Project description:The timing of reproductive development determines spike architecture and thus yield in temperate grasses such as barley (Hordeum vulgare L.). Reproductive development in barley is controlled by the photoperiod response gene Ppd-H1 which accelerates flowering time under long-day (LD) conditions. A natural mutation in Ppd-H1 prevalent in spring barley causes a reduced photoperiod response, and thus, late flowering under LD. However, it is not very well understood how LD and Ppd-H1 control pre-anthesis development, and thus spike architecture and yield in barley. We performed a detailed morphological analysis of the pre-anthesis development in the spring barley cultivar Scarlett and its wild barley derived introgression line S42-IL107, carrying the photoperiod responsive Ppd-H1 allele. Characterization of shoot apex development in these genotypes indicated that floral transition and initiation of floral primordia occurred under LD (16h light/ 8h dark) and short day (SD, 8h light/ 16h dark) conditions, while inflorescence and seed development strictly required LDs. Additionally, a fast photoperiod response in the presence of the dominant Ppd-H1 allele promoted floret fertility under LDs. To characterize the effects of the photoperiod and allelic variation at Ppd-H1 on gene expression during pre-anthesis development we performed RNA sequencing of leaves and developing main shoot apices during the vegetative phase and early stages of inflorescence development in Scarlett and S42-IL107 grown under SD and LD conditions. Main shoot apices of both genotypes were sampled at defined developmental stages, i.e. Waddington stage W0.5, W1.0, W2.0 and W3.5, respectively. Leaf samples were harvested from plants before (W1.0) and after floral transition (W2.0). We identified genes that were specifically regulated at floral transition independent of day-length and Ppd-H1 and thus may serve as markers for the staging of floral transition. Furthermore, we identified transcripts differentially expressed between photoperiods and between genotypes in leaves and in shoot apices. This set of transcripts might act as candidates downstream of Ppd-H1 and are correlated with the promotion of shoot apex development and higher floret fertility under LD and in the presence of the photoperiod responsive Ppd-H1 allele.

Project description:To better undersand the effects of drought stress on wheat developing seeds, the transcription profile of early developing wheat seeds under control and drought stress conditions were comparatively analyzed by using the Affymetrix wheat geneChip. Drought stress is a major yield-limiting factor for wheat. Wheat yields are particularly sensitive to drought stress during reproductive development. Early seed development stage is an important determinant of seed size, one of the yield components. We specifically examined the impact of drought stress imposed during postzygotic early seed development in wheat. We imposed a short-term drought stress on plants with day-old seeds and observed that even a short-duration drought stress significantly reduced the size of developing seeds as well as mature seeds. Drought stress delayed the developmental transition from syncytial to cellularized stage of endosperm. Coincident with reduced seed size and delayed endosperm development, a subset of genes associated with cytoskeleton organization was misregulated in developing seeds under drought-stressed. Several genes linked to hormone pathways were also differentially regulated in response to drought stress in early seeds. Notably, drought stress strongly repressed the expression of wheat storage protein genes such as gliadins, glutenins and avenins as early as 3 days after pollination. Our results provide new insights on how some of the early seed developmental events are impacted by water stress, and the underlying molecular pathways that can possibly impact both grain size and quality in wheat. Winter wheat cultivar Redland, PI 502907 (Triticum aestivum L.) was used for this study. Seedlings were vernalized at 4°C for 6 weeks and then transplanted to a one gallon pot of soil-sand mixture (3:1, v/v) and grown in a growth chamber under the following conditions: relative humidity, 50–70%; 16-h light/8-h dark photoperiod; 21°C daytime temperature and 18°C nights. Plants were watered regularly twice daily at the rate of 100ml/ per pot. Because, wheat has an asynchronous fertilization pattern for ovlues in the inflorescence, each floret needs to be specifically marked for timing the fertilization and stress induction. After spikes developed, unfertilized ovules were monitored and observed for the fertilization process. Closed wheat spikes with anthers outside were marked as fertilized. Drought stress was imposed 24h after the fertilization (HAF). Drought stress treatment was initiated by discontinuing watering on the drought treatment plants while control plants were regularly watered twice daily. Stress treatment was applied at 48 HAF and relieved at 96 HAF. The microarray study focuses on 24 HAF to 72 HAF in control and drought stress conditions. We started to impose drought stress 24HAF.

Project description:Wheat panicle development is a coordinated process of proliferation and differentiation with distinctive phase and architecture changes. However, the multiple genes involved networks controlling this process remain enigmatic. Here, we characterized and dissected common wheat panicles in the stages of vegetative stage before elongation, elongation, single ridge, double ridge, glume primodium differentiation and floret differentiation, respectively, followed by RNA-seq and bioinformatics analysis to study genome-wide mRNA transcriptome profiling in wheat early spike development. High gene expression correlations between any two stages (R2>0.97) and only 4000 Differentially Expressed Genes (DEGs) out of 49624 expressed transcripts in all stages indicated that wheat early panicle development is just controlled by an small proportion of important genes. Three subgenomes (A, B and D) contribute equally to this process. K-means clustering analysis revealed the dynamic expression patterns of DEGs and Hierarchical Clustering analysis demonstrated that single bridge stage and double bridge stage are most important for wheat panicle development. Interestingly, 306 transcription factors (TFs) with various functions from different families were identified and the spatial-temporal expression patterns of some were verified by quantitative PCR or in situ hybridization. At early stages, repressing flowering TFs combined with AP2/ERF TFs and cytokinin promote inflorescence meristem development and repress meristem differentiation. At single ridge and double ridge stages, highly expressed stress-response TFs balance the interaction between stress response and development. During reproductive stages, crosstalk between auxin and cytokinin coordinate the meristem proliferation and differentiation, and promoting flowering TFs with polarity establishment TFs and MADS-box TFs promote floral meristem generation and floral organ identity and development. This dataset provided an ideal resource for wheat panicle developmental research. Our study uncovered the regulatory network for coordinated wheat early spike development and would eventually contribute to the improvement of grain number and crop yield.

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Photoperiod-1 regulation of wheat inflorescence development

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