Dexmedetomidine affects the NOX4/Nrf2 pathway to improve renal antioxidant capacity.

OBJECTIVES: The study aimed to investigate the protective effects of dexmedetomidine (DEX) on renal injury caused by acute stress in rats and explore the protective pathways of DEX on rat kidneys in terms of oxidative stress. METHODS: An acute restraint stress model was utilized, where rats were restrained for 3 hours after a 15-minute swim. Biochemical tests and histopathological sections were conducted to evaluate renal function, along with the measurement of oxidative stress and related pathway proteins. KEY FINDINGS: The open-field experiments validated the successful establishment of the acute stress model. Acute stress-induced renal injury led to increased NADPH oxidase 4 (NOX4) protein expression and decreased expression levels of nuclear transcription factor 2 (Nrf2), heme oxygenase-1 (HO-1), and NAD(P)H: quinone oxidoreductase 1 (NQO1). Following DEX treatment, there was a significant reduction in renal NOX4 expression. The DEX-treated group exhibited normalized renal biochemical results and less damage observed in pathological sections compared to the acute stress group. CONCLUSIONS: The findings suggest that DEX treatment during acute stress can impact the NOX4/Nrf2/HO-1/NQO1 signaling pathway and inhibit oxidative stress, thereby preventing acute stress-induced kidney injury. Additionally, DEX shows promise for clinical applications in stress syndromes.

Meta-analysis of Helicobacter pylori eradication therapy using vonoprazan as an acid suppressor compared with bismuth quadruple therapy.

BACKGROUND: Vonoprazan, a novel acid suppressant, has recently emerged as a regimen for eradicating Helicobacter pylori. However, uncertainties exist about the effectiveness and safety of VPZ-based regimens compared with those of bismuth-based quadruple therapy in eradicating H. pylori. The present meta-analysis was performed to compare the effectiveness and safety of vonoprazan-based regimens with those of bismuth quadruple therapy in eradicating H. pylori. MATERIALS AND METHODS: All randomized controlled trials and non-randomized controlled trials comparing the vonoprazan-based therapy with the bismuth quadruple therapy were included in this meta-analysis. Information was also extracted by two evaluators, and if heterogeneity existed, a random-effects model was used to calculate the combined relative ratio and 95% confidence interval; otherwise, a fixed-effects model was used. And subgroup analyses were performed to explore the sources of heterogeneity. RESULTS: A total of 10 studies, comprising 2587 patients were included in the meta-analysis. The results showed that the combined eradication rate of patients treated with the vonoprazan-based regimen was significantly higher than that of patients treated with bismuth quadruple therapy, in both intention-to-treat and per-protocol analyses, and the differences were statistically significant. Among the intention-to-treat analyses results: (90.28% vs. 83.64% [odds ratio (OR) = 1.85, 95% confidence interval (CI) (1.27, 2.70), p = 0.001]); in the per-protocol analyses: (94.80% vs. 89.88%, [OR = 2.25, 95% CI (1.37, 3.69), p = 0.001]). The occurrence of adverse events was significantly lower in patients treated with vonoprazan-based regimens than in those treated with bismuth quadruple therapy, (14.50% vs. 25.89%, [OR = 0.49, 95% CI (0.32, 0.75), p = 0.001]). CONCLUSIONS: For eradicating H. pylori, vonoprazan-based regimens are remarkably advantageous over bismuth quadruple therapy. Furthermore, vonoprazan-based regimens exhibit a lower rate of adverse events than bismuth quadruple therapy.

The diagnostic performance of V' and U' variables as an objective index of pink-color sign for diagnosing esophageal cancerous lesions.

