Transcriptomic analysis of pollen-pistil interactions in almond (Prunus dulcis) identifies candidate genes for components of gametophytic self-incompatibility
The cultivated almond exhibits self-incompatibility of the gametophytic type regulated by the S-locus, which is expressed in both the pistil (S-RNase) and pollen (SFB protein). Although almond cultivars are mostly self-incompatible, some cultivars have been found to be self-compatible. For a long time, self-compatibility was unequivocally associated only with the presence of the Sf haplotype. However, recent studies reported the existence of self-incompatible almond cultivars carrying the Sf genotype. This finding suggests the involvement of new, hitherto undiscovered components involved in the almond self-incompatibility system. The aim of this study was to clarify the transcription pattern of the S-genes and to look for additional components of the gametophytic self-incompatibility system in almond. Transcriptome analysis of un-pollinated pistils and incompatible and compatible pollinations of self-compatible and self-incompatible almonds carrying the Sf haplotype was performed using high-throughput RNA sequencing technologies. Among the unigenes, 1357 were shown to be differentially expressed, and gene ontology annotation revealed that they are mostly involved in metabolic processes and binding molecular functions. The expression trend of fourteen representative genes, some of which are putatively involved in the self-(in)compatible response, was confirmed by RT-qPCR. This transcriptomic analysis provides candidate genes for almond components of gametophytic self-incompatibility and could be used as reference for subsequent comparative transcriptomic analyses of pollen and pistil.
KeywordsAlmond Self-incompatibility Gene expression Pollen-pistil interaction RNA-Seq qPCR
E.M. Gómez acknowledges the receipt of a FPI scholarship and a short stay scholarship both from MINECO.
Data archiving statement
RNA-Seq reads obtained have been deposited in the ArrayExpress database at EMBL-EBI (www.ebi.ac.uk/arrayexpress) under accession number E-MTAB-6164.
EM Gómez designed RNA-Seq and RT-qPCR experiments, performed the experiments, analyzed the data and wrote the manuscript. M Buti analyzed the data and wrote the manuscript. DJ Sargent assisted in design of RNA-Seq and RT-qPCR experiments, and critically revised the contents and the English of the manuscript. F Dicenta coordinated the project. E Ortega conceived and coordinated the project, was involved in interpretation of data and wrote the manuscript.
This work has been financially supported by the projects “Mejora Genética del Almendro” and “Breeding stone fruit species assisted by molecular tools” funded by “Ministerio de Economía y Competitividad” (MINECO) (grant AGL2013-48577-C2-1-R) and “Fundación Séneca” (grant 19879/GERM/15), respectively.
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