A complete understanding of ionome homeostasis requires a thorough investigation of the dynamics of the nutrient networks in plants. This review focuses on the complexity of interactions occurring ...between S and other nutrients, and these are addressed at the level of the whole plant, the individual tissues, and the cellular compartments. With regards to macronutrients, S deficiency mainly acts by reducing plant growth, which in turn restricts the root uptake of, for example, N, K, and Mg. Conversely, deficiencies in N, K, or Mg reduce uptake of S. TOR (target of rapamycin) protein kinase, whose involvement in the co-regulation of C/N and S metabolism has recently been unravelled, provides a clue to understanding the links between S and plant growth. In legumes, the original crosstalk between N and S can be found at the level of nodules, which show high requirements for S, and hence specifically express a number of sulfate transporters. With regards to micronutrients, except for Fe, their uptake can be increased under S deficiency through various mechanisms. One of these results from the broad specificity of root sulfate transporters that are up-regulated during S deficiency, which can also take up some molybdate and selenate. A second mechanism is linked to the large accumulation of sulfate in the leaf vacuoles, with its reduced osmotic contribution under S deficiency being compensated for by an increase in Cl uptake and accumulation. A third group of broader mechanisms that can explain at least some of the interactions between S and micronutrients concerns metabolic networks where several nutrients are essential, such as the synthesis of the Mo co-factor needed by some essential enzymes, which requires S, Fe, Zn and Cu for its synthesis, and the synthesis and regulation of Fe-S clusters. Finally, we briefly review recent developments in the modelling of S responses in crops (allocation amongst plant parts and distribution of mineral versus organic forms) in order to provide perspectives on prediction-based approaches that take into account the interactions with other minerals such as N.
Including more grain legumes in cropping systems is important for the development of agroecological practices and the diversification of protein sources for human and animal consumption. Grain legume ...yield and quality is impacted by abiotic stresses resulting from fluctuating availabilities in essential nutrients such as iron deficiency chlorosis (IDC). Promoting plant iron nutrition could mitigate IDC that currently impedes legume cultivation in calcareous soils, and increase the iron content of legume seeds and its bioavailability. There is growing evidence that plant microbiota contribute to plant iron nutrition and might account for variations in the sensitivity of pea cultivars to iron deficiency and in fine to seed nutritional quality. Pyoverdine (pvd) siderophores synthesized by pseudomonads have been shown to promote iron nutrition in various plant species (Arabidopsis, clover and grasses). This study aimed to investigate the impact of three distinct ferripyoverdines (Fe-pvds) on iron status and the ionome of two pea cultivars (cv.) differing in their tolerance to IDC, (cv. S) being susceptible and (cv. T) tolerant. One pvd came from a pseudomonad strain isolated from the rhizosphere of cv. T (pvd1T), one from cv. S (pvd2S), and the third from a reference strain C7R12 (pvdC7R12). The results indicated that Fe-pvds differently impacted pea iron status and ionome, and that this impact varied both according to the pvd and the cultivar. Plant iron concentration was more increased by Fe-pvds in cv. T than in cv. S. Iron allocation within the plant was impacted by Fe-pvds in cv. T. Furthermore, Fe-pvds had the greatest favorable impact on iron nutrition in the cultivar from which the producing strain originated. This study evidences the impact of bacterial siderophores on pea iron status and pea ionome composition, and shows that this impact varies with the siderophore and host-plant cultivar, thereby emphasizing the specificity of these plant-microorganisms interactions. Our results support the possible contribution of pyoverdine-producing pseudomonads to differences in tolerance to IDC between pea cultivars. Indeed, the tolerant cv. T, as compared to the susceptible cv. S, benefited from bacterial siderophores for its iron nutrition to a greater extent.
Plants are sessile organisms whose survival depends on their strategy to cope with dynamic, stressful conditions. It is urgent to improve the ability of crops to adapt to recurrent stresses in order ...to alleviate the negative impacts on their productivity. Although our knowledge of plant adaptation to drought has been extensively enhanced during the last decades, recent studies have tackled plant responses to recurrent stresses. The present review synthesizes the major findings from studies addressing plant responses to multiple drought events, and demonstrates the ability of plants to memorize drought stress. Stress memory is described as a priming effect allowing a different response to a reiterated stress when compared to a single stress event. Here, by specifically focusing on water stress memory at the plant cycle level, we describe the different underlying processes at the molecular, physiological and morphological levels in crops as well as in the model species
. Moreover, a conceptual analysis framework is proposed to study drought stress memory. Finally, the essential role of interactions between plants and soil microorganisms is emphasized during reiterated stresses because their plasticity can play a key role in supporting overall plant resilience.
