Root Elongation In Response Research Articles

Modelling sugarcane root elongation in response to mechanical stress as an indicator of soil physical quality

Modelling sugarcane root elongation in response to mechanical stress as an indicator of soil physical quality

NIGT1.4 maintains primary root elongation in response to salt stress through induction of ERF1 in Arabidopsis.

Plants employ various molecular mechanisms to maintain primary root elongation upon salt stress. Identification of key functional genes, therein, is important for improving crop salt tolerance. Through analyzing natural variation of the primary root length of Arabidopsis natural population under salt stress, we identified NIGT1.4, encoding an MYB transcription factor, as a novel contributor to maintained root growth under salt stress. Using both T-DNA knockout and functional complementation, NIGT1.4 was confirmed to have a role in promoting primary root growth in response to salt stress. The expression of NIGT1.4 in the root was shown induced by NaCl treatments in an ABA-dependent manner. SnRK2.2 and 2.3 were shown to interact with and phosphorylate NIGT1.4 individually. The growth of the primary root of snrk2.2/2.3/2.6 triple mutant was shown sensitive to salt stress, which was similar to nigt1.4 plants. Using DNA affinity purification sequencing, ERF1, a known positive regulator for primary root elongation and salt tolerance, was identified as a target gene for NIGT1.4. The transcriptional induction of ERF1 by salt stress was shown absent in nigt1.4 background. NIGT1.4 was also confirmed to bind to the promoter region of ERF1 by yeast one-hybrid experiment and to induce the expression of ERF1 by dual-luciferase analysis. All data support the notion that salt- and ABA-elicited NIGT1.4 induces the expression of ERF1 to regulate downstream functional genes that contribute to maintained primary root elongation. NIGT1.4-ERF1, therefore, acts as a signaling node linking regulators for stress resilience and root growth, providing new insights for breeding salt-tolerant crops.

Dynamics of root–microbe interactions governing crop phosphorus acquisition after straw amendment

Dynamics of root–microbe interactions governing crop phosphorus acquisition after straw amendment

Interaction of BES1 and LBD37 transcription factors modulates brassinosteroid-regulated root forging response under low nitrogen in arabidopsis.

Brassinosteriod (BR) plays important roles in regulation of plant growth, development and environmental responses. BR signaling regulates multiple biological processes through controlling the activity of BES1/BZR1 regulators. Apart from the roles in the promotion of plant growth, BR is also involved in regulation of the root foraging response under low nitrogen, however how BR signaling regulate this process remains unclear. Here we show that BES1 and LBD37 antagonistically regulate root foraging response under low nitrogen conditions. Both the transcriptional level and dephosphorylated level of BES1, is significant induced by low nitrogen, predominantly in root. Phenotypic analysis showed that BES1 gain-of-function mutant or BES1 overexpression transgenic plants exhibits progressive outgrowth of lateral root in response to low nitrogen and BES1 negatively regulates repressors of nitrate signaling pathway and positively regulates several key genes required for NO3 - uptake and signaling. In contrast, BES1 knock-down mutant BES1-RNAi exhibited a dramatical reduction of lateral root elongation in response to low N. Furthermore, we identified a BES1 interacting protein, LBD37, which is a negative repressor of N availability signals. Our results showed that BES1 can inhibit LBD37 transcriptional repression on N-responsive genes. Our results thus demonstrated that BES1-LBD37 module acts critical nodes to integrate BR signaling and nitrogen signaling to modulate the root forging response at LN condition.

OsSPL14 is involved in nitrogen-deficiency-induced root elongation in rice

OsSPL14 is involved in nitrogen-deficiency-induced root elongation in rice

Lotus japonicus HAR1 regulates root morphology locally and systemically under a moderate nitrate condition in the absence of rhizobia.

