ORIGINAL PAPER Influence of mitochondria on gene expression in a citrus cybrid Jean-Baptiste Bassene • Yann Froelicher • Luis Navarro • Patrick Ollitrault • Gema Ancillo Received: 10 November 2010 / Revised: 10 January 2011 / Accepted: 14 January 2011 / Published online: 10 February 2011 Ó Springer-Verlag 2011 Abstract The production of cybrids, combining nucleus of a species with alien cytoplasmic organelles, is a valuable method used for improvement of various crops. Several citrus cybrids have been created by somatic hybridization. These genotypes are interesting models to analyze the impact of cytoplasmic genome change on nuclear genome expression. Herein, we report genome-wide gene expres- sion analysis in leaves of a citrus cybrid between C. retic- ulata cv ‘Willowleaf mandarin’ and C. limon cv ‘Eureka lemon’ compared with its lemon parent, using a Citrus 20K cDNA microarray. Molecular analysis showed that this cybrid possesses nuclear and chloroplast genomes of Eur- eka lemon plus mitochondria from Willowleaf mandarin and, therefore, can be considered as a lemon bearing for- eign mitochondria. Mandarin mitochondria influenced the expression of a large set of lemon nuclear genes causing an over-expression of 480 of them and repression of 39 genes. Quantitative real-time RT–PCR further confirmed the credibility of microarray data. Genes over-expressed in cybrid leaves are predominantly attributed to the functional category ‘‘cellular protein metabolism’’ whereas in the down-regulated none functional category was enriched. Overall, mitochondria replacement affected different nuclear genes including particularly genes predicted to be involved in mitochondrial retrograde signaling. Mito- chondria regulate all cell structures even chloroplast status. These results suggest that nuclear gene expression is modulated with respect to new information received from the foreign organelle, with the final objective to suit spe- cific needs to ensure better cell physiological balance. Keywords Citrus Á Cybrid Á cDNA microarrays Á Gene expression Á Transcriptome Introduction Organelles may alter the expression of nuclear genes through a communication termed retrograde signalling. Cytoplasm substitution could have positive effects on important agronomic traits such as cytoplasmic male ste- rility (CMS) (Prakash et al. 2001; Yamamoto et al. 1997), drought tolerance (Uprety and Tomar 1993), improved disease and pathogen resistance (Banga et al. 1984; Vol- uevich and Buloichik 1992), starch production (Lossl et al. 2000). On the other hand, substitution of the cytoplasm may manifest abnormal morphology of stems, leaves and flowers (Leino et al. 2003; Newton et al. 2004; Pelletier and Budar 2007), reduced cold tolerance and lack of chlorophyll (Kato et al. 1990; Zubko et al. 2001). Various studies showed that new nucleo–cytoplasmic interactions resulting from cytoplasm replacement, rearrangements or cytoplasmic mutations would be behind these particular phenotypes (Hanson 1991; Allen 2005; Bogdanova 2007). Communicated by R. Rose. Electronic supplementary material The online version of this article (doi:10.1007/s00299-011-1014-1) contains supplementary material, which is available to authorized users. J.-B. Bassene Á Y. Froelicher Á P. Ollitrault Centre de Coope ´ration Internationale en Recherche Agronomique pour le De ´veloppement (CIRAD), UPR ame ´lioration ge ´ne ´tique des espe `ces a ` multiplication ve ´ge ´tative, Avenue Agropolis-TA A-75/02, 34398 Montpellier Cedex 5, France L. Navarro Á P. Ollitrault Á G. Ancillo (&) Instituto Valenciano de Investigaciones Agrarias (IVIA), Centro de Proteccion Vegetal y Biotecnologı ´a, Ctra. Moncada-Na ´quera Km 5, 46113 Moncada, Valencia, Spain e-mail: ancillo@ivia.es 123 Plant Cell Rep (2011) 30:1077–1085 DOI 10.1007/s00299-011-1014-1