Assessing the long-term priorities of pancreaticoduodenectomy survivors.

BACKGROUND: This study assessed the long-term quality of life (QOL) and priorities of pancreaticoduodenectomy (PD) survivors. METHODS: Survivors were surveyed via internet-based support groups. The relative importance of longevity, experience, costs, and QOL were assessed. RESULTS: The PD cohort (n = 247, 35%) was 60 ± 12 years, 71% female, and 93% white. With moderate agreement, patients ranked survival most important, followed by functional and emotional well-being; costs and experience were least important (W = 35.7%, p < 0.001). Well-being improved throughout survivorship (P-QOL: 39 ± 12 at ≤3 mo vs 43 ± 12 at >10 y, p = 0.170; M-QOL: 38 ± 13 at ≤3 mo vs 44 ± 16 at >10 y; p = 0.015) but remained below the general population (p < 0.001). PD patients with benign diagnoses ranked functional independence as most important (2.00 ± 1.13 vs 2.63 ± 1.19, p < 0.001, W = 41.1%); PD patients with malignant diagnoses regarded overall survival most important (2.10 ± 1.20 vs 1.82 ± 1.22, p < 0.16, W = 35.1%). The mean rank order of priorities remained concordant between short-term (<1 year) and long-term (>5 years) survivors. CONCLUSION: PD survivors experience long-term mental and physical health impairments, underscoring the importance of functional and emotional support. Survivors place paramount importance on overall survival, functional independence, and emotional well-being. Cancer survivors prioritize longevity, while survivors of chronic benign conditions prioritize functional independence.

Xyloglucan Remodeling Defines Auxin-Dependent Differential Tissue Expansion in Plants.

Size control is a fundamental question in biology, showing incremental complexity in plants, whose cells possess a rigid cell wall. The phytohormone auxin is a vital growth regulator with central importance for differential growth control. Our results indicate that auxin-reliant growth programs affect the molecular complexity of xyloglucans, the major type of cell wall hemicellulose in eudicots. Auxin-dependent induction and repression of growth coincide with reduced and enhanced molecular complexity of xyloglucans, respectively. In agreement with a proposed function in growth control, genetic interference with xyloglucan side decorations distinctly modulates auxin-dependent differential growth rates. Our work proposes that auxin-dependent growth programs have a spatially defined effect on xyloglucan's molecular structure, which in turn affects cell wall mechanics and specifies differential, gravitropic hypocotyl growth.

A substrate of the ABC transporter PEN3 stimulates bacterial flagellin (flg22)-induced callose deposition in Arabidopsis thaliana.

Nonhost resistance of Arabidopsis thaliana against Phytophthora infestans, a filamentous eukaryotic microbe and the causal agent of potato late blight, is based on a multilayered defense system. Arabidopsis thaliana controls pathogen entry through the penetration-resistance genes PEN2 and PEN3, encoding an atypical myrosinase and an ABC transporter, respectively, required for synthesis and export of unknown indole compounds. To identify pathogen-elicited leaf surface metabolites and further unravel nonhost resistance in Arabidopsis, we performed untargeted metabolite profiling by incubating a P. infestans zoospore suspension on leaves of WT or pen3 mutant Arabidopsis plants. Among the plant-secreted metabolites, 4-methoxyindol-3-yl-methanol and S-(4-methoxy-indol-3-yl-methyl) cysteine were detected in spore suspensions recollected from WT plants, but at reduced levels from the pen3 mutant plants. In both whole-cell and microsome-based assays, 4-methoxyindol-3-yl-methanol was transported in a PEN3-dependent manner, suggesting that this compound is a PEN3 substrate. The syntheses of both compounds were dependent on functional PEN2 and phytochelatin synthase 1. None of these compounds inhibited mycelial growth of P. infestans in vitro Of note, exogenous application of 4-methoxyindol-3-yl methanol slightly elevated cytosolic Ca2+ levels and enhanced callose deposition in hydathodes of seedlings treated with a bacterial pathogen-associated molecular pattern (PAMP), flagellin (flg22). Loss of flg22-induced callose deposition in leaves of pen3 seedlings was partially reverted by the addition of 4-methoxyindol-3-yl methanol. In conclusion, we have identified a specific indole compound that is a substrate for PEN3 and contributes to the plant defense response against microbial pathogens.

TWISTED DWARF1 Mediates the Action of Auxin Transport Inhibitors on Actin Cytoskeleton Dynamics.

