title: Nonreciprocal complementation of KNOX gene function in land plants.
abstract: Class I KNOTTED-LIKE HOMEOBOX (KNOX) proteins regulate development of the multicellular diploid sporophyte in both mosses and flowering plants; however, the morphological context in which they function differs. In order to determine how Class I KNOX function was modified as land plants evolved, phylogenetic analyses and cross-species complementation assays were performed. Our data reveal that a duplication within the charophyte sister group to land plants led to distinct Class I and Class II KNOX gene families. Subsequently, Class I sequences diverged substantially in the nonvascular bryophyte groups (liverworts, mosses and hornworts), with moss sequences being most similar to those in vascular plants. Despite this similarity, moss mutants were not complemented by vascular plant KNOX genes. Conversely, the Arabidopsis brevipedicellus (bp-9) mutant was complemented by the PpMKN2 gene from the moss Physcomitrella patens. Lycophyte KNOX genes also complemented bp-9 whereas fern genes only partially complemented the mutant. This lycophyte/fern distinction is mirrored in the phylogeny of KNOX-interacting BELL proteins, in that a gene duplication occurred after divergence of the two groups. Together, our results imply that the moss MKN2 protein can function in a broader developmental context than vascular plant KNOX proteins, the narrower scope having evolved progressively as lycophytes, ferns and flowering plants diverged.
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
authors.forename: Eftychios
authors.initials: E
authors.lastname: Frangedakis
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
authors.forename: Denis
authors.initials: D
authors.lastname: Saint-Marcoux
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Moody
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
authors.forename: Ester
authors.initials: E
authors.lastname: Rabbinowitsch
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
authors.forename: Jane A
authors.initials: JA
authors.lastname: Langdale
mesh_terms: D001499:Bayes Theorem; D019669:Embryophyta / Q000235:genetics*; D019143:Evolution, Molecular; D020440:Gene Duplication; D017343:Genes, Plant; D005816:Genetic Complementation Test; D016013:Likelihood Functions; D000073658:Loss of Function Mutation / Q000235:genetics; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D013045:Species Specificity; D019076:Transgenes
chemical_list: D010940:Plant Proteins
keywords: 
  Ceratopteris richardii
  ; 
  Physcomitrella patens
  ; 
  Selaginella kraussiana
  ; Arabidopsis; KNOTTED homeobox genes; cross-species complementation; land plant evolution; phylogeny