The local and long-distance signaling pathways mediated by the leucine-rich repeat receptor kinase HAR1 suppress root branching and promote primary root length in response to nitrate supply. The root morphology of higher plants changes plastically to effectively absorb nutrients and water from the soil. In particular, legumes develop root organ nodules, in which symbiotic rhizobia fix atmospheric nitrogen in nitrogen-poor environments. The number of nodules formed in roots is negatively regulated by a long-distance signaling pathway that travels through shoots called autoregulation of nodulation (AON). In the model plant Lotus japonicus, defects in AON genes, such as aleucine-rich repeat receptor kinase HYPERNODULATION ABERRANT ROOT FORMATION 1 (HAR1), an orthologue of CLAVATA1, and the F-box protein TOO MUCH LOVE (TML), induce the formation of an excess number of nodules. The loss-of-function mutant of HAR1 exhibits a short and bushy root phenotype in the absence of rhizobia. We show that the har1 mutant exhibits high nitrate sensitivity during root development. The uninfected har1 mutant significantly increased lateral root number and reduced primary root length in the presence of 3mM nitrate, compared with the wild-type and tml mutant. Grafting experiments indicated that local and long-distance signaling pathways via root- and shoot-acting HAR1 additively regulated root morphology under the moderate nitrate concentrations. These findings allow us topropose that HAR1-mediated signaling pathways control the root system architecture by suppressing lateral root branching and promoting primary root elongation in response to nitrate availability.

SPL14/17 act downstream of strigolactone signalling to modulate rice root elongation in response to nitrate supply

Nitrogen (N) is an essential major nutrient for food crops. Although ammonium (NH4 + ) is the primary N source of rice, nitrate (NO3 - ) can also be absorbed and utilized. Rice responds to NO3 - application by altering its root morphology, such as root elongation. Strigolactones (SLs) are important modulators of root length. However, the roles of SLs and their downstream genes in NO3 - -induced root elongation remain unclear. Here, the levels of total N and SL (4-deoxyorobanchol), and the responses of seminal root (SR) lengths to NH4 + and NO3 - were investigated in rice plants. NO3 - -promoted SR elongation, possibly due to short-term signal perception and long-term nutrient function. Compared with NH4 + condition, higher SL signalling/levels and less D53 protein were recorded in roots of NO3 - -treated rice plants. In contrast to wild-type (WT) plants, SR lengths of d mutants were less responsive to NO3 - condition, and application of rac-GR24 (SL analogue) restored SR length in d10 (SL-biosynthesis mutant) but not in d3,d14 and d53 (SL-responsive mutants), suggesting that higher SL signalling/levels participated in NO3 - -induced root elongation. D53 interacted with SPL17, and inhibited SPL17-mediated transactivation from PIN1b promoter. Mutation of SPL14/17 and PIN1b caused insensitivity of root elongation response to NO3 - and rac-GR24 applications. Therefore, we presented that perception of SLs by D14 led to degradation of D53 via the proteasome system, which released the suppression of SPL14/17-modulated the transcription of PIN1b, and resultedin root elongation under NO3 - supply.

The identification of critical time windows of postnatal root elongation in response to Wnt/β-catenin signaling.

In this study, we attempted to define the precise window of time for molar root elongation using a gain-of-function mutation of β-catenin model. Both the control and constitutively activated β-catenin (CA-β-cat) mice received a one-time tamoxifen administration (for activation of β-catenin at newborn, postnatal day 3, or 5, or 7, or 9) and were harvested at the same stage of P21. Multiple approaches were used to define the window of time of postnatal tooth root formation. In the early activation groups (tamoxifen induction at newborn, or P3 or P5), there was a lack of molar root elongation in the CA-β-cat mice. When induced at P7, the root length was slightly reduced at P21. However, the root length was essentially the same as that in the control when β-cat activated at P9. This study indicates that root elongation occurs in a narrow time of window, which is highly sensitive to a change of β-catenin levels. Molecular studies showed a drastic decrease in the levels of nuclear factor I-C (NFIC) and osterix (OSX), plus sharp reductions of odontoblast differentiation markers, including Nestin, dentin sialoprotein (DSP), and dentin matrix protein 1 (DMP1) at both mRNA and protein levels. Murine molar root elongation is precisely regulated by the Wnt/β-catenin signaling within a narrow window of time (newborn to day 5).

