NKS1/ELMO4 is an integral protein of a pectin synthesis protein complex and maintains Golgi morphology and cell adhesion in Arabidopsis.

Adjacent plant cells are connected by specialized cell wall regions, called middle lamellae, which influence critical agricultural characteristics, including fruit ripening and organ abscission. Middle lamellae are enriched in pectin polysaccharides, specifically homogalacturonan (HG). Here, we identify a plant-specific Arabidopsis DUF1068 protein, called NKS1/ELMO4, that is required for middle lamellae integrity and cell adhesion. NKS1 localizes to the Golgi apparatus and loss of NKS1 results in changes to Golgi structure and function. The nks1 mutants also display HG deficient phenotypes, including reduced seedling growth, changes to cell wall composition, and tissue integrity defects. These phenotypes are comparable to qua1 and qua2 mutants, which are defective in HG biosynthesis. Notably, genetic interactions indicate that NKS1 and the QUAs work in a common pathway. Protein interaction analyses and modeling corroborate that they work together in a stable protein complex with other pectin-related proteins. We propose that NKS1 is an integral part of a large pectin synthesis protein complex and that proper function of this complex is important to support Golgi structure and function.

Tip Growth Defective1 interacts with the cellulose synthase complex to regulate cellulose synthesis in Arabidopsis thaliana.

Plant cells possess robust and flexible cell walls composed primarily of cellulose, a polysaccharide that provides structural support and enables cell expansion. Cellulose is synthesised by the Cellulose Synthase A (CESA) catalytic subunits, which form cellulose synthase complexes (CSCs). While significant progress has been made in unravelling CSC function, the trafficking of CSCs and the involvement of post-translational modifications in cellulose synthesis remain poorly understood. In order to deepen our understanding of cellulose biosynthesis, this study utilised immunoprecipitation techniques with CESA6 as the bait protein to explore the CSC and its interactors. We have successfully identified the essential components of the CSC complex and, notably, uncovered novel interactors associated with CSC trafficking, post-translational modifications, and the coordination of cell wall synthesis. Moreover, we identified TIP GROWTH DEFECTIVE 1 (TIP1) protein S-acyl transferases (PATs) as an interactor of the CSC complex. We confirmed the interaction between TIP1 and the CSC complex through multiple independent approaches. Further analysis revealed that tip1 mutants exhibited stunted growth and reduced levels of crystalline cellulose in leaves. These findings suggest that TIP1 positively influences cellulose biosynthesis, potentially mediated by its role in the S-acylation of the CSC complex.

Phosphate starvation regulates cellulose synthesis to modify root growth.

In the model plant Arabidopsis (Arabidopsis thaliana), the absence of the essential macro-nutrient phosphate reduces primary root growth through decreased cell division and elongation, requiring alterations to the polysaccharide-rich cell wall surrounding the cells. Despite its importance, the regulation of cell wall synthesis in response to low phosphate levels is not well understood. In this study, we show that plants increase cellulose synthesis in roots under limiting phosphate conditions, which leads to changes in the thickness and structure of the cell wall. These changes contribute to the reduced growth of primary roots in low-phosphate conditions. Furthermore, we found that the cellulose synthase complex (CSC) activity at the plasma membrane increases during phosphate deficiency. Moreover, we show that this increase in the activity of the CSC is likely due to alterations in the phosphorylation status of cellulose synthases in low-phosphate conditions. Specifically, phosphorylation of CELLULOSE SYNTHASE 1 (CESA1) at the S688 site decreases in low-phosphate conditions. Phosphomimic versions of CESA1 with an S688E mutation showed significantly reduced cellulose induction and primary root length changes in low-phosphate conditions. Protein structure modeling suggests that the phosphorylation status of S688 in CESA1 could play a role in stabilizing and activating the CSC. This mechanistic understanding of root growth regulation under limiting phosphate conditions provides potential strategies for changing root responses to soil phosphate content.

Mining the Australian Grains Gene Bank for Rust Resistance in Barley.

