title: Genetical genomics of Populus leaf shape variation.
abstract: BACKGROUND
  Leaf morphology varies extensively among plant species and is under strong genetic control. Mutagenic screens in model systems have identified genes and established molecular mechanisms regulating leaf initiation, development, and shape. However, it is not known whether this diversity across plant species is related to naturally occurring variation at these genes. Quantitative trait locus (QTL) analysis has revealed a polygenic control for leaf shape variation in different species suggesting that loci discovered by mutagenesis may only explain part of the naturally occurring variation in leaf shape. Here we undertook a genetical genomics study in a poplar intersectional pseudo-backcross pedigree to identify genetic factors controlling leaf shape. The approach combined QTL discovery in a genetic linkage map anchored to the Populus trichocarpa reference genome sequence and transcriptome analysis.
  
  
  RESULTS
  A major QTL for leaf lamina width and length:width ratio was identified in multiple experiments that confirmed its stability. A transcriptome analysis of expanding leaf tissue contrasted gene expression between individuals with alternative QTL alleles, and identified an ADP-ribosylation factor (ARF) GTPase (PtARF1) as a candidate gene for regulating leaf morphology in this pedigree. ARF GTPases are critical elements in the vesicular trafficking machinery. Disruption of the vesicular trafficking function of ARF by the pharmacological agent Brefeldin A (BFA) altered leaf lateral growth in the narrow-leaf P. trichocarpa suggesting a molecular mechanism of leaf shape determination. Inhibition of the vesicular trafficking processes by BFA interferes with cycling of PIN proteins and causes their accumulation in intercellular compartments abolishing polar localization and disrupting normal auxin flux with potential effects on leaf expansion.
  
  
  CONCLUSIONS
  In other model systems, ARF proteins have been shown to control the localization of auxin efflux carriers, which function to establish auxin gradients and apical-basal cell polarity in developing plant organs. Our results support a model where PtARF1 transcript abundance changes the dynamics of endocytosis-mediated PIN localization in leaf cells, thus affecting lateral auxin flux and subsequently lamina leaf expansion. This suggests that evolution of differential cellular polarity plays a significant role in leaf morphological variation observed in subgenera of genus Populus.
authors.affiliation: School of Forest Resources and Conservation, University of Florida, P.O. Box 110410, Gainesville, FL, 32611, USA. ddrost1@gmail.com.|Plant Molecular and Cellular Biology Graduate Program, University of Florida, P.O. Box 110690, Gainesville, FL, 32611, USA. ddrost1@gmail.com.|Seminis, Inc., 37437 State Highway 16, Woodland, CA, 95695, USA. ddrost1@gmail.com.
authors.forename: Derek R
authors.initials: DR
authors.lastname: Drost
authors.affiliation: School of Forest Resourse and Environmental Sciences, Michigan Technological University, Houghton, MI, 49931, USA. spuranik@mtu.edu.
authors.forename: Swati
authors.initials: S
authors.lastname: Puranik
authors.affiliation: School of Forest Resources and Conservation, University of Florida, P.O. Box 110410, Gainesville, FL, 32611, USA. novaes@ufg.br.|Escola de Agronomia, Universidade Federal de Goiás, Rodovia Goiânia/Nova Veneza, Km0 - Caixa Postal 131, Goiânia, GO, 74690-900, Brazil. novaes@ufg.br.
authors.forename: Evandro
authors.initials: E
authors.lastname: Novaes
authors.affiliation: School of Forest Resources and Conservation, University of Florida, P.O. Box 110410, Gainesville, FL, 32611, USA. cboaventura@gmail.com.|Escola de Agronomia, Universidade Federal de Goiás, Rodovia Goiânia/Nova Veneza, Km0 - Caixa Postal 131, Goiânia, GO, 74690-900, Brazil. cboaventura@gmail.com.
authors.forename: Carolina R D B
authors.initials: CR
authors.lastname: Novaes
authors.affiliation: School of Forest Resources and Conservation, University of Florida, P.O. Box 110410, Gainesville, FL, 32611, USA. scderv@ufl.edu.
authors.forename: Christopher
authors.initials: C
authors.lastname: Dervinis
authors.affiliation: School of Forest Resourse and Environmental Sciences, Michigan Technological University, Houghton, MI, 49931, USA. ogailing@mtu.edu.
authors.forename: Oliver
authors.initials: O
authors.lastname: Gailing
authors.affiliation: School of Forest Resources and Conservation, University of Florida, P.O. Box 110410, Gainesville, FL, 32611, USA. mkirst@ufl.edu.|Plant Molecular and Cellular Biology Graduate Program, University of Florida, P.O. Box 110690, Gainesville, FL, 32611, USA. mkirst@ufl.edu.|University of Florida Genetics Institute, University of Florida, P.O. Box 103610, Gainesville, FL, 32611, USA. mkirst@ufl.edu.
authors.forename: Matias
authors.initials: M
authors.lastname: Kirst
mesh_terms: D020727:ADP-Ribosylation Factors / Q000235:genetics* / Q000378:metabolism; D020126:Brefeldin A / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000235:genetics* / Q000378:metabolism; D006824:Hybridization, Genetic; D018515:Plant Leaves / Q000033:anatomy & histology* / Q000235:genetics; D032107:Populus / Q000033:anatomy & histology / Q000235:genetics*; D040641:Quantitative Trait Loci; D059467:Transcriptome
chemical_list: D020126:Brefeldin A; D020558:GTP Phosphohydrolases; D020727:ADP-Ribosylation Factors