Ufmylation reconciles salt stress-induced unfolded protein responses via ER-phagy in Arabidopsis.

In plants, the endomembrane system is tightly regulated in response to environmental stresses for maintaining cellular homeostasis. Autophagosomes, the double membrane organelles forming upon nutrient deprivation or stress induction, degrade bulky cytosolic materials for nutrient turnover. Though abiotic stresses have been reported to induce plant autophagy, few receptors or regulators for selective autophagy have been characterized for specific stresses. Here, we have applied immunoprecipitation followed by tandem mass spectrometry using the autophagosome marker protein ATG8 as bait and have identified the E3 ligase of the ufmylation system Ufl1 as a bona fide ATG8 interactor under salt stress. Notably, core components in the ufmylation cascade, Ufl1 and Ufm1, interact with the autophagy kinase complexes proteins ATG1 and ATG6. Cellular and genetic analysis showed that Ufl1 is important for endoplasmic reticulum (ER)-phagy under persisting salt stress. Loss-of-function mutants of Ufl1 display a salt stress hypersensitive phenotype and abnormal ER morphology. Prolonged ER stress responses are detected in ufl1 mutants that phenocopy the autophagy dysfunction atg5 mutants. Consistently, expression of ufmylation cascade components is up-regulated by salt stress. Taken together, our study demonstrates the role of ufmylation in regulating ER homeostasis under salt stress through ER-phagy.

WRKY6 transcription factor modulates root potassium acquisition through promoting expression of AKT1 in Arabidopsis.

Potassium (K+), being an essential macronutrient in plants, plays a central role in many aspects. Root growth is highly plastic and is affected by many different abiotic stresses including nutrient deficiency. The Shaker-type K+ channel Arabidopsis (Arabidopsis thaliana) K+ Transporter 1 (AKT1) is responsible for K+ uptake under both low and high external K+ conditions. However, the upstream transcription factor of AKT1 is not clear. Here, we demonstrated that the WRKY6 transcription factor modulates root growth to low potassium (LK) stress in Arabidopsis. WRKY6 showed a quick response to LK stress and also to many other abiotic stress treatments. The two wrky6 T-DNA insertion mutants were highly sensitive to LK treatment, whose primary root lengths were much shorter, less biomass and lower K+ content in roots than those of wild-type plants, while WRKY6-overexpression lines showed opposite phenotypes. A further investigation showed that WRKY6 regulated the expression of the AKT1 gene via directly binding to the W-box elements in its promoter through EMSA and ChIP-qPCR assays. A dual luciferase reporter analysis further demonstrated that WRKY6 enhanced the transcription of AKT1. Genetic analysis further revealed that the overexpression of AKT1 greatly rescued the short root phenotype of the wrky6 mutant under LK stress, suggesting AKT1 is epistatic to WRKY6 in the control of LK response. Further transcriptome profiling suggested that WRKY6 modulates LK response through a complex regulatory network. Thus, this study unveils a transcription factor that modulates root growth under potassium deficiency conditions by affecting the potassium channel gene AKT1 expression.

A unique AtSar1D-AtRabD2a nexus modulates autophagosome biogenesis in Arabidopsis thaliana.

In eukaryotes, secretory proteins traffic from the endoplasmic reticulum (ER) to the Golgi apparatus via coat protein complex II (COPII) vesicles. Intriguingly, during nutrient starvation, the COPII machinery acts constructively as a membrane source for autophagosomes during autophagy to maintain cellular homeostasis by recycling intermediate metabolites. In higher plants, essential roles of autophagy have been implicated in plant development and stress responses. Nonetheless, the membrane sources of autophagosomes, especially the participation of the COPII machinery in the autophagic pathway and autophagosome biogenesis, remains elusive in plants. Here, we provided evidence in support of a novel role of a specific Sar1 homolog AtSar1d in plant autophagy in concert with a unique Rab1/Ypt1 homolog AtRabD2a. First, proteomic analysis of the plant ATG (autophagy-related gene) interactome uncovered the mechanistic connections between ATG machinery and specific COPII components including AtSar1d and Sec23s, while a dominant negative mutant of AtSar1d exhibited distinct inhibition on YFP-ATG8 vacuolar degradation upon autophagic induction. Second, a transfer DNA insertion mutant of AtSar1d displayed starvation-related phenotypes. Third, AtSar1d regulated autophagosome progression through specific recognition of ATG8e by a noncanonical motif. Fourth, we demonstrated that a plant-unique Rab1/Ypt1 homolog AtRabD2a coordinates with AtSar1d to function as the molecular switch in mediating the COPII functions in the autophagy pathway. AtRabD2a appears to be essential for bridging the specific AtSar1d-positive COPII vesicles to the autophagy initiation complex and therefore contributes to autophagosome formation in plants. Taken together, we identified a plant-specific nexus of AtSar1d-AtRabD2a in regulating autophagosome biogenesis.