Plant growth and architecture is regulated by the polar distribution of the hormone auxin. Polarity and flexibility of this process is provided by constant cycling of auxin transporter vesicles along actin filaments, coordinated by a positive auxin-actin feedback loop. Both polar auxin transport and vesicle cycling are inhibited by synthetic auxin transport inhibitors, such as 1-N-naphthylphthalamic acid (NPA), counteracting the effect of auxin; however, underlying targets and mechanisms are unclear. Using NMR, we map the NPA binding surface on the Arabidopsis thaliana ABCB chaperone TWISTED DWARF1 (TWD1). We identify ACTIN7 as a relevant, although likely indirect, TWD1 interactor, and show TWD1-dependent regulation of actin filament organization and dynamics and that TWD1 is required for NPA-mediated actin cytoskeleton remodeling. The TWD1-ACTIN7 axis controls plasma membrane presence of efflux transporters, and as a consequence act7 and twd1 share developmental and physiological phenotypes indicative of defects in auxin transport. These can be phenocopied by NPA treatment or by chemical actin (de)stabilization. We provide evidence that TWD1 determines downstream locations of auxin efflux transporters by adjusting actin filament debundling and dynamizing processes and mediating NPA action on the latter. This function appears to be evolutionary conserved since TWD1 expression in budding yeast alters actin polarization and cell polarity and provides NPA sensitivity.

Evaluation of THUNDERBEAT® in open liver resection- a single-center experience.

BACKGROUND: THUNDERBEAT® (TB) (Olympus Medical Systems Corp., Tokyo, Japan) is a dynamic energy system device that simultaneously delivers ultrasonically generated frictional heat energy and electrically generated bipolar energy. TB is being routinely used in various operative procedures, however, less is known about its utility in liver resection. We, herein, report our early experience of using TB in open liver resection particularly in patients with normal or near-normal liver parenchyma. METHODS: We retrospectively reviewed the clinical characteristics, and evaluated the perioperative outcome of twenty-eight patients who underwent liver resection with TB, and twenty-four patients who underwent liver resection with basic procedure in our institution. The resection type was stratified into: major hepatectomy; resection of 3 or more than 3 Couinauds segments, and minor hepatectomy; resection of less than 3 Couinauds segments. RESULTS: Liver resection time (mean ± SD) in TB group with major hepatectomy was significantly shorter: 16.7 ± 8.8 compared to 62.8 ± 39.4 min in basic procedure group (P < 0.0001). Accordingly, the liver resection time (mean ± SD) in TB group with minor hepatectomy was also significantly shorter, 8.3 ± 2.9 min compared to 45.2 ± 23.9 min in liver resection with basic procedure (P < 0.001). No significant difference was observed between the groups in terms of intraoperative blood transfusion ratio, postoperative complication and postoperative liver dysfunction. CONCLUSION: TB as a new energy device can offer a safe, reliable and substantially rapid liver resection particularly in patients with normal or near-normal liver parenchyma.

A Critical View on ABC Transporters and Their Interacting Partners in Auxin Transport.

Different subclasses of ATP-binding cassette (ABC) transporters have been implicated in the transport of native variants of the phytohormone auxin. Here, the putative, individual roles of key members belonging to the ABCB, ABCD and ABCG families, respectively, are highlighted and the knowledge of their assumed expression and transport routes is reviewed and compared with their mutant phenotypes. Protein-protein interactions between ABC transporters and regulatory components during auxin transport are summarized and their importance is critically discussed. There is a focus on the functional interaction between members of the ABCB family and the FKBP42, TWISTED DWARF1, acting as a chaperone during plasma membrane trafficking of ABCBs. Further, the mode and relevance of functional ABCB-PIN interactions is diagnostically re-evaluated. A new nomenclature describing precisely the most likely ABCB-PIN interaction scenarios is suggested. Finally, available tools for the detection and prediction of ABC transporter interactomes are summarized and the potential of future ABC transporter interactome maps is highlighted.

A 2-Stage Surgical and Endovascular Treatment of Rare Multiple Aneurysms of Pancreatic Arteries.