Global barley production is threatened by plant pathogens, especially the rusts. In this study we used a targeted genotype-by-sequencing (GBS) assisted GWAS approach to identify rust resistance alleles in a collection of 287 genetically distinct diverse barley landraces and historical cultivars available in the Australian Grains Genebank (AGG) and originally sourced from Eastern Europe. The accessions were challenged with seven US-derived cereal rust pathogen races including Puccinia hordei (Ph-leaf rust) race 17VA12C, P. coronata var. hordei (Pch-crown rust) race 91NE9305 and five pathogenically diverse races of P. striiformis f. sp. hordei (Psh-stripe rust) (PSH-33, PSH-48, PSH-54, PSH-72 and PSH-100) and phenotyped quantitatively at the seedling stage. Novel resistance factors were identified on chromosomes 1H, 2H, 4H and 5H in response to Pch, whereas a race-specific QTL on 7HS was identified that was effective only to Psh isolates PSH-72 and PSH-100. A major effect QTL on chromosome 5HL conferred resistance to all Psh races including PSH-72, which is virulent on all 12 stripe rust differential tester lines. The same major effect QTL was also identified in response to leaf rust (17VA12C) suggesting this locus contains several pathogen specific rust resistance genes or the same gene is responsible for both leaf rust and stripe rust resistance. Twelve accessions were highly resistant to both leaf and stripe rust diseases and also carried the 5HL QTL. We subsequently surveyed the physical region at the 5HL locus for across the barley pan genome variation in the presence of known resistance gene candidates and identified a rich source of high confidence protein kinase and antifungal genes in the QTL region.

Potential prosthetic arterio-venous graft dissection: A rare case.

Arterio-venous fistulas (AVFs) are recommended as the first line vascular access option in patients requiring hemodialysis in end-stage renal disease (ESRD). Prosthetic grafts have been used successfully as an alternative in cases where AVF is not feasible. We present a rare case of dissection of the prosthetic graft. Knowledge and recognition of this complication is important in making correct diagnosis and deciding appropriate treatment.

Risk stratification of renal transplant recipients using routine parameters: Implication of learning from SARS-CoV-2 into transplant follow-up program.

BACKGROUND: Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection is a global pandemic that is associated with a high risk of morbidity and mortality among recipients of solid organ transplantation. In the course of acute SARS-CoV-2 infection, various laboratory markers have been identified as predictors for high risk of mortality. AIM: To risk stratify renal transplant recipients (RTxR) using general demographic parameters, comorbidities and routine laboratory markers for the severity of the disease and its outcomes. We believe that learning about these routinely moni tored parameters can help us plan better strategies for the RTxR follow-up program. METHODS: This present study includes RTxR who acquired SARS-CoV-2 infection from March 2020 to February 2021. We recorded the basic demographics, comorbidities and routine laboratory markers. We investigated the impact of SARS-CoV-2 infection on RTxRs and risk-stratified the progression of disease severity and outcomes in terms of recovery or mortality. RESULTS: From 505 RTxRs in our renal transplant follow-up program, 29 (7.75%) RTxRs had PCR-positive SARS-CoV-2 infection. We recorded 8 deaths from SARS-CoV-2 infection giving an overall mortality rate of 1.6% but a significant 27.6% mortality in SARS-CoV-2 positive recipients. Age more than 68 years, non-Caucasian ethnicity and male gender were associated with a significant drop in survival probability; P ≤ 0.001. < 0.001 and < 0.0001 respectively. 87.5% of the deceased were diabetic; P ≤ 0.0.0001. Estimated glomerular filtration rate of less than 26 mL/min/1.73 m2, serum albumin less than 20 g/L, Hemoglobin less than 9.6 g/L and serum calcium less than 1.70 mmol/L were all associated with significantly increased risk of mortality; P = 0.0128, < 0.001, < 0.0001 and 0.0061 respectively. CONCLUSION: This study has identified some routinely used modifiable parameters in predicting a higher risk of mortality and morbidity. This knowledge can be used in RTxR follow-up programs by addressing these parameters early to help reduce the morbidity and mortality in RTxRs.

Preventing MQTT Vulnerabilities Using IoT-Enabled Intrusion Detection System.

The advancement in the domain of IoT accelerated the development of new communication technologies such as the Message Queuing Telemetry Transport (MQTT) protocol. Although MQTT servers/brokers are considered the main component of all MQTT-based IoT applications, their openness makes them vulnerable to potential cyber-attacks such as DoS, DDoS, or buffer overflow. As a result of this, an efficient intrusion detection system for MQTT-based applications is still a missing piece of the IoT security context. Unfortunately, existing IDSs do not provide IoT communication protocol support such as MQTT or CoAP to validate crafted or malformed packets for protecting the protocol implementation vulnerabilities of IoT devices. In this paper, we have designed and developed an MQTT parsing engine that can be integrated with network-based IDS as an initial layer for extensive checking against IoT protocol vulnerabilities and improper usage through a rigorous validation of packet fields during the packet-parsing stage. In addition, we evaluate the performance of the proposed solution across different reported vulnerabilities. The experimental results demonstrate the effectiveness of the proposed solution for detecting and preventing the exploitation of vulnerabilities on IoT protocols.

