Plant extracellular self-DNA inhibits growth and induces immunity via the jasmonate signaling pathway.

Plants have evolved sophisticated mechanisms to detect various forms of danger. Damage-associated molecular patterns (DAMPs) are endogenous danger molecules that are released from damaged cells and activate the innate immunity. Recent evidence suggests that plant extracellular self-DNA (esDNA) can serve as a DAMP molecule. However, the mechanisms by which esDNA functions are largely unknown. In this study, we confirmed that esDNA inhibits root growth and triggers reactive oxygen species (ROS) production in a concentration- and species-specific manner in Arabidopsis (Arabidopsis thaliana) and tomato (Solanum lycopersicum L.). Furthermore, by combining RNA sequencing, hormone measurement, and genetic analysis, we found that esDNA-mediated growth inhibition and ROS production are achieved through the jasmonic acid (JA) signaling pathway. Specifically, esDNA induces JA production and the expression of JA-responsive genes. The esDNA-mediated growth inhibition, ROS production, and gene expression are impaired in the JA-related mutants. Finally, we found that the JA signaling pathway is required for the esDNA-elicited resistance against the pathogens Botrytis cinerea and Pseudomonas syringae pv. tomato DC3000. This finding highlights the importance of JA signaling in esDNA-mediated biological effects, thereby providing insight into how esDNA functions as a DAMP.

Is early bilateral compression ultrasonography and D-dimer monitoring appropriately for prophylaxis and diagnosis of deep venous thrombosis after cesarean section women: a single-center observation study of Chinese Han population.

BACKGROUND: Venous thromboembolism (VTE) is most prevalent among parturients following a cesarean section (CS). The objective of this study was to assess the practical utility of bilateral compression ultrasonography (CUS) of the lower limbs, coupled with D-dimer monitoring, in the early diagnosis of VTE within the Han Chinese population. METHODS: Our prospective observational study included 742 women who underwent CUS and D-dimer testing on the first day post-CS. Subsequently, telephone or outpatient follow-ups were conducted until 42 days postpartum. States of hypercoagulation and thrombosis, as indicated by CUS, were classified as CUS abnormal. A D-dimer level ≥ 3 mg/l was considered the D-dimer warning value. Early ambulation and mechanical prophylaxis were universally recommended for all parturients post-CS. A sequential diagnostic strategy, based on the 2015 RCOG VTE risk-assessment tool, was employed. Therapeutic doses of low-molecular-weight heparin (LMWH) were administered for the treatment of thromboembolic disease. Prophylactic doses of LMWH were given for VTE prophylaxis in parturients with hypercoagulative status accompanied by D-dimer levels ≥ 3 mg/l. All high-risk women (RCOG score ≥ 4 points) were additionally treated with preventive LMWH. Statistical analyses were conducted using the R statistical software, with a two-sided P value < 0.05 considered statistically significant. RESULTS: Fifteen cases of VTE and 727 instances without VTE were observed. The overall VTE rate post-CS was 2.02% (15/742), with 66.7% (10/15) being asymptomatic. Eleven patients received a VTE diagnosis on the first postpartum day. Among the 41 parturients exhibiting hypercoagulation ultrasound findings and D-dimer levels ≥ 3 mg/l, despite receiving pharmacological VTE prophylaxis with LMWH, 4.88% (2/41) in the high-risk group were eventually diagnosed with VTE. A total of 30.86% (229/742) exhibited normal ultrasound findings and D-dimer levels < 3 mg/l on the first day post-CS, with no VTE occurrences in the postpartum follow-up. According to RCOG's recommendation, 78.03% (579/742) of cesarean delivery women should receive prophylactic anticoagulation, while only 20.62% (153/742) met our criterion for prophylactic anticoagulation. CONCLUSION: The strategy of timely routine bilateral CUS and D-dimer monitoring is conducive to the early diagnosis and treatment of VTE, significantly reducing the use of LMWH in the Chinese Han population.

Rapid generation of a tomato male sterility system and its feasible application in hybrid seed production.

