Project description:The absence of meiosis and sex are expected to lead to mutation accumulation in asexual (apomictic) plants. We have performed a double-validated analysis of copy number variation (CNV) on 10 biological replicates each of diploid sexual and diploid apomictic Boechera using a high-density (>700K) custom microarray, in order to compare mutation accumulation in the form of CNV between the transcribing regions of their genomes. The Boechera genome demonstrated higher levels of depleted compared to enriched CNV, irrespective of reproductive mode. Genome-wide patterns of CNV revealed four divergent lineages, three of which were characterized by both sexual and apomictic genotypes. Hence genome-wide CNV is reflective of at least 3 independent origins (i.e. expression) of apomixis from different sexual genetic backgrounds. CNV distributions for different families of transposable elements (TEs) were lineage specific, and a trend for enrichment in LINE/L1 and LTR/Copia elements in lineage 3 apomicts is consistent with sex and meiosis being mechanisms for purging genomic parasites. We hypothesize that significant overrepresentation of specific gene ontology classes (e.g. pollen-pistil interaction) in apomicts implies that gene enrichment could be an adaptive mechanism for genome stability in diploid apomicts by providing a polyploid-like system for buffering the effects of deleterious mutations.
Project description:The expression of 30362 plant genes from uninfected flowers of Boechera stricta, uninfected steam and leaves of B. stricta and infected B. stricta with Puccinia monoica forming pseudoflowers. We hybridized cDNA from each sample to an Arabidopsis thaliana gene expression 4x72K format NimbleGen array (ATH6_60mer_expr).
Project description:The expression of 30362 plant genes from uninfected flowers of Boechera stricta, uninfected steam and leaves of B. stricta and infected B. stricta with Puccinia monoica forming pseudoflowers. We hybridized cDNA from each sample to an Arabidopsis thaliana gene expression 4x72K format NimbleGen array (ATH6_60mer_expr). We used a eukaryotic gene expression array design No.5048 from NimbleGen (Cat No. A4511001-00-01). Each 5048 array measures the expression level of 30,362 target genes from Arabidopsis thaliana in a 4-plex format 4x72K with with 72,000 probes per array, a total of two probes per target gene, and 60-mer probe length. Total RNA samples recovered from infected leaves of Boechera stricta with Puccinia monoica (pseudoflowers) and uninfected stem and leaves of B. stricta. Experiments included three/two biological repllicates from each sample. We carried out total RNA extractions for all samples using RNAesy Plant Mini Kit (Qiagen, Cat No. 74904). cDNA synthesis was performed by NimbleGen.
Project description:Sexual reproduction (meiosis and syngamy) is the major form of reproduction in diploid Boechera species, but most species hybrids reproduce by apomixis (unreduced gametophyte formation followed by parthenogenesis of the unreduced egg). In this study, we used Arabidopsis microarrays to detail global programs of gene expression underlying sexual and apomictic modes of reproduction.
Project description:Apomixis differs from sexual reproduction only in three major aspects: While the sexual megaspore mother cell undergoes meiosis, the apomictic initial cell omits or aborts meiosis (apomeiosis); the unreduced egg cell of apomicts forms an embryo without fertilization (parthenogenesis), and formation of functional endosperm requires specific developmental adaptations. Currently, our knowledge about the gene regulatory programs underlying apomixis is scarce. We used the apomict Boechera gunnisoniana, a close relative of Arabidopsis thaliana, to investigate the transcriptional basis underlying apomeiosis and parthenogenesis. Here, we present the first comprehensive reference transcriptome for reproductive development in an apomictic species. To compare sexual and apomictic development at the cellular level, we then used a combination of laser-assisted microdissection with microarray and RNA-Seq analysis. Our study yields important new insights into the transcriptional basis underlying apomixis. Cell-type specific transcriptome profiles were generated from the apomictic initial cell (2 biological replicates), surrounding sporophytic tissues (sporo_nucellus; 2 biological replicates), egg cell, central cell and synergid cells (one sample each) from the triploid pseudogamous obligate apomict Boechera gunnisoniana by heterologous hybridization on the Affymetrix ATH1 arrays.
