Abstract
Gigantism is a key component of the domestication syndrome, a suite of traits that differentiates crops from their wild relatives. Allometric gigantism is strongly marked in horticultural crops, causing disproportionate increases in the size of edible parts such as stems, leaves or fruits. Tomato (Solanum lycopersicum) has attracted attention as a model for fruit gigantism, and many genes have been described controlling this trait. However, the genetic basis of a corresponding increase in size of vegetative organs contributing to isometric gigantism, has remained relatively unexplored. Here, we identified a 0.4 Mbp region on chromosome 7 in introgression lines (ILs) from the wild species Solanum pennellii in two different tomato genetic backgrounds (cv. M82 and cv. Micro-Tom) that controls vegetative and reproductive organ size in tomato. The locus, named ORGAN SIZE (ORG), was fine-mapped using genotype-by-sequencing. A survey of literature revealed that ORG overlaps with previously mapped QTLs controlling tomato fruit weight during domestication. Alleles from the wild species led to reduced cell number in different organs, which was partially compensated by greater cell expansion in leaves but not in fruits. The result was a proportional reduction in leaf, flower and fruit size in the ILs harbouring the wild alleles. These findings suggest that selection for large fruit during domestication also tends to select for increases in leaf size by influencing cell division. Since leaf size is relevant for both source-sink balance and crop adaptation to different environments, the discovery of ORG could allow fine-tuning of these parameters.
One sentence summary A locus that controls isometric size increase in vegetative and reproductive organs of tomato through changes in cell division
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instruction for Authors (www.plantphysiol.org) is: Lázaro E. P. Peres (lazaro.peres{at}usp.br)
M.H.V performed the experiments using A.V.O.F. methods and analysed the data; C.R.F.F. provided technical assistance to M.H.V.; K.M. performed experiments using F.M. methods and analysed the data with assistance from Z.K.; A.Z. and A.J.T. analysed the data and wrote the article with contributions of all the authors; L.E.P.P conceived, designed and supervised the research, and agrees to serve as corresponding author.
Authors for contact: Agustin Zsögön agustin.zsogon{at}ufv.br, Lázaro Peres lazaro.peres{at}usp.br