Aneurysms of pancreatic arteries (PAs) are often found incidentally during evaluation of other abdominal pathology. Aneurysms involving multiple PAs are rarely reported in the literature. In case reports of PA aneurysm, inferior pancreaticoduodenal artery is the usual site of aneurysm occurrence. PA aneurysms can be treated surgically by aneurysm exclusion, excision, and by endovascular techniques. However, no clear consensus exists regarding treatment modality, leaving the surgeon to determine the most appropriate approach bearing in mind their experience, anatomical location of the aneurysm, involved artery, and urgency of the procedure. We report a rare PA aneurysm involving dorsal pancreatic artery (DPA) and anterior inferior pancreaticoduodenal artery (AIPDA) associated with celiac stenosis that was incidentally diagnosed in a patient with hepatic hemangioma. In addition, we reviewed data from the literature on patients with diffuse or multiple PA aneurysms and discuss the treatment modality in these rare variants. Both surgical and endovascular procedures are equally advocated in treatment of multiple PA aneurysms. In our report, we demonstrate a 2-stage surgical and endovascular treatment modality; DPA aneurysm that was not suitable for endovascular treatment was surgically resected and an iliohepatic bypass was made between left common iliac artery and AIPDA to ensure good hepatic perfusion. One month after the first procedure, AIPDA aneurysm was treated with endovascular embolization. Two-stage surgical and endovascular procedure may represent a useful strategy to treat aneurysms involving multiple PAs.

The auxin transporter, OsAUX1, is involved in primary root and root hair elongation and in Cd stress responses in rice (Oryza sativa L.).

Auxin and cadmium (Cd) stress play critical roles during root development. There are only a few reports on the mechanisms by which Cd stress influences auxin homeostasis and affects primary root (PR) and lateral root (LR) development, and almost nothing is known about how auxin and Cd interfere with root hair (RH) development. Here, we characterize rice osaux1 mutants that have a longer PR and shorter RHs in hydroponic culture, and that are more sensitive to Cd stress compared to wild-type (Dongjin). OsAUX1 expression in root hair cells is different from that of its paralogous gene, AtAUX1, which is expressed in non-hair cells. However, OsAUX1, like AtAUX1, localizes at the plasma membrane and appears to function as an auxin tranporter. Decreased auxin distribution and contents in the osaux1 mutant result in reduction of OsCyCB1;1 expression and shortened PRs, LRs and RHs under Cd stress, but may be rescued by treatment with the membrane-permeable auxin 1-naphthalene acetic acid. Treatment with the auxin transport inhibitors 1-naphthoxyacetic acid and N-1-naphthylphthalamic acid increased the Cd sensitivity of WT rice. Cd contents in the osaux1 mutant were not altered, but reactive oxygen species-mediated damage was enhanced, further increasing the sensitivity of the osaux1 mutant to Cd stress. Taken together, our results indicate that OsAUX1 plays an important role in root development and in responses to Cd stress.

Correction: Learning from each other: ABC transporter regulation by protein phosphorylation in plant and mammalian systems.

The ABC (ATP-binding cassette) transporter family in higher plants is highly expanded compared with those of mammalians. Moreover, some members of the plant ABCB subfamily display very high substrate specificity compared with their mammalian counterparts that are often associated with multidrug resistance (MDR) phenomena. In this review we highlight prominent functions of plant and mammalian ABC transporters and summarize our knowledge on their post-transcriptional regulation with a focus on protein phosphorylation. A deeper comparison of regulatory events of human cystic fibrosis transmembrane conductance regulator (CFTR) and ABCB1 from the model plantArabidopsisreveals a surprisingly high degree of similarity. Both physically interact with orthologues of the FK506-binding proteins (FKBPs) that chaperon both transporters to the plasma membrane in an action that seems to involve Hsp90. Further both transporters are phosphorylated at regulatory domains that connect both nucleotide-binding folds. Taken together it appears that ABC transporters exhibit an evolutionary conserved but complex regulation by protein phosphorylation, which apparently is, at least in some cases, tightly connected with protein-protein interactions (PPI).

Learning from each other: ABC transporter regulation by protein phosphorylation in plant and mammalian systems.

The ABC (ATP-binding cassette) transporter family in higher plants is highly expanded compared with those of mammalians. Moreover, some members of the plant ABC subfamily B (ABCB) display very high substrate specificity compared with their mammalian counterparts that are often associated with multi-drug resistance phenomena. In this review, we highlight prominent functions of plant and mammalian ABC transporters and summarize our knowledge on their post-transcriptional regulation with a focus on protein phosphorylation. A deeper comparison of regulatory events of human cystic fibrosis transmembrane conductance regulator (CFTR) and ABCB1 from the model plant Arabidopsis reveals a surprisingly high degree of similarity. Both physically interact with orthologues of the FK506-binding proteins that chaperon both transporters to the plasma membrane in an action that seems to involve heat shock protein (Hsp)90. Further, both transporters are phosphorylated at regulatory domains that connect both nt-binding folds. Taken together, it appears that ABC transporters exhibit an evolutionary conserved but complex regulation by protein phosphorylation, which apparently is, at least in some cases, tightly connected with protein-protein interactions (PPI).