Human mineral malnutrition or hidden hunger is considered a global challenge, affecting a large proportion of the world’s population. The reduction in the mineral content of edible plant products is ...frequently found in cultivars bred for higher yields, and is probably increased by intensive agricultural practices. The filling of grain with macro and micronutrients is partly the result of a direct allocation from root uptake and remobilization from vegetative tissues. The aim of this bibliographic review is to focus on recent knowledge obtained from ionomic analysis of plant tissues in order to build a global appraisal of the potential remobilization of all macro and micronutrients, and especially those from leaves. Nitrogen is always remobilized from leaves of all plant species, although with different efficiencies, while nutrients such as K, S, P, Mg, Cu, Mo, Fe and Zn can be mobilized to a certain extent when plants are facing deficiencies. On the opposite, there is few evidence for leaf mobilization of Ca, Mn, Ni and B. Mechanisms related to the remobilization process (remobilization of mineral forms from vacuolar and organic compounds associated with senescence, respectively) are also discussed in the context of drought, an abiotic stress that is thought to increase and known to modulate the ionic composition of grain in crops.
As drought is increasingly frequent in the context of climate change it is a major constraint for crop growth and yield. The ability of plants to maintain their yield in response to drought depends ...not only on their ability to tolerate drought, but also on their capacity to subsequently recover. Post-stress recovery can indeed be decisive for drought resilience and yield stability. Pea (
), as a legume, has the capacity to fix atmospheric nitrogen through its symbiotic interaction with soil bacteria within root nodules. Biological nitrogen fixation is highly sensitive to drought which can impact plant nitrogen nutrition and growth. Our study aimed at dynamically evaluating whether the control of plant N status after drought could affect nodulated pea plant's ability to recover. Two pea genotypes, Puget and Kayanne, displaying different drought resilience abilities were compared for their capacity to tolerate to, and to recover from, a 2-weeks water-deficit period applied before flowering. Physiological processes were studied in this time-series experiment using a conceptual structure-function analysis framework focusing on whole plant carbon, nitrogen, and water fluxes combined to two
CO
and
N
labeling experiments. While Puget showed a yield decrease compared to well-watered plants, Kayanne was able to maintain its yield. During the recovery period, genotype-dependent strategies were observed. The analysis of the synchronization of carbon, nitrogen, and water related traits dynamics during the recovery period and at the whole plant level, revealed that plant growth recovery was tightly linked to N nutrition. In Puget, the initiation of new nodules after water deficit was delayed compared to control plants, and additional nodules developed, while in Kayanne the formation of nodules was both rapidly and strictly re-adjusted to plant growth needs, allowing a full recovery. Our study suggested that a rapid re-launch of N acquisition, associated with a fine-tuning of nodule formation during the post-stress period is essential for efficient drought resilience in pea leading to yield stability.
Peas, as legume crops, could play a major role in the future of food security in the context of worldwide human nutrient deficiencies coupled with the growing need to reduce consumption of animal ...products. However, pea yields, in terms of quantity and quality (i.e. grain content), are both susceptible to climate change, and more specifically to water deficits, which nowadays occur more frequently during crop growth cycles and tend to last longer. The impact of soil water stress on plant development and plant growth is complex, as its impact varies depending on soil water availability (through the modulation of elements available in the soil), and by the plant's ability to acclimate to continuous stress or to memorize previous stress events.
To identify the strategies underlying these plant responses to water stress events, pea plants were grown in controlled conditions under optimal water treatment and different types of water stress; transient (during vegetative or reproductive periods), recurrent, and continuous (throughout the plant growth cycle). Traits related to water, carbon, and ionome uptake and uses were measured and allowed the identification typical plant strategies to cope with water stress.
Our results highlighted (i) the common responses to the three types of water stress in shoots, involving manganese (Mn) in particular, (ii) the potential implications of boron (B) for root architecture modification under continuous stress, and (iii) the establishment of an "ecophysiological imprint" in the root system
an increase in nodule numbers during the recovery period.
Legume plants, such as peas, are of significant nutritional interest for both humans and animals. However, plant nutrition and thus, seed composition, depends on soil mineral nutrient availability. ...Understanding the impact of their deprivation on the plant mineral nutrient content, net uptake, and remobilization is of key importance but remains complex as the elements of the plant ionome are linked in intricate networks, one element deprivation impacting uptake and remobilization of other nutrients. To get a better insight into pea mineral nutrition, the transitory deprivations of 13 mineral nutrients were imposed during the vegetative growth phase. Thereafter, plants were grown under optimal mineral conditions until physiological maturity. Plant nutritional status and seed quality impacts caused by the deprivations were characterized using measurement of mineral nutrient concentration and plant biomass allocation. Our results highlight: (i) the preferential allocation of dry weight and elements to shoots at the expense of the roots under non-limiting conditions, and more particularly to the tendrils in comparison to the other shoot organs, (ii) the positive and/or negative impact of one mineral nutrient deprivation on other elements of the ionome, (iii) four different remobilization strategies for eight mineral nutrients, and (iv) possible strategies to improve seed quality
fine control of fertilization during a period of mineral nutrient deficiency.
