Small-molecule screens to study lateral root development

Development of the root system is essential for proper plant growth and development. Extension of the root system is achieved by the continuous establishment of new meristems in existing parental root tissues, which leads to the development of lateral roots. This process of lateral root organogenesis consists of different developmental stages, which are all controlled by the plant hormone auxin. In this chapter, we describe a screening method in Arabidopsis thaliana to identify small synthetic molecules that interfere with the process of lateral root development during specific developmental stages

Frequency of the Pectoralis Minor Compression Syndrome in Patients Treated for Thoracic Outlet Syndrome

BACKGROUND: Pectoralis minor compression syndrome (PMCS) is a compression of the neurovascular structures in the subpectoral tunnel and remains underestimated in the management of patients with thoracic outlet syndrome (TOS). Its underdiagnosis may be responsible for incomplete or failed treatment. The aim of the study was to evaluate the frequency of PMCS in our experience. METHODS: We retrospectively reviewed all patients treated for TOS in our department. We selected those in whom PMCS was diagnosed with a systematic dynamic arteriography. Surgery was performed using the Roos axillary approach when a first rib resection was associated or an elective approach when a first rib resection was not associated. RESULTS: From January 2004 to December 2014, 374 surgeries for TOS were performed in 279 patients, which included 90 men (sex ratio = 0.48) with a mean age of 40.1 ± 10 years old. Among these patients, 63 (22.5%) underwent 82 interventions (21.9%) for PMCS, including 26 men (sex ratio = 0.70, P < 0.05) with a mean age of 37.9 ± 9.4 years old. Tenotomy of the pectoralis minor muscle was performed using axillary approach if it was associated with a first rib resection in 74 cases (90.2%) or through an elective approach in 8 cases (9.8%) if it was isolated. Four (4.9%) postoperative complications were found (1 hematoma [1.2%], 1 hemothorax [1.2%], 1 scapula alata [1.2%], and 1 subclavian vein thrombosis [1.2%]), all after an axillary approach. In 63 cases (79.7%), preoperative symptoms were resolved. In 14 cases (17.7%), symptom resolution was incomplete, and 2 patients (2.6%) had recurrent symptoms. CONCLUSIONS: Evaluation of PMCS in TOS is justified by its frequency and the simplicity and low morbidity of the surgical procedure

The circadian clock rephases during lateral root organ initiation in Arabidopsis thaliana

The endogenous circadian clock enables organisms to adapt their growth and development to environmental changes. Here we describe how the circadian clock is employed to coordinate responses to the key signal auxin during lateral root (LR) emergence. In the model plant, Arabidopsis thaliana, LRs originate from a group of stem cells deep within the root, necessitating that new organs emerge through overlying root tissues. We report that the circadian clock is rephased during LR development. Metabolite and transcript profiling revealed that the circadian clock controls the levels of auxin and auxin-related genes including the auxin response repressor IAA14 and auxin oxidase AtDAO2. Plants lacking or overexpressing core clock components exhibit LR emergence defects. We conclude that the circadian clock acts to gate auxin signalling during LR development to facilitate organ emergence

Multiscale modelling of auxin transport in the plant-root elongation zone

In the root elongation zone of a plant, the hormone auxin moves in a polar manner due to active transport facilitated by spatially distributed influx and efflux carriers present on the cell membranes. To understand how the cell-scale active transport and passive diffusion combine to produce the effective tissue-scale flux, we apply asymptotic methods to a cell-based model of auxin transport to derive systematically a continuum description from the spatially discrete one. Using biologically relevant parameter values, we show how the carriers drive the dominant tissue-scale auxin flux and we predict how the overall auxin dynamics are affected by perturbations to these carriers, for example, in knockout mutants. The analysis shows how the dominant behaviour depends on the cells' lengths, and enables us to assess the relative importance of the diffusive auxin flux through the cell wall. Other distinguished limits are also identified and their potential roles discussed. As well as providing insight into auxin transport, the study illustrates the use of multiscale (cell to tissue) methods in deriving simplified models that retain the essential biology and provide understanding of the underlying dynamics

Oak root response to ectomycorrhizal symbiosis establishment: RNA-Seq derived transcript identification and expression profiling

Ectomycorrhizal symbiosis is essential for the life and health of trees in temperate and boreal forests where it plays a major role in nutrient cycling and in functioning of the forest ecosystem. Trees with ectomycorrhizal root tips are more tolerant to environmental stresses, such as drought, and biotic stresses such as root pathogens. Detailed information on these molecular processes is essential for the understanding of symbiotic tissue development in order to optimize the benefits of this natural phenomenon. Next generation sequencing tools allow the analysis of non model ectomycorrhizal plant-fungal interactions that can contribute to find the "symbiosis toolkits" and better define the role of each partner in the mutualistic interaction. By using 454 pyrosequencing we compared ectomycorrhizal cork oak roots with non-symbiotic roots. From the two cDNA libraries sequenced, over 2 million reads were obtained that generated 19,552 cork oak root unique transcripts. A total of 2238 transcripts were found to be differentially expressed when ECM roots were compared with non-symbiotic roots. Identification of up- and down-regulated gens in ectomycorrhizal roots lead to a number of insights into the molecular mechanisms governing this important symbiosis. In cork oak roots, ectomycorrhizal colonization resulted in extensive cell wall remodelling, activation of the secretory pathway, alterations in flavonoid biosynthesis, and expression of genes involved in the recognition of fungal effectors. In addition, we identified genes with putative roles in symbiotic processes such as nutrient exchange with the fungal partner, lateral root formation or root hair decay. These findings provide a global overview of the transcriptome of an ectomycorrhizal host root, and constitute a foundation for future studies on the molecular events controlling this important symbiosis.This work was funded by the Portuguese Foundation for Science and Technology (www.fct.pt) in the frame of the project Cork Oak EST Consortium SOBREIRO/0034/2009. Post-doc grant to MS was supported by the Portuguese Foundation for Science and Technology (SFRH/BPD/25661/2005). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript