Revelation of ancestral roles of KNOX genes by a functional analysis of Physcomitrella homologues

KNOX genes are indispensable elements of indeterminate apical growth programmes of vascular plant sporophytes. Since little is known about the roles of such genes in non-vascular plants, functional analysis of moss KNOX homologues (MKN genes) was undertaken using the genetically amenable model plant...

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Bibliographic Details
Published in:Plant cell reports 2007-12, Vol.26 (12), p.2039-2054
Main Authors: Singer, S. D, Ashton, N. W
Format: Article
Language:English
Subjects:
Biological and medical sciences
Blotting, Southern
Bryopsida - genetics
Bryopsida - growth & development
double and triple mutants
Fundamental and applied biological sciences. Psychology
Gene Expression Regulation, Plant
Genes
Genes. Genome
Genotype & phenotype
Homeodomain Proteins - genetics
Homeodomain Proteins - physiology
KNOX gene functions
Models, Genetic
Molecular and cellular biology
Molecular genetics
mosses and liverworts
Mutation
Phenotype
Physcomitrella
Physcomitrella patens
Plant Proteins - genetics
Plant Proteins - physiology
Plants, Genetically Modified
Polymerase Chain Reaction
Single
Targeted gene knockout
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Summary:KNOX genes are indispensable elements of indeterminate apical growth programmes of vascular plant sporophytes. Since little is known about the roles of such genes in non-vascular plants, functional analysis of moss KNOX homologues (MKN genes) was undertaken using the genetically amenable model plant, Physcomitrella patens. Three MKN genes were inactivated by targeted gene knockout to produce single, double and triple mutants. MKN2 (a class 1 KNOX gene) mutants were characterised by premature sporogenesis, abnormal sporophyte ontogeny and irregular spore development. MKN4 (a second class 1 gene) mutants were phenotypically normal. MKN1-3 (a class 2 KNOX gene) mutants exhibited defects in spore coat morphology. Analysis of double and triple mutants revealed that the abnormal sporophytic phenotype of MKN2 mutants was accentuated by mutating MKN4 and to a lesser degree by mutating MKN1-3. The aberrant spore phenotype of MKN1-3 and MKN2 mutants was exacerbated by mutating MKN4. This study provides the first instance in which an abnormal phenotype has been associated with the disruption of a class 2 KNOX gene as well as the first demonstrated case of functional redundancy between a class 1 and a class 2 KNOX gene. We conclude that KNOX genes play significant roles in programming sporophytic development in moss and we provide evidence that ancestral function(s) of this gene family were instrumental in the successful transition of plants to a terrestrial environment.
ISSN:0721-7714
1432-203X
DOI:10.1007/s00299-007-0409-5