Plasticity Of Root System Research Articles

Cryptic variation in RNA-directed DNA-methylation controls lateral root development when auxin signalling is perturbed

Maintaining the right balance between plasticity and robustness in biological systems is important to allow adaptation while maintaining essential functions. Developmental plasticity of plant root systems has been the subject of intensive research, but the mechanisms underpinning robustness remain unclear. Here, we show that potassium deficiency inhibits lateral root organogenesis by delaying early stages in the formation of lateral root primordia. However, the severity of the symptoms arising from this perturbation varies within a natural population of Arabidopsis and is associated with the genetic variation in CLSY1, a key component of the RNA-directed DNA-methylation machinery. Mechanistically, CLSY1 mediates the transcriptional repression of a negative regulator of root branching, IAA27, and promotes lateral root development when the auxin-dependent proteolysis pathway fails. Our study identifies DNA-methylation-mediated transcriptional repression as a backup system for post-translational protein degradation which ensures robust development and performance of plants in a challenging environment.

Mycorrhizal impacts on root trait plasticity of six maize varieties along a phosphorus supply gradient

Plasticity of plants refers to their ability to produce different phenotypes in different environments. Plants show plasticity aboveground as well as belowground. The influence of the arbuscular mycorrhizal fungal (AMF) symbiosis on root plasticity is poorly known. This study aimed to quantify plasticity of root-system related, morphological, physiological or mycorrhizal traits along a soil phosphorus (P) supply gradient. Six varieties of maize (Zea mays L.) were grown in pots with or without AMF at five rates of P supply. Fifteen root traits were measured and calculated after seven weeks of growth. Root system traits (biomass and length) and physiological traits (phosphatase activity at the root surface and in the rhizosphere) showed high plasticity along the P gradient, whereas morphological traits (specific root length and root diameter) exhibited low plasticity. Mycorrhizal presence reduced root-system plasticity (biomass and length), increased morphological-trait plasticity (specific root length and proportion of fine roots), but had little effects on other traits. Our results indicate that trait plasticity related to the root system constitutes the most important adaptive strategy for maize to variation in P supply, and that the mycorrhizal symbiosis reduces root-system plasticity.

Soil compaction and the architectural plasticity of root systems.

Soil compaction is a serious global problem, and is a major cause of inadequate rooting and poor yield in crops around the world. Root system architecture (RSA) describes the spatial arrangement of root components within the soil and determines the plant's exploration of the soil. Soil strength restricts root growth and may slow down root system development. RSA plasticity may have an adaptive value, providing environmental tolerance to soil compaction. However, it is challenging to distinguish developmental retardation (apparent plasticity) or responses to severe stress from those root architectural changes that may provide an actual environmental tolerance (adaptive plasticity). In this review, we outline the consequences of soil compaction on the rooting environment and extensively review the various root responses reported in the literature. Finally, we discuss which responses enhance root exploration capabilities in tolerant genotypes, and to what extent these responses might be useful for breeding. We conclude that RSA plasticity in response to soil compaction is complex and can be targeted in breeding to increase the performance of crops under specific agronomical conditions.

Root plasticity and Pi recycling within plants contribute to low-P tolerance in Tibetan wild barley

BackgroundBarley is a low phosphorus (P) demand cereal crop. Tibetan wild barley, as a progenitor of cultivated barley, has revealed outstanding ability of tolerance to low-P stress. However, the underlying mechanisms of low-P adaption and the relevant genetic controlling are still unclear.ResultsWe identified low-P tolerant barley lines in a doubled-haploid (DH) population derived from an elite Tibetan wild barley accession and a high-yield cultivar. The tolerant lines revealed greater root plasticity in the terms of lateral root length, compared to low-P sensitive lines, in response to low-P stress. By integrating the QTLs associated with root length and root transcriptomic profiling, candidate genes encoding isoflavone reductase, nitrate reductase, nitrate transporter and transcriptional factor MYB were identified. The differentially expressed genes (DEGs) involved the growth of lateral root, Pi transport within cells as well as from roots to shoots contributed to the differences between low-P tolerant line L138 and low-P sensitive lines L73 in their ability of P acquisition and utilization.ConclusionsThe plasticity of root system is an important trait for barley to tolerate low-P stress. The low-P tolerance in the elite DH line derived from a cross of Tibetan wild barley and cultivated barley is characterized by enhanced growth of lateral root and Pi recycling within plants under low-P stress.

