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DOCTORAL RESEARCH



           Supervisors  DR CATHERINE KIDNER
                                   PROFESSOR ANDREW HUDSON

            Institutions  UNIVERSITY OF EDINBURGH
                                 ROYAL BOTANIC GARDENS EDINBURGH
                                (RBGE)




THE GENETICS OF LEAF SHAPE VARIATION IN BEGONIA



Begonia is one of the largest plant genera, with over 2 000 species, and displays an extraordinary range of leaf shapes across diverse environments along the tropics. As a genus, Begonia provides a unique system for studying the evolution of leaf form and allows insight into the genetic and environmental drivers of morphological diversity.  
   


PATTERNS OF LEAF SHAPE VARIATION IN BEGONIA
  • The leaves of 154 Begonia species from RBGE’s living collection were plotted against the working phylogeny.
  • A mormophetric analysis of leaf outlines was conducted using elliptical Fourier analysis to quantify shape.
  • A pipeline for identifying subtle shape differences was established using closely-related Begonias.


Left: Leaf scans for nine species of Begonia: Begonia listada, Begonia wollnyi, Begonia acetosella, Begonia yapenensis, Begonia bogneri, Begonia bipinnatifida, Begonia luxurians, Begonia angularis and Begonia grandis. 
Middle: Leaf shape variation across the Begonia phylogeny.
Right: The morphospace of shape in Begonia section Gireouidia with the morphological diversity of each species in the section projected onto the overall morphospace. 
THE GENETIC PATHWAYS REGULATING LEAF SHAPE  
 
Begonia genomes species               B. luxurians vegetative bud
 
B. conchifolia                                      B. plebeja
 
B. luxurians                                         B. parviflora
  • Key leaf developmental genes in 12 Begoniaceae species were identified for differences in copy number. 
  • The candidate genes responsible for leaf shape traits were obtained using QTL analysis. 
  • Two pairs of sister species were studied: 1) Begonia conchifolia and Begonia plebeja, and Begonia luxurians and Begonia parviflora. Tissue-specific gene expression was then analysed in both leaf and vegetative bud from each species and compared.


Left: QTLs identified for leaf dissection index.
Right: Gene expression data for candidate genes found only in the vegetative bud tissue of both B. conchifolia and B. plebeja.



Gene expression patterns observed between the leaf, petiole attachment (PA) and vegetative bud (VB) tissues of B. luxurians (Blux) and B. parviflora (Bparvi) in two key leaf developmental gene groups (CUC and KANADI).