Predicting the combined toxicity of binary metal mixtures (Cu–Ni and Zn–Ni) to wheat

Predicting the combined toxicity of binary metal mixtures (Cu–Ni and Zn–Ni) to wheat

Low nitrogen induces root elongation via auxin-induced acid growth and auxin-regulated target of rapamycin (TOR) pathway in maize

Low nitrogen induces root elongation via auxin-induced acid growth and auxin-regulated target of rapamycin (TOR) pathway in maize

The Root Foraging Response under Low Nitrogen Depends on DWARF1-Mediated Brassinosteroid Biosynthesis

Root developmental plasticity enables plants to adapt to limiting or fluctuating nutrient conditions in the soil. When grown under nitrogen (N) deficiency, plants develop a more exploratory root system by increasing primary and lateral root length. However, mechanisms underlying this so-called foraging response remain poorly understood. We performed a genome-wide association study in Arabidopsis (Arabidopsis thaliana) and we show here that noncoding variations of the brassinosteroid (BR) biosynthesis gene DWARF1 (DWF1) lead to variation of the DWF1 transcript level that contributes to natural variation of root elongation under low N. In addition to DWF1, other central BR biosynthesis genes upregulated under low N include CONSTITUTIVE PHOTOMORPHOGENIC DWARF, DWF4, and BRASSINOSTEROID-6-OXIDASE 2 Phenotypic characterization of knockout and knockdown mutants of these genes showed significant reduction of their root elongation response to low N, suggesting a systemic stimulation of BR biosynthesis to promote root elongation. Moreover, we show that low N-induced root elongation is associated with aboveground N content and that overexpression of DWF1 significantly improves plant growth and overall N accumulation. Our study reveals that mild N deficiency induces key genes in BR biosynthesis and that natural variation in BR synthesis contributes to the root foraging response, complementing the impact of enhanced BR signaling observed recently. Furthermore, these results suggest a considerable potential of BR biosynthesis to genetically engineer plants with improved N uptake.

The physiological mechanism underlying root elongation in response to nitrogen deficiency in crop plants.

In response to low nitrogen stress, multiple hormones together with nitric oxide signaling pathways work synergistically and antagonistically in crop root elongation. Changing root morphology allows plants to adapt to soil nutrient availability. Nitrogen is the most important essential nutrient for plant growth. An important adaptive strategy for crops responding to nitrogen deficiency is root elongation, thereby accessing increased soil space and nitrogen resources. Multiple signaling pathways are involved in this regulatory network, working together to fine-tune root elongation in response to soil nitrogen availability. Based on existing research, we propose a model to explain how different signaling pathways interact to regulate root elongation in response to low nitrogen stress. In response to a low shoot nitrogen status signal, auxin transport from the shoot to the root increases. High auxin levels in the root tip stimulate the production of nitric oxide, which promotes the synthesis of strigolactones to accelerate cell division. In this process, cytokinin, ethylene, and abscisic acid play an antagonistic role, while brassinosteroids and auxin play a synergistic role in regulating root elongation. Further study is required to identify the QTLs, genes, and favorable alleles which control the root elongation response to low nitrogen stress in crops.

Citrate synthesis and exudation confer Al resistance in alfalfa (Medicago sativa L.)

Alfalfa is the most important forage legume but sensitive to aluminum (Al), which largely limits its growth in acid soils. To improve Al resistance in alfalfa, responses to Al toxicity were investigated for understanding of the mechanisms of Al resistance in alfalfa. Growth performance and Al resistance in forty-two cultivars was evaluated. Organic acids synthesis and exudation as well as the key genes in response to Al were investigated. Alfalfa cultivars showed diversity in Al resistance. Compared to the sensitive cultivar ‘Magnum 801’, the Al resistant cultivar ‘WL414’ had higher relative root elongation in response to Al toxicity, with less accumulation of Al. Al activated citrate and malate exudation in alfalfa, with higher citrate exudation and concentration as well as higher levels of citrate synthase (CS) activity, MsCS, MsALMT1, and MsMATE22 transcripts in root apex in WL414 than in Magnum 801. Citrate exudation is the major mechanism in Al resistance in alfalfa. Alfalfa cultivars had diversity in Al resistance. Citrate synthesis and exudation plays a key role in Al resistance in alfalfa. Higher levels of citrate concentration and exudation are associated with Al resistance in Al resistant cultivar as compared with the sensitive cultivar.

