title: Large changes in anatomy and physiology between diploid Rangpur lime (Citrus limonia) and its autotetraploid are not associated with large changes in leaf gene expression.
abstract: Very little is known about the molecular origin of the large phenotypic differentiation between genotypes arising from somatic chromosome set doubling and their diploid parents. In this study, the anatomy and physiology of diploid (2x) and autotetraploid (4x) Rangpur lime (Citrus limonia Osbeck) seedlings has been characterized. Growth of 2x was more vigorous than 4x although leaves, stems, and roots of 4x plants were thicker and contained larger cells than 2x that may have a large impact on cell-to-cell water exchanges. Leaf water content was higher in 4x than in 2x. Leaf transcriptome expression using a citrus microarray containing 21 081 genes revealed that the number of genes differentially expressed in both genotypes was less than 1% and the maximum rate of gene expression change within a 2-fold range. Six up-regulated genes in 4x were targeted to validate microarray results by real-time reverse transcription-PCR. Five of these genes were apparently involved in the response to water deficit, suggesting that, in control conditions, the genome expression of citrus autotetraploids may act in a similar way to diploids under water-deficit stress condition. The sixth up-regulated gene which codes for a histone may also play an important role in regulating the transcription of growth processes. These results show that the large phenotypic differentiation in 4x Rangpur lime compared with 2x is not associated with large changes in genome expression. This suggests that, in 4x Rangpur lime, subtle changes in gene expression may be at the origin of the phenotypic differentiation of 4x citrus when compared with 2x.
authors.affiliation: Centre de Coopération Internationale en Recherche Agronomique pour Dévelopement, UPR amélioration génétique des espèces à multiplication végétative, Instituto Valenciano de Investigaciones Agrarias, E-46113 Moncada-Valencia, Spain.
authors.forename: Thierry
authors.initials: T
authors.lastname: Allario
authors.forename: Javier
authors.initials: J
authors.lastname: Brumos
authors.forename: Jose Manuel
authors.initials: JM
authors.lastname: Colmenero-Flores
authors.forename: Francisco
authors.initials: F
authors.lastname: Tadeo
authors.forename: Yann
authors.initials: Y
authors.lastname: Froelicher
authors.forename: Manuel
authors.initials: M
authors.lastname: Talon
authors.forename: Luis
authors.initials: L
authors.lastname: Navarro
authors.forename: Patrick
authors.initials: P
authors.lastname: Ollitrault
authors.forename: Raphaël
authors.initials: R
authors.lastname: Morillon
mesh_terms: D002957:Citrus / Q000033:anatomy & histology* / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D004171:Diploidy; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D045332:Photosystem II Protein Complex / Q000378:metabolism; D010858:Pigmentation / Q000235:genetics; D018515:Plant Leaves / Q000033:anatomy & histology* / Q000166:cytology / Q000235:genetics* / Q000502:physiology; D018517:Plant Roots / Q000033:anatomy & histology / Q000235:genetics; D018547:Plant Stems / Q000033:anatomy & histology / Q000235:genetics; D011123:Polyploidy; D020133:Reverse Transcriptase Polymerase Chain Reaction; D036226:Seedlings / Q000033:anatomy & histology / Q000235:genetics
chemical_list: D045332:Photosystem II Protein Complex