Project description:Ovule formation is essential for realizing crop yield as it determines seed number. The underlying molecular mechanism, however, remains elusive. Here, we show that cell wall invertase (CWIN) functions as a positive regulator of ovule initiation in Arabidopsis. In situ hybridization revealed that CWIN2 and CWIN4 were expressed at the placenta region where ovule primordia initiated. Specific silencing of CWIN2 and 4 by using targeted artificial microRNA driven by an ovule-specific SEEDSTICK promoter (pSTK) resulted in a significant reduction of CWIN transcript and activity, which blocked ovule initiation and aggravated ovule abortion. Surprisingly, there was no induction of carbon starvation genes in the transgenic lines and supplement of extra carbon to newly forming floral buds failed to recover the ovule phenotype. The findings indicate that suppression of CWIN did not lead to carbon starvation. Interestingly, a group of hexose transporters was downregulated in the transgenic plants and two representative transporter genes, STP9 and SWEET8 were spatially co-expressed with CWIN2 and CWIN4, suggesting a coupling between CWIN and hexose transporters for ovule initiation. RNA-Seq analysis identified differentially expressed genes encoding putative extracellular receptor-like-kinases (RLKs), MADS-box transcription factors including STK and early auxin response genes, SAURs, in response to CWIN-silencing. Collectively, our data demonstrate the essential role that CWIN plays in ovule initiation likely through sugar signalling instead of carbon nutrient contribution. We propose that CWIN-mediated sugar signalling may be perceived by, and transmitted through, hexose transporters or RLKs to regulate ovule formation by modulating downstream auxin signalling and MADS-box transcription factors.
Project description:To investigate the effect of simulated shade on the genetic network regulating ovule development, we treated Arabidopsis adult plants with W or simulated shade (W+FR) for up to 24 h. After extracting total RNA from floral buds we performed gene expression profiling analysis using data from RNA-seq of two different treatments at different time points
Project description:Ovule development is a key process for plant reproduction that ensures correct seed production. Understanding the molecular mechanisms that control ovule formation will also provide new approaches to increase crop yield for breeding. Several molecular factors and plant hormones, including gibberellins, are involved in ovule initiation and development. Gibberellins control ovule development by the destabilization of DELLA proteins, whereas DELLA activity has been proved to act as a positive factor for ovule primordia emergence. But the molecular mechanism by which DELLA act remained unknown. Here we have proved that DELLA proteins control ovule initiation by the formation of a protein complex with the CUC2 transcription factor. The DELLA protein GAI requires CUC2 to promote ovule primordia formation, thus GAI would function by its direct protein-protein interaction with CUC2 in cells of the placenta that determine the boundary regions between ovules during pistil development. Analysis of GAI-CUC2 interaction and colocalization in placenta support this hypothesis. Moreover, molecular analysis of the loci at which GAI protein may act as transcriptional co-regulators in a CUC2-dependent manner identified a subset of target genes that would be regulated by the GAI-CUC2 complex and contribute to regulate ovule primordia emergence.
Project description:Hypericum perforatum L. (2n=4x=32) is an attractive model system for the study of aposporous apomixis. The earliest phenotypic features of aposporous apomixis in this species are the mitotic formation of unreduced embryo sacs from a somatic cell of the ovule nucellus and the avoidance of meiosis. In this research we addressed gene expression variation in sexual and apomictic plants, by focusing on the ovule nucellus, which is the cellular domain primarily involved into the differentiation of meiocyte precursors and aposporous embryo sacs. Gene expression analysis performed by RNAseq identified 396 differentially expressed genes and 1834 transcripts displaying phenotype-specific expression. Overall, our data suggest that phenotypic expression of aposporous apomixis is concomitant with the modulation of key genes involved in cell patterning, RNA splicing and RNA-directed DNA methylation.
Project description:We are interested in examining the transcriptional hierarchies that are required for proper formation and function of the carpel margin meristem in Arabidopsis thaliana. The carpel margin meristem (CMM) gives rise to the ovule primorida (which begin to form around flower stage 8). We know that the loss of the seuss-3 (seu-3) and aintegumenta-1(ant-1) separately leads to a mild disruption of ovule formation, while the loss of both causes a complete loss of ovule formation. In this study we wanted to examine expression levels changed between each single mutant and the double mutant. We dissected out stage 8-10 carpel of each of the four genotypes (seu-3, ant-1, Col-0, seu-3 ant-1) pooling 15-25 carpels into one biological replicate. Then using 16 ATH1 arrays we hybridized, amplified and labeled cDNA to 16 arrays (4 replicates for each genotype). We then analyzed our data to reveal transcripts that went down in the double compared to either single mutant, and transcripts that went down more than additively in the double mutant compared to added level of the decrease of the single mutant levels.
Project description:This experiment was designed to identify genes expressed preferentially in the two integuments of the Arabidopsis ovule. Pistils from wild type and two ovule mutants were compared against each aintegumenta-4 (ant-4) which lacks both integuments and inner no outer (ino-1) which lacks the outer integument. Genes that are highly expressed only in the integuments were expected to be reduced in expression in the mutants, as compared with wild type. Pistils containing ovules through all stages of ovule development prior to pollination were pooled for one experiment (FULL arrays), and for two separate experiments, a set of early differentiation stages (EARLY arrays) and a set of later differentiation stages (LATE ARRAYS) were pooled. Wild type and mutant lines are in the ecotype Landsberg erecta.
Project description:Here we identify and characterize a spontaneous mutant allele that disrupts the initiation and specification of the ovule integument in Mimulus nudatus. The mutant phenotype is characterized by the early arrest of the ovule integument or alternatively, the delayed development of a carpel-like structure in place of the integument. Additionally, medusa mutant ovule primordia fail to develop female gametophytic structures. Morphological analyses indicate that a nucellar domain is specified within the ovule and a megaspore-like cell is often specified, but that cell aborts before generating the female gametophyte. We mapped the position of the mutation to a location on Chromosome1. Mapping revealed a primary candidate gene that was a member of a family of MADS-domain containing transcription factors with sequence similarity to the Arabidopsis BEL1 gene (At5G41410) and is an orthologue of the Mimulus guttatus gene MgTOL.A0789.1. Analysis of the sequence of the Mimulus nudatus homolog (referred hereafter as MnBEL1) locus, revealed the insertion of a mitochondrial DNA genomic fragment within the MnBEL1 locus that segregated with the medusa mutant phenotype. The mitochondrial insertion sequence is predicted to disrupt the coding sequence of MnBEL1. RNA expression analysis revealed dramatically reduced levels of the expression of the MnBEL1 in gynoecia from medusa mutant plants relative to wild type sisters. RNA seq analysis revealed that the medusa mutant seedpods failed to express MnBEL1 at wildtype levels. RNA sequence data comparisons between wildtype and medusa mutant seedpods also identified a set of genes, that are expressed in wildtype seedpods, but that are expressed at very low levels or that are not detected in the medusa seed pods. Homologues of many of these genes have been previously shown to be strongly expressed in female gametophyte in Arabidopsis. This RNA seq analysis further indicates a strong developmental disruption and identifies sets of genes with expected roles in female gametophyte development in Mimulus species for further investigation. Our evidence strongly suggests that MnBEL1 is a true functional orthologue of AtBEL1. To the best of our knowledge, these studies provide the first mutational analysis of a BEL1 orthologue outside of Arabidopsis and indicate the functional conservation of this gene between Mimulus and Arabidopsis. This work also presents the first identification of a mutational event in Mimulus that is linked to an insertion of a mitochondrial sequence in the nuclear genome.