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The scarcity of freshwater is an increasing concern in flood-irrigated rice, whilst excessive use of nitrogen fertilizers is costly and contributes to environmental pollution. To co-ordinate growth adaptation under prolonged exposure to limited water or excess nitrogen supply, plants employ complex systems for signalling and regulation of metabolic processes. There is limited information on the involvement of one of the most important post-translational modifications (PTMs), protein phosphorylation, in plant adaptation to long-term changes in resource supply. Oryza sativa cv. Nipponbare was grown under two regimes of nitrogen from the time of germination to final harvest. Twenty-five days after germination, water was withheld from half the pots in each nitrogen treatment and low water supply continued for an additional 26 days, while the remaining pots were well watered. Leaves from all four groups of plants were harvested after 51 days in order to test whether phosphorylation of leaf proteins responded to prior abiotic stress events. The dominant impact of these resources is exerted in leaves, where PTMs have been predicted to occur. Proteins were extracted and phosphopeptides were analysed by nanoLC-MS/MS analysis, coupled with label-free quantitation. Water and nitrogen regimes triggered extensive changes in phosphorylation of proteins involved in membrane transport, such as the aquaporin OsPIP2-6, a water channel protein. Our study reveals phosphorylation of several peptides belonging to proteins involved in RNA-processing and carbohydrate metabolism, suggesting that phosphorylation events regulate the signalling cascades that are required to optimize plant response to resource supply.

Proton-pumping pyrophosphatases (H + -PPases) have been shown to enhance biomass and yield. However, to date, there has been little work towards identify genes encoding H + -PPases in bread wheat ( Triticum aestivum ) ( TaVP s) and limited knowledge on how the expression of these genes varies across different growth stages and tissue types. In this study, the IWGSC database was used to identify two novel TaVP genes, TaVP4 and TaVP5 , and elucidate the complete homeolog sequences of the three known TaVP genes, bringing the total number of bread wheat TaVP s from 9 to 15. Gene expression levels of each TaVP homeolog were assessed using quantitative real-time PCR (qRT-PCR) in four diverse wheat varieties in terms of phenotypic traits related to high vacuolar pyrophosphatase expression. Homeolog expression was analyzed across multiple tissue types and developmental stages. Expression levels of the TaVP homeologs were found to vary significantly between varieties, tissues and plant developmental stages. During early development (Z10 and Z13), expressions of TaVP1 and TaVP2 homeologs were higher in shoot tissue than root tissue, with both shoot and root expression increasing in later developmental stages (Z22). TaVP2-D was expressed in all varieties and tissue types and was the most highly expressed homeolog at all developmental stages. Expression of the TaVP3 homeologs was restricted to developing grain (Z75), while TaVP4 homeolog expression was higher at Z22 than earlier developmental stages. Variation in TaVP4B was detected among varieties at Z22 and Z75, with Buck Atlantico (high biomass) and Scout (elite Australian cultivar) having the highest levels of expression. These findings offer a comprehensive overview of the bread wheat H + -PPase family and identify variation in TaVP homeolog expression that will be of use to improve the growth, yield, and abiotic stress tolerance of bread wheat., Competing Interests: The authors declare that they have no conflict of interest., (© 2021 The Authors. Plant Direct published by American Society of Plant Biologists and the Society for Experimental Biology and John Wiley & Sons Ltd.)