Exotic shrub species (Caragana korshinskii) is more resistant to extreme natural drought than native species (Artemisia gmelinii) in a semiarid revegetated ecosystem

Droughts of increasing frequency and severity are expected to have a great impact on vegetation restoration in semiarid ecosystems by reducing water availability to plants. Understanding the functional plasticity of root systems in plant water uptake and the response to extreme droughts is of critical importance for predicting revegetation dynamics under future extreme climates. Sampling was undertaken over a two-year period to investigate the seasonality of water use strategy and growing status of one mature exotic shrub species Caragana korshinskii and one native subshrub species Artemisia gmelinii in both its young and mature growing stages. We investigated stable isotopes, made in situ soil water observations, and recorded functional root distribution. The spring and summer drought in 2015, especially the record low precipitation in July, allowed us to examine the impact of extreme drought on plant water sources and stem mortality. The results revealed that both exotic and native species exhibited significant seasonal patterns in water source use, following shifts in soil water content; they were overall positively correlated with soil water availability. The exotic species C. korshinskii used more soil water from subsurface layers compared to the native species A. gmelinii. The prolonged drought reduced the plasticity of water use strategy and resulted in clear stem mortality of both the young and mature native species but not the exotic species. The results indicate that the native shrub A. gmelinii is less resistant to extreme natural drought than exotic shrub C. korshinskii and hence could be more severely affected by future extreme climatic episodes. This implies that vegetation restoration may be greatly disturbed by extreme droughts in semiarid ecosystems.

Simplifying the root dynamics: from complex hormone–environment interactions to specific root architectural modulation

The recent unveiling of the intriguing interactions among phytohormones and environmental cues in regulating root architecture for optimum plant acclimation has opened new avenues for research. Additional functions of transcriptional as well as protein-level regulators are being identified, uncovering novel interactions between hormonal and environmental signaling pathways, for shaping the root system architecture (RSA). Owing to the importance of root architectural dynamics under constantly encountered external factors, it is crucial to have a regular and comprehensive update of these interactions, affecting RSA, in order to improve crop performance. Moreover, it is equally important to identify and highlight, in crop species, the crucial regulators, which actively mediate hormonal as well as hormone–environment interactions, but have so far been characterized only in model plants such as Arabidopsis. Such updates will open up new research possibilities for plant biologists in extending the present knowledge on root system plasticity from Arabidopsis to economically important crop plants. Here, we provide a consolidated review of the recent findings on novel inter-hormonal and hormone–environment interactions with special emphasis on key downstream regulators and signaling pathways. We conclude by dissecting the gaps and challenges encountered at present, with an outline for future perspectives to channel the enormous information on hormone–environment regulation of RSA, towards a common output in the form of specific modulation of RSA components.

Non-canonical WOX11-mediated root branching contributes to plasticity in Arabidopsis root system architecture.

Lateral roots (LRs), which originate from the growing root, and adventitious roots (ARs), which are formed from non-root organs, are the main contributors to the post-embryonic root system in Arabidopsis. However, our knowledge of how formation of the root system is altered in response to diverse inductive cues is limited. Here, we show that WOX11 contributes to root system plasticity. When seedlings are grown vertically on medium, WOX11 is not expressed in LR founder cells. During AR initiation, WOX11 is expressed in AR founder cells and activates LBD16. LBD16 also functions in LR formation and is activated in that context by ARF7/19 and not by WOX11. This indicates that divergent initial processes that lead to ARs and LRs may converge on a similar mechanism for primordium development. Furthermore, we demonstrated that when plants are grown in soil or upon wounding on medium, the primary root is able to produce both WOX11-mediated and non-WOX11-mediated roots. The discovery of WOX11-mediated root-derived roots reveals a previously uncharacterized pathway that confers plasticity during the generation of root system architecture in response to different inductive cues.

