Evolution of MADS-box gene induction by FLO/LFY genes

Some MADS-box genes function as floral homeotic genes. The Arabidopsis LFY gene is a positive regulator of floral homeotic genes, and homologs of the FLO/LFY gene family in other angiosperms and gymnosperms are likely to have a similar function. To investigate the origin of the floral homeotic gene regulatory cascade involving the FLO/LFY gene, FLO/LFY homologs were cloned from a leptosporangiate ferns (Ceratopteris richardii), two eusporangiate ferns (Angiopteris lygodiifolia and Botrychium multifiduin var. robustum), three fern allies (Psilotum nudum, Equisetum arvense, and Isoetes asiatica) , and a moss (Physcomitrella patens). The FLO/LFY gene phylogenetic tree in dicates that both duplication and loss of FLO/LFY homologs occurred during the course of vascular plant evolution. The expression patterns of the Cera topteris LFY genes (CrLFY1 and 2) were assessed. CrLFY1 expression was prom inent in tissues including shoot tips and circinate reproductive leaves, bu t very weak in other tissues examined. Expression of CrLFY2 was also promin ent in tissues, including shoot tips and circinate reproductive leaves. The se patterns of expression are dissimilar to that of any Ceratopteris MADS-b ox gene previously reported, suggesting that the induction of MADS-box gene s by FLO/LFY is not established at the stage of ferns.