The impact of coronavirus disease 2019 pandemic on working dynamics of junior and middle grade doctors in the United Kingdom: Learning from their experience requires immediate improvement in health care planning and management-An outcome analysis of a nationwide survey.

OBJECTIVES: Severe acute respiratory syndrome coronavirus 2 (coronavirus disease 2019) pandemic had an unprecedented impact on health services across the world resulting in increased demand of intensive care capacity, opening Nightingale hospitals, and mass movement of doctors across various specialities. This unplanned redeployment raised concerns among various health care workers. The objective of the current study is to explore working dynamics and experience of junior and middle grade doctors during current pandemic. METHODS: We organised a nationwide cross-sectional survey of junior and middle grade doctors working in the United Kingdom. The survey was aimed to study their level of participation during coronavirus disease 2019 pandemic and its impact on their clinical practices and well-being. RESULTS: In total, 1564 completed questionnaires with representations from all regions of the United Kingdom were included. The mean age of respondents was 30.64 years (95% confidence interval +1.025; standard deviation = 9.9057). There were 51.5% females with significantly more participants from Black, Asian, and minority ethnic group (n = 835, p = 0.0073); 963 (61.6%, p ⩽ 0.0001) doctors were redeployed outside their primary speciality. The major redeployments were from other specialities to Intensive Therapy Units (41.8%, p ⩽ 0.001); 63.3% of respondents spend more than 8 weeks in redeployed speciality (p ⩽ 0.0001). There was a significant impact of coronavirus disease 2019 on personal, mental, and physical well-being of doctors. The major areas requiring immediate attention include proper leadership and clinical support (64.1%), pre-redeployment planning and induction (48.5%), redeployment according to the skills and/or in familiar specialities (44.6%), and regular mental and physical well-being checks (37%). CONCLUSION: The outcome of the survey concluded with four major recommendations, including the need to have a named supervisor for these doctors, structured induction program, regular well-being checks, and involving them in crisis planning. These recommendations will help to shape future health care policies and management particularly when it is related to redeployment of doctors during any crisis or pandemic.

Safety and Efficacy of Kidney Transplants From Older Adult Living Donors: A Comparative Analysis of Donor and Recipient Outcomes.

OBJECTIVES: We investigated the safety of donor nephrectomy from older adult donors (age ≥60 years), as well as long-term donor, recipient, and graft outcomes. MATERIALS AND METHODS: We retrospectively analyzed data from 307 living donor kidney transplants from 1996 to 2016 and defined 2 cohorts based on donor age. Cohort A comprised donors aged 60 years and older, and cohort B comprised donors from 18 to 59 years old. We recorded donor and recipient perioperative complications, outcomes, and survival rates and used SPSS and MedCalc statistical software programs for data analyses. RESULTS: The mean follow-up period for donor-recipient pairs in cohort A was 97 months (SD, 25.1 months) with median 108 months (IQR, 92-108 months) and in cohort B was 100.57 months (SD, 25.45 months) with median 120 months (IQR, 84-120 months). Mean donor age in cohort A was 64.13 years (SD, 3.78 years) with median 63 years (IQR, 61-66.5 years) and in cohort B was 41.08 years (SD, 9.15 years) with median 41 years (IQR, 34.5-48 years) (P < .001, cohort A vs B). Mean recipient age in cohort A was 47.65 years (SD, 14.26 years) with median 48.5 years (IQR, 35.5-61 years) and in cohort B was 43.55 years (SD, 13.15 years) with median 40.5 years (IQR, 33.5-54 years) (P < .001, cohort A vs B). Both cohorts showed no significant differences in perioperative donor and recipient complications. Renal function (measured as estimated glomerular filtration rate) in remaining native kidneys of cohort A showed no significant decline during median 8-year follow-up (P = .089 and P < .414, respectively). There were no significant differences in survival rates for donors, recipients, and grafts. CONCLUSIONS: Living donor kidney transplant from older adult donors is safe and effective with good long-term patient and allograft survival.

Kidney transplantation and patients who decline SARS-CoV-2 vaccination: an ethical framework.