KEY MESSAGE: A practical approach for the rapid generation and feasible application of green hypocotyl male-sterile (GHMS) tm6 dfr lines in tomato hybrid breeding was established. Male sterility enables reduced cost and high seed purity during hybrid seed production. However, progress toward its commercial application has been slow in tomato due to the disadvantages of most natural male-sterile mutants. Here, we developed a practical method for efficient tomato hybrid seed production using a male-sterile system with visible marker, which was rapidly generated by CRISPR/Cas9-mediated gene editing. Two closely linked genes, TM6 and DFR, which were reported to be candidates of ms15 (male sterile-15) and aw (anthocyanin without) locus, respectively, were knocked out simultaneously in two elite tomato inbred lines. Mutagenesis of both genes generated green hypocotyl male-sterile (GHMS) lines. The GHMS lines exhibited male sterility across different genetic backgrounds and environmental conditions. They also showed green hypocotyl due to defective anthocyanin accumulation, which serves as a reliable visible marker for selecting male-sterile plants at the seedling stage. We further proposed a strategy for multiplying the GHMS system and verified its high efficiency in stable male sterility propagation. Moreover, elite hybrid seeds were produced using GHMS system for potential side effects evaluation, and no adverse influences were found on seed yield, seed quality as well as important agronomic traits. This study provides a practical approach for the rapid generation and feasible application of male sterility in tomato hybrid breeding.

MYC2 Regulates the Termination of Jasmonate Signaling via an Autoregulatory Negative Feedback Loop.

In tomato (Solanum lycopersicum), as in other plants, the immunity hormone jasmonate (JA) triggers genome-wide transcriptional changes in response to pathogen and insect attack. These changes are largely regulated by the basic helix-loop-helix (bHLH) transcription factor MYC2. The function of MYC2 depends on its physical interaction with the MED25 subunit of the Mediator transcriptional coactivator complex. Although much has been learned about the MYC2-dependent transcriptional activation of JA-responsive genes, relatively less studied is the termination of JA-mediated transcriptional responses and the underlying mechanisms. Here, we report an unexpected function of MYC2 in regulating the termination of JA signaling through activating a small group of JA-inducible bHLH proteins, termed MYC2-TARGETED BHLH1 (MTB1), MTB2, and MTB3. MTB proteins negatively regulate JA-mediated transcriptional responses via their antagonistic effects on the functionality of the MYC2-MED25 transcriptional activation complex. MTB proteins impair the formation of the MYC2-MED25 complex and compete with MYC2 to bind to its target gene promoters. Therefore, MYC2 and MTB proteins form an autoregulatory negative feedback circuit to terminate JA signaling in a highly organized manner. We provide examples demonstrating that gene editing tools such as CRISPR/Cas9 open up new avenues to exploit MTB genes for crop protection.

The Sm gene conferring resistance to gray leaf spot disease encodes an NBS-LRR (nucleotide-binding site-leucine-rich repeat) plant resistance protein in tomato.

KEY MESSAGES: Gray leaf spot (GLS) resistance in tomato is controlled by one major dominant locus, Sm. Sm was fine mapped, and the nucleotide-binding site-leucine-rich repeat (NBS-LRR) gene Solyc11g020100 was identified as a candidate gene for Sm. Further functional analysis indicated that this gene confers high resistance to Stemphylium lycopersici in tomato. Tomato (Solanum Lycopersicum) is widely consumed and cultivated in the world. Gray leaf spot (GLS), caused by Stemphylium lycopersici (S. lycopersici), is one of the most devastating diseases in tomato production. To date, only one resistance gene, Sm, which confers high resistance against GLS disease, has been identified in the wild tomato species Solanum pimpinellifolium. This resistance locus (comprising the Sm gene) has been transferred into the cultivated variety 'Motelle'. Although several studies have reported the mapping of the Sm gene, it has not been cloned, limiting the utilization in tomato breeding. Here, we cloned Sm using a map-based cloning strategy. The Sm gene was mapped in a region of 160 kb at chromosome 11 between two markers, namely, M390 and M410, by using an F2 population from a cross between the resistant cultivar 'Motelle' (Mt) and susceptible line 'Moneymaker' (Mm). Three clustered NBS-LRR (nucleotide-binding site-leucine-rich repeat) resistance genes, namely, Solyc11g020080 (R1), Solyc11g020090 (R2), and Solyc11g020100 (R3) were identified in this interval. Nonsynonymous SNPs were identified in only the open reading frame (ORF) of R3, suggesting it as a strong candidate for the Sm gene. Furthermore, gene silencing of R3 abolished the high resistance to S. lycopersici in Motelle, demonstrating that this gene confers high resistance to S. lycopersici. The cloning of Sm may speed up its utilization for breeding resistant tomato varieties and represents an important step forward in our understanding of the mechanism underlying the resistance to GLS.