BACKGROUND: The pink-color sign (PCS) has been widely used for diagnosing esophageal squamous cell carcinoma (ESCC) during Lugol's iodine chromoendoscopy. However, the identification of the PCS only relies on the subjective assessments made by the endoscopist, which could lead to bias and disagreement. Previous research has indicated that the V' variable can, as an objective index, define the PCS in the LU'V' color space. We aimed to validate the diagnostic performance of the PCS defined by the V' variable alone and attempt to improve the diagnostic performance by combining the V' and U' variables. METHODS: We re-examined 231 subjects with Lugol's unstained lesions (LULs) from a previously reported prospective trial. The diagnostic performance of the method using V' variable alone (V' alone method), the combination method using V' and U' variables (V' + U' method), and the endoscopists were calculated and compared. RESULTS: A total of 236 LULs were included, among which 46 were histologically confirmed to be cancerous lesions. The sensitivity, specificity, and accuracy of the V' alone method were 73.91% (95% CI 58.87-85.73%), 79.47% (95% CI 73.03-84.98%), and 78.39% (95% CI 72.59-83.47%) in the external validation cohort, respectively. It is inferior to endoscopists in terms of specificity and accuracy. The V' + U' method demonstrated a diagnostic performance comparable to the experienced endoscopists, with sensitivity, specificity, and accuracy of 76.74% (95% CI 61.37-88.25%), 88.64% (95% CI 83.00-92.92%), and 86.30% (95% CI 81.03-90.56%), respectively. CONCLUSION: The V' alone method exhibited lower specificity and accuracy than the experienced endoscopist and the V' + U' method. However, the modified V' + U' method demonstrated a diagnostic performance comparable to experienced endoscopists. Utilizing the objective index of the PCS could provide valuable support in clinical decision-making.

Cancer associated fibroblast derived SLIT2 drives gastric cancer cell metastasis by activating NEK9.

The secretory properties of cancer-associated fibroblasts (CAFs) play predominant roles in shaping a pro-metastatic tumor microenvironment. The present study demonstrated that SLIT2, an axon guidance protein, produced by CAFs and promoted gastric cancer (GC) metastasis in two gastric cancer cell lines (AGS and MKN45) by binding to roundabout guidance receptor 1 (ROBO1). Mass-spectrometry analysis revealed that ROBO1 could interact with NEK9, a serine/threonine kinase. And their mutual binding activities were further enhanced by SLIT2. Domain analysis revealed the kinase domain of NEK9 was critical in its interaction with the intracellular domain (ICD) of ROBO1, and it also directly phosphorylated tripartite motif containing 28 (TRIM28) and cortactin (CTTN) in AGS and MKN45 cells. TRIM28 function as a transcriptional elongation factor, which directly facilitate CTTN activation. In addition, Bioinformatics analysis and experimental validation identified transcriptional regulation of STAT3 and NF-κB p100 by TRIM28, and a synergetic transcription of CTTN by STAT3 and NF-κB p100 was also observed in AGS and MKN45. Therefore, CAF-derived SLIT2 increased the expression and phosphorylation levels of CTTN, which induced cytoskeletal reorganization and GC cells metastasis. A simultaneous increase in the expression levels of NEK9, TRIM28 and CTTN was found in metastatic GC lesions compared with paired non-cancerous tissues and primary cancer lesions via IHC and Multiplex IHC. The analysis of the data from a cohort of patients with GC revealed that increased levels of NEK9, TRIM28 and CTTN were associated with a decreased overall survival rate. On the whole, these findings revealed the connections of CAFs and cancer cells through SLIT2/ROBO1 and inflammatory signaling, and the key molecules involved in this process may serve as potential biomarkers and therapeutic targets for GC.

Identification of the Karyopherin Superfamily in Maize and Its Functional Cues in Plant Development.

