Nicotiana benthamiana XYLEM CYSTEINE PROTEASE genes facilitate tracheary element formation in interfamily grafting.

Grafting is a plant propagation technique widely used in agriculture. A recent discovery of the capability of interfamily grafting in Nicotiana has expanded the potential combinations of grafting. In this study, we showed that xylem connection is essential for the achievement of interfamily grafting and investigated the molecular basis of xylem formation at the graft junction. Transcriptome and gene network analyses revealed gene modules for tracheary element (TE) formation during grafting that include genes associated with xylem cell differentiation and immune response. The reliability of the drawn network was validated by examining the role of the Nicotiana benthamiana XYLEM CYSTEINE PROTEASE (NbXCP) genes in TE formation during interfamily grafting. Promoter activities of NbXCP1 and NbXCP2 genes were found in differentiating TE cells in the stem and callus tissues at the graft junction. Analysis of a Nbxcp1;Nbxcp2 loss-of-function mutant indicated that NbXCPs control the timing of de novo TE formation at the graft junction. Moreover, grafts of the NbXCP1 overexpressor increased the scion growth rate as well as the fruit size. Thus, we identified gene modules for TE formation at the graft boundary and demonstrated potential ways to enhance Nicotiana interfamily grafting.

Feelings toward medicine in remote areas among medical students aiming to become generalists : A comparison with other specialists.

Geographic maldistribution of physicians is a serious problem in Japan, resulting in a few physicians in remote areas. We distributed questionnaires to 396 medical students at Tokushima University from 2013 to 2016. We examined the intensity of medical students toward medicine in remote areas by using a visual analog scale and investigated what medical specialty they chose after two years of clinical training. The intensity of interest in medicine and the intensity of willingness to contribute to it in remote areas were statistically higher among medical students who intended to choose general medicine. After graduation, only five participants chose to specialize in general medicine. Of the 14 medical students who originally chose general medicine, six chose internal medicine, three chose general medicine, and the others chose surgery, neurosurgery, anesthesiology, orthopedics, or emergency medicine. This study demonstrated that medical students who intend to choose general medicine have a higher intensity of willingness to contribute to medicine in remote areas, indicating that the support program for these students to become general practitioners after graduation increases the number of physicians in remote areas. J. Med. Invest. 70 : 129-134, February, 2023.

Regulation of the iron-deficiency response by IMA/FEP peptide.

Iron (Fe) is an essential micronutrient for plant growth and development, participating in many significant biological processes including photosynthesis, respiration, and nitrogen fixation. Although abundant in the earth's crust, most Fe is oxidized and difficult for plants to absorb under aerobic and alkaline pH conditions. Plants, therefore, have evolved complex means to optimize their Fe-acquisition efficiency. In the past two decades, regulatory networks of transcription factors and ubiquitin ligases have proven to be essential for plant Fe uptake and translocation. Recent studies in Arabidopsis thaliana (Arabidopsis) suggest that in addition to the transcriptional network, IRON MAN/FE-UPTAKE-INDUCING PEPTIDE (IMA/FEP) peptide interacts with a ubiquitin ligase, BRUTUS (BTS)/BTS-LIKE (BTSL). Under Fe-deficient conditions, IMA/FEP peptides compete with IVc subgroup bHLH transcription factors (TFs) to interact with BTS/BTSL. The resulting complex inhibits the degradation of these TFs by BTS/BTSL, which is important for maintaining the Fe-deficiency response in roots. Furthermore, IMA/FEP peptides control systemic Fe signaling. By organ-to-organ communication in Arabidopsis, Fe deficiency in one part of a root drives the upregulation of a high-affinity Fe-uptake system in other root regions surrounded by sufficient levels of Fe. IMA/FEP peptides regulate this compensatory response through Fe-deficiency-triggered organ-to-organ communication. This mini-review summarizes recent advances in understanding how IMA/FEP peptides function in the intracellular signaling of the Fe-deficiency response and systemic Fe signaling to regulate Fe acquisition.

NAC103 mutation alleviates DNA damage in an Arabidopsis thaliana mutant sensitive to excess boron.

