Biology subjects

Farmer, E.

Publications and source records attributed to Farmer, E..

4 recordsLinked to original sources

bioRxiv2023

Guanylate cyclase activity of TIR1/AFB auxin receptorsin rapid auxin responses

The plant hormone auxin is perceived by TIR1/AFB receptors, which mediate transcriptional reprogramming via a ubiquitination- and cAMP-dependent mechanism. Same receptors mediate also rapid, non-transcriptional growth responses that are mechanistically less well understood. Here, we demonstrate that TIR1/AFB receptors possess not only adenylate cyclase but also guanylate cyclase activity. Auxin perception independently activates cAMP and cGMP production by TIR1/AFBs in vitro and elevates both cAMP and cGMP levels in planta. Genetic and synthetic biology approaches revealed that AFB1 guanylate cyclase activity is required for the rapid cytosolic Ca2+ transients and root growth inhibition. This unprecedented combination of adenylate and guanylate cyclase activities within a single hormone receptor establishes a new paradigm for how one perception mechanism can mediate distinct downstream responses. One-Sentence SummaryTIR1/AFB auxin receptors possess both, adenylate and guanylate cyclase activities, mediating transcriptional reprogramming and rapid Ca2+-dependent growth responses, respectively.

plant biology↗

bioRxiv2022

Mechanodetection of neighbor plants elicits adaptive leaf movements through calcium dynamics

Plants detect their neighbors via various cues, including reflected light and touching of leaf tips, which elicit in upward leaf movement (hyponasty). It is currently unknown how touch is sensed and how the signal is transferred from the leaf tip to the petiole base that drives hyponasty. Here, we show that touch-induced hyponasty involves a signal transduction pathway that is distinct from light-mediated hyponasty. We found that mechanostimulation of the leaf tip upon touching causes cytosolic calcium ([Ca2+]cyt induction in leaf tip trichomes that spreads towards the petiole. Both perturbation of the calcium response and the absence of trichomes inhibit touch-induced hyponasty. Finally, using plant competition assays, we show that touch-induced hyponasty is adaptive in dense stands of Arabidopsis. We thus establish a novel, adaptive mechanism regulating hyponastic leaf movement in response to mechanostimulation by neighbors in dense vegetation.

plant biology↗

bioRxiv2020

A triresidue motif in the GLUTAMATE RECEPTOR-LIKE 3.3 C-tail interacts with IMPAIRED SUCROSE INDUCTION 1 and controls long distance wound signaling

Arabidopsis Clade 3 GLUTAMATE RECEPTOR-LIKE (GLRs) genes are primary players in wound-induced electrical signaling and jasmonate-activated defense responses. As cation-permeable ion channels, previous studies have focused on resolving their gating properties and structures. However, little is known regarding to the regulatory mechanism of these channel proteins. Here, we report that the C-tail of GLR3.3 contains key elements that control its function in long distance wound signaling. GLR3.3 without its C-tail failed to rescue the glr3.3a mutant. To further investigate the underlying mechanism, we performed a yeast two-hybrid screen. IMPAIRED SUCROSE INDUCTION 1 (ISI1) was identified as an interactor with both the C-tail and the full-length GLR3.3 in planta. Reduced function isi1 mutants had enhanced electrical activity and jasmonate-regulated defense responses. Furthermore, we found that a triresidue motif RFL (R884, F885 and L886) in the GLR3.3 C-tail is essential for interacting with ISI1. RFL mutation abolished GLR3.3 function in electrical signaling and jasmonate-mediated defense gene activation. Our study shows the importance of the C-tail in GLR3.3 function, and reveals parallels with the ipnotropic glutamate receptor regulation in animal cells.

plant biology↗

bioRxiv2019

Improving diagnosis and monitoring of treatment response in pulmonary tuberculosis using the molecular bacterial load assay (MBLA)

ObjectivesBetter outcomes in tuberculosis require new diagnostic and treatment monitoring tools. In this paper we evaluated the utility of a marker of M. tuberculosis viable count, the Molecular Bacterial Load assay (MBLA) for diagnosis and treatment monitoring of tuberculosis in a high burden setting. MethodsPatients with smear positive pulmonary tuberculosis from two sites in Tanzania and one each in Malawi and Mozambique. Sputum samples were taken weekly for the first 12 weeks of treatment and evaluated by MBLA and mycobacterial growth indicator tube method (MGIT). ResultsThe results of high and low positive control samples confirmed inter site reproducibility. Over the 12 weeks of treatment there was a steady decline in the viable bacterial load as measured by the MBLA that corresponds to rise in time to a positive result (TTP) in the Mycobacterial Growth Indicator Tube. Both MBLA and MGIT provided similar time to test negativity. Importantly, as treatment progressed samples in MGIT were increasingly likely to be contaminated, which compromised the acquisition of results but did not affect MBLA samples. ConclusionsMBLA produces a reproducible measure of Mtb viable count comparable to that of MGIT that is not compromised by contamination in a real-world setting. As a molecular test, the results can be available in as little as four hours and could allow health care professionals to identify rapidly patients who are failing therapy.

microbiology↗