Appropriate nucleo-cytoplasmic partitioning of proteins is a vital regulatory mechanism in phytohormone signaling and plant development. However, how this is achieved remains incompletely understood. The Karyopherin (KAP) superfamily is critical for separating the biological processes in the nucleus from those in the cytoplasm. The KAP superfamily is divided into Importin α (IMPα) and Importin ß (IMPß) families and includes the core components in mediating nucleocytoplasmic transport. Recent reports suggest the KAPs play crucial regulatory roles in Arabidopsis development and stress response by regulating the nucleo-cytoplasmic transport of members in hormone signaling. However, the KAP members and their associated molecular mechanisms are still poorly understood in maize. Therefore, we first identified seven IMPα and twenty-seven IMPß genes in the maize genome and described their evolution traits and the recognition rules for substrates with nuclear localization signals (NLSs) or nuclear export signals (NESs) in plants. Next, we searched for the protein interaction partners of the ZmKAPs and selected the ones with Arabidopsis orthologs functioning in auxin biosynthesis, transport, and signaling to predict their potential function. Finally, we found that several ZmKAPs share similar expression patterns with their interacting proteins, implying their function in root development. Overall, this article focuses on the Karyopherin superfamily in maize and starts with this entry point by systematically comprehending the KAP-mediated nucleo-cytoplasmic transport process in plants, and then predicts the function of the ZmKAPs during maize development, with a perspective on a closely associated regulatory mechanism between the nucleo-cytoplasmic transport and the phytohormone network.

Emergency Removal of Ingested Foreign Bodies in 586 Adults at a Single Hospital in China According to the European Society of Gastrointestinal Endoscopy (ESGE) Recommendations: A 10-Year Retrospective Study.

BACKGROUND The 2016 European Society of Gastrointestinal Endoscopy (ESGE) guidelines recommend that ingested foreign bodies in the upper gastrointestinal (GI) tract are removed as an emergency within 6 hours, with an endoscopic approach that is individualized according to the type of foreign body identified. This retrospective study evaluated the 10-year experience of a single hospital in China performing emergency removal of ingested foreign bodies in 586 adults. MATERIAL AND METHODS Between 2011 and 2020, medical records of 642 adults with a diagnosis of foreign bodies ingestion were retrospectively screened. The timing of endoscopic intervention was classified according to ESGE recommendations. Uni- and multivariate analyses were performed. RESULTS We included 586 patients. The median (range) diameter of foreign bodies was 2.5 (1-24) cm: for sharp ones it was 2.5 (1.5-4.0) cm and for long ones it was 16.9 (10-24) cm. The most common site of foreign body lodgment was the esophagus (n=481; 82.1%); 45.6% (n=252) received emergent removal within 6 hours, while 32.2% (n=178) underwent urgent removal within 24 hours. There were 583 (99.5%) foreign bodies removed successfully and the complication rate was 17.9%. Major complications occurred in 45 patients (7.7%). Female sex and non-emergent endoscopy after 6 hours were significantly associated with a higher overall complications rate. For major complications, older age, time interval >24 hours, and sharper objects were associated with major complications. CONCLUSIONS The findings from this retrospective study support the ESGE statement that endoscopic removal of ingested foreign bodies from the upper GI tract within 6 hours reduces complication rates for adults in the emergency setting.

Discovery and preclinical profile of LX-039, a novel indole-based oral selective estrogen receptor degrader (SERD).

We previously described the discovery of a novel indole series compounds as oral SERD for ER positive breast cancer treatment. Further SAR exploration focusing on substitutions on indole moiety of compound 12 led to the discovery of a clinical candidate LX-039. We report herein its profound anti-tumor activity, desirable ER antagonistic characteristics combined with favorable pharmacokinetic and preliminary safety properties. LX-039 is currently in clinical trial (NCT04097756).

A CGA/EGFR/GATA2 positive feedback circuit confers chemoresistance in gastric cancer.

