IFR) are expressed in leaves, roots, seedlings, nodules, reproductive tissues; flavone synthase II (FS-II) is expressed in roots, leaves, seeds, reproductive tissues; flavone synthase I (FLS) is expressed in leaves, roots, nodules, seeds, shoots; flavonoid 3-hydroxylase (F3H) is expressed in roots, nodules, seeds; UDPG-flavonoid glucosyl transferase (UFGT) is expressed in leaves; chalcone reductase (CHR) is expressed in seedlings, roots; and DFR is expressed in roots, nodules, leaves.
These observations are consistent with the hypothesis that duplicated flavonoid genes have highly specialized function, and this specialization is necessary to give an adequate response to a variety of different environmental stresses.