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Precise genome editing of Dense and Erect Panicle 1 promotes rice sheath blight resistance and yield production in japonica rice

The primary goals of crop breeding are to enhance yield and improve disease resistance. However, the "trade-off" mechanism, in which signalling pathways for resistance and yield are antagonistically regulated, poses challenges for achieving both simultaneously. Previously, we demonstrated that knock-out mutants of the Dense and Erect Panicle 1 (DEP1) gene can significantly enhance rice resistance to sheath blight (ShB), and we mapped DEP1's association with panicle length. In this study, we discovered that dep1 mutants significantly reduced rice yield. Nonetheless, truncated DEP1 was able to achieve both ShB resistance and yield increase in japonica rice. To further explore the function of truncated DEP1 in promoting yield and ShB resistance, we generated CRISPR/Cas9-mediated genome editing mutants, including a full-length deletion mutant of DEP1, named dep1, and a truncated version, dep1-cys. Upon inoculation with Rhizoctonia solani, the dep1-cys mutant demonstrated stronger ShB resistance than the dep1 mutant. Additionally, dep1-cys increased yield per plant, whereas dep1 reduced it. Compared to the full DEP1 protein, the truncated DEP1 (dep1-cys) demonstrated a decreased interaction affinity with IDD14 and increased affinity with IDD10, which are known to positively and negatively regulate ShB resistance through the activation of PIN1a and ETR2, respectively. The dep1-cys mutant exhibited higher PIN1a and lower ETR2 expression than wild-type plants, suggesting that dep1-cys modulated IDD14 and IDD10 interactions to regulate PIN1a and ETR2, thereby enhancing ShB resistance. Overall, these data indicate that precise genome editing of DEP1 could simultaneously improve both ShB resistance and yield, effectively mitigating trade-off regulation in rice.

IDD10-NAC079 transcription factor complex regulates sheath blight resistance by inhibiting ethylene signaling in rice

INTRODUCTION

Rhizoctonia solani Kühn is a pathogen causing rice sheath blight (ShB). Ammonium transporter 1 (AMT1) promotes resistance of rice to ShB by activating ethylene signaling. However, how AMT1 activates ethylene signaling remains unclear.

OBJECTIVE

In this study, the indeterminate domain 10 (IDD10)-NAC079 interaction model was used to investigate whether ethylene signaling is modulated downstream of ammonium signaling and modulates ammonium-mediated ShB resistance.

METHODS

RT-qPCR assay was used to identify the relative expression levels of nitrogen and ethylene related genes. Yeast two-hybrid assays, Bimolecular fluorescence complementation (BiFC) and Co-immunoprecipitation (Co-IP) assay were conducted to verify the IDD10-NAC079-calcineurin B-like interacting protein kinase 31 (CIPK31) transcriptional complex. Yeast one-hybrid assay, Chromatin immunoprecipitation (ChIP) assay, and Electrophoretic mobility shift assay (EMSA) were used to verify whether ETR2 was activated by IDD10 and NAC079. Ethylene quantification assay was used to verify ethylene content in IDD10 transgenic plants. Genetic analysis is used to detect the response of IDD10, NAC079 and CIPK31 to ShB infestation.

RESULTS

IDD10-NAC079 forms a transcription complex that activates ETR2 to inhibit the ethylene signaling pathway to negatively regulating ShB resistance. CIPK31 interacts and phosphorylates NAC079 to enhance its transcriptional activation activity. In addition, AMT1-mediated ammonium absorption and subsequent N assimilation inhibit the expression of IDD10 and CIPK31 to activate the ethylene signaling pathway, which positively regulates ShB resistance.

CONCLUSION

The study identified the link between ammonium and ethylene signaling and improved the understanding of the rice resistance mechanism.

Transcriptional activation of BolBCAT4 genes enhanced aliphatic glucosinolate accumulation in cabbage

Aliphatic glucosinolates are a large group of plant-specialized metabolites in Brassica vegetables, and some of their degradation products are key nutrients with significant beneficial effects on human health. Increasing the nutritional quality is one of the central research questions and breeding goals for Brassica vegetables. Major progress has been made in understanding transcriptional regulation of aliphatic glucosinolates biosynthesis in the model plant, while little is known about it in Brassica vegetables. In this study, we used cabbage to study the transcriptional regulation of BolBCAT4 genes, the first set of biosynthetic genes in methionine-derived aliphatic glucosinolate metabolism, and identified and functionally validated four upstream positive regulators of BolBCAT4 genes, BolMYB3R, BolbHLH153, BolMED4 and BolERF74, with consistent phenotypic effects of inducing short-chain aliphatic glucosinolates, including glucoraphanin. Our work confirmed the biological functions of BolBCAT4 genes, identified dozens of candidate upstream regulators, and provided valuable regulatory mechanisms and breeding targets for enhancing the nutritional quality of cabbage.

Novel Regulators and Their Epistatic Networks in Arabidopsis' Defence Responses to Alternaria alternata Infection

Necrotrophic pathogens cause serious threats to agricultural crops, and understanding the resistance genes and their genetic networks is key to breeding new plant cultivars with better resistance traits. Although Alternaria alternata causes black spot in important leafy brassica vegetables, and leads to significant loss of yield and food quality, little is known about plant-A. alternata interactions. In this study, we used a unique and large collection of single, double and triple mutant lines of defence metabolite regulators in Arabidopsis to explore how these transcription factors and their epistatic networks may influence A. alternata infections. This identified nine novel regulators and 20 pairs of epistatic interactions that modulate Arabidopsis plants' defence responses to A. alternata infection. We further showed that the glucosinolate 4-methoxy-indol-3-ylmethyl is the only glucosinolate consistently responsive to A. alternata infection in Col-0 ecotype. With the further exploration of the regulators and the genetic networks on modulating the accumulation of glucosinolates under A. alternata infection, an inverted triangle regulatory model was proposed for Arabidopsis plants' defence responses at a metabolic level and a phenotypic level.

Effects of particle size on toxicity, bioaccumulation, and translocation of zinc oxide nanoparticles to bok choy (Brassica chinensis L.) in garden soil

The indiscriminate use of zinc oxide nanoparticles (ZnO NPs) in daily life can lead to their release into soil environment. These ZnO NPs can be taken up by crops and translocated to their edible part, potentially causing risks to the ecosystem and human health. In this study, we conducted pot experiments to determine phytotoxicity, bioaccumulation and translocation depending on the size (10 - 30 nm, 80 - 200 nm and 300 nm diameter) and concentration (0, 100, 500 and 1000 mg Zn/kg) of ZnO NPs and Zn ion (Zn2+) in bok choy, a leafy green vegetable crop. After 14 days of exposure, our results showed that large-sized ZnO NPs (i.e., 300 nm) at the highest concentration exhibited greater phytotoxicity, including obstruction of leaf and root weight (42.5 % and 33.8 %, respectively) and reduction of chlorophyll a and b content (50.2 % and 85.2 %, respectively), as well as changes in the activities of oxidative stress responses compared to those of small-sized ZnO NPs, although their translocation ability was relatively lower than that of smaller ones. The translocation factor (TF) values decreased as the size of ZnO NPs increased, with TF values of 0.68 for 10 - 30 nm, 0.55 for 80 - 200 nm, and 0.27 for 300 nm ZnO NPs, all at the highest exposure concentration. Both the results of micro X-ray fluorescence (μ-XRF) spectrometer and bio-transmission electron microscopy (bio-TEM) showed that the Zn elements were mainly localized at the edges of leaves exposed to small-sized ZnO NPs. However, the Zn elements upon exposure to large-sized ZnO NP were primarily observed in the primary veins of leaves in the μ-XRF data, indicating a limitation in their ability to translocate from roots to leaves. This study not only advances our comprehension of the environmental impact of nanotechnology but also holds considerable implications for the future of sustainable agriculture and food safety.