Excess boron (B) is toxic to plants and thereby causes DNA damage and cell death in root meristems. However, the underlying mechanisms which link boron and DNA damage remain unclear. It has been reported that the rpt5a-6 mutant of the 26S proteasome is sensitive to excess boron, resulting in more frequent cell death in root meristem and reduced root elongation. In this study, we showed that a reduction in root growth in the rpt5a mutant in the presence of high boron levels is repressed by a mutation in NAC domain containing transcription factor NAC103, a substrate of the proteasome, which functions in the unfolded protein response pathway. The mutation in NAC103 alleviated excess-B-induced DNA damage and cell death in root meristems of the rpt5a mutant. Superoxide ( O 2 - ) staining with nitroblue tetrazolium revealed that boron stress causes O 2 - accumulation in root tips, which was higher in the rpt5a-6 mutant, whereas the accumulation was lower in the rpt5a-6 nac103-3 double mutant. Our work demonstrates the overall involvement of NAC103 in maintaining healthy root meristem under excess boron conditions in the absence of RPT5A proteasome subunit.

PECT1, a rate-limiting enzyme in phosphatidylethanolamine biosynthesis, is involved in the regulation of stomatal movement in Arabidopsis.

An Arabidopsis mutant displaying impaired stomatal responses to CO2 , cdi4, was isolated by a leaf thermal imaging screening. The mutated gene PECT1 encodes CTP:phosphorylethanolamine cytidylyltransferase. The cdi4 exhibited a decrease in phosphatidylethanolamine levels and a defect in light-induced stomatal opening as well as low-CO2 -induced stomatal opening. We created RNAi lines in which PECT1 was specifically repressed in guard cells. These lines are impaired in their stomatal responses to low-CO2 concentrations or light. Fungal toxin fusicoccin (FC) promotes stomatal opening by activating plasma membrane H+ -ATPases in guard cells via phosphorylation. Arabidopsis H+ -ATPase1 (AHA1) has been reported to be highly expressed in guard cells, and its activation by FC induces stomatal opening. The cdi4 and PECT1 RNAi lines displayed a reduced stomatal opening response to FC. However, similar to in the wild-type, cdi4 maintained normal levels of phosphorylation and activation of the stomatal H+ -ATPases after FC treatment. Furthermore, the cdi4 displayed normal localization of GFP-AHA1 fusion protein and normal levels of AHA1 transcripts. Based on these results, we discuss how PECT1 could regulate CO2 - and light-induced stomatal movements in guard cells in a manner that is independent and downstream of the activation of H+ -ATPases. [Correction added on 15 May 2023, after first online publication: The third sentence is revised in this version.].

Complementary and alternative medicines chosen for specific health problems: Internet survey using the I-CAM-Q in Japan: A STROBE-compliant cross-sectional study.

This study investigated the different complementary and alternative medicines (CAMs) adopted by people in Japan, as well as the health problems treated with CAMs. Understanding more about this topic will facilitate the appropriate incorporation of CAMs into conventional medicine when treating health problems. Data were collected through an online survey based on the International Questionnaire to Measure Use of Complementary and Alternative Medicine (I-CAM-Q). The study examined CAM utilization among people aged 20 years or older; 164 valid responses were collected (18.9%). We adopted a cross-sectional design. We then compared the relationships between the specific health problems reported by participants, their self-help practices, and the kinds of healthcare specialists consulted. We also examined participants' reasons for using CAMs and their responses regarding the usefulness of the CAMs adopted. We found that self-help/CAM practices differed for specific health problems. Participants with musculoskeletal and heart problems were more likely to use poultices. Those with respiratory and digestive problems were more likely to practice yoga, tai chi, and qigong. Those with digestive and neurological problems were more likely to use aromatherapy. The I-CAM-Q questionnaire also revealed the purpose and usefulness of the CAMs utilized as well as the participants' attitudes regarding conventional medicine. The study showed that participants find physicians less helpful than other options for treating their health problems. Additionally, when asked whether it was helpful to consult with a specific professional for health problems, there was a higher percentage of participants who answered "Very helpful" for professionals, like massage, judo, acupuncture, and moxibustion therapists, than for physicians. The results of this study will help to inform medical providers of the most appropriate types of CAMs for dealing with various health problems.

Analysis of plasmodesmata permeability using cultured tobacco BY-2 cells entrapped in microfluidic chips.