Mediator complex subunit MED25 physically interacts with DST to regulate spikelet number in rice.

Grain number is a flexible trait and contributes significantly to grain yield. In rice, the zinc finger transcription factor DROUGHT AND SALT TOLERANCE (DST) controls grain number by directly regulating cytokinin oxidase/dehydrogenase 2 (OsCKX2) expression. Although specific upstream regulators of the DST-OsCKX2 module have been identified, the mechanism employed by DST to regulate the expression of OsCKX2 remains unclear. Here, we demonstrate that DST-interacting protein 1 (DIP1), known as Mediator subunit OsMED25, acts as an interacting coactivator of DST. Phenotypic analyses revealed that OsMED25-RNAi and the osmed25 mutant plants exhibited enlarged panicles, with enhanced branching and spikelet number, similar to the dst mutant. Genetic analysis indicated that OsMED25 acts in the same pathway as the DST-OsCKX2 module to regulate spikelet number per panicle. Further biochemical analysis showed that OsMED25 physically interacts with DST at the promoter region of OsCKX2, and then recruits RNA polymerase II (Pol II) to activate OsCKX2 transcription. Thus, OsMED25 was involved in the communication between DST and Pol II general transcriptional machinery to regulate spikelet number. In general, our findings reveal a novel function of OsMED25 in DST-OsCKX2 modulated transcriptional regulation, thus enhancing our understanding of the regulatory mechanism underlying DST-OsCKX2-mediated spikelet number.

A biotechnology-based male-sterility system for hybrid seed production in tomato.

Incorporating male sterility into hybrid seed production reduces its cost and ensures high varietal purity. Despite these advantages, male-sterile lines have not been widely used to produce tomato (Solanum lycopersicum) hybrid seeds. We describe the development of a biotechnology-based breeding platform that utilized genic male sterility to produce hybrid seeds. In this platform, we generated a novel male-sterile tomato line by clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 (Cas9)-mediated mutagenesis of a stamen-specific gene SlSTR1 and devised a transgenic maintainer by transforming male-sterile plants with a fertility-restoration gene linked to a seedling-colour gene. Offspring of crosses between a hemizygous maintainer and the homozygous male-sterile plant segregated into 50% non-transgenic male-sterile plants and 50% male-fertile maintainer plants, which could be easily distinguished by seedling colour. This system has great practical potential for hybrid seed breeding and production as it overcomes the problems intrinsic to other male-sterility systems and can be easily adapted for a range of tomato cultivars and diverse vegetable crops.

Mutation of a Conserved Motif of PP2C.D Phosphatases Confers SAUR Immunity and Constitutive Activity.

The phytohormone auxin promotes the growth of plant shoots by stimulating cell expansion via plasma membrane (PM) H+-ATPase activation, which facilitates cell wall loosening and solute uptake. Mechanistic insight was recently obtained by demonstrating that auxin-induced SMALL AUXIN UP RNA (SAUR) proteins inhibit D-CLADE TYPE 2C PROTEIN PHOSPHATASE (PP2C.D) activity, thereby trapping PM H+-ATPases in the phosphorylated, activated state, but how SAURs bind PP2C.D proteins and inhibit their activity is unknown. Here, we identified a highly conserved motif near the C-terminal region of the PP2C.D catalytic domain that is required for SAUR binding in Arabidopsis (Arabidopsis thaliana). Missense mutations in this motif abolished SAUR binding but had no apparent effect on catalytic activity. Consequently, mutant PP2C.D proteins that could not bind SAURs exhibited constitutive activity, as they were immune to SAUR inhibition. In planta expression of SAUR-immune pp2c.d2 or pp2c.d5 derivatives conferred severe cell expansion defects and corresponding constitutively low levels of PM H+-ATPase phosphorylation. These growth defects were not alleviated by either auxin treatment or 35S:StrepII-SAUR19 coexpression. In contrast, a PM H+-ATPase gain-of-function mutation that results in a constitutively active H+ pump partially suppressed SAUR-immune pp2c.d5 phenotypes, demonstrating that impaired PM H+-ATPase function is largely responsible for the reduced growth of the SAUR-immune pp2c.d5 mutant. Together, these findings provide crucial genetic support for SAUR-PP2C.D regulation of cell expansion via modulation of PM H+-ATPase activity. Furthermore, SAUR-immune pp2c.d derivatives provide new genetic tools for elucidating SAUR and PP2C.D functions and manipulating plant organ growth.

