Gene Expression Pattern in Olive Tree Organs (Olea europaea L.)

peer-reviewedThe olive tree (Olea europaea L.) was one of the first plant species in history to be domesticated. Throughout olive domestication, gene expression has undergone drastic changes that may affect tissue/organ-specific genes. This is an RNA-seq study of the transcriptomic activity of different tissues/organs from adult olive tree cv. “Picual” under field conditions. This analysis unveiled 53,456 genes with expression in at least one tissue, 32,030 of which were expressed in all organs and 19,575 were found to be potential housekeeping genes. In addition, the specific expression pattern in each plant part was studied. The flower was clearly the organ with the most exclusively expressed genes, 3529, many of which were involved in reproduction. Many of these organ-specific genes are generally involved in regulatory activities and have a nuclear protein localization, except for leaves, where there are also many genes with a plastid localization. This was also observed in stems to a lesser extent. Moreover, pathogen defense and immunity pathways were highly represented in roots. These data show a complex pattern of gene expression in different organs, and provide relevant data about housekeeping and organ-specific genes in cultivated olive

Transposon activation is a major driver in the genome evolution of cultivated olive trees ( Olea europaea L.)

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Transcriptomic time-series analysis of early development in olive from germinated embryos to juvenile tree

Abstract Background Despite its relevance, almost no studies account for the genetic control in the early stages of tree development, i.e. from germination on. This study seeks to make a quite complete transcriptome for olive development and to elucidate the dynamic regulation of the transcriptomic response during the early-juvenile period by RNAseq time-series expression analysis. The transcriptome was made from 342,049,597 paired-end reads of 101 bp in length. The assembled transcriptome contained 109,125 unigenes (N50 = 1490 bp, average length = 839). Results The time-series-expression analysis showed that, embryonic structures present at the first month after the induction of germination reached a more differentiated state in two-month-old seedlings. Once the plants were between three and four months old and reached a size around 6–7 nodes, the first developmental stages appeared to be complete and the developing seedling became a juvenile plant. In addition, an AGL-gene was rapidly downregulated during the induction of germination. The repression of this gene was very strong, as evidenced by the low levels of gene expression during plant development from the embryonic seedling to undetectable levels of expression in the adult tree. These results suggest that this gene may be involved in seed dormancy and could be a repressor of the germination. Also, an APL1-like olive gene was found to be expressed at high levels during flowering, and was also expressed during the cold incubation in the activation of embryo germination, suggesting a probable role in embryonic development. Conclusions The early development from germination to the juvenile stage of olive seedlings occurred when plants reached a size around 6–7 nodes, and general changes of relevant groups of genes involved in development are described. An AGL-gene was proposed to be involved in germination repression. An APL1-like gene was found to have a probable role in embryonic development

Transcriptomic Analysis of Olea europaea L. Roots during the Verticillium dahliae Early Infection Process

Olive cultivation is affected by a wide range of biotic constraints. Verticillium wilt of olive is one of the most devastating diseases affecting this woody crop, inflicting major economic losses in many areas, particularly within the Mediterranean Basin. Little is known about gene-expression changes during plant infection by Verticillium dahliae of woody plants such as olive. A complete RNA-seq transcriptomic analysis of olive tree roots was made. Trinity assembler proved to be the best option to assemble the olive and V. dahliae transcriptomes. The olive transcriptome (Oleup) consisted of 68,259 unigenes (254,252 isoforms/transcripts), and the V. dahliae transcriptome (Vedah) consisted of 37,425 unigenes (52,119 isoforms/transcripts). Most unigenes of the Oleup transcriptome corresponded to cellular processes (12,339), metabolic processes (10,974), single-organism processes (7263), and responses to stimuli (5114). As for the Vedah transcriptome, most unigenes correspond to metabolic processes (25,372), cellular processes (23,718), localization (6385), and biological regulation (4801). Differential gene-expression analysis of both transcriptomes was made at 2 and 7 d post-infection. The induced genes of both organisms during the plant-pathogen interaction were clustered in six subclusters, depending on the expression patterns during the infection. Subclusters A to C correspond to plant genes, and subcluster D to F correspond to V. dahliae genes. A relevant finding was that the differentially expressed gene (DEGs) included in subclusters B and C were highly enriched in proteolysis as well as protein-folding and biosynthesis genes. In addition, a reactive oxygen species (ROS) defense was induced first in the pathogen and later in the plant roots.This work was supported by Grant AGR-5948 from Junta de Andalucía (Consejería de Economía, Innovación y Ciencia) and Ministerio de Economía y Competitividad. Technical and human support provided by CICT of Universidad de Jaén (UJA, MINECO, Junta de Andalucía, FEDER) is gratefully acknowledged.Peer reviewe

Transposon activation is a major driver in the genome evolution of cultivated olive trees ( Olea europaea

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