title: The genetic architecture of constitutive and induced trichome density in two new recombinant inbred line populations of Arabidopsis thaliana: phenotypic plasticity, epistasis, and bidirectional leaf damage response.
abstract: BACKGROUND
  Herbivory imposes an important selective pressure on plants. In Arabidopsis thaliana leaf trichomes provide a key defense against insect herbivory; however, trichome production incurs a fitness cost in the absence of herbivory. Previous work on A. thaliana has shown an increase in trichome density in response to leaf damage, suggesting a mechanism by which the cost associated with constitutively high trichome density might be mitigated; however, the genetic basis of trichome density induction has not been studied.
  
  
  RESULTS
  Here, we describe the mapping of quantitative trait loci (QTL) for constitutive and damage induced trichome density in two new recombinant inbred line populations of A. thaliana; mapping for constitutive and induced trichome density also allowed for the investigation of damage response (plasticity) QTL. Both novel and previously identified QTL for constitutive trichome density and the first QTL for induced trichome density and response are identified. Interestingly, two of the four parental accessions and multiple RILs in each population exhibited lower trichome density following leaf damage, a response not previously described in A. thaliana. Importantly, a single QTL was mapped for the response phenotype and allelic variation at this locus appears to determine response trajectory in RILs. The data also show that epistatic interactions are a significant component of the genetic architecture of trichome density.
  
  
  CONCLUSIONS
  Together, our results provide further insights into the genetic architecture of constitutive trichome density and new insights into induced trichome density in A. thaliana specifically and to our understanding of the genetic underpinnings of natural variation generally.
authors.forename: Rebecca H
authors.initials: RH
authors.lastname: Bloomer
authors.forename: Alan M
authors.initials: AM
authors.lastname: Lloyd
authors.affiliation: Institute of Fundamental Sciences, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand. v.v.symonds@massey.ac.nz.
authors.forename: V Vaughan
authors.initials: VV
authors.lastname: Symonds
mesh_terms: D017360:Arabidopsis / Q000033:anatomy & histology* / Q000235:genetics*; D002874:Chromosome Mapping; D003433:Crosses, Genetic; D004843:Epistasis, Genetic; D005838:Genotype; D007178:Inbreeding; D018895:Microsatellite Repeats / Q000235:genetics; D010641:Phenotype; D018515:Plant Leaves / Q000235:genetics / Q000502:physiology*; D040641:Quantitative Trait Loci / Q000235:genetics; D019655:Quantitative Trait, Heritable; D011995:Recombination, Genetic / Q000235:genetics*; D064201:Trichomes / Q000033:anatomy & histology* / Q000235:genetics*