Roots vary their permeability to aid radial transport of solutes towards xylem vessels in response to nutritional cues. Nitrogen (N) depletion was previously shown to induce early suberization of endodermal cell walls and reduce hydraulic conductivity of barley roots suggesting reduced apoplastic transport of ions (Armand et al., 2019). Suberization may also limit transcellular ion movement by blocking access to transporters (Barberon et al., 2016). The aim of this study was to confirm that N depletion induced suberization in the roots of barley and demonstrate that this was a specific effect in response to NO 3 - depletion. Furthermore, in roots with early and enhanced suberization, we assessed their ability for transporter-mediated NO 3 - influx. N depletion induced lateral root elongation and early and enhanced endodermal suberization of the seminal root of each genotype. Both root to shoot NO 3 - translocation and net N uptake was half that of plants supplied with steady-state NO 3 - . Genes with predicted functions in suberin synthesis (HvHORST) and NO 3 - transport (HvNRT2.2) were induced under N-deplete conditions. N-deplete roots had a higher capacity for high-affinity NO 3 - influx in early suberized roots than under optimal NO 3 - . In conclusion, NO 3 - depletion induced early and enhanced suberization in the roots of barley, however, suberization did not restrict transcellular NO 3 - transport., (Copyright © 2020 Elsevier GmbH. All rights reserved.)

Background: The absorption, translocation, accumulation and excretion of substances are fundamental processes in all organisms including plants, and have been successfully studied using radiotracers labelled with 11 C, 13 N, 14 C and 22 Na since 1939. Sodium is one of the most damaging ions to the growth and productivity of crops. Due to the significance of understanding sodium transport in plants, a significant number of studies have been carried out to examine sodium influx, compartmentation, and efflux using 22 Na- or 24 Na-labeled salts. Notably, however, most of these studies employed destructive methods, which has limited our understanding of sodium flux and distribution characteristics in real time, in live plants. Positron emission tomography (PET) has been used successfully in medical research and diagnosis for decades. Due to its ability to visualise and assess physiological and metabolic function, PET imaging has also begun to be employed in plant research. Here, we report the use of a clinical PET scanner with a 22 Na tracer to examine 22 Na-influx dynamics in barley plants (Hordeum vulgare L. spp. Vulgare-cultivar Bass) under variable nutrient levels, alterations in the day/night light cycle, and the presence of sodium channel inhibitors., Results: 3D dynamic PET images of whole plants show readily visible 22 Na translocation from roots to shoots in each examined plant, with rates influenced by both nutrient status and channel inhibition. PET images show that plants cultivated in low-nutrient media transport more 22 Na than plants cultivated in high-nutrient media, and that 22 Na uptake is suppressed in the presence of a cation-channel inhibitor. A distinct diurnal pattern of 22 Na influx was discernible in curves displaying rates of change of relative radioactivity. Plants were found to absorb more 22 Na during the light period, and anticipate the change in the light/dark cycle by adjusting the sodium influx rate downward in the dark period, an effect not previously described experimentally., Conclusions: We demonstrate the utility of clinical PET/CT scanners for real-time monitoring of the temporal dynamics of sodium transport in plants. The effects of nutrient deprivation and of ion channel inhibition on sodium influx into barley plants are shown in two proof-of-concept experiments, along with the first-ever 3D-imaging of the light and dark sodium uptake cycles in plants. This method carries significant potential for plant biology research and, in particular, in the context of genetic and treatment effects on sodium acquisition and toxicity in plants.

Water and nitrogen availability limit crop productivity globally more than most other environmental factors. Plant availability of macronutrients such as nitrate is, to a large extent, regulated by the amount of water available in the soil, and, during drought episodes, crops can become simultaneously water and nitrogen limited. In this review, we explore the intricate relationship between water and nitrogen transport in plants, from transpiration-driven mass flow in the soil to uptake by roots via membrane transporters and channels and transport to aerial organs. We discuss the roles of root architecture and of suberized hydrophobic root barriers governing apoplastic water and nitrogen movement into the vascular system. We also highlight the need to identify the signalling cascades regulating water and nitrogen transport, as well as the need for targeted physiological analyses of plant traits influencing water and nitrogen uptake. We further advocate for incorporation of new phenotyping technologies, breeding strategies, and agronomic practices to improve crop yield in water- and nitrogen-limited production systems., (© The Author(s) 2020. Published by Oxford University Press on behalf of the Society for Experimental Biology.)