Participation of Nitrate Sensor NRT1.1 in the Control of Cytokinin Level and Root Elongation under Normal Conditions and Nitrogen Deficit

NRT1.1 nitrate transporter acts as a nitrate sensor in some plant responses. We tried to check if it may be involved in the control of cytokinin level in the plants known to be involved in the growth responses to nitrate level. The experimental objects were Arabidopsis thaliana plants of the original ecotype Columbia (Col-0) and chl1-5 mutants. The effects of the NRT1.1 gene mutation in chl1-5 plants on hormonal and growth responses to nitrogen starvation were studied. Two types of growing conditions were used: (1) plants were placed on either standard Hoagland–Arnon or modified solution, where potassium and calcium nitrates were substituted with their chlorides; (2) plants were placed on Pryanishnikov medium, where ammonium nitrate serves as the source of nitrogen and nitrogen deficiency being modeled by its withdrawal from the medium. It has been first shown that mutation of the NRT1.1 resulted in a decline in cytokinin level in the roots of chl1-5 mutants, while roots of wild type plants were longer in accordance with lower cytokinin content in them; this hormone is known to inhibit root elongation. Cytokinin content decreased in A. thaliana, Columbia ecotype, paralleled by acceleration of root elongation in response to both variants of nitrogen starvation, while chl1-5 roots responded in this way only when nitrogen was withdrawn from Pryanishnikov solution. Substitution of nitrates by chlorides in the Hoagland–Arnon solution had no effects on either chl1-5 roots’ length or cytokinin content in them. The results suggested the involvement of NRT1.1 transceptor in the control of cytokinin level and root elongation rate in the nitrate but not in ammonium starved plants, confirming the specificity of response.

CHITINASE LIKE1 Regulates Root Development of Dark-Grown Seedlings by Modulating Ethylene Biosynthesis in Arabidopsis thaliana.

The plant hormone ethylene plays a regulatory role in development in light- and dark-grown seedlings. We previously isolated a group of small-molecule compounds with a quinazolinone backbone, which were named acsinones (for ACC synthase inhibitor quinazolinones), that act as uncompetitive inhibitors of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS). Thus, the triple response phenotype, which consists of shortened hypocotyls and roots, radial swelling of hypocotyls and exaggerated curvature of apical hooks, was suppressed by acsinones in dark-grown (etiolated) ethylene overproducer (eto) seedlings. Here, we describe our isolation and characterization of an Arabidopsis revert to eto1 9 (ret9) mutant, which showed reduced sensitivity to acsinones in etiolated eto1 seedlings. Map-based cloning of RET9 revealed an amino acid substitution in CHITINASE LIKE1 (CTL1), which is required for cell wall biogenesis and stress resistance in Arabidopsis. Etiolated seedlings of ctl1ret9 showed short hypocotyls and roots, which were augmented in combination with eto1-4. Consistently, ctl1ret9 seedlings showed enhanced sensitivity to exogenous ACC to suppress primary root elongation as compared with the wild type. After introducing ctl1ret9 to mutants completely insensitive to ethylene, genetic analysis indicated that an intact ethylene response pathway is essential for the alterations in root and apical hook but not hypocotyl in etiolated ctl1ret9 seedlings. Furthermore, a mild yet significantly increased ethylene level in ctl1 mutants was related to elevated mRNA level and activity of ACC oxidase (ACO). Moreover, genes associated with ethylene biosynthesis (ACO1 and ACO2) and response (ERF1 and EDF1) were upregulated in etiolated ctl1ret9 seedlings. By characterizing a new recessive allele of CTL1, we reveal that CTL1 negatively regulates ACO activity and the ethylene response, which thus contributes to understanding a role for ethylene in root elongation in response to perturbed cell wall integrity.