Stress responses of native and exotic grasses in a Neotropical savanna predict impacts of global change on invasion spread

Communities subject to stress, including those with low invasibility, may be dominated by exotic generalist species. African grasses are aggressive invasive species in Neotropical savannas, where their response to abiotic stress remains unknown. We assessed the role of waterlogging and canopy closure on the presence, abundance and reproductive tillering of African and native grasses in a Neotropical savanna in southeastern Brazil. We obtained abundance and reproductive tillering data of exotic (Melinis minutiflora, Melinis repens and Urochloa decumbens) and common native grasses in 20 sites. We also determined the groundwater depth, soil surface water potential and canopy cover at these sites. The grass species generally had a low frequency and performed poorly where soil remained waterlogged throughout the year, except for two native species. Most native species were exclusive to either well-drained savannas or better drained wet grasslands. However, two species (Loudetiopsis chrysothrix and Trachypogon spicatus) occurred in both vegetation types. Two exotic species (M. minutiflora and M. repens) were less common but demonstrated reasonable performance in wet grasslands, possibly due to their root system plasticity. Furthermore, U. decumbens had a lower occurrence, density and reproductive tillering at these sites, but was successful at sites where the groundwater level was slightly deeper. Although the favourable water regime in the savannas increases their invasibility in general, resistance to invasion by African grasses may be greater at microsites with high canopy closure, where these species showed lower performance and did not affect the abundance of co-occurring native grasses. In summary, the Brazilian savanna becomes more susceptible to the spread of African grasses when disturbances decrease canopy closure or lower rainfall associated with climate change reduces the average groundwater depth and consequently releases invasive species from soil waterlogging in grasslands.

Evolutionary divergences in root system morphology, allocation, and nitrogen uptake in species from high- versus low-fertility soils.

Root morphology and nutrient uptake processes are essential for acquisition of mineral resources from soil. However, our understanding of how root form and function have diverged across environments is limited. In this study, we addressed hypotheses of adaptive differentiation using three pairs of Helianthus species chosen as phylogenetically-independent contrasts with respect to native soil nutrients. Under controlled environmental conditions, root morphology, allocation, and nitrogen (N) uptake (using a 15N tracer) were assessed for seedlings under both high and low N treatments. Species native to low nutrient soils (LNS) had lower total root length than those native to high nutrient soils (HNS), reflecting the slower growth rates of species from less fertile environments. Contrary to expectations, species did not consistently differ in specific root length, root tissue density, or root system plasticity, and species native to LNS had lower root:total mass ratio and higher 15N uptake rates than species native to HNS. Overall, these evolutionary divergences provide support for adaptive differentiation among species, with repeated evolution of slow-growing root systems suited for low resource availability in LNS. However, species native to LNS maintain a high capacity for N uptake, potentially as a means of maximising nutrient acquisition from transient pulses.

Knockdown of the partner protein OsNAR2.1 for high-affinity nitrate transport represses lateral root formation in a nitrate-dependent manner.

The morphological plasticity of root systems is critical for plant survival, and understanding the mechanisms underlying root adaptation to nitrogen (N) fluctuation is critical for sustainable agriculture; however, the molecular mechanism of N-dependent root growth in rice remains unclear. This study aimed to identify the role of the complementary high-affinity NO3− transport protein OsNAR2.1 in NO3−-regulated rice root growth. Comparisons with wild-type (WT) plants showed that knockdown of OsNAR2.1 inhibited lateral root (LR) formation under low NO3− concentrations, but not under low NH4+ concentrations. 15N-labelling NO3− supplies (provided at concentrations of 0–10 mM) demonstrated that (i) defects in LR formation in mutants subjected to low external NO3− concentrations resulted from impaired NO3− uptake, and (ii) the mutants had significantly fewer LRs than the WT plants when root N contents were similar between genotypes. LR formation in osnar2.1 mutants was less sensitive to localised NO3− supply than LR formation in WT plants, suggesting that OsNAR2.1 may be involved in a NO3−-signalling pathway that controls LR formation. Knockdown of OsNAR2.1 inhibited LR formation by decreasing auxin transport from shoots to roots. Thus, OsNAR2.1 probably functions in both NO3− uptake and NO3−-signalling.