Programmed cell death regulator BAP2 is required for IRE1-mediated unfolded protein response in Arabidopsis

Environmental and physiological situations can challenge the balance between protein synthesis and folding capacity of the endoplasmic reticulum (ER) and cause ER stress, a potentially lethal condition. The unfolded protein response (UPR) restores ER homeostasis or actuates programmed cell death (PCD) when ER stress is unresolved. The cell fate determination mechanisms of the UPR are not well understood, especially in plants. Here, we integrate genetics and ER stress profiling with natural variation and quantitative trait locus analysis of 350 natural accessions of the model species Arabidopsis thaliana. Our analyses implicate a single nucleotide polymorphism to the loss of function of the general PCD regulator BON-ASSOCIATED PROTEIN2 (BAP2) in UPR outcomes. We establish that ER stress-induced BAP2 expression is antagonistically regulated by the UPR master regulator, inositol-requiring enzyme 1 (IRE1), and that BAP2 controls adaptive UPR amplitude in ER stress and ignites pro-death mechanisms in conditions of UPR insufficiency.

Gibberellic acid signaling promotes resistance to saline-alkaline stress by increasing the uptake of ammonium in rice

Gibberellic acid (GA) plays important roles in diverse biological processes in plants. However, its function in rice (Oryza sativa) resistance to saline-alkaline (SAK) stress is unclear. This study showed that SAK stimuli changed GA signaling gene expression levels. Genetic analyses using the mutants of key GA signaling regulators, Slender rice 1 (SLR1) and Dwarf 1(D1), demonstrated that SLR1 negatively, while D1 positively regulated the resistance of rice to SAK stress, suggesting that the GA signaling positively regulates the resistance of rice to SAK. Further analyses revealed that SLR1 interacted with and inhibited the transcription activation activity of IDD10 and bZIP23. Furthermore, IDD10 interacted with bZIP23 to activate Ammonium transporter 1;2 (AMT1;2), and slr1, IDD10 OX and bZIP23 OX accumulated more ammonium (NH4+), while idd10 and bzip23 accumulated less NH4+ than the wild-type (WT). In addition, the bzip23 mutant was more sensitive to SAK, while bZIP23 OX was less sensitive compared with the WT, suggesting that bZIP23 positively regulates the resistance of rice to SAK. These findings demonstrate that GA signaling promoted rice's SAK resistance by regulating NH4+ uptake through the SLR1-IDD10-bZIP23 pathway.

Host adaptation and specialization in Tetranychidae mites

Composite generalist herbivores are comprised of host-adapted populations that retain the ability to shift hosts. The degree and overlap of mechanisms used by host-adapted generalist and specialist herbivores to overcome the same host plant defenses are largely unknown. Tetranychidae mites are exceptionally suited to address the relationship between host adaptation and specialization in herbivores as this group harbors closely related species with remarkably different host ranges-an extreme generalist the two-spotted spider mite (Tetranychus urticae Koch [Tu]) and the Solanaceous specialist Tetranychus evansi (Te). Here, we used tomato-adapted two-spotted spider mite (Tu-A) and Te populations to compare mechanisms underlying their host adaptation and specialization. We show that both mites attenuate induced tomato defenses, including protease inhibitors (PIs) that target mite cathepsin L digestive proteases. While Te solely relies on transcriptional attenuation of PI induction, Tu and Tu-A have elevated constitutive activity of cathepsin L proteases, making them less susceptible to plant anti-digestive proteins. Tu-A and Te also rely on detoxification of tomato constitutive defenses. Te uses esterase and P450 activities, while Tu-A depends on the activity of all major detoxification enzymatic classes to disarm tomato defensive compounds to a lesser extent. Thus, even though both Tu-A and Te use similar mechanisms to counteract tomato defenses, Te can better cope with them. This finding is congruent with the ecological and evolutionary times required to establish mite adaptation and specialization states, respectively.

Nanoscale Structure-Property Relations in Self-Regulated Polymer-Grafted Nanoparticle Composite Structures

Using a model system of poly(methyl methacrylate)-grafted silica nanoparticles (PMMA-NP) and poly(styrene-ran-acrylonitrile) (SAN), we generate unique polymer nanocomposite (PNC) morphologies by balancing the degree of surface enrichment, phase separation, and wetting within the films. Depending on the annealing temperature and time, thin films undergo different stages of phase evolution, resulting in homogeneously dispersed systems at low temperatures, enriched PMMA-NP layers at the PNC interfaces at intermediate temperatures, and three-dimensional bicontinuous structures of PMMA-NP pillars sandwiched between two PMMA-NP wetting layers at high temperatures. Using a combination of atomic force microscopy (AFM), AFM nanoindentation, contact angle goniometry, and optical microscopy, we show that these self-regulated structures lead to nanocomposites with increased elastic modulus, hardness, and thermal stability compared to analogous PMMA/SAN blends. These studies demonstrate the ability to reliably control the size and spatial correlations of both the surface-enriched and phase-separated nanocomposite microstructures, which have attractive technological applications where properties such as wettability, toughness, and wear resistance are important. In addition, these morphologies lend themselves to substantially broader applications, including: (1) structural color applications, (2) tuning optical adsorption, and (3) barrier coatings.

Comparative bioaccumulation, translocation, and phytotoxicity of metal oxide nanoparticles and metal ions in soil-crop system

Exposure of the soil environment to metal nanoparticles (MNPs) has been extensive because of their indiscriminate use and the disposal of MNP products in various applications. In MNP-amended soil, various crops can absorb the nanoparticles, and accumulation of the MNPs in farm products has potential risks for bioconcentration in humans and livestock. Here, we evaluated the comparative bioaccumulation, translocation, and phytotoxicity of MNPs (ZnO and CuO NPs) and metal ions (Zn(NO3)2 and Cu(NO3)2) in four different crops, namely lettuce, radish, bok choy, and tomato. We carried out pot experiments to evaluate the phytotoxicity in the crops from the presence of MNPs and metal ions. Phytotoxicity from different treatments differed depending on the plant species, and metal types. In addition, exposure to Zn and Cu showed positive dose-dependent effects on their bioaccumulation in each crop. However, there were no significant differences in metal bioaccumulation depending on whether the crops were exposed to MNPs or metal ions. By calculating the bioconcentration factor (BCF) and translocation factor (TF), we were able to estimate the biological uptake and translocation abilities of MNPs and metal ions for each crop. It was found that lettuce and radish had greater BCFs than bok choy and tomato, while bok choy and tomato had higher TFs. Also, the uptake and translocation of Zn were better than those of Cu. However, the values for BCF and TF for each crop showed no significant differences between MNP and metal ion exposure. A micro X-ray fluorescence (μ-XRF) spectrometer analysis demonstrated that only Zn elements appeared in the primary veins and edges of all leaves and the storage root of radish. Our study aims to estimate bioaccumulation, translocation, and the implied potential risks from MNPs accumulated in different plant species.

The evening complex promotes maize flowering and adaptation to temperate regions

Maize (Zea mays) originated in southern Mexico and has spread over a wide latitudinal range. Maize expansion from tropical to temperate regions has necessitated a reduction of its photoperiod sensitivity. In this study, we cloned a quantitative trait locus (QTL) regulating flowering time in maize and show that the maize ortholog of Arabidopsis thaliana EARLY FLOWERING3, ZmELF3.1, is the causal locus. We demonstrate that ZmELF3.1 and ZmELF3.2 proteins can physically interact with ZmELF4.1/4.2 and ZmLUX1/2, to form evening complex(es; ECs) in the maize circadian clock. Loss-of-function mutants for ZmELF3.1/3.2 and ZmLUX1/2 exhibited delayed flowering under long-day and short-day conditions. We show that EC directly represses the expression of several flowering suppressor genes, such as the CONSTANS, CONSTANS-LIKE, TOC1 (CCT) genes ZmCCT9 and ZmCCT10, ZmCONSTANS-LIKE 3, and the PSEUDORESPONSE REGULATOR (PRR) genes ZmPRR37a and ZmPRR73, thus alleviating their inhibition, allowing florigen gene expression and promoting flowering. Further, we identify two closely linked retrotransposons located in the ZmELF3.1 promoter that regulate the expression levels of ZmELF3.1 and may have been positively selected during postdomestication spread of maize from tropical to temperate regions during the pre-Columbian era. These findings provide insights into circadian clock-mediated regulation of photoperiodic flowering in maize and new targets of genetic improvement for breeding.

