Mechanisms underlying root system architecture adaptation to low phosphate environment

Author(s):  
Sigal Savaldi-Goldstein ◽  
Siobhan M. Brady

In order to advance our understanding towards potential biotechnology improvement of plant performance, we studied root responses to limited P in two different plants, Arabidopsis and tomato. Arabidopsis is among the most studied model plants that allows rapid application of molecular and developmental experiments while tomato is an important crop, with application in agriculture. Using Arabidopsis we found that steroid hormones modulate the extent of root elongation in response to limited P, by controlling the accumulation of iron in the root. We also found that the availability of P and iron control the activity of the steroid hormone in the root. Finally, we revealed the genes involved in this nutrient-hormone interaction. Hence, the ferroxidase LPR1 that promotes iron accumulation in response to low P is repressed by the transcription factor BES1/BZR1. Low P inhibits the steroid hormone pathway by enhancing the accumulation of BKI1. High levels of BKI1 inhibit the activity of the steroid hormone receptor at the cell surface and iron accumulation increases inside the root, resulting in a slow growth. Together, the extent of root elongation depends on interactions between an internal cue (steroid hormone) and cues derived from the availability of P and iron in the environment. Using tomato, we found that the response of two cultivated tomato varieties (M82 and New Yorker) to limited P is distinct from that of the wild species, Solanumpennellii. This is implicated at both the levels of root development and whole plant physiology. Specifically, while the root system architecture of cultivated tomato is modulated by limited P availability, that of the wild type species remained unaffected. The wild species appears to be always behaving as if it is always in phosphate deprived conditions, despite sufficient levels of phosphate. Hyper-accumulation of metals appears to mediate this response. Together, this knowledge will be used to isolate new genes controlling plant adaptation to limited P environment. 

2018 ◽  
Vol 19 (12) ◽  
pp. 3927
Author(s):  
Katerina Lay ◽  
Hideki Takahashi

The root system architecture (RSA) of plants is highly dependent on the surrounding nutrient environment. The uptake of essential nutrients triggers various signaling cascades and fluctuations in plant hormones to elicit physical changes in RSA. These pathways may involve signaling components known as small signaling peptides (SSPs), which have been implicated in a variety of plant developmental processes. This review discusses known nutrient-responsive SSPs with a focus on several subclasses that have been shown to play roles in root development. Most functionally well-characterized cases of SSP-mediated changes in RSA are found in responses to nitrogen (N) and phosphorus (P) availability, but other nutrients have also been known to affect the expression of SSP-encoding genes. These nutrient-responsive SSPs may interact downstream with leucine-rich repeat receptor kinases (LRR-RKs) to modulate hormone signaling and cellular processes impacting plant root development. SSPs responsive to multiple nutrient cues potentially act as mediators of crosstalk between the signaling pathways. Study of SSP pathways is complicated because of functional redundancy within peptide and receptor families and due to their functionality partly associated with post-translational modifications; however, as genomic research and techniques progress, novel SSP-encoding genes have been identified in many plant species. Understanding and characterizing the roles of SSPs influencing the root phenotypes will help elucidate the processes that plants use to optimize nutrient acquisition in the environment.


2019 ◽  
Author(s):  
Marco Giovannetti ◽  
Christian Göschl ◽  
Stig U. Andersen ◽  
Stanislav Kopriva ◽  
Wolfgang Busch