On average less than half of the applied N is captured by crops, thus there is scope and need to improve N uptake in cereals. With nitrate (NO 3 - ) being the main form of N available to cereal crops there has been a significant global research effort to understand plant NO 3 - uptake. Despite this, our knowledge of the NO 3 - uptake system is not sufficient to easily target ways to improve NO 3 - uptake. Based on this there is an identified need to better understand the NO 3 - uptake system and the signalling molecules that modulate it. With strong transcriptional control governing the NO 3 - uptake system, we also need new leads for modulating transcription of NO 3 - transporter genes., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Maximizing NO 3 - uptake during seedling development is important as it has a major influence on plant growth and yield. However, little is known about the processes leading to, and involved in, the initiation of root NO 3 - uptake capacity in developing seedlings. This study examines the physiological processes involved in root NO 3 - uptake and metabolism, to gain an understanding of how the NO 3 - uptake system responds to meet demand as maize seedlings transition from seed N use to external N capture. The concentrations of seed-derived free amino acids within root and shoot tissues are initially high, but decrease rapidly until stabilizing eight days after imbibition (DAI). Similarly, shoot N% decreases, but does not stabilize until 12-13 DAI. Following the decrease in free amino acid concentrations, root NO 3 - uptake capacity increases until shoot N% stabilizes. The increase in root NO 3 - uptake capacity corresponds with a rapid rise in transcript levels of putative NO 3 - transporters, ZmNRT2.1 and ZmNRT2.2. The processes underlying the increase in root NO 3 - uptake capacity to meet N demand provide an insight into the processes controlling N uptake., (© 2017 The Authors. Journal of Integrative Plant Biology Published by Wiley Publishing Asia Pty Ltd on behalf of Institute of Botany, Chinese Academy of Sciences.)

Constitutive expression of the Arabidopsis vacuolar proton-pumping pyrophosphatase (H + -PPase) gene (AVP1) increases plant growth under various abiotic stress conditions and, importantly, under nonstressed conditions. Many interpretations have been proposed to explain these phenotypes, including greater vacuolar ion sequestration, increased auxin transport, enhanced heterotrophic growth, and increased transport of sucrose from source to sink tissues. In this review, we evaluate all the roles proposed for AVP1, using findings published to date from mutant plants lacking functional AVP1 and transgenic plants expressing AVP1. It is clear that AVP1 is one protein with many roles, and that one or more of these roles act to enhance plant growth. The complexity suggests that a systems biology approach to evaluate biological networks is required to investigate these intertwined roles., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Cereal varieties with improved salinity tolerance are needed to achieve profitable grain yields in saline soils. The expression of AVP1, an Arabidopsis gene encoding a vacuolar proton pumping pyrophosphatase (H⁺-PPase), has been shown to improve the salinity tolerance of transgenic plants in greenhouse conditions. However, the potential for this gene to improve the grain yield of cereal crops in a saline field has yet to be evaluated. Recent advances in high-throughput nondestructive phenotyping technologies also offer an opportunity to quantitatively evaluate the growth of transgenic plants under abiotic stress through time. In this study, the growth of transgenic barley expressing AVP1 was evaluated under saline conditions in a pot experiment using nondestructive plant imaging and in a saline field trial. Greenhouse-grown transgenic barley expressing AVP1 produced a larger shoot biomass compared to null segregants, as determined by an increase in projected shoot area, when grown in soil with 150 mM NaCl. This increase in shoot biomass of transgenic AVP1 barley occurred from an early growth stage and also in nonsaline conditions. In a saline field, the transgenic barley expressing AVP1 also showed an increase in shoot biomass and, importantly, produced a greater grain yield per plant compared to wild-type plants. Interestingly, the expression of AVP1 did not alter barley leaf sodium concentrations in either greenhouse- or field-grown plants. This study validates our greenhouse-based experiments and indicates that transgenic barley expressing AVP1 is a promising option for increasing cereal crop productivity in saline fields., (© 2013 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.)