Vicarious learning and communication self-efficacy: A pediatric end-of-life simulation for pre-licensure nursing students

BACKGROUND

End-of-life clinical experiences, particularly in pediatrics, are quite limited for pre-licensure nursing students. Though effective, end-of-life simulations can be costly, require facilitators trained in palliative and end-of-life care, and are restricted by limited space and time availability. Such barriers prompt the question as to whether there is an effective alternative to simulation by which students can gain improved self-efficacy in therapeutic communication during pediatric end-of-life situations.

PURPOSE

Bandura's Social Cognitive Theory and work exploring self-efficacy posits that vicarious learning provides learners opportunities to gain experience and knowledge through observation of peers in simulated settings. This study evaluated the effectiveness of vicarious versus active learning on pre-licensure nursing students' perceived self-efficacy in providing therapeutic communication during a pediatric end-of-life situation.

METHOD

Data were collected over three time points - pre-simulation, post-simulation, and post-debriefing - using a modified Self-Efficacy in Communication Scale.

RESULTS

Learners in both groups had significant improvement in self-efficacy across all time points. Only two items had significant differences between vicarious and active learner groups, but the effect was minor.

CONCLUSION

Vicarious learning presents as a viable pedagogical approach for providing pre-licensure nursing students important learning opportunities related to pediatric end-of-life simulations during both the scenario and debriefing.

Maize Seedling Growth and Hormone Response Assays Using the Rolled Towel Method

Root system architecture is a critical factor in maize health and stress resilience. Determining the genetic and environmental factors that shape maize root system architecture is an active research area. However, the ability to phenotype juvenile root systems is hindered by the use of field-grown and soil-based systems. An alternative to soil- and field-based growing conditions for maize seedlings is a controlled environment with a soil-free medium, which can facilitate root system phenotyping. Here, we describe how to grow maize under soil-free conditions for up to 12 days to facilitate root phenotyping. Maize seeds are sterilized and planted on specialized seed germination paper to minimize fungal contamination and ensure synchronized seedling growth, followed by imaging at the desired time point. The root images are then analyzed to quantify traits of interest, such as primary root length, lateral root density, seminal root length, and seminal root number. In addition, juvenile shoot traits can be quantified using manual annotation methods. We also outline the steps for performing rigorous hormone response assays for four classical phytohormones: auxin, brassinosteroid, cytokinin, and jasmonic acid. This protocol can be rapidly scaled up and is compatible with genetic screens and sample collection for downstream molecular analyses such as transcriptomics and proteomics. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Maize seedling rolled towel assay and phenotyping Basic Protocol 2: Maize seedling hormone response assays using the rolled towel assay.

β-Cyanoalanine synthase protects mites against Arabidopsis defenses

Glucosinolates are antiherbivory chemical defense compounds in Arabidopsis (Arabidopsis thaliana). Specialist herbivores that feed on brassicaceous plants have evolved various mechanisms aimed at preventing the formation of toxic isothiocyanates. In contrast, generalist herbivores typically detoxify isothiocyanates through glutathione conjugation upon exposure. Here, we examined the response of an extreme generalist herbivore, the two-spotted spider mite Tetranychus urticae (Koch), to indole glucosinolates. Tetranychus urticae is a composite generalist whose individual populations have a restricted host range but have an ability to rapidly adapt to initially unfavorable plant hosts. Through comparative transcriptomic analysis of mite populations that have differential susceptibilities to Arabidopsis defenses, we identified β-cyanoalanine synthase of T. urticae (TuCAS), which encodes an enzyme with dual cysteine and β-cyanoalanine synthase activities. We combined Arabidopsis genetics, chemical complementation and mite reverse genetics to show that TuCAS is required for mite adaptation to Arabidopsis through its β-cyanoalanine synthase activity. Consistent with the β-cyanoalanine synthase role in detoxification of hydrogen cyanide (HCN), we discovered that upon mite herbivory, Arabidopsis plants release HCN. We further demonstrated that indole glucosinolates are sufficient for cyanide formation. Overall, our study uncovered Arabidopsis defenses that rely on indole glucosinolate-dependent cyanide for protection against mite herbivory. In response, Arabidopsis-adapted mites utilize the β-cyanoalanine synthase activity of TuCAS to counter cyanide toxicity, highlighting the mite's ability to activate resistant traits that enable this extreme polyphagous herbivore to exploit cyanogenic host plants.

Recruitment of an ancient branching program to suppress carpel development in maize flowers

Carpels in maize undergo programmed cell death in half of the flowers initiated in ears and in all flowers in tassels. The HD-ZIP I transcription factor gene GRASSY TILLERS1 (GT1) is one of only a few genes known to regulate this process. To identify additional regulators of carpel suppression, we performed a gt1 enhancer screen and found a genetic interaction between gt1 and ramosa3 (ra3). RA3 is a classic inflorescence meristem determinacy gene that encodes a trehalose-6-phosphate (T6P) phosphatase (TPP). Dissection of floral development revealed that ra3 single mutants have partially derepressed carpels, whereas gt1;ra3 double mutants have completely derepressed carpels. Surprisingly, gt1 suppresses ra3 inflorescence branching, revealing a role for gt1 in meristem determinacy. Supporting these genetic interactions, GT1 and RA3 proteins colocalize to carpel nuclei in developing flowers. Global expression profiling revealed common genes misregulated in single and double mutant flowers, as well as in derepressed gt1 axillary meristems. Indeed, we found that ra3 enhances gt1 vegetative branching, similar to the roles for the trehalose pathway and GT1 homologs in the eudicots. This functional conservation over ∼160 million years of evolution reveals ancient roles for GT1-like genes and the trehalose pathway in regulating axillary meristem suppression, later recruited to mediate carpel suppression. Our findings expose hidden pleiotropy of classic maize genes and show how an ancient developmental program was redeployed to sculpt floral form.

Recruitment of an ancient branching program to suppress carpel development in maize flowers

Floral morphology is immensely diverse. One developmental process acting to shape this diversity is growth suppression. For example, grass flowers exhibit extreme diversity in floral sexuality, arising through differential suppression of stamens or carpels. The genes regulating this growth suppression and how they have evolved remain largely unknown. We discovered that two classic developmental genes with ancient roles in controlling vegetative branching were recruited to suppress carpel development in maize. Our results highlight the power of forward genetics to reveal unpredictable genetic interactions and hidden pleiotropy of developmental genes. More broadly, our findings illustrate how ancient gene functions are recruited to new developmental contexts in the evolution of plant form.

Carpels in maize undergo programmed cell death in half of the flowers initiated in ears and in all flowers in tassels. The HD-ZIP I transcription factor gene GRASSY TILLERS1 (GT1) is one of only a few genes known to regulate this process. To identify additional regulators of carpel suppression, we performed a gt1 enhancer screen and found a genetic interaction between gt1 and ramosa3 (ra3). RA3 is a classic inflorescence meristem determinacy gene that encodes a trehalose-6-phosphate (T6P) phosphatase (TPP). Dissection of floral development revealed that ra3 single mutants have partially derepressed carpels, whereas gt1;ra3 double mutants have completely derepressed carpels. Surprisingly, gt1 suppresses ra3 inflorescence branching, revealing a role for gt1 in meristem determinacy. Supporting these genetic interactions, GT1 and RA3 proteins colocalize to carpel nuclei in developing flowers. Global expression profiling revealed common genes misregulated in single and double mutant flowers, as well as in derepressed gt1 axillary meristems. Indeed, we found that ra3 enhances gt1 vegetative branching, similar to the roles for the trehalose pathway and GT1 homologs in the eudicots. This functional conservation over ∼160 million years of evolution reveals ancient roles for GT1-like genes and the trehalose pathway in regulating axillary meristem suppression, later recruited to mediate carpel suppression. Our findings expose hidden pleiotropy of classic maize genes and show how an ancient developmental program was redeployed to sculpt floral form.