WRKY55 transcription factor positively regulates leaf senescence and the defense response by modulating the transcription of genes implicated in the biosynthesis of reactive oxygen species and salicylic acid in Arabidopsis.

Reactive oxygen species (ROS) and salicylic acid (SA) are two factors regulating leaf senescence and defense against pathogens. However, how a single gene integrates both ROS and SA pathways remains poorly understood. Here, we show that Arabidopsis WRKY55 transcription factor positively regulates ROS and SA accumulation, and thus leaf senescence and resistance against the bacterial pathogen Pseudomonas syringaeWRKY55 is predominantly expressed in senescent leaves and encodes a transcriptional activator localized to nuclei. Both inducible and constitutive overexpression of WRKY55 accelerates leaf senescence, whereas mutants delay it. Transcriptomic sequencing identified 1448 differentially expressed genes, of which 1157 genes are upregulated by WRKY55 expression. Accordingly, the ROS and SA contents in WRKY55-overexpressing plants are higher than those in control plants, whereas the opposite occurs in mutants. Moreover, WRKY55 positively regulates defense against P. syringae Finally, we show that WRKY55 activates the expression of RbohD, ICS1, PBS3 and SAG13 by binding directly to the W-box-containing fragments. Taken together, our work has identified a new WRKY transcription factor that integrates both ROS and SA pathways to regulate leaf senescence and pathogen resistance.

ADP-ribosylation factor D1 modulates Golgi morphology, cell plate formation, and plant growth in Arabidopsis.

ADP-ribosylation factor (ARF) family proteins, one type of small guanine-nucleotide-binding (G) proteins, play a central role in regulating vesicular traffic and organelle structures in eukaryotes. The Arabidopsis (Arabidopsis thaliana) genome contains more than 21 ARF proteins, but relatively little is known about the functional heterogeneity of ARF homologs in plants. Here, we characterized the function of a unique ARF protein, ARFD1B, in Arabidopsis. ARFD1B exhibited both cytosol and punctate localization patterns, colocalizing with a Golgi marker in protoplasts and transgenic plants. Distinct from other ARF1 homologs, overexpression of a dominant-negative mutant form of ARFD1B did not alter the localization of the Golgi marker mannosidase I (ManI)-RFP in Arabidopsis cells. Interestingly, the ARFD1 artificial microRNA knockdown mutant arfd1 displayed a deleterious growth phenotype, while this phenotype was restored in complemented plants. Further, confocal imaging and transmission electron microscopy analyses of the arfd1 mutant revealed defective cell plate formation and abnormal Golgi morphology. Pull-down and liquid chromatography-tandem mass spectrometry analyses identified Coat Protein I (COPI) components as interacting partners of ARFD1B, and subsequent bimolecular fluorescence complementation, yeast (Saccharomyces cerevisiae) two-hybrid, and co-immunoprecipitation assays further confirmed these interactions. These results demonstrate that ARFD1 is required for cell plate formation, maintenance of Golgi morphology, and plant growth in Arabidopsis.

WRKY42 transcription factor positively regulates leaf senescence through modulating SA and ROS synthesis in Arabidopsis thaliana.

Leaf senescence represents the final stage of leaf growth and development, and its onset and progression are strictly regulated; however, the underlying regulatory mechanisms remain largely unknown. In this study we found that WRKY42 was highly induced during leaf senescence. Loss-of-function wrky42 mutants showed delayed leaf senescence whereas the overexpression of WRKY42 accelerated senescence. Transcriptome analysis revealed 2721 differentially expressed genes between wild-type and WRKY42-overexpressing plants, including genes involved in salicylic acid (SA) and reactive oxygen species (ROS) synthesis as well as several senescence-associated genes (SAGs). Moreover, WRKY42 activated the transcription of isochorismate synthase 1 (ICS1), respiratory burst oxidase homolog F (RbohF) and a few SAG genes. Consistently, the expression of these genes was reduced in wrky42 mutants but was markedly increased in transgenic Arabidopsis overexpressing WRKY42. Both in vitro electrophoretic mobility shift assays (EMSAs) and in vivo chromatin immunoprecipitation and dual luciferase assays demonstrated that WRKY42 directly bound to the promoters of ICS1 and RbohF, as well as a few SAGs, to activate their expression. Genetic analysis further showed that mutations of ICS1 and RbohF suppressed the early senescence phenotype evoked by WRKY42 overexpression. Thus, we have identified WRKY42 as a novel transcription factor positively regulating leaf senescence by directly activating the transcription of ICS1, RbohF and SAGs, without any seed yield penalty.