MYC2 Orchestrates a Hierarchical Transcriptional Cascade That Regulates Jasmonate-Mediated Plant Immunity in Tomato.

The hormone jasmonate (JA), which functions in plant immunity, regulates resistance to pathogen infection and insect attack through triggering genome-wide transcriptional reprogramming in plants. We show that the basic helix-loop-helix transcription factor (TF) MYC2 in tomato (Solanum lycopersicum) acts downstream of the JA receptor to orchestrate JA-mediated activation of both the wounding and pathogen responses. Using chromatin immunoprecipitation sequencing (ChIP-seq) coupled with RNA sequencing (RNA-seq) assays, we identified 655 MYC2-targeted JA-responsive genes. These genes are highly enriched in Gene Ontology categories related to TFs and the early response to JA, indicating that MYC2 functions at a high hierarchical level to regulate JA-mediated gene transcription. We also identified a group of MYC2-targeted TFs (MTFs) that may directly regulate the JA-induced transcription of late defense genes. Our findings suggest that MYC2 and its downstream MTFs form a hierarchical transcriptional cascade during JA-mediated plant immunity that initiates and amplifies transcriptional output. As proof of concept, we showed that during plant resistance to the necrotrophic pathogen Botrytis cinerea, MYC2 and the MTF JA2-Like form a transcription module that preferentially regulates wounding-responsive genes, whereas MYC2 and the MTF ETHYLENE RESPONSE FACTOR.C3 form a transcription module that preferentially regulates pathogen-responsive genes.

An Arabidopsis Plasma Membrane Proton ATPase Modulates JA Signaling and Is Exploited by the Pseudomonas syringae Effector Protein AvrB for Stomatal Invasion.

Stomata are natural openings through which many pathogenic bacteria enter plants. Successful bacterial pathogens have evolved various virulence factors to promote stomatal opening. Here, we show that the Pseudomonas syringae type III effector protein AvrB induces stomatal opening and enhances bacterial virulence in a manner dependent on RPM1-INTERACTING4 (RIN4), which promotes stomatal opening by positively regulating the Arabidopsis plasma membrane H(+)-ATPase (AHA1), which is presumed to directly regulate guard cell turgor pressure. In support of a role of AHA1 in AvrB-induced stomatal opening, AvrB enhances ATPase activity in plants. Unexpectedly, AHA1 promotes the interaction between the jasmonate (JA) receptor CORONATINE INSENSITIVE1 (COI1) and JASMONATE ZIM-DOMAIN (JAZ) proteins and enhances JA signaling. JA signaling is required for optimum stomatal infection in AHA1-active plants. Similarly, AvrB also induces the COI1-JAZ9 interaction and the degradation of multiple JAZ proteins. AvrB-induced stomatal opening and virulence require the canonical JA signaling pathway, which involves the COI1 and NAC transcription factors. The findings thus point to a previously unknown pathway exploited by P. syringae that acts upstream of COI1 to regulate JA signaling and stomatal opening.

Closely related NAC transcription factors of tomato differentially regulate stomatal closure and reopening during pathogen attack.

