Stress responses in alfalfa (Medicago sativa L.). 15. Characterization and expression patterns of members of a subset of the chalcone synthase multigene family.

We have identified five different full length chalcone synthase (CHS) cDNA clones from a cDNA library produced from transcripts isolated from an elicitor-treated alfalfa cell suspension culture. Nucleotide sequence similarity between the clones varied from 88-93%. Oligonucleotides based on divergent sequences in the 5'-untranslated regions of the clones could distinguish individual genes, or groups of genes, and their corresponding transcripts. Developmentally regulated expression of the CHS transcripts was predominantly in roots and root nodules; other unidentified members of the CHS gene family are expressed in stems, leaves and nodules. One of the CHS transcripts was strongly expressed in floral tissue. All the CHS transcripts studied were induced in elicitor-treated cell suspension cultures. Transcripts were also induced in roots in response to wounding or spraying with various elicitors, and in leaves infected with Phoma medicaginis (but not in wounded leaves). The induction kinetics of CHS2 transcripts were more rapid and/or transient than those of other members of the CHS family in CuCl2-treated roots and Phoma-infected leaves. The results are discussed in terms of the evolution and functions of the CHS gene family in legumes.