Histone demethylases control root elongation in response to stress-signaling hormone abscisic acid

ABSTRACTAbscisic acid (ABA) plays critical roles during plant growth and development in response to various stresses. Arabidopsis thaliana histone demethylases JUMONJI-C DOMAIN-CONTAINING PROTEIN 30 (JMJ30) and JMJ32 control ABA-mediated growth arrest during the post-germination stage (2–3 days after germination). However, the roles of JMJ30 and JMJ32 in ABA responses at later stages of plant development remain largely unknown. Here, we show that JMJ30 and JMJ32 mediate ABA responses during root development. In the presence of ABA, jmj30 jmj32 double mutants display longer primary roots than the wild type. Loss-of-function mutation in the SNF1-RELATED PROTEIN KINASE 2.8 (SnRK2.8) gene also led to a longer primary root phenotype in response to ABA. Analysis of JMJ30/JMJ32 and SnRK2.8 expression suggested that they act in the same pathway to mediate ABA responses during root elongation at the seedling stage. Our findings highlight the importance of the JMJ30/JMJ32-SnRK2.8 module at two different developmental stages.

There is a direct link between allantoin concentration and cadmium tolerance in Arabidopsis

There is a direct link between allantoin concentration and cadmium tolerance in Arabidopsis

Strigolactones are required for nitric oxide to induce root elongation in response to nitrogen and phosphate deficiencies in rice.

The response of the root system architecture to nutrient deficiencies is critical for sustainable agriculture. Nitric oxide (NO) is considered a key regulator of root growth, although the mechanisms remain unknown. Phenotypic, cellular and genetic analyses were undertaken in rice to explore the role of NO in regulating root growth and strigolactone (SL) signalling under nitrogen-deficient and phosphate-deficient conditions (LN and LP). LN-induced and LP-induced seminal root elongation paralleled NO production in root tips. NO played an important role in a shared pathway of LN-induced and LP-induced root elongation via increased meristem activity. Interestingly, no responses of root elongation were observed in SL d mutants compared with wild-type plants, although similar NO accumulation was induced by sodium nitroprusside (SNP) application. Application of abamine (the SL inhibitor) reduced seminal root length and pCYCB1;1::GUS expression induced by SNP application in wild type; furthermore, comparison with wild type showed lower SL-signalling genes in nia2 mutants under control and LN treatments and similar under SNP application. Western blot analysis revealed that NO, similar to SL, triggered proteasome-mediated degradation of D53 protein levels. Therefore, we presented a novel signalling pathway in which NO-activated seminal root elongation under LN and LP conditions, with the involvement of SLs.

The sensitivity of an hydroponic lettuce root elongation bioassay to metals, phenol and wastewaters

The sensitivity of an hydroponic lettuce root elongation bioassay to metals, phenol and wastewaters

Rapid root elongation by phreatophyte seedlings does not imply tolerance of water table decline

Despite high rates of root elongation during phreatophyte establishment, once connection to groundwater has occurred and leaf area develops, seedlings demonstrate limited capacity for root elongation in response to groundwater decline. In a water-limited environment, rapid root elongation immediately after germination can be critical for a plant to reach deeper water sources such as a water table to avoid water deficit stress. However, once plants have accessed a water table, their continued survival may depend on their ability to adapt their root distribution to changes in the depth to a water table. In glasshouse experiments using two Banksia species with contrasting water requirements, we investigated (1) the rate of root elongation by young seedlings in the presence of a shallow water table, and (2) whole plant response to rapid water table decline using older seedlings that had established root contact with a water table. The results of the first experiment agree with the hypothesis that the facultative phreatophyte, B. attenuata, has a faster rate of root elongation than the obligate phreatophyte, B. littoralis. These differences are likely related to the contrasting habitat preferences of the two species. Older seedlings in the second experiment demonstrated a water-saving response to a declining water table, rapidly closing stomata to limit water loss. Additionally, roots did not elongate to follow the water table and plants were quickly disconnected from the saturated zone. For the two phreatophytic Banksia species, the capacity for rapid root growth by young seedlings did not translate to an ability for established seedlings to adapt their root distribution to survive rapid water table decline.