Rapid specialization of counter defenses enables two-spotted spider mite to adapt to novel plant hosts

Genetic adaptation, occurring over a long evolutionary time, enables host-specialized herbivores to develop novel resistance traits and to efficiently counteract the defenses of a narrow range of host plants. In contrast, physiological acclimation, leading to the suppression and/or detoxification of host defenses, is hypothesized to enable broad generalists to shift between plant hosts. However, the host adaptation mechanisms used by generalists composed of host-adapted populations are not known. Two-spotted spider mite (TSSM; Tetranychus urticae) is an extreme generalist herbivore whose individual populations perform well only on a subset of potential hosts. We combined experimental evolution, Arabidopsis thaliana genetics, mite reverse genetics, and pharmacological approaches to examine mite host adaptation upon the shift of a bean (Phaseolus vulgaris)-adapted population to Arabidopsis. We showed that cytochrome P450 monooxygenases are required for mite adaptation to Arabidopsis. We identified activities of two tiers of P450s: general xenobiotic-responsive P450s that have a limited contribution to mite adaptation to Arabidopsis and adaptation-associated P450s that efficiently counteract Arabidopsis defenses. In approximately 25 generations of mite selection on Arabidopsis plants, mites evolved highly efficient detoxification-based adaptation, characteristic of specialist herbivores. This demonstrates that specialization to plant resistance traits can occur within the ecological timescale, enabling the TSSM to shift to novel plant hosts.

Knockout of FER decreases cadmium concentration in roots of Arabidopsis thaliana by inhibiting the pathway related to iron uptake

Identifying the genes that affect cadmium (Cd) accumulation in plants is a prerequisite for minimizing dietary Cd uptake from contaminated edible parts of plants by genetic engineering. This study showed that Cd stress inhibited the expression of FERONIA (FER) gene in the roots of wild-type Arabidopsis. Knockout of FER in fer-4 mutants downregulated the Cd-induced expression of several genes related to iron (Fe) uptake, including IRT1, bHLH38, NRAMP1, NRAMP3, FRO2 andFIT. In addition, the Cd concentration in fer-4 mutant roots reduced to approximately half of that in the wild-type seedlings. As a result, the Cd tolerance of fer-4 was higher. Furthermore, increased Fe supplementation had little effect on the Cd tolerance of fer-4 mutants, but clearly improved the Cd tolerance of wild-type seedlings, showing that the alleviation of Cd toxicity by Fe depends on the action of FER. Taken together, the findings demonstrate that the knockout of FER might provide a strategy to reduce Cd contamination and improve the Cd tolerance in plants by regulating the pathways related to Fe uptake.

"Developing Capabilities". Inclusive Extracurricular Enrichment Programs to Improve the Well-Being of Gifted Adolescents

The educational inclusion of gifted students requires not only equity but also emotional accessibility and social participation. However, different studies indicate that gifted students constitute a vulnerable group (for example, the incidence of bullying is higher). Psychosocial variables are determinants for the development and expression of giftedness, particularly during adolescence. This study analyzes the impact of an inclusive extracurricular enrichment program for gifted secondary school students on the well-being of adolescents. The program was based on the enrichment model of Renzulli and Reis (2016). The objective was to develop a cluster to facilitate high-achieving learning in collaboration with teachers, administrators, and guidance counselors from their schools as well as university professors and students that would address their emotions and socialization across the board and benefit or involve their peers in their regular classrooms. The intervention took place over two years: eight sessions, one afternoon per week, for five months during each school year. The sample consisted of 47 students from the first and second years of compulsory secondary education (Educación Secundaria Obligatoria - ESO) (age, mean (M) = 12.57, standard deviation (SD) = 0.82) during the first year and 27 students from the first, second, and third years of ESO (age, M = 13.48, SD = 0.94) during the second year; 61.4% were girls. Participants completed a questionnaire before (T1) and (T3) and after (T2) and (T4) each intervention. The results show better outcomes for psychological and subjective well-being, more positive moods, and a significant reduction in school fears. The results from this study indicate the importance of educational screening and support for gifted students to promote their well-being through collaborative enrichment activities.

Multiple indole glucosinolates and myrosinases defend Arabidopsis against Tetranychus urticae herbivory

Arabidopsis (Arabidopsis thaliana) defenses against herbivores are regulated by the jasmonate (JA) hormonal signaling pathway, which leads to the production of a plethora of defense compounds. Arabidopsis defense compounds include tryptophan-derived metabolites, which limit Arabidopsis infestation by the generalist herbivore two-spotted spider mite, Tetranychus urticae. However, the phytochemicals responsible for Arabidopsis protection against T. urticae are unknown. Here, we used Arabidopsis mutants disrupted in the synthesis of tryptophan-derived secondary metabolites to identify phytochemicals involved in the defense against T. urticae. We show that of the three tryptophan-dependent pathways found in Arabidopsis, the indole glucosinolate (IG) pathway is necessary and sufficient to assure tryptophan-mediated defense against T. urticae. We demonstrate that all three IGs can limit T. urticae herbivory, but that they must be processed by myrosinases to hinder T. urticae oviposition. Putative IG breakdown products were detected in mite-infested leaves, suggesting in planta processing by myrosinases. Finally, we demonstrate that besides IGs, there are additional JA-regulated defenses that control T. urticae herbivory. Together, our results reveal the complexity of Arabidopsis defenses against T. urticae that rely on multiple IGs, specific myrosinases, and additional JA-dependent defenses.

Improved Plant Nitrate Status Involves in Flowering Induction by Extended Photoperiod

The floral transition stage is pivotal for sustaining plant populations and is affected by several environmental factors, including photoperiod. However, the mechanisms underlying photoperiodic flowering responses are not fully understood. Herein, we have shown that exposure to an extended photoperiod effectively induced early flowering in Arabidopsis plants, at a range of different nitrate concentrations. However, these photoperiodic flowering responses were attenuated when the nitrate levels were suboptimal for flowering. An extended photoperiod also improved the root nitrate uptake of by NITRATE TRANSPORTER 1.1 (NRT1.1) and NITRATE TRANSPORTER 2.1 (NRT2.1), whereas the loss of function of NRT1.1/NRT2.1 in the nrt1.1-1/2.1-2 mutants suppressed the expression of the key flowering genes CONSTANS (CO) and FLOWERING LOCUS T (FT), and reduced the sensitivity of the photoperiodic flowering responses to elevated levels of nitrate. These results suggest that the upregulation of root nitrate uptake during extended photoperiods, contributed to the observed early flowering. The results also showed that the sensitivity of photoperiodic flowering responses to elevated levels of nitrate, were also reduced by either the replacement of nitrate with its assimilation intermediate product, ammonium, or by the dysfunction of the nitrate assimilation pathway. This indicates that nitrate serves as both a nutrient source for plant growth and as a signaling molecule for floral induction during extended photoperiods.

DiCoExpress: a tool to process multifactorial RNAseq experiments from quality controls to co-expression analysis through differential analysis based on contrasts inside GLM models

BACKGROUND

RNAseq is nowadays the method of choice for transcriptome analysis. In the last decades, a high number of statistical methods, and associated bioinformatics tools, for RNAseq analysis were developed. More recently, statistical studies realised neutral comparison studies using benchmark datasets, shedding light on the most appropriate approaches for RNAseq data analysis.

RESULTS

DiCoExpress is a script-based tool implemented in R that includes methods chosen based on their performance in neutral comparisons studies. DiCoExpress uses pre-existing R packages including FactoMineR, edgeR and coseq, to perform quality control, differential, and co-expression analysis of RNAseq data. Users can perform the full analysis, providing a mapped read expression data file and a file containing the information on the experimental design. Following the quality control step, the user can move on to the differential expression analysis performed using generalized linear models thanks to the automated contrast writing function. A co-expression analysis is implemented using the coseq package. Lists of differentially expressed genes and identified co-expression clusters are automatically analyzed for enrichment of annotations provided by the user. We used DiCoExpress to analyze a publicly available RNAseq dataset on the transcriptional response of Brassica napus L. to silicon treatment in plant roots and mature leaves. This dataset, including two biological factors and three replicates for each condition, allowed us to demonstrate in a tutorial all the features of DiCoExpress.