Some properties of man-made Dnieper Steppe ecosystems

Physico-chemical and hydrogeological properties of technogenic ecotope landscapes are unique in the world. Their development has created a new, completely unexplored problem of recultivation of disturbed lands. The ecological and biological evaluation of ecotypes is the leading place because it is the basis of targeted restoration of fertility of such anthropogenic tumors. As tests for the development of waste quarry sectors in the long-term stationary trials there were tested 23 species of higher plants. In the steppe of Ukraine the greatest ecological and biological according to technogenic ecotopes showed alfalfa and sainfoin. They are plant-dominants, accumulate large quantities of biomass, creating pockets of concentrations of elements in soil fertility, improve the sanitary conditions of the surrounding area. The nature translocational process in higher plants was identified. It completely depends on their biological features and is the creation of their root systems with the same structure and therefore their distribution in the thickness of elafotopos who are able to provide plants with nutrients and to produce the maximum possible efficiency in data soil-ecological conditions. Alfalfa and sainfoin showed great ecological plasticity of root systems. On the poverty of ecotopes batteries they reacted by increasing the surface and length of roots. It is established that the saturation of ecotopes roots is directly proportional to their mass, and the surface root system and its length are values associated with root mass. With the depth of the absorbing working surface root systems increases. The mathematical model of calculation of the ecological and biological characteristics of root systems of plants and progressive framework method of selection of soil monoliths with roots. After washing, the roots are reported to air-dry state and are distributed through the thickness of 4 factions: more than 5 mm, 5–1, 1–0,5 and less than 0.5 mm. This allows you to get an idea about the structure of the root system and its distribution in the thickness of ecotopes, as well as to determine the portion of the roots through which the greatest absorption of water and food items. The features of the development of the underground part of plants that is the basis for the development of practical methods of influence on ecotopia. For example, alfalfa is useful for sodding slope plots dump pits or eroded fields, and sainfoin – to create water-stable structural units. It is shown that the qualitative indicators of ecotopes strictly determine the morphology and aboveground and underground parts, as well as the number and weight of nodules in legumes. In the thickness of ecotopes man-made landscapes is the basis for the creation of primary consorting relations are root systems of perennial leguminous grasses. They determine the structure of microbial cenosis and regulate the number of microorganisms. Adaptation of perennial legumes and soil microorganisms to the variability of environmental conditions in the deep ecotypes reflects their close interaction with the factors of this unique environment. Overburden, the unconsolidated rocks have a high stimulatory effect on the development of microorganisms. In 10–15 years after the removal of the "day" the surface sets up a pool of microorganisms and is manifested microbiological profile, the pattern of which reflects the diversity of ecotopia. There was determined the intensity of decomposition of roots in a layer of technogenic ecotopes landscapes. It falls in the direction from the zonal soil to gray-green clay. For the year transformed to 80 % of the roots of alfalfa and to 66 % in winter wheat. First of all the thin roots of the legumes were destroyed in the spring. It was shown increased sidorovskaya role of kulturpflanzen, especially species of alfalfa and sainfoin. They are plant-dominants and create pockets of concentration of the soil platoro-Diya. Soil formation begins with the surface, gradually spreading to the lower layers of ecotopes.