Plasmodesmata are unique channel structures in plants that link the fluid cytoplasm between adjacent cells. Plants have evolved these microchannels to allow trafficking of nutritious substances as well as regulatory factors for intercellular communication. However, tracking the behavior of plasmodesmata in real time is difficult because they are located inside tissues. Hence, a system was constructed to monitor the movement of substances by plasmodesmata using tobacco BY-2 cells, which are linearly organized cells, and a microfluidic device that traps them in place and facilitates observation. After targeting one cell for photobleaching, recovery of the lost H2B-GFP protein was detected within 200 min. No recovery was detected in that time frame by photobleaching the entire cell filaments. This suggested that the recovery of H2B-GFP protein was not due to de novo protein synthesis, but rather to translocation from neighboring cells. The transport of H2B-GFP protein was not observed when sodium chloride, a compound known to cause plasmodesmata closure, was present in the microfluid channel. Thus, using the microfluidic device and BY-2 cells, it was confirmed that the behavior of plasmodesmata could be observed in real time under controllable conditions.

Systemic Regulation of Iron Acquisition by Arabidopsis in Environments with Heterogeneous Iron Distributions.

Nutrient distribution within the soil is generally heterogeneous. Plants, therefore, have evolved sophisticated systemic processes enabling them to optimize their nutrient acquisition efficiency. By organ-to-organ communication in Arabidopsis thaliana, for instance, iron (Fe) starvation in one part of a root drives the upregulation of a high-affinity Fe-uptake system in other root regions surrounded by sufficient levels of Fe. This compensatory response through Fe-starvation-triggered organ-to-organ communication includes the upregulation of Iron-regulated transporter 1 (IRT1) gene expression on the Fe-sufficient side of the root; however, the molecular basis underlying this long-distance signaling remains unclear. Here, we analyzed gene expression by RNA-seq analysis of Fe-starved split-root cultures. Genome-wide expression analysis showed that localized Fe depletion in roots upregulated several genes involved in Fe uptake and signaling, such as IRT1, in a distant part of the root exposed to Fe-sufficient conditions. This result indicates that long-distance signaling for Fe demand alters the expression of a subset of genes responsible for Fe uptake and coumarin biosynthesis to maintain a level of Fe acquisition sufficient for the entire plant. Loss of IRON MAN/FE-UPTAKE-INDUCING PEPTIDE (IMA/FEP) leads to the disruption of compensatory upregulation of IRT1 in the root surrounded by sufficient Fe. In addition, our split-root culture-based analysis provides evidence that the IMA3/FEP1-MYB10/72 pathway mediates long-distance signaling in Fe homeostasis through the regulation of coumarin biosynthesis. These data suggest that the signaling of IMA/FEP, a ubiquitous family of metal-binding peptides, is critical for organ-to-organ communication in response to Fe starvation under heterogeneous Fe conditions in the surrounding environment.

Development of microfluidic chip for entrapping tobacco BY-2 cells.

The tobacco BY-2 cell line has been used widely as a model system in plant cell biology. BY-2 cells are nearly transparent, which facilitates cell imaging using fluorescent markers. As cultured cells are drifted in the medium, therefore, it was difficult to observe them for a long period. Hence, we developed a microfluidic device that traps BY-2 cells and fixes their positions to allow monitoring the physiological activity of cells. The device contains 112 trap zones, with parallel slots connected in series at three levels in the flow channel. BY-2 cells were cultured for 7 days and filtered using a sieve and a cell strainer before use to isolate short cell filaments consisting of only a few cells. The isolated cells were introduced into the flow channel, resulting in entrapment of cell filaments at 25 out of 112 trap zones (22.3%). The cell numbers increased through cell division from 1 to 4 days after trapping with a peak of mitotic index on day 2. Recovery experiments of fluorescent proteins after photobleaching confirmed cell survival and permeability of plasmodesmata. Thus, this microfluidic device and one-dimensional plant cell samples allowed us to observe cell activity in real time under controllable conditions.

Regulation of ammonium acquisition and use in Oryza longistaminata ramets under nitrogen source heterogeneity.