De novo and acquired resistance are major impediments to the efficacy of conventional and targeted cancer therapy. In unselected gastric cancer (GC) patients with advanced disease, trials combining chemotherapy and an anti-EGFR monoclonal antibody have been largely unsuccessful. In an effort to identify biomarkers of resistance so as to better select patients for such trials, we screened the secretome of chemotherapy-treated human GC cell lines. We found that levels of CGA, the α-subunit of glycoprotein hormones, were markedly increased in the conditioned media of chemoresistant GC cells, and CGA immunoreactivity was enhanced in GC tissues that progressed on chemotherapy. CGA levels in plasma increased in GC patients who received chemotherapy, and this increase was correlated with reduced responsiveness to chemotherapy and poor survival. Mechanistically, secreted CGA was found to bind to EGFR and activate EGFR signaling, thereby conferring a survival advantage to GC cells. N-glycosylation of CGA at Asn52 and Asn78 is required for its stability, secretion, and interaction with EGFR. GATA2 was found to activate CGA transcription, whose increase, in turn, induced the expression and phosphorylation of GATA2 in an EGFR-dependent manner, forming a positive feedback circuit that was initiated by GATA2 autoregulation upon sublethal exposure to chemotherapy. Based on this circuit, combination strategies involving anti-EGFR therapies or targeting CGA with microRNAs (miR-708-3p and miR-761) restored chemotherapy sensitivity. These findings identify a clinically actionable CGA/EGFR/GATA2 circuit and highlight CGA as a predictive biomarker and therapeutic target in chemoresistant GC.

Transcriptional super-enhancers control cancer stemness and metastasis genes in squamous cell carcinoma.

Cancer stem cells (CSCs) play a critical role in invasive growth and metastasis of human head and neck squamous cell carcinoma (HNSCC). Although significant progress has been made in understanding the self-renewal and pro-tumorigenic potentials of CSCs, a key challenge remains on how to eliminate CSCs and halt metastasis effectively. Here we show that super-enhancers (SEs) play a critical role in the transcription of cancer stemness genes as well as pro-metastatic genes, thereby controlling their tumorigenic potential and metastasis. Mechanistically, we find that bromodomain-containing protein 4 (BRD4) recruits Mediators and NF-κB p65 to form SEs at cancer stemness genes such as TP63, MET and FOSL1, in addition to oncogenic transcripts. In vivo lineage tracing reveals that disrupting SEs by BET inhibitors potently inhibited CSC self-renewal and eliminated CSCs in addition to elimination of proliferating non-stem tumor cells in a mouse model of HNSCC. Moreover, disrupting SEs also inhibits the invasive growth and lymph node metastasis of human CSCs isolated from human HNSCC. Taken together, our results suggest that targeting SEs may serve as an effective therapy for HNSCC by eliminating CSCs.

NEK9, a novel effector of IL-6/STAT3, regulates metastasis of gastric cancer by targeting ARHGEF2 phosphorylation.

Rationale: Inflammatory stimuli from the tumor microenvironment play important roles in cancer progression. However, the mechanism of promotion of cancer metastasis by inflammation in gastric cancer (GC) is poorly understood. Methods: The roles of NEK9 were validated via loss-of-function and gain-of-function experiments in vitro and in an animal model of metastasis. Cytoskeletal reorganization-associated molecules were detected by GST pull-down. The regulation of ARHGEF2 by NEK9 was investigated by phosphoproteomics analysis, immunoprecipitation (IP) and in vitro kinase assay. The transcriptional regulation of miR-520f-3p was studied using luciferase reporter and chromatin immunoprecipitation (ChIP). The expression of these proteins in GC tissues was examined by immunohistochemistry. Results: NEK9 directly regulates cell motility and RhoA activation in GC. The phosphorylation of ARHGEF2 by NEK9 is the key step of this process. NEK9 is a direct target of miR-520f-3p, which is transcriptionally suppressed by IL-6-mediated activation of STAT3. A decrease in miR-520f-3p leads to the amplification of IL-6/STAT3 by targeting GP130. A simultaneous elevation of the levels of NEK9, GP130 and p-STAT3 was confirmed in the lymph nodes and distant metastases. An increase in NEK9, GP130 and STAT3 is associated with reduced overall survival of GC patients. Conclusion: This study demonstrates that activation of STAT3 by IL-6 transcriptionally suppresses miR-520f-3p and diminishes the inhibitory effects of miR-520f-3p on NEK9 and GP130. An increase in GP130 enhances this signaling, and NEK9 directly influences cell motility and RhoA activation by targeting the phosphorylation of ARHGEF2. Targeting the IL-6-STAT3-NEK9 pathway may be a new strategy for GC treatment.