As SARS-CoV-2 vaccines have started to be rolled out, a key question facing transplant units has been whether listing for transplantation should be contingent on recipients having received a vaccine. We aimed to provide an ethical framework when considering potential transplant candidates who decline vaccination. We convened a working group comprising transplant professionals, lay members and patients and undertook a literature review and consensus process. This group's work was also informed by discussions in two hospital clinical ethics committees. We have reviewed arguments for and against mandating vaccination prior to listing for kidney transplantation and considered some practical difficulties which may be associated with a policy of mandated vaccination. Rather than requiring that all patients must receive the SARS-CoV-2 vaccine prior to transplant listing, we recommend considering vaccination status as one of a number of SARS-CoV-2-related risk factors in relation to transplant listing. Transplant units should engage in individualised risk-benefit discussions with patients, avoid the language of mandated treatments and strongly encourage uptake of the vaccine in all patient groups, using tailor-made educational initiatives.

Structure of Arabidopsis CESA3 catalytic domain with its substrate UDP-glucose provides insight into the mechanism of cellulose synthesis.

Cellulose is synthesized by cellulose synthases (CESAs) from the glycosyltransferase GT-2 family. In plants, the CESAs form a six-lobed rosette-shaped CESA complex (CSC). Here we report crystal structures of the catalytic domain of Arabidopsis thaliana CESA3 (AtCESA3CatD) in both apo and uridine diphosphate (UDP)-glucose (UDP-Glc)-bound forms. AtCESA3CatD has an overall GT-A fold core domain sandwiched between a plant-conserved region (P-CR) and a class-specific region (C-SR). By superimposing the structure of AtCESA3CatD onto the bacterial cellulose synthase BcsA, we found that the coordination of the UDP-Glc differs, indicating different substrate coordination during cellulose synthesis in plants and bacteria. Moreover, structural analyses revealed that AtCESA3CatD can form a homodimer mainly via interactions between specific beta strands. We confirmed the importance of specific amino acids on these strands for homodimerization through yeast and in planta assays using point-mutated full-length AtCESA3. Our work provides molecular insights into how the substrate UDP-Glc is coordinated in the CESAs and how the CESAs might dimerize to eventually assemble into CSCs in plants.

Systematic Review and Meta-analysis of COVID-19 and Kidney Transplant Recipients, the South West London Kidney Transplant Network Experience.

INTRODUCTION: There is paucity of literature comparing outcomes of kidney transplant patients with COVID-19 to that of dialysis and waitlisted patients. This report describes our data, provides comparative analysis, together with a meta-analysis of published studies, and describes our protocols to restart the transplant program. METHODS: Data were analyzed on kidney transplant, dialysis, and waitlisted patients tested positive for SARS-CoV-2 (nasopharyngeal swab polymerase chain reaction [PCR] test) between March 1, 2020, and June 30, 2020, together with a meta-analysis of 16 studies. RESULTS: Twenty-three of 1494 kidney transplant patients tested positive for SARS-CoV-2 compared with 123 of 1278 hemodialysis patients (1.5% vs. 9.6%, P < 0.001) and 12 of 253 waitlisted patients (1.5% vs. 4.7%, P = 0.002). Nineteen patients required hospital admission, of whom 6 died and 13 developed AKI. The overall case fatality ratio was 26.1% compared with patients on hemodialysis (27.6%, P = 0.99) and waitlisted patients (8.3%, P = 0.38). Within our entire cohort, 0.4% of transplant patients died compared with 0.4% of waitlisted patients and 2.7% of hemodialysis patients. Patients who died were older (alive [median age 71 years] vs. dead [median age 59 years], P = 0.01).In a meta-analysis of 16 studies, including ours, the pooled case fatality ratio was 24% (95% confidence interval [CI] 19%, 28%); AKI proportion in 10 studies was 50% (95% CI 45%, 56%), with some evidence against no heterogeneity between studies (P = 0.02). CONCLUSIONS: From our cohort of transplant patients, a significantly lower proportion of patients contracted COVID-19 compared with waitlisted and dialysis patients. The case fatality ratio was comparable to that of the dialysis cohort and to a pooled case fatality ratio from a meta-analysis of 16 studies. The pooled AKI ratio in the meta-analysis was similar to our results.

Mortality Rates in Transplant Recipients and Transplantation Candidates in a High-prevalence COVID-19 Environment.