Oryza longistaminata, a wild rice, vegetatively reproduces and forms a networked clonal colony consisting of ramets connected by rhizomes. Although water, nutrients, and other molecules can be transferred between ramets via the rhizomes, inter-ramet communication in response to spatially heterogeneous nitrogen availability is not well understood. We studied the response of ramet pairs to heterogeneous nitrogen availability using a split hydroponic system that allowed each ramet root to be exposed to different conditions. Ammonium uptake was compensatively enhanced in the sufficient-side root when roots of the ramet pairs were exposed to ammonium-sufficient and ammonium-deficient conditions. Comparative transcriptome analysis revealed that a gene regulatory network for effective ammonium assimilation and amino acid biosynthesis was activated in the sufficient-side roots. Allocation of absorbed nitrogen from the nitrogen-sufficient to the nitrogen-deficient ramets was rather limited. Nitrogen was preferentially used for newly growing axillary buds on the sufficient-side ramets. Biosynthesis of trans-zeatin (tZ), a cytokinin, was upregulated in response to the nitrogen supply, but tZ appeared not to target the compensatory regulation. Our results also implied that the O. longistaminata putative ortholog of rice (Oryza sativa) C-terminally encoded peptide1 plays a role as a nitrogen-deficient signal in inter-ramet communication, providing compensatory upregulation of nitrogen assimilatory genes. These results provide insights into the molecular basis for efficient growth strategies of asexually proliferating plants growing in areas where the distribution of ammonium ions is spatially heterogeneous.

Cell-cell adhesion in plant grafting is facilitated by ß-1,4-glucanases.

Plant grafting is conducted for fruit and vegetable propagation, whereby a piece of living tissue is attached to another through cell-cell adhesion. However, graft compatibility limits combinations to closely related species, and the mechanism is poorly understood. We found that Nicotiana is capable of graft adhesion with a diverse range of angiosperms. Comparative transcriptomic analyses on graft combinations indicated that a subclade of ß-1,4-glucanases secreted into the extracellular region facilitates cell wall reconstruction near the graft interface. Grafting was promoted by overexpression of the ß-1,4-glucanase. Using Nicotiana stem as an interscion, we produced tomato fruits on rootstocks from other plant families. These findings demonstrate that the process of cell-cell adhesion is a potential target to enhance plant grafting techniques.

Past infections are associated with low levels of anti-citrullinated protein autoantibodies in rheumatoid arthritis.

Background : Rheumatoid arthritis (RA), an autoimmune disease of unknown etiology, is believed to occur as the result of actions of genetic and environmental factors. In this study, we examined the relation of past histories about infectious diseases with the levels anti-citrullinated protein autoantibodies (ACPA) in RA. Methods : Results of a questionnaire about histories of infectious diseases were obtained from 85 patients with RA, and were analyzed. Results : Significantly lower level of ACPA was detected in patients with the history of tonsillitis, otitis media or urinary cystitis than in those without it. There was no difference in the level of ACPA in RA patients between with and without cold / influenza, rubella, chickenpox, herpes labialis or herpes zoster. When RA patients were divided into two groups, high-level and low-level ACPA, multiple logistic regression analysis revealed that the history of otitis media was a significantly independent factor for the low level of ACPA. There was no significant relation between the level of rheumatoid factor and histories of infectious diseases. Conclusion : This study clarified that the past history of otitis media is associated with the low level of ACPA in RA. J. Med. Invest. 67 : 182-188, February, 2020.

Micrografting device for testing systemic signaling in Arabidopsis.

Grafting techniques have been applied in studies of systemic, long-distance signaling in several model plants. Seedling grafting in Arabidopsis, known as micrografting, enables investigation of the molecular mechanisms of systemic signaling between shoots and roots. However, conventional micrografting requires a high level of skill, limiting its use. Thus, an easier user-friendly method is needed. Here, we developed a silicone microscaled device, the micrografting chip, to obviate the need for training and to generate less stressed and more uniformly grafted seedlings. The chip has tandemly arrayed units, each of which consists of a seed pocket for seed germination and a micro-path with pairs of pillars for hypocotyl holding. Grafting, including seed germination, micrografting manipulation and establishment of tissue reunion, is performed on the chip. Using the micrografting chip, we evaluated the effect of temperature and the carbon source on grafting, and showed that a temperature of 27°C and a sucrose concentration of 0.5% were optimal. We also used the chip to investigate the mechanism of systemic signaling of iron status using a quadruple nicotianamine synthase (nas) mutant. The constitutive iron-deficiency response in the nas mutant because of iron accumulation in shoots was significantly rescued by grafting of wild-type shoots or roots, suggesting that shoot- and root-ward translocation of nicotianamine-iron complexes and/or nicotianamine is essential for iron mobilization. Thus, our micrografting chip will promote studies of long-distance signaling in plants.