CONCLUSIONS

DiCoExpress is an R script-based tool allowing users to perform a full RNAseq analysis from quality controls to co-expression analysis through differential analysis based on contrasts inside generalized linear models. DiCoExpress focuses on the statistical modelling of gene expression according to the experimental design and facilitates the data analysis leading the biological interpretation of the results.

CBL-INTERACTING PROTEIN KINASE 9 regulates ammonium-dependent root growth downstream of IDD10 in rice (Oryza sativa)

BACKGROUND AND AIMS

INDETERMINATE DOMAIN 10 (IDD10) is a key transcription factor gene that activates the expression of a large number of NH4+-responsive genes including AMMONIUM TRANSPORTER 1;2 (AMT1;2). Primary root growth of rice (Oryza sativa) idd10 mutants is hypersensitive to NH4+. The involvement of CALCINEURIN B-LIKE INTERACTING PROTEIN KINASE (CIPK) genes in the action of IDD10 on NH4+-mediated root growth was investigated.

METHODS

Quantitative reverse transcription-PCR was used to analyse NH4+- and IDD10-dependent expression of CIPK genes. IDD10-regulated CIPK target genes were identified using electrophoretic mobility shift assays, chromatin immunoprecipitation and transient transcription assays. Root growth rate, ammonium content and 15N uptake of cipk mutants were measured to determine their sensitivity to NH4+ and to compare these phenotypes with those of idd10. The genetic relationship between CIPK9 OX and idd10 was investigated by crosses between the CIPK9 and IDD10 lines.

KEY RESULTS

AMT1;2 was overexpressed in idd10 to determine whether NH4+-hypersensitive root growth of idd10 resulted from limitations in NH4+ uptake or from low cellular levels of NH4+. High NH4+ levels in idd10/AMT1;2 OX did not rescue the root growth defect. Next, the involvement of CIPK genes in NH4+-dependent root growth and interactions between IDD10 and CIPK genes was investigated. Molecular analysis revealed that IDD10 directly activated transcription of CIPK9 and CIPK14. Expression of CIPK8, 9, 14/15 and 23 was sensitive to exogenous NH4+. Further studies revealed that cipk9 and idd10 had almost identical NH4+-sensitive root phenotypes, including low efficiency of 15NH4+ uptake. Analysis of plants containing both idd10 and CIPK9 OX showed that CIPK9 OX could rescue the NH4+-dependent root growth defects of idd10.

CONCLUSIONS

CIPK9 was involved in NH4+-dependent root growth and appeared to act downstream of IDD10. This information will be useful in future explorations of NH4+ signalling in plants.

Characterization of Maize Phytochrome-Interacting Factors in Light Signaling and Photomorphogenesis

Increasing planting density has been an effective means of increasing maize (Zea mays ssp. mays) yield per unit of land area over the past few decades. However, high-density planting will cause a reduction in the ratio of red to far-red incident light, which could trigger the shade avoidance syndrome and reduce yield. The molecular mechanisms regulating the shade avoidance syndrome are well established in Arabidopsis (Arabidopsis thaliana) but poorly understood in maize. Here, we conducted an initial functional characterization of the maize Phytochrome-Interacting Factor (PIF) gene family in regulating light signaling and photomorphogenesis. The maize genome contains seven distinct PIF genes, which could be grouped into three subfamilies: ZmPIF3s, ZmPIF4s, and ZmPIF5s Similar to the Arabidopsis PIFs, all ZmPIF proteins are exclusively localized to the nucleus and most of them can form nuclear bodies upon light irradiation. We show that all of the ZmPIF proteins could interact with ZmphyB. Heterologous expression of each ZmPIF member could partially or fully rescue the phenotype of the Arabidopsis pifq mutant, and some of these proteins conferred enhanced shade avoidance syndrome in Arabidopsis. Interestingly, all ZmPIF proteins expressed in Arabidopsis are much more stable than their Arabidopsis counterparts upon exposure to red light. Moreover, the Zmpif3, Zmpif4, and Zmpif5 knockout mutants generated via CRISPR/Cas9 technology all showed severely suppressed mesocotyl elongation in dark-grown seedlings and were less responsive to simulated shade treatment. Taken together, our results reveal both conserved and distinct molecular properties of ZmPIFs in regulating light signaling and photomorphogenesis in maize.

Gene expression responses of tomato inoculated with Pectobacterium carotovorum subsp. carotovorum

Defense responses of tomato (Solanum lycopersicum L.) against attack by Pectobacterium carotovorum subsp. carotovorum (Pcc), the causal agent of soft rot diseases, were studied. The expression of some tomato defense genes were evaluated by real‐time PCR quantification analysis, 24 and 72 hr after actively growing tomato plants were inoculated with Pcc. These included: MYB transcriptor factor, ethylene response element‐binding protein, suppressor of the G2 allele of Skp1, cytochrome P450, small Sar1 GTPase, hydroxycinnamoyl‐CoA:quinate hydroxycinnamoyl transferase, pathogenesis‐related protein 1a, endo‐1,3‐beta‐glucanase, chitinase, proteinase inhibitor, defensin, CC‐NBS‐LRR resistance protein, and phenylalanine ammonia lyase. The results showed dynamic transcriptomic changes, with transcripts exhibiting different expression kinetics at 24 and 72 hr to confer resistance to tomato against Pcc infection.

Development of near infrared spectroscopy methodology for human albumin determination using a new calibration approach

Though near infrared spectroscopy (NIRS) has been applied widely in the field of pharmaceutical, there is still a bottleneck which limits its development. The main barrier is that conventional NIRS calibration method is based on experiences and trials, which causes the established model is not stable and difficult to explain. Therefore, a new strategy which was based on design of experiment (DoE) combined with statistical analysis was provided to solve the limitations. A pre-processing method library was set up first and orthogonal experiment design was then introduced to investigate the effects and interactions of different pre-processing methods. Paired t-test was used to select the most suitable pre-processing method. Finally, the pre-processing method selected above and three commonly used variable selection methods (CARS, UVE, VIP) were combined randomly to select the best calibration model. The results showed that the new calibration approach could provide a reasonable way for researchers to establish a more stable, objective calibration model.

Regulation of GDSL Lipase Gene Expression by the MPK3/MPK6 Cascade and Its Downstream WRKY Transcription Factors in Arabidopsis Immunity

Mitogen-activated protein kinase (MAPK) cascades serve as unified signaling modules in plant development and defense response. Previous reports demonstrated an essential role of Arabidopsis GLIP1, a member of the GDSL-like-motif lipase family, in both local and systemic resistance. GLIP1 expression is highly induced by pathogen attack. However, the one or more signaling pathways involved are unknown. Here, we report that two pathogen-responsive MAPKs, MPK3 and MPK6, are implicated in regulating gene expression of GLIP1 as well as GLIP3 and GLIP4. After gain-of-function activation, MPK3 and MPK6 can strongly induce the expression of GLIP1, GLIP3, and GLIP4. Both GLIP1 and GLIP3 contribute to the plant resistance to Botrytis cinerea. WRKY33, a MPK3/MPK6 substrate, is essential for the MPK3/MPK6-dependent GLIP1 induction. In addition, WRKY2 and WRKY34, two close homologs of WRKY33, have a minor effect in MPK3/MPK6-regulated GLIP1 expression in B. cinerea-infected plants. Chromatin immunoprecipitation-quantitative polymerase chain reaction analysis demonstrated that the GLIP1 gene is a direct target of WRKY33. In addition, we demonstrated that MPK3/MPK6-induced GLIP1 expression is independent of ethylene and jasmonic acid, two important hormones in plant defense. Our results provide insights into the regulation of the GLIP family at the transcriptional level in plant immunity.

SlMYC1 Regulates Type VI Glandular Trichome Formation and Terpene Biosynthesis in Tomato Glandular Cells

Tomato (Solanum lycopersicum) glandular trichomes function as biochemical factories that synthesize a diverse array of specialized metabolites. Terpenoids are the most diverse class of plant specialized metabolites, with volatile mono- and sesquiterpenes playing important roles in plant defense. Although the biosynthetic pathways of volatile terpenes in tomato glandular trichomes have been well described, little is known about their regulation. Here, we demonstrate that SlMYC1, a basic helix-loop-helix transcription factor, differentially regulates mono- and sesquiterpene biosynthesis in the type VI glandular trichomes of tomato leaves and stems. SlMYC1 functions as a positive regulator of monoterpene biosynthesis in both leaf and stem trichomes but as a negative regulator of sesquiterpene biosynthesis in stem trichomes. SlMYC1 is also essential for type VI glandular trichome development, as knocking down SlMYC1 led to the production of smaller type VI glandular trichomes at lower densities, and knocking out this gene led to their absence. Our findings reveal a role for SlMYC1 not only in type VI glandular trichome development but also in the regulation of terpene biosynthesis in tomato.