Barnyard grass (Echinochloa crus-galli (L.) P.Beauv) is less competitive on rice (Oryza sativa L.) when phosphorus (P) is applied to deeper layers in P-deficient and moisture-limited soils

Barnyard grass (Echinochloa crus-galli (L.) P.Beauv) is a major C4 weed in rice fields. We aimed to explore a management strategy to reduce its competition with rice (Oryza sativa L.) (C3) in low-phosphorus (P) soil with varying soil moisture availability. Therefore, we investigated the effect of P placement at different depths. The main experiment was conducted in pots (15 cm diameter, 70 cm height) filled with P-deficient soil as a replacement series with different plant combinations (rice and barnyard grass monocultures; four plants per pot, and a mixture of rice and barnyard grass; two plants of each species per pot) with two P placement depths (0–5 and 15–20 cm from the soil surface) and three moisture treatments (continuous flooding - CF, alternate wetting and drying - AWD, and top soil drying - TSD from flowering). The pots were maintained until crop maturity. A rhizobox experiment supplemented the main experiment to study the root system plasticity during the initial growth stages (i.e., after 14 and 28 days of growth). Placement of P in a deeper soil layer (15–20 cm) reduced the growth and P uptake of barnyard grass by over 70 and 80 %, respectively, irrespective of the plant combination, and moisture treatments, while such reductions were not observed in rice. Reduced growth and P uptake of barnyard grass were associated with the arrested root elongation even from the very early growth stages failing to search for P applied to 15–20 cm soil layer. In contrast, root elongation of rice increased from early growth stages when P was applied at 15–20 cm soil depth and reached the P-supplied soil layer to ensure P uptake. Average root diameter decreased by 12 %, and the percentage fine root production (i.e., < 0.4 mm diameter) increased by 8 % when P was applied at 15–20 cm deep compared with those at 0–5 cm depth. Phosphorous placement at 15–20 cm soil depth reduced the competitive ability of barnyard grass over rice in P-deficient soils, irrespective of the soil moisture management method.

The combined effects of a long-term experimental drought and an extreme drought on the use of plant-water sources in a Mediterranean forest.

Vegetation in water-limited ecosystems relies strongly on access to deep water reserves to withstand dry periods. Most of these ecosystems have shallow soils over deep groundwater reserves. Understanding the functioning and functional plasticity of species-specific root systems and the patterns of or differences in the use of water sources under more frequent or intense droughts is therefore necessary to properly predict the responses of seasonally dry ecosystems to future climate. We used stable isotopes to investigate the seasonal patterns of water uptake by a sclerophyll forest on sloped terrain with shallow soils. We assessed the effect of a long-term experimental drought (12years) and the added impact of an extreme natural drought that produced widespread tree mortality and crown defoliation. The dominant species, Quercus ilex, Arbutus unedo and Phillyrea latifolia, all have dimorphic root systems enabling them to access different water sources in space and time. The plants extracted water mainly from the soil in the cold and wet seasons but increased their use of groundwater during the summer drought. Interestingly, the plants subjected to the long-term experimental drought shifted water uptake toward deeper (10-35cm) soil layers during the wet season and reduced groundwater uptake in summer, indicating plasticity in the functional distribution of fine roots that dampened the effect of our experimental drought over the long term. An extreme drought in 2011, however, further reduced the contribution of deep soil layers and groundwater to transpiration, which resulted in greater crown defoliation in the drought-affected plants. This study suggests that extreme droughts aggravate moderate but persistent drier conditions (simulated by our manipulation) and may lead to the depletion of water from groundwater reservoirs and weathered bedrock, threatening the preservation of these Mediterranean ecosystems in their current structures and compositions.

