Cell number regulator genes in Prunus provide candidate genes for the control of fruit size in sweet and sour cherry

U R Rosyara,J Quero-Garcia,E Van Der Knaap,A Cabrera,P De Franceschi,E Dirlewanger,L Dondini,A M Sebolt,A F Iezzoni,T Stegmeir,J A Campoy

doi:10.1007/s11032-013-9872-6

Abstract

Striking increases in fruit size distinguish cultivated descendants from small-fruited wild progenitors for fleshy fruited species such as Solanum lycopersicum (tomato) and Prunus spp. (peach, cherry, plum, and apricot). The first fruit weight gene identified as a result of domestication and selection was the tomato FW2.2 gene. Members of the FW2.2 gene family in corn (Zea mays) have been named CNR (Cell Number Regulator) and two of them exert their effect on organ size by modulating cell number. Due to the critical roles of FW2.2/CNR genes in regulating cell number and organ size, this family provides an excellent source of candidates for fruit size genes in other domesticated species, such as those found in the Prunus genus. A total of 23 FW2.2/CNR family members were identified in the peach genome, spanning the eight Prunus chromosomes. Two of these CNRs were located within confidence intervals of major quantitative trait loci (QTL) previously discovered on linkage groups 2 and 6 in sweet cherry (Prunus avium), named PavCNR12 and PavCNR20, respectively. An analysis of haplotype, sequence, segregation and association with fruit size strongly supports a role of PavCNR12 in the sweet cherry linkage group 2 fruit size QTL, and this QTL is also likely present in sour cherry (P. cerasus). The finding that the increase in fleshy fruit size in both tomato and cherry associated with domestication may be due to changes in members of a common ancestral gene family supports the notion that similar phenotypic changes exhibited by independently domesticated taxa may have a common genetic basis.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-013-9872-6) contains supplementary material, which is available to authorized users.

Highlights

Cultivated fruit and vegetable crops often bear little phenotypic resemblance to their wild ancestors (Paran and van der Knaap 2007)
We identified the FW2.2/cell number regulators (CNR) gene family characterized by the conserved PLAC8 domain in the genome of peach (Guo et al 2010; Guo and Simmons 2011)
Because of the role in fruit size in tomato, we sought to determine whether members of the CNR family might underlie fruit weight quantitative trait loci (QTL) in other species

Summary

Introduction

Cultivated fruit and vegetable crops often bear little phenotypic resemblance to their wild ancestors (Paran and van der Knaap 2007). The resulting selection of alleles from wild progenitors, many of which may have arisen as spontaneous mutations, led to dramatic changes in plant traits associated with the domestication syndrome (Hammer 1984), including increases in the size of edible organs such as fleshy fruit. Domestication-associated increases in fleshy fruit size occurred in diverse plant families such as the Cucurbitaceae (Nunez-Palenius et al 2008; Esteras et al 2011; Paris et al 2012), Solanaceae (Tanksley 2004; Paran and van der Knaap 2007; Wang et al 2008; Meyer et al 2012) and Rosaceae (Miller and Gross 2011). The over-expression of ZmCNR1 resulted in a reduction of overall plant stature, by acting as a negative cell number regulator in multiple tissues, while ZmCNR2 affected organ and plant size (Guo et al 2010)

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