Export of salicylic acid from the chloroplast requires the multidrug and toxin extrusion-like transporter EDS5.

Salicylic acid (SA) is central for the defense of plants to pathogens and abiotic stress. SA is synthesized in chloroplasts from chorismic acid by an isochorismate synthase (ICS1); SA biosynthesis is negatively regulated by autoinhibitory feedback at ICS1. Genetic studies indicated that the multidrug and toxin extrusion transporter ENHANCED DISEASE SUSCEPTIBILITY5 (EDS5) of Arabidopsis (Arabidopsis thaliana) is necessary for SA accumulation after biotic and abiotic stress, but so far it is not understood how EDS5 controls the biosynthesis of SA. Here, we show that EDS5 colocalizes with a marker of the chloroplast envelope and that EDS5 functions as a multidrug and toxin extrusion-like transporter in the export of SA from the chloroplast to the cytoplasm in Arabidopsis, where it controls the innate immune response. The location at the chloroplast envelope supports a model of the effect of EDS5 on SA biosynthesis: in the eds5 mutant, stress-induced SA is trapped in the chloroplast and inhibits its own accumulation by autoinhibitory feedback.

Middle-preserving pancreatectomy with reversed pancreaticogastrostomy: report of a case.

Parenchyma-sparing pancreatic resections have been reported increasingly in recent years; however, for multifocal diseases involving the head and the tail of the pancreas, total pancreatectomy is still the preferred procedure. The possible consequence of this procedure is loss of normal pancreatic parenchyma, resulting in insufficiency of pancreatic exocrine and endocrine functions. Various types of limited resection have been introduced for isolated or multiple pancreatic lesions, depending on the location of the tumor. Even for multifocal diseases, if the pancreatic body is spared, a middle-preserving pancreatectomy (MPP) can be performed to assure maximal pancreatic function and uncompromised quality of life. Yet, few papers have introduced the feasibility of MPP for a better outcome. This report describes a new surgical technique for MPP using an alternative approach for the remnant pancreas anastomosis. We used this technique successfully to remove a bifocal neoplasm: adenocarcinoma of the distal bile duct and mucinous cyst adenoma in the tail of the pancreas.

Navigating Precision Oncology: Insights from an Integrated Clinical Data and Biobank Repository Initiative across a Network Cancer Program.

Advancing cancer treatment relies on the rapid translation of new scientific discoveries to patient care. To facilitate this, an oncology biobank and data repository program, also referred to as the "Moonshot" program, was launched in 2021 within the Integrated Network Cancer Program of the Allegheny Health Network. A clinical data program (CDP) and biospecimen repository were established, and patient data and blood and tissue samples have been collected prospectively. To date, the study has accrued 2920 patients, predominantly female (61%) and Caucasian (90%), with a mean age of 64 ± 13 years. The most common cancer sites were the endometrium/uterus (12%), lung/bronchus (12%), breast (11%), and colon/rectum (11%). Of patients diagnosed with cancer, 34% were diagnosed at stage I, 25% at stage II, 26% at stage III, and 15% at stage IV. The CDP is designed to support our initiative in advancing personalized cancer research by providing a comprehensive array of patient data, encompassing demographic characteristics, diagnostic details, and treatment responses. The "Moonshot" initiative aims to predict therapy responses and clinical outcomes through cancer-related biomarkers. The CDP facilitates this initiative by fostering data sharing, enabling comparative analyses, and informing the development of novel diagnostic and therapeutic methods.

An LRR receptor kinase controls ABC transporter substrate preferences during plant growth-defense decisions.

