Biology subjects

Nolan, T. M.

Publications and source records attributed to Nolan, T. M..

4 recordsLinked to original sources

bioRxiv2021

Interplay between brassinosteroids and TORC signaling in Arabidopsis revealed by integrated multi-dimensional analysis

Brassinosteroids (BR) and Target of Rapamycin Complex (TORC) are two major processes coordinating plant growth and stress responses. BRs function through a signaling pathway to extensively regulate gene expression and TORC is known to regulate translation and autophagy. Recent studies revealed that these two pathways crosstalk, but a system-wide view of their interplay is still missing. Thus, we performed transcriptome, proteome, and phosphoproteome profiling of Arabidopsis mutants with altered levels of either BIN2 or RAPTOR1B, two key players in BR and TORC signaling, respectively. We found that perturbation of BIN2 or RAPTOR1B levels affects a common set of gene-products involved in growth and stress responses. Additionally, we performed Multiplexed Assay for Kinase Specificity (MAKS), which provided a system-wide view of direct BIN2 substrates. Furthermore, phosphoproteomic data was used to reconstruct a kinase-signaling network and to identify novel proteins dependent on BR and/or TORC signaling pathways. Loss of function mutants of many of these proteins led to an altered BR response and/or modulated autophagy activity. Altogether, these results provide genome-wide evidence for crosstalk between BR and TORC signaling and established a kinase signaling network that defines the molecular mechanisms of BR and TORC interactions in the regulation of plant growth/stress balance.

plant biology↗

bioRxiv2020

Integrated omics networks reveal the temporal signaling events of brassinosteroid response in Arabidopsis

Brassinosteroids (BRs) are plant steroid hormones that are known to regulate cell division and stress response. We used a systems biology approach to integrate multi-omic datasets and unravel the molecular signaling events of BR response in Arabidopsis. We profiled the levels of 32,549 transcripts, 9,035 protein groups, and 26,950 phosphorylation sites from Arabidopsis seedlings treated with brassinolide (BL, most active BR) for six different lengths of time. We then constructed a network inference pipeline called Spatiotemporal Clustering and Inference of Omics Networks (SC-ION) that was able to integrate these multi-omic data into one, cohesive regulatory network. Our network illustrates the signaling cascade of BR response, starting with kinase-substrate phosphorylation and ending with transcriptional regulation. We used our network predictions to identify putative, relevant phosphorylation sites on the TF BRI1-EMS-SUPPRESSOR 1 (BES1); the importance of which we experimentally validated. Additionally, we identified an uncharacterized TF, which we named BRONTOSAURUS (BRON), that regulates cell division. Further, we show that bron mutant roots are hypersensitive to BL. Together, this work demonstrates the power of integrative network analysis applied to multiomic data and provides fundamental insights into the molecular signaling events occurring during BR response.

plant biology↗

bioRxiv2020

A single cell Arabidopsis root atlas reveals developmental trajectories in wild type and cell identity mutants

SummaryCell fate acquisition is a fundamental developmental process in all multicellular organisms. Yet, much is unknown regarding how a cell traverses the pathway from stem cell to terminal differentiation. Advances in single cell genomics1 hold promise for unraveling developmental mechanisms2–3 in tissues4, organs5–6, and organisms7–8. However, lineage tracing can be challenging for some tissues9 and integration of high-quality datasets is often necessary to detect rare cell populations and developmental states10,11. Here, we harmonized single cell mRNA sequencing data from over 110,000 cells to construct a comprehensive atlas for a stereotypically developing organ with indeterminate growth, the Arabidopsis root. To test the utility of the atlas to interpret new datasets, we profiled mutants for two key transcriptional regulators at single cell resolution, shortroot and scarecrow. Although both transcription factors are required for early specification of cell identity12, our results suggest the existence of an alternative pathway acting in mature cells to specify endodermal identity, for which SHORTROOT is required. Uncovering the architecture of this pathway will provide insight into specification and stabilization of the endodermis, a tissue analogous to the mammalian epithelium. Thus, the atlas is a pivotal advance for unraveling the transcriptional programs that specify and maintain cell identity to regulate organ development in space and time.Competing Interest StatementPNB is the co-founder and Chair of the Scientific Advisory Board of Hi Fidelity Genetics, Inc, a company that works on crop root growth.View Full Text

plant biology↗

bioRxiv2020

Robotic Assay for Drought (RoAD): An Automated Phenotyping System for Brassinosteroid and Drought Response

Brassinosteroids (BRs) are a group of plant steroid hormones involved in regulating growth, development, and stress responses. Many components of the BR pathway have previously been identified and characterized. However, BR phenotyping experiments are typically performed on petri plates and/or in a low-throughput manner. Additionally, the BR pathway has extensive crosstalk with drought responses, but drought experiments are time-consuming and difficult to control. Thus, we developed Robotic Assay for Drought (RoAD) to perform BR and drought response experiments in soil-grown Arabidopsis plants. RoAD is equipped with a bench scale, a precisely controlled watering system, an RGB camera, and a laser profilometer. It performs daily weighing, watering, and imaging tasks and is capable of administering BR response assays by watering plants with Propiconazole (PCZ), a BR biosynthesis inhibitor. We developed image processing algorithms for both plant segmentation and phenotypic trait extraction in order to accurately measure traits in 2-dimensional (2D) and 3-dimensional (3D) spaces including plant surface area, leaf length, and leaf width. We then applied machine learning algorithms that utilized the extracted phenotypic parameters to identify image-derived traits that can distinguish control, drought, and PCZ-treated plants. We carried out PCZ and drought experiments on a set of BR mutants and Arabidopsis accessions with altered BR responses. Finally, we extended the RoAD assays to perform BR response assays using PCZ in Zea mays (maize) plants. This study establishes an automated and non-invasive robotic imaging system as a tool to accurately measure morphological and growth-related traits of Arabidopsis and maize plants, providing insights into the BR-mediated control of plant growth and stress responses.

plant biology↗