MADS-Box Transcription Factor AGL21 Regulates Lateral Root Development and Responds to Multiple External and Physiological Signals

Plant root system morphology is dramatically influenced by various environmental cues. The adaptation of root system architecture to environmental constraints, which mostly depends on the formation and growth of lateral roots, is an important agronomic trait. Lateral root development is regulated by the external signals coordinating closely with intrinsic signaling pathways. MADS-box transcription factors are known key regulators of the transition to flowering and flower development. However, their functions in root development are still poorly understood. Here we report that AGL21, an AGL17-clade MADS-box gene, plays a crucial role in lateral root development. AGL21 was highly expressed in root, particularly in the root central cylinder and lateral root primordia. AGL21 overexpression plants produced more and longer lateral roots while agl21 mutants showed impaired lateral root development, especially under nitrogen-deficient conditions. AGL21 was induced by many plant hormones and environmental stresses, suggesting a function of this gene in root system plasticity in response to various signals. Furthermore, AGL21 was found positively regulating auxin accumulation in lateral root primordia and lateral roots by enhancing local auxin biosynthesis, thus stimulating lateral root initiation and growth. We propose that AGL21 may be involved in various environmental and physiological signals-mediated lateral root development and growth.

Root trait characteristics and genotypic response in wheat under different water regimes

Under limiting water resources, root system response of genotypes to soil-water conditions with enhanced shoot biomass holds the key for development of improved genotypes. Based on the hypothesis of root biomass contribution to higher yields under limiting conditions which might be attributed to the root system plasticity of genotypes, a set of thirty-four genotypes were evaluated under three moisture regimes in a pot experiment for root system traits. Total root dry matter had a positive association with total shoot dry matter (0.35). The identified genotypes showed greater yields and higher stress tolerance index (STI) in an independent field experiment. Root dry matter positively correlated with stress tolerance index on grain yields in both the years. The total variation was partitioned into principal components and GGE biplots were studied to identify the best performing genotypes under the three environments for root dry biomass and related traits. HD2932 appeared to be the winner genotype under different regimes. These results might be helpful in identifying donors for moisture stress tolerance that can be utilized in wheat breeding programmes for accelerated development of varieties with improved root systems.

AtMYB93 is a novel negative regulator of lateral root development in Arabidopsis.

Plant root system plasticity is critical for survival in changing environmental conditions. One important aspect of root architecture is lateral root development, a complex process regulated by hormone, environmental and protein signalling pathways.Here we show, using molecular genetic approaches, that the MYB transcription factor AtMYB93 is a novel negative regulator of lateral root development in Arabidopsis.We identify AtMYB93 as an interaction partner of the lateral-root-promoting ARABIDILLO proteins. Atmyb93 mutants have faster lateral root developmental progression and enhanced lateral root densities, while AtMYB93-overexpressing lines display the opposite phenotype. AtMYB93 is expressed strongly, specifically and transiently in the endodermal cells overlying early lateral root primordia and is additionally induced by auxin in the basal meristem of the primary root. Furthermore, Atmyb93 mutant lateral root development is insensitive to auxin, indicating that AtMYB93 is required for normal auxin responses during lateral root development.We propose that AtMYB93 is part of a novel auxin-induced negative feedback loop stimulated in a select few endodermal cells early during lateral root development, ensuring that lateral roots only develop when absolutely required. Putative AtMYB93 homologues are detected throughout flowering plants and represent promising targets for manipulating root systems in diverse crop species.

Hormonal Response and Root Architecture in Arabidopsis thaliana Subjected to Heavy Metals

In this work, specific concentrations of cadmium, copper and zinc in double combination, were supplied for 12 days to growing seedlings of the model species Arabidopsis thaliana. Metal accumulation was measured in roots and shoots. Microscopic analyses revealed that root morphology was affected by metals, and that the root and shoot levels of indole-3-acetic acid, trans-zeatin riboside and dihydrozeatin riboside varied accordingly. Minor modifications in gibberellic acid levels occurred in the Zinc treatments, whereas abscisic acid level did not change after the exposition to metals. Reverse transcription polymerase chain reaction analysis of some genes involved in auxin and cytokinin synthesis (AtAAO, AtNIT and AtIPT) revealed that their expression were not affected by metal treatments. The root morphological alterations that resulted in an increased surface area, due to the formation of root hairs and lateral roots, could be signs of the response to metal stress in terms of a functionally-addressed reorientation of root growth. The root system plasticity observed could be important for better understanding the manner in which the root architecture is shaped by environmental and hormonal stimuli.