AbstractPhosphate is a key nutrient for plants and as it is needed in high quantities. It is highly immobile in the soil and represents a major limiting factor for plant productivity. Plants have evolved different solutions to forage the soil for phosphate and to adapt to phosphate limitation ranging from a profound tuning of their root system architecture and metabolic profile to the evolution of widespread mutualistic interactions, such as those with arbuscular mycorrhizal fungi (AM symbiosis). Despite the prevalence of AM symbiosis throughout land plants, most studies aimed at identifying genes that regulate plant responses to phosphate have been conducted in species incapable of AM symbiosis, such as Arabidopsis. Here we elucidated plant responses and their genetic basis to different phosphate levels in a plant species that is widely used as a model for AM symbiosis: Lotus japonicus. Rather than focusing on a single model strain, we measured root growth and anion content in response to different levels of phosphate in a large panel of Lotus japonicus natural accessions. This allowed us not only to uncover common as well as divergent responses within this species, but also enabled Genome Wide Association Studies by which we identified new genes regulating phosphate homeostasis in Lotus. Under low phosphate conditions, we uncovered a correlation between plant biomass and the decrease of plant phosphate concentration in plant tissues, suggesting a dilution effect. Altogether our data of the genetic and phenotypic variation within a species capable of AM complements studies that have been conducted in Arabidopsis, and advances our understanding of the continuum of genotype by phosphate level interaction that exists throughout dicot plants.Author SummaryPhosphate represents a major limiting factor for plant productivity. Plants have evolved different solutions to adapt to phosphate limitation ranging from a profound tuning of their root system architecture and metabolic profile to the evolution of widespread mutualistic interactions, such as arbuscular mycorrhizal symbiosis. Here we elucidated plant responses and their genetic basis to different phosphate levels in model legume plant species, Lotus japonicus, a plant commonly used for studying arbuscular mycorhizal symbiosis. We investigated Lotus responses to phosphate levels by combining high throughput root system architecture phenotyping and nutrient measurements with a natural variation approach. We investigated relations between root phenotypic responses and nutrient accumulation and we uncovered, under low phosphate conditions, a correlation between plant biomass and the decrease of plant phosphate concentration in plant tissues, suggesting a dilution effect. By means of Genome Wide Association mapping and integration of multiple traits, we identified new genes regulating phosphate homeostasis in Lotus.


2020 ◽  
Vol 11 ◽  
Author(s):  
Waldiodio Seck ◽  
Davoud Torkamaneh ◽  
François Belzile

Increasing the understanding genetic basis of the variability in root system architecture (RSA) is essential to improve resource-use efficiency in agriculture systems and to develop climate-resilient crop cultivars. Roots being underground, their direct observation and detailed characterization are challenging. Here, were characterized twelve RSA-related traits in a panel of 137 early maturing soybean lines (Canadian soybean core collection) using rhizoboxes and two-dimensional imaging. Significant phenotypic variation (P < 0.001) was observed among these lines for different RSA-related traits. This panel was genotyped with 2.18 million genome-wide single-nucleotide polymorphisms (SNPs) using a combination of genotyping-by-sequencing and whole-genome sequencing. A total of 10 quantitative trait locus (QTL) regions were detected for root total length and primary root diameter through a comprehensive genome-wide association study. These QTL regions explained from 15 to 25% of the phenotypic variation and contained two putative candidate genes with homology to genes previously reported to play a role in RSA in other species. These genes can serve to accelerate future efforts aimed to dissect genetic architecture of RSA and breed more resilient varieties.


BMC Genomics ◽  
2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Admas Alemu ◽  
Tileye Feyissa ◽  
Marco Maccaferri ◽  
Giuseppe Sciara ◽  
Roberto Tuberosa ◽  
...  

Abstract Background Genetic improvement of root system architecture is essential to improve water and nutrient use efficiency of crops or to boost their productivity under stress or non-optimal soil conditions. One hundred ninety-two Ethiopian durum wheat accessions comprising 167 historical landraces and 25 modern cultivars were assembled for GWAS analysis to identify QTLs for root system architecture (RSA) traits and genotyped with a high-density 90 K wheat SNP array by Illumina. Results Using a non-roll, paper-based root phenotyping platform, a total of 2880 seedlings and 14,947 seminal roots were measured at the three-leaf stage to collect data for total root length (TRL), total root number (TRN), root growth angle (RGA), average root length (ARL), bulk root dry weight (RDW), individual root dry weight (IRW), bulk shoot dry weight (SDW), presence of six seminal roots per seedling (RT6) and root shoot ratio (RSR). Analysis of variance revealed highly significant differences between accessions for all RSA traits. Four major (− log10P ≥ 4) and 34 nominal (− log10P ≥ 3) QTLs were identified and grouped in 16 RSA QTL clusters across chromosomes. A higher number of significant RSA QTL were identified on chromosome 4B particularly for root vigor traits (root length, number and/or weight). Conclusions After projecting the identified QTLs on to a high-density tetraploid consensus map along with previously reported RSA QTL in both durum and bread wheat, fourteen nominal QTLs were found to be novel and could potentially be used to tailor RSA in elite lines. The major RGA QTLs on chromosome 6AL detected in the current study and reported in previous studies is a good candidate for cloning the causative underlining sequence and identifying the beneficial haplotypes able to positively affect yield under water- or nutrient-limited conditions.