Climate change is forecasted to induce more drought stress events. Water scarcity is already the most limiting abiotic stress for crop production. With higher food demand, there is a need for ...sustainable solutions to cope with the loss of productivity due to water stress. It is known that plant growth-promoting rhizobacteria (PGPR) can colonize plant roots and increase plant growth. However, there is actually no sustainable method to decrease the impact of water stress. Therefore, we hypothesized that an application of thuricin-17, a molecule produced by the PGPR
Bacillus thuringiensis
, could enhance soybean tolerance to water stress. We grew soybean plants for 1 month in growth chambers in order to evaluate their response to thuricin-17 root application under drought, in association with the inoculation of N
2
-fixing
Bradyrhizobium japonicum
. We measured traits reflecting root architecture: number of tips, root diameter, root length, number of nodules; water fluxes: water potential, stomatal conductance; carbon nutrition: leaf area, photosynthetic rate, biomass and carbon partitioning; nitrogen nutrition: nitrogen partitioning and hormone signalling: abscisic acid concentration during the vegetative growth period. Our results show that thuricin-17 application under water stress increased plant biomass by 17 %, thus masking drought impact. This effect is due to modifications of below-ground structures, with 37 % increase of root and 55 % increase of nodule biomass, and to slight increases of leaf area and photosynthetic rate. We also observed that application of thuricin-17 induced a 30 % increase of root abscisic acid, an increase of root length and of leaf water potential. Finally, thuricin-17 induced an activation of nodule formation by 40 %, a partial restoration of nodule-specific activity, nodule growth and consequently, an increase by 17 % of the total nitrogen amount in the plant. Overall, our findings reveal a new method to decrease the negative impact of water stress. Results also demonstrate that the plant restored an adequate water and N balance by changing its root structure.
Soybean
Glycine max
(L.) Merr is the legume with the largest cultivated area worldwide and its yield depends largely on symbiotic nitrogen fixation and root architecture. This study aimed to explore ...the genetic variability of root architectural traits and di-nitrogen fixing activity in a small collection of nine European cultivars belonging to the same maturity group during their early stages. New image analysis approaches were implemented to characterise root architecture at high throughput. Significant genetic variability was identified for the width of the root system, root density, and for nitrogen fixation. This study allowed us to highlight trade-offs among root and nodule traits, and structural and functional traits. Finally, both the image analysis approach and the results could be used for breeding programs of soybean, that could take into account the root system architecture, when the plant interacts in symbiosis with N
2
-fixing bacteria.
Le soja
Glycine max
(L.) Merr est la légumineuse la plus cultivée au monde et son rendement dépend largement de son architecture racinaire et de la fixation symbiotique de l’azote atmosphérique. Cette étude vise à explorer la variabilité génétique des traits d’architecture racinaire et de l’activité de fixation de diazote au cours des stades précoces de développement, dans une petite collection de neuf cultivars européens appartenant au même groupe de maturité. De nouvelles approches d’analyse d’image ont été mises en œuvre pour caractériser l’architecture racinaire à haut débit. Une variabilité génétique a pu être identifiée pour la largeur du système racinaire, la densité des racines et pour la fixation de l’azote. Cette étude nous a également permis de mettre en évidence les compromis entre traits racinaires et nodulaires, et des compromis entre traits structuraux et fonctionnels. L’approche d’analyse d’image et les résultats générés dans cette étude pourraient être remobilisés pour les programmes de sélection du soja, qui pourraient prendre en compte l’architecture du système racinaire, lorsque la plante interagit en symbiose avec des bactéries fixatrices de N
2
.
Plant and soil types are usually considered as the two main drivers of the rhizosphere microbial communities. The aim of this work was to study the effect of both N availability and plant genotype on ...the plant associated rhizosphere microbial communities, in relation to the nutritional strategies of the plant-microbe interactions, for six contrasted Medicago truncatula genotypes. The plants were provided with two different nutrient solutions varying in their nitrate concentrations (0 mM and 10 mM). First, the influence of both nitrogen availability and Medicago truncatula genotype on the genetic structure of the soil bacterial and fungal communities was determined by DNA fingerprint using Automated Ribosomal Intergenic Spacer Analysis (ARISA). Secondly, the different nutritional strategies of the plant-microbe interactions were evaluated using an ecophysiological framework. We observed that nitrogen availability affected rhizosphere bacterial communities only in presence of the plant. Furthermore, we showed that the influence of nitrogen availability on rhizosphere bacterial communities was dependent on the different genotypes of Medicago truncatula. Finally, the nutritional strategies of the plant varied greatly in response to a modification of nitrogen availability. A new conceptual framework was thus developed to study plant-microbe interactions. This framework led to the identification of three contrasted structural and functional adaptive responses of plant-microbe interactions to nitrogen availability.
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