Clues about the ancestral roles of plant MADS-box genes from a functional analysis of moss homologues.

Classic MIKC-type MADS-box genes MIKC(c) genes) are indispensable elements in the genetic programming of pattern formation, including the segmental organisation of angiosperm flowers, in seed plants. Since little is known about the functions of MIKC(c) genes in non-seed plants, a functional analysis of moss MIKC(c) homologues was performed using the genetically amenable, simple model plant, Physcomitrella patens. Expression of moss homologues was knocked down using an antisense RNA approach or abolished by generating transformants with gene knockouts. The knocked down ("antisense") transformants displayed a multifaceted mutant phenotype comprising delayed gametangia formation, diminished sporophyte yield and, in the most extremely affected cases, abnormal sporophyte development and altered leaf morphogenesis. Knocked out transformants were phenotypically normal. Analysis of in situ MIKC(c) gene expression using transgenic strains containing MIKC(c) promoter-GUS fusions showed that these genes are generally expressed ubiquitously in vegetative and reproductive tissues. We conclude that MIKC(c) genes play significant roles in morphogenetic programming of the moss. Functional redundancy characterises some members of the gene group. Our findings provide clues concerning the ancestral roles of some MIKC(c) genes that may be represented in the genomes of diverse extant plant taxa.