Callose Synthesis Suppresses Cell Death Induced by Low-Calcium Conditions in Leaves.

Despite the importance of preventing calcium (Ca) deficiency disorders in agriculture, knowledge of the molecular mechanisms underlying plant adaptations to low-Ca conditions is limited. In this study, we provide evidence for a crucial involvement of callose synthesis in the survival of Arabidopsis (Arabidopsis thaliana) under low-Ca conditions. A mutant sensitive to low-Ca conditions, low calcium sensitive3 (lcs3), exhibited high levels of cell death in emerging leaves and had defects in its expanding true leaves under low-Ca conditions. Further analyses showed that the causal mutation was located in a putative ß-1,3-glucan (callose) synthase gene, GLUCAN SYNTHASE-LIKE10 (GSL10). Yeast complementation assay results showed that GSL10 encodes a functional callose synthase. Ectopic callose significantly accumulated in wild-type plants under low-Ca conditions, but at a low level in lcs3 The low-Ca sensitivity of lcs3 was phenocopied by the application of callose synthase inhibitors in wild-type plants, which resulted in leaf expansion failure, cell death, and reduced ectopic callose levels under low-Ca conditions. Transcriptome analyses showed that the expression of genes related to cell wall and defense responses was altered in both wild-type plants under low-Ca conditions and in lcs3 under normal-Ca conditions, suggesting that GSL10 is required for the alleviation of both cell wall damage and defense responses caused by low Ca levels. These results suggest that callose synthesis is essential for the prevention of cell death under low-Ca conditions and plays a key role in plants' survival strategies under low-Ca conditions.

Japanese elderly individuals wish for enteral tube feeding more strongly for their parents than for themselves.

[Introduction] The purpose of this study was to investigate the differences in the preference of enteral tube feeding between elderly inhabitants of Mugi town, Tokushima Prefecture, Japan, and their parents in various physical conditions. [Methods] This population-based questionnaire survey studied 300 randomly selected participants aged 65-80 years. Respondents were to consider a situation where eating was difficult, and were questioned on their desire for tube feeding, using a visual analogue scale (VAS) ranging from "do not want tube feeding (0)" to "want tube feeding (100)." [Results] Valid responses of 103 (34.4%) participants were analyzed. Under conditions of being "healthy," "bedridden," "with dementia," and "bedridden and with dementia," the median (IQR) of the VAS values for the desire for tube feeding were 31.8 (3.3 to 83.8), 19.3 (2.4 to 52.3), 5.2 (0.7 to 18.9), 4.0 (0.3 to 15.2) for respondents and 55.2 (11.6 to 92.2), 48.7 (5.5 to 85.5), 9.0 (1.2 to 46.8), 5.1 (0.1 to 36.5) for parents, respectively. The VAS values for the parents were significantly higher (p=0.001, 0.002, 0.001, and 0.01, respectively for the four conditions described) for the same items. [Conclusion] Surrogate decisions made by family members often differ from what the patients would have desired. J. Med. Invest. 66 : 258-263, August, 2019.

Predictive factors associated with the therapeutic response in patients with polymyalgia rheumatica and remitting seronegative symmetrical synovitis with pitting edema syndrome.

Polymyalgia rheumatica (PMR) and remitting seronegative symmetrical synovitis with pitting edema (RS3PE) syndrome are common inflammatory rheumatic diseases in the elderly. In this study, we investigate predictive factors which correspond to subsequent disease control of PMR and RS3PE syndrome. Twenty four patients, which contained 18 PMR and 6 RS3PE syndrome, were treated with initial dosages of 10-20 mg per day oral prednisolone, and the dosage of prednisolone was then tapered. Significantly higher initial CRP was observed in patients with poor disease control than in those with good disease control afterwards. The number of patients with negative CRP after 4 weeks was significantly more in patients with good disease control after 1 year than in those with poor disease control. Patients were shown to be in good disease control status after 1 year when CRP after 4 weeks became negative even if they had initial high CRP. Our study clarify that to make CRP negative after 4 weeks is associated with subsequent suppression of the disease activity and with decreased dosages of corticosteroids. J. Med. Invest. 66 : 112-118, February, 2019.

Control of proliferation in the haploid meristem by CLE peptide signaling in Marchantia polymorpha.