The exporter of the auxin precursor indole-3-butyric acid (IBA), ABCG36/PDR8/PEN3, from the model plant Arabidopsis has recently been proposed to also function in the transport of the phytoalexin camalexin. Based on these bonafide substrates, it has been suggested that ABCG36 functions at the interface between growth and defense. Here, we provide evidence that ABCG36 catalyzes the direct, ATP-dependent export of camalexin across the plasma membrane. We identify the leucine-rich repeat receptor kinase, QIAN SHOU KINASE1 (QSK1), as a functional kinase that physically interacts with and phosphorylates ABCG36. Phosphorylation of ABCG36 by QSK1 unilaterally represses IBA export, allowing camalexin export by ABCG36 conferring pathogen resistance. As a consequence, phospho-dead mutants of ABCG36, as well as qsk1 and abcg36 alleles, are hypersensitive to infection with the root pathogen Fusarium oxysporum, caused by elevated fungal progression. Our findings indicate a direct regulatory circuit between a receptor kinase and an ABC transporter that functions to control transporter substrate preference during plant growth and defense balance decisions.

Demographics and diagnoses at rural health camps in Nepal: cross-sectional study.

BACKGROUND: The charity 'Health Partnership Nepal' is committed to both improving global health care and providing medical training links between Nepal and the UK. This paper analyses data gathered at rural health camps. AIM: To describe the demographics, diagnoses and treatments offered to people attending three rural health camps in Nepal during 2009. Design Cross-sectional study. Setting Three free health care camps established within the Nuwakot district of Nepal during April-May 2009. Camps were staffed by doctors including GPs, nurses and medical students from London and Kathmandu. METHODS: Attendees had treatment sheets completed which recorded their demographics, diagnoses and dispensed medications. RESULTS: The mean age of the 1903 consecutive patients attending was 42.8 years (range one month to 98 years) of whom 68.6% were female and 13.7% were children. The majority, 82.3%, were agricultural workers. For adults (n = 1574), the most frequent complaints were stomach pain 20.1%, musculoskeletal pain 19.3% and visual acuity problems 6.1%. Stomach pain was significantly more common in women than men [21.2% (236/1064) versus 14.5% (65/449) P < 0.01]. For children (n = 249), the most common diagnoses were helminthiasis 10.4%, conjunctivitis 7.6% and upper respiratory tract infection 7.2%. Overall, opthalmological, gastroenterological and rheumatological diagnoses were significantly more common in Nepalese than UK general practice patients. Of 1109 recorded prescriptions, the most common were multivitamins 23%, oral analgesics 15% and oral antibiotics 14%. CONCLUSIONS: There is a considerable unmet disease burden within rural districts of Nepal particularly for stomach pain, musculoskeletal pain and visual acuity problems. When planning similar rurally based health camps, we recommend recruiting GPs and ophthalmologists.

Endoreplication mediates cell size control via mechanochemical signaling from cell wall.

Endoreplication is an evolutionarily conserved mechanism for increasing nuclear DNA content (ploidy). Ploidy frequently scales with final cell and organ size, suggesting a key role for endoreplication in these processes. However, exceptions exist, and, consequently, the endoreplication-size nexus remains enigmatic. Here, we show that prolonged tissue folding at the apical hook in Arabidopsis requires endoreplication asymmetry under the control of an auxin gradient. We identify a molecular pathway linking endoreplication levels to cell size through cell wall remodeling and stiffness modulation. We find that endoreplication is not only permissive for growth: Endoreplication reduction enhances wall stiffening, actively reducing cell size. The cell wall integrity kinase THESEUS plays a key role in this feedback loop. Our data thus explain the nonlinearity between ploidy levels and size while also providing a molecular mechanism linking mechanochemical signaling with endoreplication-mediated dynamic control of cell growth.

Inspiration amidst crisis: e-learning in a medical school of Nepal during COVID-19 pandemic.

The Coronavirus disease (COVID-19) pandemic continues to shut down colleges and universities including medical schools all over the world, thus pushing medical schools to seek e-learning to maintain continuity of curriculum. Although developed countries are comfortable learning through the internet, low-income countries like Nepal with limited experience in e-learning have used this lockdown as an opportunity to develop online classes. This crisis has clearly revealed the importance of e-learning in for medical educators in Nepal to disseminate knowledge beyond the restrictions of geography and other barriers.

La pandémie de la maladie à coronavirus (COVID-19) continue de provoquer la fermeture des collèges et des universités partout dans le monde, incitant les facultés de médecine à recourir à l'enseignement en ligne pour maintenir la continuité des programmes d'études. Tandis que les pays développés s'adaptent bien à l'enseignement en ligne, les pays à faible revenu comme le Népal, qui ont une expérience limitée de cette technologie, ont profité du confinement pour mettre au point des cours en ligne. La crise a mis en évidence l'importance de cette modalité d'enseignement pour les enseignants en médecine au Népal dans la mesure où elle leur permet de surmonter les contraintes géographiques et d'autres barrières à la diffusion des connaissances.