The FUSED LEAVES1-ADHERENT1 regulatory module is required for maize cuticle development and organ separation.

All aerial epidermal cells in land plants are covered by the cuticle, an extracellular hydrophobic layer that provides protection against abiotic and biotic stresses and prevents organ fusion during development. Genetic and morphological analysis of the classic maize adherent1 (ad1) mutant was combined with genome-wide binding analysis of the maize MYB transcription factor FUSED LEAVES1 (FDL1), coupled with transcriptional profiling of fdl1 mutants. We show that AD1 encodes an epidermally-expressed 3-KETOACYL-CoA SYNTHASE (KCS) belonging to a functionally uncharacterized clade of KCS enzymes involved in cuticular wax biosynthesis. Wax analysis in ad1 mutants indicates that AD1 functions in the formation of very-long-chain wax components. We demonstrate that FDL1 directly binds to CCAACC core motifs present in AD1 regulatory regions to activate its expression. Over 2000 additional target genes of FDL1, including many involved in cuticle formation, drought response and cell wall organization, were also identified. Our results identify a regulatory module of cuticle biosynthesis in maize that is conserved across monocots and eudicots, and highlight previously undescribed factors in lipid metabolism, transport and signaling that coordinate organ development and cuticle formation.

Long-term oral vancomycin for refractory inflammatory bowel diseases without Clostridium difficile infection: Lessons from primary sclerosing cholangitis.

Dysbiosis is a prominent feature of inflammatory bowel diseases (IBD). However, the efficacy of using antibiotics aiming at the aberrant gut microflora for IBD treatment are either unsuccessful or not persistent. In contrast, long-term oral vancomycin has been proved effective in controlling both the bile duct and gut inflammation of primary sclerosing cholangitis (PSC), an autoimmune disease against the intra- and extrahepatic bile ducts that holds a high rate of concomitant IBD and shares many common characteristics with IBD, including similar dysbiosis patterns. Two discrepancies of antibiotic usage might explain the dramatically different responses of the two diseases toward this strategy. First, the vast majority of antibiotic formulas for IBD management consist of broad-spectrum antibiotics mainly targeting gram-negative bacteria with some covering anaerobes and gram-positive ones, while vancomycin used for PSC treatment almost exclusively targets gram-positive bacteria. Several lines of clues suggested that gram-positive microorganisms might be responsible for the chronic inflammation observed in IBD and PSC. Second, improvement of liver test in PSC patients is usually observed after a relatively long period of oral vancomycin treatment (more than 12 weeks) and it takes even longer for gut mucosal healing. Moreover, long-term low dose oral vancomycin is required to prevent PSC recurrence. However, most trials of using antibiotics for IBD management is aiming at inducing remission with short treatment course (most less than 2 weeks) without maintenance. We hypothesize that the host antimicrobial response favors the growth of certain gram-positive intestinal bacteria in genetically predisposed individuals which is responsible for the aberrant immunological reaction towards the gut mucosa. Oral vancomycin induces disease remission by suppressing the pathogenic gram-positive microorganisms, but long course is needed since the gut inflammation is usually severe than that concomitant with PSC. Moreover, long-term maintenance is required to prevent the rebound of the pathogens and flare of the intestinal inflammation.

Design, syntheses and evaluations of novel indole derivatives as orally selective estrogen receptor degraders (SERD).

