Biology subjects

Vollbrecht, E.

Publications and source records attributed to Vollbrecht, E..

7 recordsLinked to original sources

bioRxiv2026

Ontogenetic and time-course transcriptomic analyses of maize leaf primordia reveal regulators of transverse vein development

Leaf vein patterning varies greatly among land plants and is linked to leaf structure and function. C4 plants, such as maize, have a denser arrangement of veins than C3 plants, which is hypothesized to be a pre-adaptive trait for C4 photosynthesis. Therefore, understanding how leaf veins are patterned has implications for maximizing photosynthetic efficiency. Major maize leaf veins, called longitudinal veins, are arranged in parallel and are interconnected by transverse veins. Recent work has established molecular factors controlling longitudinal vein development; however, it is unknown how transverse veins are patterned. Here, we investigated how transverse veins establish connections within the maize vascular network. We performed anatomical analyses of transverse veins and found that despite asynchronous development, transverse veins fully integrate into the longitudinal vein network. Tracing the ontogeny of transverse vein development using the marker PIN1a-YFP, we found that two sets of two initial cells on opposing sides of adjacent longitudinal veins recruit intervening ground cells to form the provascular strand. Treatment with auxin inhibitors did not abolish transverse vein initiation, suggesting an auxin-independent pre-pattern for transverse vein initiation. Through time-course RNAseq of leaf primordia, we identified a transcriptional signature that precedes transverse vein development. Two genes that belong to this gene cluster, EREB41 and EREB114, are necessary for transverse vein formation. Together, our studies establish the ontogeny of maize transverse vein development and reveal how new vascular connections are specified, assembled, and integrated into an existing vascular network.

plant biology↗

bioRxiv2025

MATERNAL AUTOPHAGY CONTRIBUTES TO GRAIN YIELD IN MAIZE

Maize is an important crop species that is cultivated worldwide, and increasing maize yield is one of the major goals of plant breeding. The subcellular degradation and recycling pathway known as autophagy is involved in many plant developmental processes including vegetative growth, reproductive development, seed development, and senescence. Here, we demonstrate that maize autophagy-defective atg10 mutants have delayed flowering and reduced kernel size, weight and number, leading to reduced grain yield. Reciprocal crosses between mutant and parental lines indicate that the maternal plant is the major contributor to the kernel phenotype in atg10 mutants, rather than the seed genotype. We hypothesize that this may be due to detrimental effects on nutrient remobilization from maternal tissue to seeds during kernel development, leading to reduced yield.

plant biology↗

bioRxiv2025

Recessive antimorph alleles reveal novel functions of the OPAQUE1 myosin XI in maize

Ideal plant architecture optimizes canopy structure and increases grain yield in maize. However, its underlying genetic mechanisms remain poorly characterized. Two recessive, EMS-induced maize mutants were identified that have reduced stature, opaque kernels, and abnormal subsidiary cell division, and are allelic to opaque1 (o1). These two new missense alleles, o1-2995 and o1-tan62, unlike the loss-of-function alleles previously identified, generate O1 protein but paradoxically generate more severe morphological defects. These defects include reduced internode elongation and partial suppression of excessive tassel and ear branching in ramosa1 (ra1), ra2, and ra3 mutants. We show that o1-2995 and o1-tan62 are novel alleles of o1, and play a role in plant growth via internode elongation, subsidiary cell division positioning, leaf patterning, inflorescence development, and overall plant architecture.

plant biology↗

bioRxiv2024

An effective and safe maize seed chipping protocol using clipping pliers with applications in small-scale genotyping and marker-assisted breeding

In applications such as marker-assisted breeding and positional cloning, tissue sampling and plant tracking are vital steps in the genotyping pipeline. They enable the identification of desirable seedlings, saving time and reducing the cost, space, and handling required for growing adult plants, especially for greenhouses and winter nurseries. Small-scale marker-assisted selection laboratories rely heavily on leaf-based genotyping, which involves over-planting large, segregating populations followed by leaf sampling, genotyping, and backtracking to identify desired individuals, which is costly and laborious. Thus, there is a need to adopt seed-based genotyping to reduce costs and save time. Therefore, we developed a safe and cheap seed-chipping protocol using clipping pliers to chip seeds to genotype before planting. To identify a cost-effective and high throughput DNA extraction method, we tested four extraction methods and assessed the quality of the seed DNA using PCR. For three of the methods, seed-based DNA was of comparable quality to DNA extracted from leaf punches. We also compared seed- and leaf-derived DNA from the same individuals in a segregating population to test for genotyping miscalls that could arise due to the presence of maternally derived pericarp in the seed samples and found zero miscalls of 43 potential instances. Germination rates of chipped and unchipped seeds were the same for the inbreds tested, B73 and Mo17. However, chipped seeds grew slower until [~]14 days after sowing. Overall, seed sampling using clipping pliers provides a simple, reliable, and high-throughput method to identify specific genotypes before planting. Key FeaturesO_LIProvides a quick, safe, and cheap sampling technique for maize kernels that may also be suitable for other plants with relatively large seeds. C_LIO_LIIncludes procedures and materials to track and organize samples within and across batches involving hundreds to thousands of seeds. C_LIO_LISeeds can be sampled and genotyped relatively quickly for planting; in one day 384 seeds can be sampled, processed for DNA, and genotyped by PCR. C_LI

plant biology↗

bioRxiv2022

Interspecies transfer of syntenic RAMOSA1 orthologs and promoter cis sequences impacts maize inflorescence architecture