Growth and phosphorus nutrition of rice when inorganic fertiliser application is partly replaced by straw under varying moisture availability in sandy and clay soils

The combined effects of (1) reduced soil moisture availability, (2) reduced application of inorganic fertilisers while incorporating straw, (3) soil type, and their effects on growth, root system plasticity, phosphorus (P) nutrition of rice, and soil P dynamics are poorly known, but very important when aiming to increase the efficiency of water and P use. Using large pots a three-factor factorial experiment was conducted with two moisture treatments (i.e. continuous flooding, and draining of top soil after flowering while subsoil was kept moist through capillary action), three fertilisation treatments; with (P1) and without (P0) applications of inorganic P fertilisers, and 25 % of inorganic fertilisers reduced while incorporating straw (5 t ha−1), and soil type (i.e. clay and sandy soils with 15 and 9 mg P kg−1 soil, respectively in P0). Shoot and root growth, root system plasticity, P nutrient status and soil P dynamics were measured. Straw incorporation with reduced inorganic fertiliser application ensured a higher shoot dry weight and yield only in flooded clay soil as compared with P0 and P1, and a similar shoot dry weight and yield to P1 under drained clay soil. A positive growth response was facilitated by an increased water-use efficiency and rate of photosynthesis in shoots, and increased root system plasticity through the production of greater root length, more roots in deep soil layers, and an increased fraction of fine roots. Straw enhanced P extractability in soil. Drained soil reduced P uptake (15–45 %) and increased P-use efficiency. In addition to the re-translocation of P from senescing leaves and stems under both moisture conditions, the P concentration in green leaves under drained condition was also reduced (41–72 %). Growth benefits of straw incorporation were observed in clay soil under both moisture conditions, and this was facilitated by the improved P availability, increased P uptake, and greater root system plasticity with the production of deeper and finer roots, compared with that in sandy soil, and inorganic fertiliser applications alone. As P uptake was reduced under drained soil, P re-translocation and % P allocated to panicles increased.

CLE-CLAVATA1 peptide-receptor signaling module regulates the expansion of plant root systems in a nitrogen-dependent manner.

Morphological plasticity of root systems is critically important for plant survival because it allows plants to optimize their capacity to take up water and nutrients from the soil environment. Here we show that a signaling module composed of nitrogen (N)-responsive CLE (CLAVATA3/ESR-related) peptides and the CLAVATA1 (CLV1) leucine-rich repeat receptor-like kinase is expressed in the root vasculature in Arabidopsis thaliana and plays a crucial role in regulating the expansion of the root system under N-deficient conditions. CLE1, -3, -4, and -7 were induced by N deficiency in roots, predominantly expressed in root pericycle cells, and their overexpression repressed the growth of lateral root primordia and their emergence from the primary root. In contrast, clv1 mutants showed progressive outgrowth of lateral root primordia into lateral roots under N-deficient conditions. The clv1 phenotype was reverted by introducing a CLV1 promoter-driven CLV1:GFP construct producing CLV1:GFP fusion proteins in phloem companion cells of roots. The overaccumulation of CLE2, -3, -4, and -7 in clv1 mutants suggested the amplitude of the CLE peptide signals being feedback-regulated by CLV1. When CLE3 was overexpressed under its own promoter in wild-type plants, the length of lateral roots was negatively correlated with increasing CLE3 mRNA levels; however, this inhibitory action of CLE3 was abrogated in the clv1 mutant background. Our findings identify the N-responsive CLE-CLV1 signaling module as an essential mechanism restrictively controlling the expansion of the lateral root system in N-deficient environments.

Nitrogen application enhanced the expression of developmental plasticity of root systems triggered by mild drought stress in rice

Background The promoted root growth under developmental plasticity triggered specifically by mild drought stress (MDS) is known to contribute to maintained water uptake and dry matter production (DMP).