BACKGROUND: The risk of COVID-19 infection in transplant recipients (TRs) is unknown. Patients on dialysis may be exposed to greater risk of infection due to an inability to isolate. Consideration of these competing risks is important before restarting suspended transplant programs. This study compared outcomes in kidney and kidney/pancreas TRs with those on the waiting list, following admission with COVID-19 in a high-prevalence region. METHODS: Audit data from all 6 London transplant centers were amalgamated. Demographic and laboratory data were collected and outcomes included mortality, intensive care (ITU) admission, and ventilation. Adult patients who had undergone a kidney or kidney/pancreas transplant, and those active on the transplant waiting list at the start of the pandemic were included. RESULTS: One hundred twenty-one TRs and 52 waiting list patients (WL) were admitted to hospital with COVID-19. Thirty-six TR died (30%), while 14 WL patients died (27% P = 0.71). There was no difference in rates of admission to ITU or ventilation. Twenty-four percent of TR required renal replacement therapy, and 12% lost their grafts. Lymphocyte nadir and D-dimer peak showed no difference in those who did and did not die. No other comorbidities or demographic factors were associated with mortality, except for age (odds ratio of 4.3 [95% CI 1.8-10.2] for mortality if aged over 60 y) in TR. CONCLUSIONS: TRs and waiting list patients have similar mortality rates after hospital admission with COVID-19. Mortality was higher in older TRs. These data should inform decisions about transplantation in the COVID era.

Associations between phytohormones and cellulose biosynthesis in land plants.

BACKGROUND: Phytohormones are small molecules that regulate virtually every aspect of plant growth and development, from basic cellular processes, such as cell expansion and division, to whole plant environmental responses. While the phytohormone levels and distribution thus tell the plant how to adjust itself, the corresponding growth alterations are actuated by cell wall modification/synthesis and internal turgor. Plant cell walls are complex polysaccharide-rich extracellular matrixes that surround all plant cells. Among the cell wall components, cellulose is typically the major polysaccharide, and is the load-bearing structure of the walls. Hence, the cell wall distribution of cellulose, which is synthesized by large Cellulose Synthase protein complexes at the cell surface, directs plant growth. SCOPE: Here, we review the relationships between key phytohormone classes and cellulose deposition in plant systems. We present the core signalling pathways associated with each phytohormone and discuss the current understanding of how these signalling pathways impact cellulose biosynthesis with a particular focus on transcriptional and post-translational regulation. Because cortical microtubules underlying the plasma membrane significantly impact the trajectories of Cellulose Synthase Complexes, we also discuss the current understanding of how phytohormone signalling impacts the cortical microtubule array. CONCLUSION: Given the importance of cellulose deposition and phytohormone signalling in plant growth and development, one would expect that there is substantial cross-talk between these processes; however, mechanisms for many of these relationships remain unclear and should be considered as the target of future studies.

The transcription and export complex THO/TREX contributes to transcription termination in plants.

Transcription termination has important regulatory functions, impacting mRNA stability, localization and translation potential. Failure to appropriately terminate transcription can also lead to read-through transcription and the synthesis of antisense RNAs which can have profound impact on gene expression. The Transcription-Export (THO/TREX) protein complex plays an important role in coupling transcription with splicing and export of mRNA. However, little is known about the role of the THO/TREX complex in the control of transcription termination. In this work, we show that two proteins of the THO/TREX complex, namely TREX COMPONENT 1 (TEX1 or THO3) and HYPER RECOMBINATION1 (HPR1 or THO1) contribute to the correct transcription termination at several loci in Arabidopsis thaliana. We first demonstrate this by showing defective termination in tex1 and hpr1 mutants at the nopaline synthase (NOS) terminator present in a T-DNA inserted between exon 1 and 3 of the PHO1 locus in the pho1-7 mutant. Read-through transcription beyond the NOS terminator and splicing-out of the T-DNA resulted in the generation of a near full-length PHO1 mRNA (minus exon 2) in the tex1 pho1-7 and hpr1 pho1-7 double mutants, with enhanced production of a truncated PHO1 protein that retained phosphate export activity. Consequently, the strong reduction of shoot growth associated with the severe phosphate deficiency of the pho1-7 mutant was alleviated in the tex1 pho1-7 and hpr1 pho1-7 double mutants. Additionally, we show that RNA termination defects in tex1 and hpr1 mutants leads to 3'UTR extensions in several endogenous genes. These results demonstrate that THO/TREX complex contributes to the regulation of transcription termination.

Cell Wall Biology: Dual Control of Cellulose Synthase Guidance.