BioMetals ◽  
2021 ◽  
Author(s):  
Ricardo Ortiz-Luevano ◽  
José López-Bucio ◽  
Miguel Martínez-Trujillo ◽  
Lenin Sánchez-Calderón

Plants ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 939
Author(s):  
Omar Azab ◽  
Abdullah Al-Doss ◽  
Thobayet Alshahrani ◽  
Salah El-Hendawy ◽  
Adel M. Zakri ◽  
...  

There is a demand for an increase in crop production because of the growing population, but water shortage hinders the expansion of wheat cultivation, one of the most important crops worldwide. Polyethylene glycol (PEG) was used to mimic drought stress due to its high osmotic potentials generated in plants subjected to it. This study aimed to determine the root system architecture (RSA) plasticity of eight bread wheat genotypes under osmotic stress in relation to the oxidative status and mitochondrial membrane potential of their root tips. Osmotic stress application resulted in differences in the RSA between the eight genotypes, where genotypes were divided into adapted genotypes that have non-significant decreased values in lateral roots number (LRN) and total root length (TRL), while non-adapted genotypes have a significant decrease in LRN, TRL, root volume (RV), and root surface area (SA). Accumulation of intracellular ROS formation in root tips and elongation zone was observed in the non-adapted genotypes due to PEG-induced oxidative stress. Mitochondrial membrane potential (∆Ψm) was measured for both stress and non-stress treatments in the eight genotypes as a biomarker for programmed cell death as a result of induced osmotic stress, in correlation with RSA traits. PEG treatment increased scavenging capacity of the genotypes from 1.4-fold in the sensitive genotype Gemmiza 7 to 14.3-fold in the adapted genotype Sakha 94. The adapted genotypes showed greater root trait values, ∆Ψm plasticity correlated with high scavenging capacity, and less ROS accumulation in the root tissue, while the non-adapted genotypes showed little scavenging capacity in both treatments, accompanied by mitochondrial membrane permeability, suggesting mitochondrial dysfunction as a result of oxidative stress.


2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Lei Feng ◽  
Wanli Xu ◽  
Guangmu Tang ◽  
Meiying Gu ◽  
Zengchao Geng

Abstract Background Raising nitrogen use efficiency of crops by improving root system architecture is highly essential not only to reduce costs of agricultural production but also to mitigate climate change. The physiological mechanisms of how biochar affects nitrogen assimilation by crop seedlings have not been well elucidated. Results Here, we report changes in root system architecture, activities of the key enzymes involved in nitrogen assimilation, and cytokinin (CTK) at the seedling stage of cotton with reduced urea usage and biochar application at different soil layers (0–10 cm and 10–20 cm). Active root absorption area, fresh weight, and nitrogen agronomic efficiency increased significantly when urea usage was reduced by 25% and biochar was applied in the surface soil layer. Glutamine oxoglutarate amino transferase (GOGAT) activity was closely related to the application depth of urea/biochar, and it increased when urea/biochar was applied in the 0–10 cm layer. Glutamic-pyruvic transaminase activity (GPT) increased significantly as well. Nitrate reductase (NR) activity was stimulated by CTK in the very fine roots but inhibited in the fine roots. In addition, AMT1;1, gdh3, and gdh2 were significantly up-regulated in the very fine roots when urea usage was reduced by 25% and biochar was applied. Conclusion Nitrogen assimilation efficiency was significantly affected when urea usage was reduced by 25% and biochar was applied in the surface soil layer at the seedling stage of cotton. The co-expression of gdh3 and gdh2 in the fine roots increased nitrogen agronomic efficiency. The synergistic expression of the ammonium transporter gene and gdh3 suggests that biochar may be beneficial to amino acid metabolism.


2018 ◽  
Vol 19 (12) ◽  
pp. 3888 ◽  
Author(s):  
Aurora Alaguero-Cordovilla ◽  
Francisco Gran-Gómez ◽  
Sergio Tormos-Moltó ◽  
José Pérez-Pérez

Plant roots exploit morphological plasticity to adapt and respond to different soil environments. We characterized the root system architecture of nine wild tomato species and four cultivated tomato (Solanum lycopersicum L.) varieties during early growth in a controlled environment. Additionally, the root system architecture of six near-isogenic lines from the tomato ‘Micro-Tom’ mutant collection was also studied. These lines were affected in key genes of ethylene, abscisic acid, and anthocyanin pathways. We found extensive differences between the studied lines for a number of meaningful morphological traits, such as lateral root distribution, lateral root length or adventitious root development, which might represent adaptations to local soil conditions during speciation and subsequent domestication. Taken together, our results provide a general quantitative framework for comparing root system architecture in tomato seedlings and other related species.


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