title: Two ancient classes of MIKC-type MADS-box genes are present in the moss Physcomitrella patens.
abstract: Characterization of seven MADS-box genes, termed PPM1-PPM4 and PpMADS1-PpMADS3, from the moss model species Physcomitrella patens is reported. Phylogeny reconstructions and comparison of exon-intron structures revealed that the genes described here represent two different classes of homologous, yet distinct, MIKC-type MADS-box genes, termed MIKC(c)-type genes-"(c)" stands for "classic"-(PPM1, PPM2, PpMADS1) and MIKC(*)-type genes (PPM3, PPM4, PpMADS2, PpMADS3). The two gene classes deviate from each other in a characteristic way, especially in a sequence stretch termed intervening region. MIKC(c)-type genes are abundantly present in all land plants which have been investigated in this respect, and give rise to well-known gene types such as floral meristem and organ identity genes. In contrast, LAMB1 from the clubmoss Lycopodium annotinum was identified as the only other MIKC(*)-type gene published so far. Our findings strongly suggest that the most recent common ancestor of mosses and vascular plants contained at least one MIKC(c)-type and one MIKC(*)-type gene. Our studies thus reveal an ancient duplication of an MIKC-type gene that occurred before the separation of the lineages that led to extant mosses and vascular plants more than about 450 MYA. The identification of bona fide K-domains in both MIKC(*)-type and MIKC(c)-type proteins suggests that the K-domain is more ancient than is suggested by a recent alternative hypothesis. MIKC(*)-type genes may have escaped identification in ferns and seed plants so far. It seems more likely, however, that they represent a class of genes which has been lost in the lineage which led to extant ferns and seed plants. The high number of P. patens MADS-box genes and the presence of a K-box in the coding region and of some potential binding sites for MADS-domain proteins and other transcription factors in the putative promoter regions of these genes suggest that MADS-box genes in mosses are involved in complex gene regulatory networks similar to those in flowering plants.
authors.affiliation: Department of Molecular Plant Genetics, Max Planck Institute for Breeding Research, Cologne, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Henschel
authors.forename: Rumiko
authors.initials: R
authors.lastname: Kofuji
authors.forename: Mitsuyasu
authors.initials: M
authors.lastname: Hasebe
authors.forename: Heinz
authors.initials: H
authors.lastname: Saedler
authors.forename: Thomas
authors.initials: T
authors.lastname: Münster
authors.forename: Günter
authors.initials: G
authors.lastname: Theissen
mesh_terms: D000595:Amino Acid Sequence; D019068:Bryopsida / Q000235:genetics*; D026161:MADS Domain Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D026161:MADS Domain Proteins