To restrict pathogen entry, plants close stomata as an integral part of innate immunity. To counteract this defense, Pseudomonas syringae pv tomato produces coronatine (COR), which mimics jasmonic acid (JA), to reopen stomata for bacterial entry. It is believed that abscisic acid (ABA) plays a central role in regulating bacteria-triggered stomatal closure and that stomatal reopening requires the JA/COR pathway, but the downstream signaling events remain unclear. We studied the stomatal immunity of tomato (Solanum lycopersicum) and report here the distinct roles of two homologous NAC (for NAM, ATAF1,2, and CUC2) transcription factors, JA2 (for jasmonic acid2) and JA2L (for JA2-like), in regulating pathogen-triggered stomatal movement. ABA activates JA2 expression, and genetic manipulation of JA2 revealed its positive role in ABA-mediated stomatal closure. We show that JA2 exerts this effect by regulating the expression of an ABA biosynthetic gene. By contrast, JA and COR activate JA2L expression, and genetic manipulation of JA2L revealed its positive role in JA/COR-mediated stomatal reopening. We show that JA2L executes this effect by regulating the expression of genes involved in the metabolism of salicylic acid. Thus, these closely related NAC proteins differentially regulate pathogen-induced stomatal closure and reopening through distinct mechanisms.

Role of tomato lipoxygenase D in wound-induced jasmonate biosynthesis and plant immunity to insect herbivores.

In response to insect attack and mechanical wounding, plants activate the expression of genes involved in various defense-related processes. A fascinating feature of these inducible defenses is their occurrence both locally at the wounding site and systemically in undamaged leaves throughout the plant. Wound-inducible proteinase inhibitors (PIs) in tomato (Solanum lycopersicum) provide an attractive model to understand the signal transduction events leading from localized injury to the systemic expression of defense-related genes. Among the identified intercellular molecules in regulating systemic wound response of tomato are the peptide signal systemin and the oxylipin signal jasmonic acid (JA). The systemin/JA signaling pathway provides a unique opportunity to investigate, in a single experimental system, the mechanism by which peptide and oxylipin signals interact to coordinate plant systemic immunity. Here we describe the characterization of the tomato suppressor of prosystemin-mediated responses8 (spr8) mutant, which was isolated as a suppressor of (pro)systemin-mediated signaling. spr8 plants exhibit a series of JA-dependent immune deficiencies, including the inability to express wound-responsive genes, abnormal development of glandular trichomes, and severely compromised resistance to cotton bollworm (Helicoverpa armigera) and Botrytis cinerea. Map-based cloning studies demonstrate that the spr8 mutant phenotype results from a point mutation in the catalytic domain of TomLoxD, a chloroplast-localized lipoxygenase involved in JA biosynthesis. We present evidence that overexpression of TomLoxD leads to elevated wound-induced JA biosynthesis, increased expression of wound-responsive genes and, therefore, enhanced resistance to insect herbivory attack and necrotrophic pathogen infection. These results indicate that TomLoxD is involved in wound-induced JA biosynthesis and highlight the application potential of this gene for crop protection against insects and pathogens.

Impact of lamivudine treatment in late pregnancy on the development of the foetal immune response to hepatitis B virus: a meta-analysis in R with the metafor package.

BACKGROUND: Hepatitis B virus (HBV) infection is a worldwide public health burden, especially in Asia and Africa. Concerns were raised that foetal exposure to HBV and antiretroviral therapy (ART) might suppress the innate immune response and reduce the production of hepatitis B surface antibody (HBsAb) in foetuses and infants. We therefore conducted the current study to evaluate the impact of ART on the development of the immune response to HBV in foetuses and infants. METHODS: We selected lamivudine instead of telbivudine or tenofovir as the intervention measurement because it was the oldest and most widely used ART during pregnancy and its safety data have been sufficiently documented. A comprehensive search was conducted in eight electronic databases, including four Chinese and four English databases. Studies that met the following eligibility criteria were included: human randomized controlled trials (RCTs); participants in the treatment group were exclusively exposed to lamivudine; participants in the control group were exposed to placebo, no treatment or hepatitis B immunoglobulin; all participants were HBV-positive pregnant women with a high viral load and the main outcome of interest was neonatal HBsAb seropositivity. Data were tabulated and analysed using R software. RESULTS: Nine RCTs were included and analysed. Compared with controls, lamivudine significantly decreased HBsAb seronegativity in the newborn within 24 h after birth (indicating the foetal immune response to HBV). Similar results were noted in infants within 6-7 months after birth and infants within 12 months (indicating the neonatal immune response to HBV vaccine). CONCLUSIONS: Lamivudine treatment in late pregnancy boosted the foetal immune response to HBV in utero and enhanced the neonatal immune response to hepatitis B vaccine after birth.