Inter-relationships between the heterotrimeric Gβ subunit AGB1, the receptor-like kinase FERONIA, and RALF1 in salinity response

Plant heterotrimeric G proteins modulate numerous developmental stress responses. Recently, receptor-like kinases (RLKs) have been implicated as functioning with G proteins and may serve as plant G-protein-coupled-receptors. The RLK FERONIA (FER), in the Catharantus roseus RLK1-like subfamily, is activated by a family of polypeptides called rapid alkalinization factors (RALFs). We previously showed that the Arabidopsis G protein β subunit, AGB1, physically interacts with FER, and that RALF1 regulation of stomatal movement through FER requires AGB1. Here, we investigated genetic interactions of AGB1 and FER in plant salinity response by comparing salt responses in the single and double mutants of agb1 and fer. We show that AGB1 and FER act additively or synergistically depending on the conditions of the NaCl treatments. We further show that the synergism likely occurs through salt-induced ROS production. In addition, we show that RALF1 enhances salt toxicity through increasing Na⁺ accumulation and decreasing K⁺ accumulation rather than by inducing ROS production, and that the RALF1 effect on salt response occurs in an AGB1-independent manner. Our results indicate that RLK epistatic relationships are not fixed, as AGB1 and FER display different genetic relationships to RALF1 in stomatal versus salinity responses.

The functional balance between the WUSCHEL-RELATED HOMEOBOX1 gene and the phytohormone auxin is a key factor for cell proliferation in Arabidopsis seedlings

The WUSCHEL-RELATED HOMEOBOX1 (WOX1) transcription factor and its homolog PRESSED FLOWER (PRS) are multifunctional regulators of leaf development that act as transcriptional repressors. These genes promote cell proliferation under certain conditions, but the related molecular mechanisms are not well understood. Here, we present a new function for WOX1 in cell proliferation. To identify the WOX1 downstream genes, we performed a microarray analysis of shoot apices of transgenic Arabidopsis thaliana lines harboring [35Sp::WOX1-glucocorticoid receptor (GR)] in which the WOX1 function was temporarily enhanced by dexamethasone. The downregulated genes were significantly enriched for the Gene Ontology term "response to auxin stimulus", whereas the significantly upregulated genes contained auxin transport-associated PIN1 and AUX1 and the auxin response factor MP, which are involved in formation of auxin response maxima. Simultaneous treatments of synthetic auxin and dexamethasone induced the formation of green compact calli and the unorganized proliferation of cells in the hypocotyl. A microarray analysis of 35Sp::WOX1-GR plants treated with indole-3-acetic acid and dexamethasone revealed that WOX1 and auxin additively influenced their common downstream genes. Furthermore, in the presence of an auxin-transport inhibitor, cell proliferation during leaf initiation was suppressed in the prs mutant but induced in a broad region of the peripheral zone of the shoot apical meristem in the ectopic WOX1-expressing line FILp::WOX1. Thus, our results clarify the additive effect of WOX1/PRS and auxin on their common downstream genes and highlight the importance of the balance between their functions in controlling cell proliferation.

Mitogen-activated protein kinases and calcium-dependent protein kinases are involved in wounding-induced ethylene biosynthesis in Arabidopsis thaliana

Ethylene, an important hormone in plant growth, development and response to environmental stimuli, is rapidly induced by mechanical injury or wounding. Although induction of ACS (1-aminocyclopropane-1-carboxylic acid synthase) gene expression has been associated with this process, the detailed regulatory mechanism is unclear. Here, we report that the wounding-induced ethylene production is modulated by both mitogen-activated protein kinase (MAPK) pathway and calcium-dependent protein kinase (CPK) pathway. Study using acs mutants demonstrated that four ACS isoforms, including ACS2, ACS6, ACS7 and ACS8, contribute to ethylene production in response to wounding. Loss-of-function analysis defines the role of MPK3 and MPK6, and their upstream MKK4 and MKK5, in wounding-induced ethylene production. They play an important role in the wounding-induced up-regulation of all four ACS genes expression. Independent of MAPK pathway, CPK5 and CPK6 are also involved in the wounding-induced ethylene production by regulating the expression of ACS2, ACS6 and ACS8 genes. Taken together, we demonstrate that two independent kinase signalling pathways, MPK3/MPK6 cascade and CPK5/CPK6, are involved in the wounding-induced ethylene biosynthesis via differential regulation of ACS genes at transcriptional level.

Phytochrome-interacting factors directly suppress MIR156 expression to enhance shade-avoidance syndrome in Arabidopsis

Plants have evolved a repertoire of strategies collectively termed the shade-avoidance syndrome to avoid shade from canopy and compete for light with their neighbors. However, the signaling mechanism governing the adaptive changes of adult plant architecture to shade is not well understood. Here, we show that in Arabidopsis, compared with the wild type, several PHYTOCHROME-INTERACTING FACTORS (PIFS) overexpressors all display constitutive shade-avoidance syndrome under normal high red to far-red light ratio conditions but are less sensitive to the simulated shade, whereas the MIR156 overexpressors exhibit an opposite phenotype. The simulated shade induces rapid accumulation of PIF proteins, reduced expression of multiple MIR156 genes, and concomitant elevated expression of the SQUAMOSA-PROMOTER BINDING PROTEIN-LIKE (SPL) family genes. Moreover, in vivo and in vitro assays indicate that PIFs bind to the promoters of several MIR156 genes directly and repress their expression. Our results establish a direct functional link between the phytochrome-PIFs and miR156-SPL regulatory modules in mediating shade-avoidance syndrome.Plants employ developmental strategies to avoid shade and compete with neighbors for light. Here, Xie et al. show that phytochrome-interacting factors, which are regulated in a light-dependent manner, directly repress MIR156 genes and promote the expression of SPL genes to enhance shade-avoidance responses.

Biochemical Principles and Functional Aspects of Pipecolic Acid Biosynthesis in Plant Immunity

The nonprotein amino acid pipecolic acid (Pip) regulates plant systemic acquired resistance and basal immunity to bacterial pathogen infection. In Arabidopsis (Arabidopsis thaliana), the lysine (Lys) aminotransferase AGD2-LIKE DEFENSE RESPONSE PROTEIN1 (ALD1) mediates the pathogen-induced accumulation of Pip in inoculated and distal leaf tissue. Here, we show that ALD1 transfers the α-amino group of l-Lys to acceptor oxoacids. Combined mass spectrometric and infrared spectroscopic analyses of in vitro assays and plant extracts indicate that the final product of the ALD1-catalyzed reaction is enaminic 2,3-dehydropipecolic acid (DP), whose formation involves consecutive transamination, cyclization, and isomerization steps. Besides l-Lys, recombinant ALD1 transaminates l-methionine, l-leucine, diaminopimelate, and several other amino acids to generate oxoacids or derived products in vitro. However, detailed in planta analyses suggest that the biosynthesis of 2,3-DP from l-Lys is the major in vivo function of ALD1. Since ald1 mutant plants are able to convert exogenous 2,3-DP into Pip, their Pip deficiency relies on the inability to form the 2,3-DP intermediate. The Arabidopsis reductase ornithine cyclodeaminase/μ-crystallin, alias SYSTEMIC ACQUIRED RESISTANCE-DEFICIENT4 (SARD4), converts ALD1-generated 2,3-DP into Pip in vitro. SARD4 significantly contributes to the production of Pip in pathogen-inoculated leaves but is not the exclusive reducing enzyme involved in Pip biosynthesis. Functional SARD4 is required for proper basal immunity to the bacterial pathogen Pseudomonas syringae Although SARD4 knockout plants show greatly reduced accumulation of Pip in leaves distal to P. syringae inoculation, they display a considerable systemic acquired resistance response. This suggests a triggering function of locally accumulating Pip for systemic resistance induction.

