Browsing by Author "O'Brien, Jose"

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    Modulation of plant root growth by nitrogen source-defined regulation of polar auxin transport
    (2021) Otvos, Krisztina; Marconi, Marco; Vega, Andrea; O'Brien, Jose; Johnson, Alexander; Abualia, Rashed; Antonielli, Livio; Montesinos, Juan Carlos; Zhang, Yuzhou; Tan, Shutang; Cuesta, Candela; Artner, Christina; Bouguyon, Eleonore; Gojon, Alain; Friml, Jiri; Gutierrez, Rodrigo A.; Wabnik, Krzysztof; Benkova, Eva
    Availability of the essential macronutrient nitrogen in soil plays a critical role in plant growth, development, and impacts agricultural productivity. Plants have evolved different strategies for sensing and responding to heterogeneous nitrogen distribution. Modulation of root system architecture, including primary root growth and branching, is among the most essential plant adaptions to ensure adequate nitrogen acquisition. However, the immediate molecular pathways coordinating the adjustment of root growth in response to distinct nitrogen sources, such as nitrate or ammonium, are poorly understood. Here, we show that growth as manifested by cell division and elongation is synchronized by coordinated auxin flux between two adjacent outer tissue layers of the root. This coordination is achieved by nitrate-dependent dephosphorylation of the PIN2 auxin efflux carrier at a previously uncharacterized phosphorylation site, leading to subsequent PIN2 lateralization and thereby regulating auxin flow between adjacent tissues. A dynamic computer model based on our experimental data successfully recapitulates experimental observations. Our study provides mechanistic insights broadening our understanding of root growth mechanisms in dynamic environments.
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    Nitrate triggered phosphoproteome changes and a PIN2 phosphosite modulating root system architecture
    (2021) Vega, Andrea; Fredes, Isabel; O'Brien, Jose; Shen, Zhouxin; otvos, Krisztina; Abualia, Rashed; Benkova, Eva; Briggs, Steven P.; Gutierrez, Rodrigo A.
    Nitrate commands genome-wide gene expression changes that impact metabolism, physiology, plant growth, and development. In an effort to identify new components involved in nitrate responses in plants, we analyze the Arabidopsis thaliana root phosphoproteome in response to nitrate treatments via liquid chromatography coupled to tandem mass spectrometry. 176 phosphoproteins show significant changes at 5 or 20 min after nitrate treatments. Proteins identified by 5 min include signaling components such as kinases or transcription factors. In contrast, by 20 min, proteins identified were associated with transporter activity or hormone metabolism functions, among others. The phosphorylation profile of NITRATE TRANSPORTER 1.1 (NRT1.1) mutant plants was significantly altered as compared to wild-type plants, confirming its key role in nitrate signaling pathways that involves phosphorylation changes. Integrative bioinformatics analysis highlights auxin transport as an important mechanism modulated by nitrate signaling at the post-translational level. We validated a new phosphorylation site in PIN2 and provide evidence that it functions in primary and lateral root growth responses to nitrate.