The homeostasis of meristems in flowering plants is maintained by cell-to-cell communication via CLE (CLAVATA3/EMBRYO SURROUNDING REGION-related) peptide hormones. In contrast, cell signals that regulate meristem activity remains elusive in bryophytes that maintain apical meristems in the gametophyte (haploid) body and undergo a gametophyte-dominant life cycle. We here show that MpCLE1 confines the proliferative activity of gametophytic meristem and affects the overall size of gametangiophores (reproductive organs) in Marchantia polymorpha, which is in sharp contrast with the meristem-promoting function of its ortholog TDIF/CLE41/CLE44 in Arabidopsis vascular meristems. Expression analysis suggests that MpCLE1 and its receptor gene MpTDR are expressed in distinct patterns across the apical meristem. These data suggest that local CLE peptide signaling may have had a role in regulating cell proliferation in the shoot meristem in the ancestral land plant and acts in both sporophytic and gametophytic meristems of extant plants.

Characteristics of medical students who would like to be a generalist physician and contribute to remote area medicine.

We administered a questionnaire to 5th grade medical students to examine the effect of community-based clinical practice on their attitudes to remote area medicine and their course after the graduation. Data from 192 students were obtained. The intensity of students' attitudes was estimated by using visual analogue scale. The intensities of the interest and a sense of fulfillment in remote area medicine were significantly increased after the practice. A significantly lower level of the intensity to become a generalist than that to become a specialist was seen in the students with low intensity in a sense of fulfillment. The percentages of the students who answered that they can work for 5 years or more in remote area were significantly lower in students with low intensity of a sense of fulfillment than in those with high intensity. A significantly higher percentage in students who worked at a familiar prefecture to them after the graduation was seen in female than in male. This study shows that the community-based practice is meaningful in increasing motivation which desire to work in remote area medicine, and that the motivation may affect their course after the graduation. J. Med. Invest. 64: 210-216, August, 2017.

Comparison of the efficacy and safety of 10-mg empagliflozin every day versus every other day in Japanese patients with Type 2 Diabetes Mellitus: a pilot trial.

The terminal elimination half-life (t1/2) of empagliflozin is 13.1 hours. Accordingly, we hypothesized that the administration of empagliflozin every other day might improve glycemic control in patients with type 2 diabetes mellitus, not being inferior to the therapy every day. We investigated the clinical effects and safety of the addition of empagliflozin every day or every other day to type 2 diabetic patients with a poor control in glycemia. Thirteen Japanese patients diagnosed as type 2 diabetes mellitus recruited to this study. Subjects were divided into two groups; one was treatment with 10 mg of empagliflozin every day (Group A), the other was 10 mg of empagliflozin every other day (Group B). The comparable study of multiple clinical indexes between the 2 groups was made before and 8, 16, and 24 weeks after the treatment. After the treatment for 24 weeks, the HbA1c level was decreased both in group A (from 7.5%±1.1% to 6.5%±0.8%) and in group B (from 7.6%±0.8% to 7.2%±0.5%). This pilot trial suggested the possibility of 10-mg every other day administration with empagliflozin for Japanese patients with type 2 diabetes mellitus. J. Med. Invest. 64: 50-57, February, 2017.

Shoot-to-root mobile polypeptides involved in systemic regulation of nitrogen acquisition.

Plants uptake nitrogen (N) from the soil mainly in the form of nitrate. However, nitrate is often distributed heterogeneously in natural soil. Plants, therefore, have a systemic long-distance signalling mechanism by which N starvation on one side of the root leads to a compensatory N uptake on the other N-rich side1,2. This systemic N acquisition response is triggered by a root-to-shoot mobile peptide hormone, C-TERMINALLY ENCODED PEPTIDE (CEP), originating from the N-starved roots3,4, but the molecular nature of the descending shoot-to-root signal remains elusive. Here, we show that phloem-specific polypeptides that are induced in leaves upon perception of root-derived CEP act as descending long-distance mobile signals translocated to each root. These shoot-derived polypeptides, which we named CEP DOWNSTREAM 1 (CEPD1) and CEPD2, upregulate the expression of the nitrate transporter gene NRT2.1 in roots specifically when nitrate is present in the rhizosphere. Arabidopsis plants deficient in this pathway show impaired systemic N acquisition response accompanied with N-deficiency symptoms. These fundamental mechanistic insights should provide a conceptual framework for understanding systemic nutrient acquisition responses in plants.