Related to ABI3/VP1-Like 1 (RAVL1) regulates brassinosteroid-mediated activation of AMT1;2 in rice (Oryza sativa)

The promotive effects of brassinosteroids (BRs) on plant growth and development have been widely investigated; however, it is not known whether BRs directly affect nutrient uptake. Here, we explored the possibility of a direct relationship between BRs and ammonium uptake via AMT1-type genes in rice (Oryza sativa). BR treatment increased the expression of AMT1;1 and AMT1;2, whereas in the mutant d61-1, which is defective in the BR-receptor gene BRI1, BR-dependent expression of these genes was suppressed. We then employed Related to ABI3/VP1-Like 1 (RAVL1), which is involved in BR homeostasis, to investigate BR-mediated AMT1 expression and its effect on NH4+ uptake in rice roots. AMT1;2 expression was lower in the ravl1 mutant, but higher in the RAVL1-overexpressing lines. EMSA and ChIP analyses showed that RAVL1 activates the expression of AMT1;2 by directly binding to E-box motifs in its promoter. Moreover, 15NH4+ uptake, cellular ammonium contents, and root responses to methyl-ammonium strongly depended on RAVL1 levels. Analysing AMT1;2 expression levels in different crosses between BRI1 and RAVL1 mutant and overexpression lines indicated that RAVL1 acts downstream of BRI1 in the regulation of AMT1;2. Thus, the present study shows how BRs may be involved in the transcriptional regulation of nutrient transporters to modulate their uptake capacity.

Brassinosteroid's multi-modular interaction with the general stress network customizes stimulus-specific responses in Arabidopsis

Adaptation to fluctuating environmental conditions is a universal feature of plant life, governed by fundamental mechanisms optimizing resource allocation. This balance is achieved in part through tightly regulated communication networks among growth and stress response signaling pathways. Understanding the communication modules between brassinosteroids (BRs), the ubiquitous hormones known to control growth and stress adaptation, and the general stress response (GSR), a rapid and transient transcriptional output in response to perturbations, provides an optimal platform to unravel new facet(s) of plant stress adaptation. Here, we explore communication facets of BR with GSR via in planta quantification of the GSR in Arabidopsis expressing luciferase driven by a functional GSR cis-element, the Rapid Stress Response Element (4xRSRE:LUC). We establish that application of exogenous BR suppresses microbe-associated molecular pattern-activated GSR, but enhances the wound-triggered GSR. The enhanced wound-activated GSR in BR-treated plants results in a greater wound-induced resistance to Botrytis cinerea. A combination of molecular genetics using BR signaling mutants and application of an activator of BR signaling, bikinin, confirms these results and places the chief point of BR-GSR interaction downstream of potential membrane receptor circuitry. These results support a multi-modular interaction between BRs and stress signaling, instrumental in customizing stimulus-specific responses in Arabidopsis.

Rapid hyperosmotic-induced Ca2+ responses in Arabidopsis thaliana exhibit sensory potentiation and involvement of plastidial KEA transporters

Plants experience hyperosmotic stress when faced with saline soils and possibly with drought stress, but it is currently unclear how plant roots perceive this stress in an environment of dynamic water availabilities. Hyperosmotic stress induces a rapid rise in intracellular Ca(2+) concentrations ([Ca(2+)]i) in plants, and this Ca(2+) response may reflect the activities of osmo-sensory components. Here, we find in the reference plant Arabidopsis thaliana that the rapid hyperosmotic-induced Ca(2+) response exhibited enhanced response magnitudes after preexposure to an intermediate hyperosmotic stress. We term this phenomenon "osmo-sensory potentiation." The initial sensing and potentiation occurred in intact plants as well as in roots. Having established a quantitative understanding of wild-type responses, we investigated effects of pharmacological inhibitors and candidate channel/transporter mutants. Quintuple mechano-sensitive channels of small conductance-like (MSL) plasma membrane-targeted channel mutants as well as double mid1-complementing activity (MCA) channel mutants did not affect the response. Interestingly, however, double mutations in the plastid K(+) exchange antiporter (KEA) transporters kea1kea2 and a single mutation that does not visibly affect chloroplast structure, kea3, impaired the rapid hyperosmotic-induced Ca(2+) responses. These mutations did not significantly affect sensory potentiation of the response. These findings suggest that plastids may play an important role in early steps mediating the response to hyperosmotic stimuli. Together, these findings demonstrate that the plant osmo-sensory components necessary to generate rapid osmotic-induced Ca(2+) responses remain responsive under varying osmolarities, endowing plants with the ability to perceive the dynamic intensities of water limitation imposed by osmotic stress.

Metabolic parameters linked by phenotype microarray to acid resistance profiles of poultry-associated Salmonella enterica

Phenotype microarrays were analyzed for 51 datasets derived from Salmonella enterica. The top 4 serotypes associated with poultry products and one associated with turkey, respectively Typhimurium, Enteritidis, Heidelberg, Infantis and Senftenberg, were represented. Datasets were partitioned initially into two clusters based on ranking by values at pH 4.5 (PM10 A03). Negative control wells were used to establish 90 respiratory units as the point differentiating acid resistance from sensitive strains. Thus, 24 isolates that appeared most acid-resistant were compared initially to 27 that appeared most acid-sensitive (24 × 27 format). Paired cluster analysis was also done and it included the 7 most acid-resistant and -sensitive datasets (7 × 7 format). Statistical analyses of ranked data were then calculated in order of standard deviation, probability value by the Student's t-test and a measure of the magnitude of difference called effect size. Data were reported as significant if, by order of filtering, the following parameters were calculated: i) a standard deviation of 24 respiratory units or greater from all datasets for each chemical, ii) a probability value of less than or equal to 0.03 between clusters and iii) an effect size of at least 0.50 or greater between clusters. Results suggest that between 7.89% and 23.16% of 950 chemicals differentiated acid-resistant isolates from sensitive ones, depending on the format applied. Differences were more evident at the extremes of phenotype using the subset of data in the paired 7 × 7 format. Results thus provide a strategy for selecting compounds for additional research, which may impede the emergence of acid-resistant Salmonella enterica in food.

Effector-Triggered Immune Response in Arabidopsis thaliana Is a Quantitative Trait

We identified loci responsible for natural variation in Arabidopsis thaliana (Arabidopsis) responses to a bacterial pathogen virulence factor, HopAM1. HopAM1 is a type III effector protein secreted by the virulent Pseudomonas syringae strain Pto DC3000. Delivery of HopAM1 from disarmed Pseudomonas strains leads to local cell death, meristem chlorosis, or both, with varying intensities in different Arabidopsis accessions. These phenotypes are not associated with differences in bacterial growth restriction. We treated the two phenotypes as quantitative traits to identify host loci controlling responses to HopAM1. Genome-wide association (GWA) of 64 Arabidopsis accessions identified independent variants highly correlated with response to each phenotype. Quantitative trait locus (QTL) mapping in a recombinant inbred population between Bur-0 and Col-0 accessions revealed genetic linkage to regions distinct from the top GWA hits. Two major QTL associated with HopAM1-induced cell death were also associated with HopAM1-induced chlorosis. HopAM1-induced changes in Arabidopsis gene expression showed that rapid HopAM1-dependent cell death in Bur-0 is correlated with effector-triggered immune responses. Studies of the effect of mutations in known plant immune system genes showed, surprisingly, that both cell death and chlorosis phenotypes are enhanced by loss of EDS1, a regulatory hub in the plant immune-signaling network. Our results reveal complex genetic architecture for response to this particular type III virulence effector, in contrast to the typical monogenic control of cell death and disease resistance triggered by most type III effectors.