Second curettage versus conventional chemotherapy in avoiding unnecessary chemotherapy and reducing the number of chemotherapy courses for patients with gestational trophoblastic neoplasia: A systematic review and meta-analysis.

BACKGROUND: Chemotherapy is the recommended treatment for gestational trophoblastic neoplasia (GTN). Second curettage had been advocated to avoid unnecessary chemotherapy and to reduce the courses of chemotherapy; however, consensus has not been reached as there are arguments claiming its inability of inducing complete regression. OBJECTIVES: The present study was performed to clarify the effectiveness of second curettage for avoiding unnecessary chemotherapy and lowering the number of chemotherapy courses in patients with post-molar GTN. SEARCH STRATEGY: Seven predominant electronic databases were searched, including four English databases and three Chinese databases, from the inception of each database until January 31, 2023. SELECTION CRITERIA: Studies were included if they were: (1) human, (2) explicitly indicated exposure to second curettage, (3) explicitly indicated control to conventional chemotherapy, (4) explicitly indicated the participants were patients with gestational trophoblastic neoplasia (GTN), and (5) compared the outcome of interest as the number of the course of chemotherapy. DATA COLLECTION AND ANALYSIS: Two authors extracted and analyzed the data independently. Disagreements were reconciled by reviewing the full text by a third author. The data of study location, data collection, study design, number of participants, intervention strategy, control strategy, the follow-up period, outcome, adverse events were analyzed. MAIN RESULTS: With regard to avoiding unnecessary chemotherapy, the overall pooled effect size of the second curettage group had a significant advantage over the conventional chemotherapy group with an OR of 0.02 (95% CI: 0.00-0.06). Meanwhile, for reducing the number of chemotherapy courses, the overall pooled effect size of the second curettage group had significant advantage over the conventional chemotherapy group with a mean difference of -2.11 (95% CI: -3.72 to -0.51). CONCLUSION: The second curettage group had a significant advantage over the conventional chemotherapy group in avoiding unnecessary chemotherapy and reducing the number of chemotherapy courses. Further larger multi-center randomized controlled trials should be conducted to confirm our results and to clarify the optimal patients' group for second curettage in patients with post-molar GTN.

The molecular feature of abnormal fetal neuromuscular development after maternal use of telbivudine or tenofovir during pregnancy in rodent model.

AIMS: Maternal treatment with nucleoside analogues such as telbivudine (LdT) and tenofovir disoproxil fumarate (TDF) has been applied worldwide. However, administration of LdT or TDF during pregnancy may affect the fetal neuromuscular development. We conducted the current study to investigate the histological pathology and transcriptomic changes pertaining to the neuromuscular system of the newborn exposed to LdT or TDF during pregnancy in rodent model. MAIN METHODS: Pregnant C57/BL6 mice were randomly divided into three arms and administered either with LdT solution (0.1 ml, 78 mg/kg/d), TDF solution (0.1 ml, 39 mg/kg/d) or normal saline solution (0.1 ml). Pups in each arm were weighed and sacrificed after birth. Both sides of quadriceps femoris muscle of the newborn were obtained. The histological observation was conducted under light microscope. The transcriptional profiling was analyzed with RNA sequencing (RNA seq). KEY FINDINGS: Four types of morphological abnormalities of the newborn neuromuscular system, being clusters of rhabdomyoblasts, skeletal muscle fibrosis, rhabdomyolysis and necrosis and immature muscle fiber bundles, were noted in both LdT group and TDF group. Moreover, both groups showed significantly decreased gross cross-sectional area of muscle fiber and significantly increased percentage of muscle lesion area. RNA seq identified a total of 164 differentially expressed genes (DEGs) essential to fetal neuromuscular development. These DEGs were involved in calcium regulation, phospholipid activity, muscle cell development, the functioning of mitochondria/endoplasmic reticulum/lysosome/cytoskeleton, the regulation of arachidonic acid and the development of nervous system. SIGNIFICANCE: Our findings suggest maternal administration of LdT or TDF lead to abnormal neuromuscular development in offspring mice. Further study should be encouraged to investigate the down-stream signaling pathways.