Cortical microtubules can direct the orientation of newly synthesized cellulose fibres in plant cell walls. However, cell wall-mediated steering mechanisms have also been anticipated. New research reveals that cellulose synthesis may be directed by pre-existing cellulose fibres in the walls.

The companion of cellulose synthase 1 confers salt tolerance through a Tau-like mechanism in plants.

Microtubules are filamentous structures necessary for cell division, motility and morphology, with dynamics critically regulated by microtubule-associated proteins (MAPs). Here we outline the molecular mechanism by which the MAP, COMPANION OF CELLULOSE SYNTHASE1 (CC1), controls microtubule bundling and dynamics to sustain plant growth under salt stress. CC1 contains an intrinsically disordered N-terminus that links microtubules at evenly distributed points through four conserved hydrophobic regions. By NMR and live cell analyses we reveal that two neighboring residues in the first hydrophobic binding motif are crucial for the microtubule interaction. The microtubule-binding mechanism of CC1 is reminiscent to that of the prominent neuropathology-related protein Tau, indicating evolutionary convergence of MAP functions across animal and plant cells.

Where to Draw the Line in Surgical Obesity for Renal Transplant Recipients: An Outcome Analysis Based on Body Mass Index.

OBJECTIVES: Renal transplant is the criterion standard treatment for patients with end-stage renal disease. Because obesity rates are increasing in the global population, international standards on renal transplant in obese patients remain a gray area. The aim of this study was to determine whether renal transplant remains the treatment of choice in an obese patient with end-stage renal disease. MATERIALS AND METHODS: We performed a retrospective analysis on all patients who underwent renal transplant in our transplant unit between January 2008 and December 2013. Patients were divided into 3 cohorts based on body mass index (cohort A was < 25 kg/m2, cohort B was 25-29.99 kg/m2, and cohort C was ≥ 30 kg/m2). Postoperative complications within 90 days after transplant were assessed using one-way analysis of variance and chi-square distribution. Patient and graft survival rates over 3 years were assessed with Kaplan-Meier analyses. RESULTS: Of 610 total patients, 92 patients (15%) were classified as "obese" (≥ 30 kg/m2) in cohort C, with 294 patients in cohort A and 224 patients in cohort B (24 patients were excluded). Regarding short-term complications during the 90-day posttransplant period, obese individuals were at increased risk of a higher number of complications (P = .039 for cohort A vs cohort C). Lymphocele in particular was associated with obesity (P = .004); fortunately, this condition had no direct impact on the graft itself and was relatively easy to monitor and treat. The long-term outlook (3 years) appeared positive, with both graft survival (92% in cohort A, 91% in cohort B, and 94% in cohort C) and patient survival (97% in cohort A, 99% in cohort B, and 97% in cohort C) being independent of patient obesity. CONCLUSIONS: Increased body mass index up to 37.5 kg/m2 was not associated with increased risk of serious postoperative morbidity or mortality after renal transplant. Surgery should be considered as the criterion standard treatment for obese patients with end-stage renal disease if they are otherwise medically fit with few or well-controlled comorbidities.

Cell wall integrity modulates Arabidopsis thaliana cell cycle gene expression in a cytokinin- and nitrate reductase-dependent manner.

During plant growth and defense, cell cycle activity needs to be coordinated with cell wall integrity. Little is known about how this coordination is achieved. Here, we investigated coordination in Arabidopsis thaliana seedlings by studying the impact of cell wall damage (CWD, caused by cellulose biosynthesis inhibition) on cytokinin homeostasis, cell cycle gene expression and cell shape in root tips. CWD inhibited cell cycle gene expression and increased transition zone cell width in an osmosensitive manner. These results were correlated with CWD-induced, osmosensitive changes in cytokinin homeostasis. Expression of CYTOKININ OXIDASE/DEHYDROGENASE 2 and 3 (CKX2, CKX3), which encode cytokinin-degrading enzymes, was induced by CWD and reduced by osmoticum treatment. In nitrate reductase1 nitrate reductase2 (nia1 nia2) seedlings, CKX2 and CKX3 transcript levels were not increased and cell cycle gene expression was not repressed by CWD. Moreover, established CWD-induced responses, such as jasmonic acid, salicylic acid and lignin production, were also absent, implying a central role of NIA1/2-mediated processes in regulation of CWD responses. These results suggest that CWD enhances cytokinin degradation rates through a NIA1/2-mediated process, leading to attenuation of cell cycle gene expression.