Killing two birds with one stone: Model plant systems as a tool to teach the fundamental concepts of gene expression while analyzing biological data

Plants are ideal systems to teach core biology concepts due to their unique physiological and developmental features. Advances in DNA sequencing technology and genomics have allowed scientists to generate genome sequences and transcriptomics data for numerous model plant species. This information is publicly available and presents a valuable tool to introduce undergraduate students to the fundamental concepts of gene expression in the context of modern quantitative biology and bioinformatics. Modern biology classrooms must provide authentic research experiences to allow developing core competencies such as scientific inquiry, critical interpretation of experimental results, and quantitative analyses of large dataset using computational approaches. Recent educational research has shown that undergraduate students struggle when connecting gene expression concepts to classic genetics, phenotypic analyses, and overall flow of biological information in living organisms, suggesting that novel approaches are necessary to enhance learning of gene expression and regulation. This review describes different strategies and resources available to instructors willing to incorporate authentic research experiences, genomic tools, and bioinformatics analyses when teaching transcriptional regulation and gene expression in undergraduate courses. A variety of laboratory exercises and pedagogy materials developed to teach gene expression using plants are discussed. This article is part of a Special Issue entitled: Plant Gene Regulatory Mechanisms and Networks, edited by Dr. Erich Grotewold and Dr. Nathan Springer.

Pathogen-Responsive MPK3 and MPK6 Reprogram the Biosynthesis of Indole Glucosinolates and Their Derivatives in Arabidopsis Immunity

Antimicrobial compounds have critical roles in plant immunity; for example, Arabidopsis thaliana and other crucifers deploy phytoalexins and glucosinolate derivatives in defense against pathogens. The pathogen-responsive MITOGEN-ACTIVATED PROTEIN KINASE3 (MPK3) and MPK6 have essential functions in the induction of camalexin, the major phytoalexin in Arabidopsis. In search of cyanide, a coproduct of ethylene and camalexin biosynthesis, we found that MPK3 and MPK6 also affect the accumulation of extracellular thiocyanate ion derived from the indole glucosinolate (IGS) pathway. Botrytis cinerea infection activates MPK3/MPK6, which promote indole-3-yl-methylglucosinolate (I3G) biosynthesis and its conversion to 4-methoxyindole-3-yl-methylglucosinolate (4MI3G). Gain- and loss-of-function analyses demonstrated that MPK3/MPK6 regulate the expression of MYB51 and MYB122, two key regulators of IGS biosynthesis, as well as CYP81F2 and IGMT1/IGMT2, which encode enzymes in the conversion of I3G to 4MI3G, through ETHYLENE RESPONSE FACTOR6 (ERF6), a substrate of MPK3/MPK6. Under the action of PENETRATION2 (PEN2), an atypical myrosinase, and PEN3, an ATP binding cassette transporter, 4MI3G is converted to extracellular unstable antimicrobial compounds, possibly isothiocyanates that can react with nucleophiles and release the stable thiocyanate ion. Recent studies demonstrated the importance of PEN2/PEN3-dependent IGS derivatives in plant immunity. Here, we report that MPK3/MPK6 and their substrate ERF6 promote the biosynthesis of IGSs and the conversion of I3G to 4MI3G, a target of PEN2/PEN3-dependent chemical defenses in plant immunity.

JAZ7 negatively regulates dark-induced leaf senescence in Arabidopsis

JASMONATE ZIM-domain (JAZ) proteins play important roles in plant defence and growth by regulating jasmonate signalling. Through data mining, we discovered that the JAZ7 gene was up-regulated in darkness. In the dark, the jaz7 mutant displayed more severe leaf yellowing, quicker chlorophyll degradation, and higher hydrogen peroxide accumulation compared with wild-type (WT) plants. The mutant phenotype of dark-induced leaf senescence could be rescued in the JAZ7-complemented and -overexpression lines. Moreover, the double mutants of jaz7 myc2 and jaz7 coi1 exhibited delayed leaf senescence. We further employed GeneChip analysis to study the molecular mechanism. Some key genes down-regulated in the triple mutant myc2 myc3 myc4 were up-regulated in the jaz7 mutant under darkness. The Gene Ontology terms 'leaf senescence' and 'cell death' were significantly enriched in the differentially expressed genes. Combining the genetic and transcriptomic analyses together, we proposed a model whereby darkness can induce JAZ7, which might further block MYC2 to suppress dark-induced leaf senescence. In darkness, the mutation of JAZ7 might partially liberate MYC2/MYC3/MYC4 from suppression, leading the MYC proteins to bind to the G-box/G-box-like motifs in the promoters, resulting in the up-regulation of the downstream genes related to indole-glucosinolate biosynthesis, sulphate metabolism, callose deposition, and JA-mediated signalling pathways. In summary, our genetic and transcriptomic studies established the JAZ7 protein as an important regulator in dark-induced leaf senescence.

Do Cupins Have a Function Beyond Being Seed Storage Proteins?

Plants continue to flourish around the site of the Chernobyl Nuclear Power Plant disaster. The ability of plants to transcend the radio-contaminated environment was not anticipated and is not well understood. The aim of this study was to evaluate the proteome of flax (Linum usitatissimum L.) during seed filling by plants grown for a third generation near Chernobyl. For this purpose, seeds were harvested at 2, 4, and 6 weeks after flowering and at maturity, from plants grown in either non-radioactive or radio-contaminated experimental fields. Total proteins were extracted and the two-dimensional gel electrophoresis (2-DE) patterns analyzed. This approach established paired abundance profiles for 130 2-DE spots, e.g., profiles for the same spot across seed filling in non-radioactive and radio-contaminated experimental fields. Based on Analysis of Variance (ANOVA) followed by sequential Bonferroni correction, eight of the paired abundance profiles were discordant. Results from tandem mass spectrometry show that four 2-DE spots are discordant because they contain fragments of the cupin superfamily-proteins. Most of the fragments were derived from the N-terminal half of native cupins. Revisiting previously published data, it was found that cupin-fragments were also involved with discordance in paired abundance profiles of second generation flax seeds. Based on these observations we present an updated working model for the growth and reproductive success of flax in a radio-contaminated Chernobyl environment. This model suggests that the increased abundance of cupin fragments or isoforms and monomers contributes to the successful growth and reproduction of flax in a radio-contaminated environment.

Pipecolic Acid Orchestrates Plant Systemic Acquired Resistance and Defense Priming via Salicylic Acid-Dependent and -Independent Pathways

We investigated the relationships of the two immune-regulatory plant metabolites, salicylic acid (SA) and pipecolic acid (Pip), in the establishment of plant systemic acquired resistance (SAR), SAR-associated defense priming, and basal immunity. Using SA-deficient sid2, Pip-deficient ald1, and sid2 ald1 plants deficient in both SA and Pip, we show that SA and Pip act both independently from each other and synergistically in Arabidopsis thaliana basal immunity to Pseudomonas syringae. Transcriptome analyses reveal that SAR establishment in Arabidopsis is characterized by a strong transcriptional response systemically induced in the foliage that prepares plants for future pathogen attack by preactivating multiple stages of defense signaling and that SA accumulation upon SAR activation leads to the downregulation of photosynthesis and attenuated jasmonate responses systemically within the plant. Whereas systemic Pip elevations are indispensable for SAR and necessary for virtually the whole transcriptional SAR response, a moderate but significant SA-independent component of SAR activation and SAR gene expression is revealed. During SAR, Pip orchestrates SA-dependent and SA-independent priming of pathogen responses in a FLAVIN-DEPENDENT-MONOOXYGENASE1 (FMO1)-dependent manner. We conclude that a Pip/FMO1 signaling module acts as an indispensable switch for the activation of SAR and associated defense priming events and that SA amplifies Pip-triggered responses to different degrees in the distal tissue of SAR-activated plants.

Discovering New Biology through Sequencing of RNA

Sequencing of RNA (RNA-Seq) was invented approximately 1 decade ago and has since revolutionized biological research. This update provides a brief historic perspective on the development of RNA-Seq and then focuses on the application of RNA-Seq in qualitative and quantitative analyses of transcriptomes. Particular emphasis is given to aspects of data analysis. Since the wet-lab and data analysis aspects of RNA-Seq are still rapidly evolving and novel applications are continuously reported, a printed review will be rapidly outdated and can only serve to provide some examples and general guidelines for planning and conducting RNA-Seq studies. Hence, selected references to frequently update online resources are given.