Grass inflorescences support floral structures that each bear a single grain, where variation in branch architecture directly impacts yield. The maize RAMOSA1 (ZmRA1) transcription factor acts as a key regulator of inflorescence development by imposing branch meristem determinacy. Here, we show RA1 transcripts accumulate in boundary domains adjacent to spikelet meristems in Sorghum bicolor (Sb) and Setaria viridis (Sv) inflorescences similar as in the developing maize tassel and ear. To evaluate functional conservation of syntenic RA1 orthologs and promoter cis sequences in maize, sorghum and setaria, we utilized interspecies gene transfer and assayed genetic complementation in a common inbred background by quantifying recovery of normal branching in highly ramified ra1-R mutants. A ZmRA1 transgene that includes endogenous upstream and downstream flanking sequences recovered normal tassel and ear branching in ra1-R. Interspecies expression of two transgene variants of the SbRA1 locus, modeled as the entire endogenous tandem duplication or just the non-frameshifted downstream copy, complemented ra1-R branching defects and induced novel fasciation and branch patterns. The SvRA1 locus lacks conserved, upstream noncoding cis sequences found in maize and sorghum; interspecies expression of an SvRA1 transgene did not or only partially recovered normal inflorescence forms. Driving expression of the SvRA1 coding region by the ZmRA1 upstream region, however, recovered normal inflorescence morphology in ra1-R. These data leveraging interspecies gene transfer suggest that cis-encoded temporal regulation of RA1 expression is a key factor in modulating branch meristem determinacy that ultimately impacts grass inflorescence architecture.

plant biology↗

bioRxiv2019

Highly expressed maize pollen genes display coordinated expression with neighboring transposable elements and contribute to pollen fitness

In flowering plants, the haploid male gametophyte (pollen) is essential for sperm delivery, double fertilization, and subsequent initiation of seed development. Pollen also undergoes dynamic epigenetic regulation of expression from transposable elements (TEs), but how this process interacts with gene regulation and function is not clearly understood. To identify components of these processes, we quantified transcript levels in four male reproductive stages of maize (tassel primordia, microspores, mature pollen, and isolated sperm cells) via RNA-seq. We found that, in contrast to Arabidopsis TE expression in pollen, TE transcripts in maize accumulate as early as the microspore stage and are also present in sperm cells. Intriguingly, coordinated expression was observed between the most highly expressed protein-coding genes and neighboring TEs, specifically in both mature pollen and sperm cells. To test the hypothesis that such elevated expression correlates with functional relevance, we measured the fitness cost (male-specific transmission defect) of GFP-tagged exon insertion mutations in over 50 genes highly expressed in pollen vegetative cell, sperm cell, or seedling (as a sporophytic control). Insertions in genes highly expressed only in seedling or primarily in sperm cells (with one exception) exhibited no difference from the expected 1:1 transmission ratio. In contrast, insertions in over 20% of vegetative cell genes were associated with significant reductions in fitness, showing a positive correlation of transcript level with non-Mendelian segregation. The gamete expressed2 (gex2) gene was the single sperm cell gene associated with reduced transmission when mutant (<35% for two independent insertions), and also triggered seed defects when crossed as a male, supporting a role for gex2 in double fertilization. Overall, our study demonstrates a developmentally programmed and coordinated transcriptional activation of TEs and genes, and further identifies maize pollen as a model in which transcriptomic data have predictive value for quantitative phenotypes.\n\nAuthor SummaryIn flowering plants, pollen is essential for delivering sperm cells to the egg and central cell for double fertilization, initiating the process of seed development. In plants with abundant pollen like maize, this process can be highly competitive. In an added layer of complexity, growing evidence indicates expression of transposable elements (TEs) is more dynamic in pollen than in other plant tissues. How these elements impact pollen function and gene regulation is not well understood. We used transcriptional profiling to generate a framework for both detailed analysis of TE expression and quantitative assessment of gene function during maize pollen development. TEs are expressed early and persist, many showing coordinate activation with highly-expressed neighboring genes in the pollen vegetative cell and sperm cells. Measuring fitness costs for a set of over 50 mutations indicates a correlation between elevated transcript level and gene function in the vegetative cell. Finally, we establish a role in fertilization for the gamete expressed2 (gex2) gene, identified based on its specific expression in sperm cells. These results highlight maize pollen as a powerful model for investigating the developmental interplay of TEs and genes, as well as for measuring fitness contributions of specific genes.

plant biology↗

bioRxiv2018

Maize YABBY drooping leaf genes regulate floret development and floral meristem determinacy

Floret units in cereals produce grain, directly impacting yield. Here we report mutations in the maize CRABS CLAW (CRC) co-orthologs drooping leaf1 (drl1) and drl2 alter the development of ear and tassel florets. Pistillate florets of drl1 ears appear sterile and display ectopic unfused carpels that fail to enclose an expanded nucellus. Staminate florets of drl1 tassels have extra stamens and retain fertile anthers. Natural variation and transposon alleles of drl2 enhance drl1 floret phenotypes by reducing floral meristem (FM) determinacy. The drl paralogs are co-expressed in lateral floral organ primordia, but not within the FM. Together, the expression patterns and indeterminate mutant FMs suggest that the drl genes regulate FM activity and impose meristem determinacy by a non-cell autonomous signal. Genetic interaction analyses of drl mutants with maize floral mutants indicate that the drl genes are required throughout floret development, illustrating their importance for proper floret patterning in maize.

plant biology↗