Most estrogen receptor positive (ER +) breast cancers depend on ER signaling pathway to develop. Clinical application of SERD fulvestrant effectively degraded ER, blocked its function and prolonged progression free survival of ER + breast cancer patients. However, current SERD suffers from limited bioavailability, therefore is given as intramuscular (IM) injection. In this paper, we report herein a novel indole series compounds with nanomolar range ER degradation potencies and oral systemic exposures. Selected compounds suppressed tumor growth in vivo in ER + MCF7 breast cancer CDX model via p.o. administration. All those data supported further optimizations of this analog to develop preclinical candidate as oral SERD for ER + breast cancer's treatment.

Discovery of 3-Quinazolin-4(3H)-on-3-yl-2,N-dimethylpropanamides as Orally Active and Selective PI3Kα Inhibitors.

Phosphoinositide 3-kinases (PI3Ks) mediate a series of events related to cell growth, proliferation, survival, and differentiation. Overexpression of PI3Ks can lead to the dysregulation of cell homeostasis and cause tumorigenesis. In this study, rationally designed compounds were investigated as PI3Kα-selective inhibitors. Our efforts culminated in the discovery of a series of quinazolin-4(3H)-one derivatives with 2-substituted-N-methylpropanamide substitutions as PI3Kα-selective inhibitors. The best compound, 10, has PI3Kα enzymatic and cellular IC50 values of 1.8 and 12.1 nM, respectively. It exhibits biochemical selectivities for PI3Kα over PI3Kß/δ/γ of 150/7.72/7.67-fold and cellular selectivities of 115/15.1/>826-fold, respectively. Compound 10 is 59% orally bioavailable with a dose-normalized AUC of 3090 nM. These effects translated into in vivo conditions, as 10 significantly time- and dose-dependently inhibited phosphorylation of Akt in BT-474 subcutaneous xenograft mice and inhibited tumor growth.

Long-read sequencing reveals genomic structural variations that underlie creation of quality protein maize.

Mutation of o2 doubles maize endosperm lysine content, but it causes an inferior kernel phenotype. Developing quality protein maize (QPM) by introgressing o2 modifiers (Mo2s) into the o2 mutant benefits millions of people in developing countries where maize is a primary protein source. Here, we report genome sequence and annotation of a South African QPM line K0326Y, which is assembled from single-molecule, real-time shotgun sequencing reads collinear with an optical map. We achieve a N50 contig length of 7.7 million bases (Mb) directly from long-read assembly, compared to those of 1.04 Mb for B73 and 1.48 Mb for Mo17. To characterize Mo2s, we map QTLs to chromosomes 1, 6, 7, and 9 using an F2 population derived from crossing K0326Y and W64Ao2. RNA-seq analysis of QPM and o2 endosperms reveals a group of differentially expressed genes that coincide with Mo2 QTLs, suggesting a potential role in vitreous endosperm formation.

NAC-type transcription factors regulate accumulation of starch and protein in maize seeds.

Grain starch and protein are synthesized during endosperm development, prompting the question of what regulatory mechanism underlies the synchronization of the accumulation of secondary and primary gene products. We found that two endosperm-specific NAC transcription factors, ZmNAC128 and ZmNAC130, have such a regulatory function. Knockdown of expression of ZmNAC128 and ZmNAC130 with RNA interference (RNAi) caused a shrunken kernel phenotype with significant reduction of starch and protein. We could show that ZmNAC128 and ZmNAC130 regulate the transcription of Bt2 and then reduce its protein level, a rate-limiting step in starch synthesis of maize endosperm. Lack of ZmNAC128 and ZmNAC130 also reduced accumulation of zeins and nonzeins by 18% and 24% compared with nontransgenic siblings, respectively. Although ZmNAC128 and ZmNAC130 affected expression of zein genes in general, they specifically activated transcription of the 16-kDa γ-zein gene. The two transcription factors did not dimerize with each other but exemplified redundancy, whereas individual discovery of their function was not amenable to conventional genetics but illustrated the power of RNAi. Given that both the Bt2 and the 16-kDa γ-zein genes were activated by ZmNAC128 or ZmNAC130, we could identify a core binding site ACGCAA contained within their target promoter regions by combining Dual-Luciferase Reporter and Electrophoretic Mobility Shift assays. Consistent with these properties, transcriptomic profiling uncovered that lack of ZmNAC128 and ZmNAC130 had a pleiotropic effect on the utilization of carbohydrates and amino acids.