An invaginated pancreaticogastrostomy following subtotal stomach-preserving pancreaticoduodenectomy: A prospective observational study.

BACKGROUND/OBJECTIVE: Postoperative pancreatic fistula (POPF) leads to life-threatening complications after pancreaticoduodenectomy (PD). Pancreaticogastrostomy (PG) often adopted as a reconstruction technique after PD to prevent POPF. Delayed gastric emptying (DGE) following PD is the most common complication that compromises the quality of life. Subtotal stomach-preserving PD (SSPPD) preserves the pooling ability of the stomach and minimize the occurrence of DGE. This study aimed to describe our PG technique following SSPPD and evaluate the perioperative outcomes. METHODS: The study included patients who underwent PG following SSPPD from August 2013 to July 2020 at our institution. An invaginated PG was performed by one-layer eight interrupted sutures with a lost stent. Patients' demographics and perioperative outcomes were documented. RESULTS: This technique was applied in 72 patients with a median age of 75 years. The median operative time was 342 min. The clinically relevant POPF, DGE and post-pancreatectomy hemorrhage was 4 (5.6%), 5 (6.9%), and 10 (13.9%), respectively. Although the drain fluid amylase concentration on postoperative day 3 was significantly higher in clinically relevant POPF (CR-POPF) positive group (median, 2006 U/L vs. 74 U/L in CR-POPF negative group, p = 0.002), none of the risk factors including disease pathology, pancreatic duct diameter, texture of pancreas and excessive blood loss were significantly associated with CR-POPF. Other morbidity ≥ Clavien-Dindo classification II occurred in 29 patients (40.3%). The 90-days operative mortality was two (2.8%). CONCLUSIONS: This novel method of one-layer invaginated PG following SSPPD is safe and dependable procedure with acceptable morbidity and mortality.

Pancreaticoduodenectomy after transcatheter aortic valve implantation in an elderly patient with severe aortic stenosis and pancreas cancer: A case report.

INTRODUCTION AND IMPORTANCE: Not only pancreatic cancer but also aortic stenosis (AS) is increasing with the aging population. There is no optimal strategy for elderly patients with both pancreatic cancer and AS. We report a case of pancreatic head cancer with severe AS undergoing pancreaticoduodenectomy (PD) after transcatheter aortic valve implantation (TAVI). CASE PRESENTATION: An 88-year-old woman was referred to our hospital because of severe AS with symptoms of heart failure. Preoperative examination revealed resectable pancreatic head cancer, so TAVI was performed before PD to reduce the perioperative risk. The patient underwent PD 34 days after TAVI, with no significant postoperative complications, and was transferred to the other hospital for rehabilitation on postoperative day 45. No recurrence was observed at more than 7 months without adjuvant therapy. CLINICAL DISCUSSION: Aortic valve replacement (AVR) is recommended before non-cardiac surgery in patients with symptomatic severe AS. Surgical aortic valve replacement (SAVR) is the standard treatment. However, owing to the highly invasive procedure and increased perioperative risk, SAVR is usually avoided in elderly patients with malignancy and severe AS. We demonstrated that TAVI followed by PD could be safely performed in high-risk elderly patients presenting with both severe AS and pancreatic head cancer. To our knowledge, this is the first case report of PD after TAVI in a patient with severe AS. CONCLUSION: We demonstrated that TAVI followed by PD could be safely performed in high-risk elderly patients presenting with severe AS and co-existing malignancy.

External Mechanical Cues Reveal a Katanin-Independent Mechanism behind Auxin-Mediated Tissue Bending in Plants.

Tissue folding is a central building block of plant and animal morphogenesis. In dicotyledonous plants, hypocotyl folds to form hooks after seedling germination that protects their aerial stem cell niche during emergence from soil. Auxin response factors and auxin transport are reported to play a key role in this process. Here, we show that the microtubule-severing enzyme katanin contributes to hook formation. However, by exposing hypocotyls to external mechanical cues mimicking the natural soil environment, we reveal that auxin response factors ARF7/ARF19, auxin influx carriers, and katanin are dispensable for apical hook formation, indicating that these factors primarily play the role of catalyzers of tissue bending in the absence of external mechanical cues. Instead, our results reveal the key roles of the non-canonical TMK-mediated auxin pathway, PIN efflux carriers, and cellulose microfibrils as components of the core pathway behind hook formation in the presence or absence of external mechanical cues.