A large family of TM3 MADS-box cDNAs in Pinus radiata includes two members with deletions of the conserved K domain

Angiosperm flower organ formation is regulated by three conserved groups of MADS-box genes, but the function of a fourth conserved group, the TM3 orthologues, remains unclear. We report the isolation of six different MADS- box cDNAs from male cones of the gymnosperm Pinus radiata. All are orthologues of TM3 and two encode proteins with different sized deletions within the conserved K domain. Both the deletions and the large number of paralogous duplications within one clade of MADS-box genes are unusual and indicate that this gene family may have been under selection to evolve new functions in conifers.