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Title: Identification of differentially expressed genes involved in self-incompatibility in Theobroma cacao L.

Author
item Royaert, Stefan
item MOCKAITIS, KEITHANNE - Indiana University
item MAY, GREG - National Center For Genome Resources
item HAIMINEN, NIINA - International Business Machines Corporation (IBM)
item PARIDA, LAXMI - International Business Machines Corporation (IBM)
item PHILLIPS-MORA, WILBERT - Catie Tropical Agricultural Research
item MARELLI, JEAN-PHILIPPE - M & M Mars Company - Brazil
item Freeman, Barbara - Barbie
item Kuhn, David
item Schnell Ii, Raymond
item MOTAMAYOR, JUAN - Mars, Inc

Submitted to: Annual International Plant & Animal Genome Conference
Publication Type: Abstract Only
Publication Acceptance Date: 1/16/2011
Publication Date: 1/16/2011
Citation: Royaert, S.E., Mockaitis, K., May, G., Haiminen, N., Parida, L., Phillips-Mora, W., Marelli, J., Freeman, B.L., Kuhn, D.N., Schnell II, R.J., Motamayor, J.C. 2011. Identification of differentially expressed genes involved in self-incompatibility in Theobroma cacao L. . Annual International Plant & Animal Genome Conference. 2011.

Interpretive Summary: Increasing yield, quality and disease resistance are important objectives for cacao breeding programs. However, self-incompatibility (SI) often restricts progress, as crosses between certain cacao germplasm accessions and breeding lines are only partially successful. Various events are involved in this SI mechanism, such as prevention of gamete fusion or fusion between the sperm nucleus and the egg nucleus, or even an arrest in embryo development after successful fertilization. We recently identified a quantitative trait locus (QTL) for SI on linkage group (LG) 4 of the genetic map based on a segregating mapping population at CATIE (Costa Rica), originating from a cross between the self-incompatible clone Pound-7 and the self-compatible clone UF-273. Preliminary data from another cross at MCCS (Brazil) between the self-incompatible clone TSH-1188 and the self-compatible clone CCN-51 identified the same QTL on LG4, but also an additional QTL on LG3. These four parents were also used to set up a time-course experiment to identify up or down regulated genes involved in SI. The mRNA of unpollinated, compatibly or incompatibly pollinated pistils, harvested at different time points during the pollination/fertilization process, was sequenced on the Illumina GAII platform. Reads were aligned to the recently available cacao genome (www.cacaogenomedb.org) and pistil-specific sequences were identified via comparison of the pistil transcriptome with the available leaf transcriptome. Up or down regulated genes were identified and genes that mapped to the QTL area on LG4 are currently under investigation. Some of those candidate genes have a function in gamete membrane fusion. Our goal is to identify loci correlated with self-compatibility or self-incompatibility to develop SNPs for marker-assisted selection and allele mining of the available germplasm for breeding purposes.

Technical Abstract: Increasing yield, quality and disease resistance are important objectives for cacao breeding programs. However, self-incompatibility (SI) often restricts progress, as crosses between certain cacao germplasm accessions and breeding lines are only partially successful. Various events are involved in this SI mechanism, such as prevention of syngamy and karyogamy or even an arrest in embryo development. We recently identified a QTL for SI on linkage group (LG) 4 using a segregating mapping population at CATIE (Costa Rica) originating from a cross between the self-incompatible clone Pound-7 and the self-compatible clone UF-273. Preliminary data from another cross at MCCS (Brazil) between the self-incompatible clone TSH-1188 and the self-compatible clone CCN-51 identified the same QTL on LG4, but also an additional QTL on LG3. These four parents were also used to set up a time-course experiment to identify differentially expressed genes involved in SI. The mRNA of unpollinated, compatibly or incompatibly pollinated pistils, harvested at different time points during the pollination/fertilization process, was sequenced on the Illumina GAII platform. Reads were aligned to the recently available cacao genome (www.cacaogenomedb.org) and pistil-specific sequences were identified via comparison of the pistil transcriptome with the available leaf transcriptome. Differentially expressed genes were identified and genes that mapped to the QTL area on LG4 are currently under investigation. Some of those candidate genes have a function in gamete membrane fusion. Our goal is to identify loci correlated with self-compatibility or self-incompatibility to develop SNPs for marker-assisted selection and allele mining of the available germplasm for breeding purposes.