Biphasic control of cell expansion by auxin coordinates etiolated seedling development.

Seedling emergence is critical for food security. It requires rapid hypocotyl elongation and apical hook formation, both of which are mediated by regulated cell expansion. How these events are coordinated in etiolated seedlings is unclear. Here, we show that biphasic control of cell expansion by the phytohormone auxin underlies this process. Shortly after germination, high auxin levels restrain elongation. This provides a temporal window for apical hook formation, involving a gravity-induced auxin maximum on the eventual concave side of the hook. This auxin maximum induces PP2C.D1 expression, leading to asymmetrical H+-ATPase activity across the hypocotyl that contributes to the differential cell elongation underlying hook development. Subsequently, auxin concentrations decline acropetally and switch from restraining to promoting elongation, thereby driving hypocotyl elongation. Our findings demonstrate how differential auxin concentrations throughout the hypocotyl coordinate etiolated development, leading to successful soil emergence.

Rapid Auxin-Mediated Cell Expansion.

The promotive effect of auxin on shoot cell expansion provided the bioassay used to isolate this central plant hormone nearly a century ago. While the mechanisms underlying auxin perception and signaling to regulate transcription have largely been elucidated, how auxin controls cell expansion is only now attaining molecular-level definition. The good news is that the decades-old acid growth theory invoking plasma membrane H+-ATPase activation is still useful. The better news is that a mechanistic framework has emerged, wherein Small Auxin Up RNA (SAUR) proteins regulate protein phosphatases to control H+-ATPase activity. In this review, we focus on rapid auxin effects, their relationship to H+-ATPase activation and other transporters, and dependence on TIR1/AFB signaling. We also discuss how some observations, such as near-instantaneous effects on ion transport and root growth, do not fit into a single, comprehensive explanation of how auxin controls cell expansion, and where more research is warranted.

A Transcriptional Network Promotes Anthocyanin Biosynthesis in Tomato Flesh.

Dietary anthocyanins are important health-promoting antioxidants that make a major contribution to the quality of fruits. It is intriguing that most tomato cultivars do not produce anthocyanins in fruit. However, the purple tomato variety Indigo Rose, which has the dominant Aft locus combined with the recessive atv locus from wild tomato species, exhibits light-dependent anthocyanin accumulation in the fruit skin. Here, we report that Aft encodes a functional anthocyanin activator named SlAN2-like, while atv encodes a nonfunctional version of the anthocyanin repressor SlMYBATV. The expression of SlAN2-like is responsive to light, and the functional SlAN2-like can activate the expression of both anthocyanin biosynthetic genes and their regulatory genes, suggesting that SlAN2-like acts as a master regulator in the activation of anthocyanin biosynthesis. We further showed that cultivated tomatoes contain nonfunctional alleles of SlAN2-like and therefore fail to produce anthocyanins. Consistently, expression of a functional SlAN2-like gene driven by the fruit-specific promoter in a tomato cultivar led to the activation of the entire anthocyanin biosynthesis pathway and high-level accumulation of anthocyanins in both the peel and flesh. Taken together, our study exemplifies that efficient engineering of complex metabolic pathways could be achieved through tissue-specific expression of master transcriptional regulators.

Gratitude and Adolescents' Subjective Well-Being in School: The Multiple Mediating Roles of Basic Psychological Needs Satisfaction at School.

Based on the relation between gratitude and general subjective well-being (SWB), and Basic Psychological Needs Theory (Ryan and Deci, 2000), the present study's aim was to use structural equation modeling to test the multiple mediational roles of the satisfaction of three basic psychological needs at school in accounting for the association between gratitude and SWB in school (school satisfaction, school affect) in adolescents. A total of 881 Chinese adolescents (427 males; Mean age = 12.97) completed a multi-measure questionnaire that tapped the targeted variables. Findings revealed that gratitude related significantly, positively to adolescents' SWB in school. Moreover, a multiple-mediators analysis suggested that relatedness and competence needs satisfaction at school mediated the relation between gratitude and SWB in school. Lastly, a multiple-mediators analysis also indicated that autonomy needs satisfaction mediated the relation between relatedness and competence needs and SWB in school. Limitations and practical applications of the study were discussed.