Project description:Maize develops separate ear and tassel inflorescences with initially similar morphology but finally different architecture and sexuality. The detailed regulatory mechanisms underlying these changes still remain largely clear. In this study, through analyzing the time-course meristem transcriptomes and floret single-cell transcriptomes of ear and tassel we revealed the regulatory dynamics and pathways underlying inflorescence development and sex differentiation. Our study provides a deep understanding of the regulatory mechanisms underlying inflorescence development and sex differentiation in maize, laying the foundation to identify new regulators and pathways for maize hybrid breeding and improvement.
Project description:The functional genome of agronomically important plant species remains largely unexplored, yet presents a virtually untapped resource for targeted crop improvement. Functional elements and regulatory DNA revealed through chromatin accessibility maps can be harnessed for manipulating gene expression to subtle phenotypic outputs that enhance productivity in specific environments. Here, we present a genome-wide view of accessible chromatin and nucleosome occupancy at a very early stage in the development of both pollen- and grain-bearing inflorescences of the important cereal crop maize (Zea mays), using an assay for differential sensitivity of chromatin to micrococcal nuclease (MNase) digestion. Results showed that in these largely undifferentiated tissues, approximately 1.5-4 percent of the genome is accessible, with the majority of MNase hypersensitive sites marking proximal promoters but also 3’ flanks of maize genes. This approach mapped regulatory elements to footprint-level resolution, and through integration of complementary transcriptome and transcription factor occupancy data, we annotated regulatory factors such as combinatorial motifs and long non-coding RNAs that potentially contribute to organogenesis in maize inflorescence development, including tissue-specific regulation between male and female structures. Finally, genome-wide association studies for inflorescence architecture traits based only on functional regions delineated by MNase hypersensitivity, revealed new SNP-trait associations in known regulators of inflorescence development. These analyses provide a first look into the cis-regulatory landscape during inflorescence differentiation in a major cereal crop, which ultimately shapes architecture and influences yield potential.
Project description:Setaria viridis is a small, rapidly growing grass species in the subfamily Panicoideae, a group that includes economically important cereal crops such as maize and sorghum. The S. viridis inflorescence displays complex branching patterns, but its early development is similar to that of other panicoid grasses, and thus is an ideal model for studying inflorescence architecture. Here we report detailed transcriptional resource that captures dynamic transitions across six sequential stages of S. viridis inflorescence development, from reproductive onset to floral organ differentiation. Co-expression analyses identified stage-specific signatures of development, which include homologs of previously known developmental genes from maize and rice, suites of transcription factors and gene family members, and genes of unknown function. This spatiotemporal co-expression map and associated analyses provide a foundation for gene discovery in S. viridis inflorescence development, and a comparative model for exploring related architectural features in agronomically important cereals.
Project description:In this study we used the maize (Zea mays) inflorescence to investigate gene networks that modulate determinacy, specifically the decision to allow branch growth. We characterized developmental transitions by associating spatiotemporal expression profiles with morphological changes resulting from genetic perturbations that disrupt steps in a pathway controlling branching. These are the RNA-seq datasets used in this study.
Project description:Background. Carbon allocation between vegetative and reproductive tissues impacts cereal grain production. Despite their great agricultural importance, sink-source relationships have not been fully characterized at early reproductive stages in maize. Here we quantify the accumulation of non-structural carbohydrates and patterns of gene expression in the top internode of the stem and the female inflorescence of maize at the onset of grain filling (reproductive stage R1). Methods. Top internode stem and female inflorescence tissues of the Puma maize inbred line were collected at reproductive stage R1 (without pollination). The accumulation of non-structural carbohydrates was quantified by spectrophotometry. Global gene expression was evaluated in both tissues by RNA sequencing. Results. At reproductive stage R1, the maize female inflorescence accumulates non-structural carbohydrates, notably starch, at higher levels than the top internode of the stem. Gene expression analysis identified 491 genes to be differentially expressed between the female inflorescence and the stem top internode. Gene ontology classification of differentially expressed genes showed enrichment for sucrose synthesis, the light-dependent reactions of photosynthesis, and transmembrane transporters. Our results suggest that sugar transporters play a key role in sugar partitioning in the maize stem and reveal previously uncharacterized differences between the female inflorescence and the top internode of the stem at early reproductive stages.
Project description:This project is to generate and analyze the transcriptomes of bract primordium of maize, and to identify the genes, pathways and networks that suppress bract outgrowth in maize inflorescence.
Project description:Directional transport of auxin is critical for inflorescence and floral development in flowering plants, but the role of auxin influx carriers (AUX1 proteins) has been largely overlooked. Taking advantage of available AUX1 mutants in Setaria viridis and maize, we uncover previously unreported aspects of plant development that are affected by auxin influx, including higher order branches in the inflorescence, stigma branch number, and glume (floral bract) development, and plant fertility. However, disruption of auxin flux does not affect all parts of the plant, with little obvious effect on inflorescence meristem size, time to flowering, and anther morphology. In double mutant studies in maize, disruptions of ZmAUX1 also affect vegetative development. A GFP-tagged construct of SvAUX1 under its native promoter showed that the AUX1 protein localizes to the plasma membrane of outer tissue layers in both roots and inflorescences, and accumulates specifically in inflorescence branch meristems, consistent with the mutant phenotype and expected auxin maxima. RNA-seq analysis finds that most gene expression modules are conserved between mutant and wildtype plants, with only a few hundred genes differentially expressed in spp1 inflorescences. Using CRISPR-Cas9 technology, we disrupted SPP1 and the other four AUX1 homologs in S. viridis. SvAUX1/SPP1 has a larger effect on inflorescence development than the others, although all contribute to plant height, tiller formation, leaf, and root development. The AUX1 importers are thus not fully redundant in S. viridis. Our detailed phenotypic characterization plus a stable GFP-tagged line offer tools for future dissection of the function of auxin influx proteins.
Project description:The depiction of maize chromatin architecture using Assay for Transposase Accessible Chromatin with high-throughput sequencing (ATAC-seq) provides great opportunities to investigate cis-regulatory elements, which is crucial for crop improvement. We demonstrate a streamlined ATAC-seq protocol for maize in which nuclei purification can be achieved without cell sorting, and using only a standard bench-top centrifuge. Our protocol, coupled with the bioinformatic analysis, provides a precise and efficient assessment of the maize chromatin landscape.
Project description:Transformation of the Arabidopsis ATHB17 gene into maize results in the expression of a truncated protein (smaller by 113 amino acids) that functions as a dominant-negative regulator that can modify activity of endogenous maize HD-Zip II transcription factors. This RNASeq experiment indicates that the observed effects of ATHB17d113 on the maize ear inflorescence and ear transcriptome are very small. Expression of ATHB17delta113 protein in maize leads to changes in ear growth resulting in increased ear size at early reproductive stages and, potentially increased sink size.