Candidate gene identification of existing or induced mutations with pipelines applicable to large genomes.

Bulked segregant analysis (BSA) is used to identify existing or induced variants that are linked to phenotypes. Although it is widely used in Arabidopsis and rice, it remains challenging for crops with large genomes, such as maize. Moreover, analysis of huge data sets can present a bottleneck linking phenotypes to their molecular basis, especially for geneticists without programming experience. Here, we identified two genes of maize defective kernel mutants with newly developed analysis pipelines that require no programing skills and should be applicable to any large genome. In the 1970s, Neuffer and Sheridan generated a chemically induced defective kernel (dek) mutant collection with the potential to uncover critical genes for seed development. To locate such mutations, the dek phenotypes were introgressed into two inbred lines to take advantage of maize haplotype variations and their sequenced genomes. We generated two pipelines that take fastq files derived from next-generation (nextGen) paired-end DNA and cDNA sequencing as input, call on several well established and freely available genomic analysis tools to call SNPs and INDELs, and generate lists of the most likely causal mutations together with variant index plots to locate the mutation to a specific sequence position on a chromosome. The pipelines were validated with a known strawberry mutation before cloning the dek mutants, thereby enabling phenotypic analysis of large genomes by next-generation sequencing.

Auxin polar transport flanking incipient primordium initiates leaf adaxial-abaxial polarity patterning.

The leaves of most higher plants are polar along their adaxial-abaxial axis, and the development of the adaxial domain (upper side) and the abaxial domain (lower side) makes the leaf a highly efficient photosynthetic organ. It has been proposed that a hypothetical signal transported from the shoot apical meristem (SAM) to the incipient leaf primordium, or conversely, the plant hormone auxin transported from the leaf primordium to the SAM, initiates leaf adaxial-abaxial patterning. This hypothetical signal has been referred to as the Sussex signal, because the research of Ian Sussex published in 1951 was the first to imply its existence. Recent results, however, have shown that auxin polar transport flanking the incipient leaf primordium, but not the Sussex signal, is the key to initiate leaf polarity. Here, we review the new findings and integrate them with other recently published results in the field of leaf development, mainly focusing on the early steps of leaf polarity establishment.

Model for the role of auxin polar transport in patterning of the leaf adaxial-abaxial axis.

Leaf adaxial-abaxial polarity refers to the two leaf faces, which have different types of cells performing distinct biological functions. In 1951, Ian Sussex reported that when an incipient leaf primordium was surgically isolated by an incision across the vegetative shoot apical meristem (SAM), a radialized structure without an adaxial domain would form. This led to the proposal that a signal, now called the Sussex signal, is transported from the SAM to emerging primordia to direct leaf adaxial-abaxial patterning. It was recently proposed that instead of the Sussex signal, polar transport of the plant hormone auxin is critical in leaf polarity formation. However, how auxin polar transport functions in the process is unknown. Through live imaging, we established a profile of auxin polar transport in and around young leaf primordia. Here we show that auxin polar transport in lateral regions of an incipient primordium forms auxin convergence points. We demonstrated that blocking auxin polar transport in the lateral regions of the incipient primordium by incisions abolished the auxin convergence points and caused abaxialized leaves to form. The lateral incisions also blocked the formation of leaf middle domain and margins and disrupted expression of the middle domain/margin-associated marker gene WUSCHEL-RELATED HOMEOBOX 1 (SlWOX1). Based on these results we propose that the auxin convergence points are required for the formation of leaf middle domain and margins, and the functional middle domain and margins ensure leaf adaxial-abaxial polarity. How middle domain and margins function in the process is discussed.