MYB106 is a negative regulator and a substrate for CRL3BPM E3 ligase in regulating flowering time in Arabidopsis thaliana.

Flowering time is crucial for successful reproduction in plants, the onset and progression of which are strictly controlled. However, flowering time is a complex and environmentally responsive history trait and the underlying mechanisms still need to be fully characterized. Post-translational regulation of the activities of transcription factors (TFs) is a dynamic and essential mechanism for plant growth and development. CRL3BPM E3 ligase is a CULLIN3-based E3 ligase involved in orchestrating protein stability via the ubiquitin proteasome pathway. Our study shows that the mutation of MYB106 induced early flowering phenotype while over-expression of MYB106 delayed Arabidopsis flowering. Transcriptome analysis of myb106 mutants reveals 257 differentially expressed genes between wild type and myb106-1 mutants, including Flowering Locus T (FT) which is related to flowering time. Moreover, in vitro electrophoretic mobility shift assays (EMSA), in vivo chromatin immunoprecipitation quantitative polymerase chain reaction (ChIP-qPCR) assays and dual luciferase assays demonstrate that MYB106 directly binds to the promoter of FT to suppress its expression. Furthermore, we confirm that MYB106 interacts with BPM proteins which are further identified by CRL3BPM E3 ligases as the substrate. Taken together, we have identified MYB106 as a negative regulator in the control of flowering time and a new substrate for CRL3BPM E3 ligases in Arabidopsis.

Ursodeoxycholic acid protects against lung injury induced by fat embolism syndrome.

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a life-threatening disease with a high mortality rate, which was a common complication of fat embolism syndrome (FES). Ursodeoxycholic acid (UDCA) has been reported to exert potent anti-inflammatory effects under various conditions. In vivo, perinephric fat was injected via tail vein to establish a rat FES model, the anti-inflammatory effects of UDCA on FES-induced lung injury were investigated through histological examination, ELISA, qRT-PCR, Western blot and immunofluorescence. In vitro, human lung microvascular endothelial cells (HPMECs) were employed to understand the protective effects of UDCA. The extent of ALI/ARDS was evaluated and validated by reduced PaO2 /FiO2 ratios, increased lung wet/dry (W/D) ratios and impaired alveolar-capillary barrier, up-regulation of ALI-related proteins in lung tissues (including myeloperoxidase [MPO], vascular cell adhesion molecule 1 [VCAM-1], intercellular cell adhesion molecule-1 [ICAM-1]), elevated protein concentration and increased proinflammatory cytokines levels (TNF-α and IL-1ß) in bronchoalveolar lavage fluid (BALF). Pre-treatment with UDCA remarkably alleviated these pathologic and biochemical changes of FES-induced ALI/ARDS; our data demonstrated that pre-treatment with UDCA attenuated the pathologic and biochemical changes of FES-induced ARDS, which provided a possible preventive therapy for lung injury caused by FES.

Ursodeoxycholic acid stimulates alveolar fluid clearance in LPS-induced pulmonary edema via ALX/cAMP/PI3K pathway.

This study aims to examine the impact of ursodeoxycholic acid (UDCA) on pulmonary edema and explore the underlying molecular mechanisms. The effects of UDCA on pulmonary edema were assessed through hematoxylin and eosin (H&E) staining, lung dry/wet (W/D) ratio, TNF-α/IL-1ß levels of bronchoalveolar lavage fluid (BALF), protein expression of epithelial sodium channel (ENaC), and Na+ /K+ -ATPase. Besides, the detailed mechanisms were explored in primary rat alveolar type (AT) II epithelial cells by determining the effects of BOC-2 (ALX [lipoxin A4 receptor] inhibitor), Rp-cAMP (cAMP inhibitor), LY294002 (PI3K inhibitor), and H89 (PKA inhibitor) on the therapeutic effects of UDCA against lipopolysaccharide (LPS)-induced changes. Histological examination suggested that LPS-induced lung injury was obviously attenuated by UDCA. BALF TNF-α/IL-1ß levels and lung W/D ratios were decreased by UDCA in LPS model rats. UDCA stimulated alveolar fluid clearance (AFC) though the upregulation of ENaC and Na+ /K+ -ATPase. BOC-2, Rp-cAMP, and LY294002 largely suppressed the therapeutic effects of UDCA. Significant attenuation of pulmonary edema and lung inflammation was revealed in LPS-challenged rats after the UDCA treatment. The therapeutic efficacy of UDCA against LPS was mainly achieved through the ALX/cAMP/PI3K pathway. Our results suggested that UDCA might be a potential drug for the treatment of pulmonary edema induced by LPS.

A2BAR activation attenuates acute lung injury by inhibiting alveolar epithelial cell apoptosis both in vivo and in vitro.

The epithelial barrier of the lung is destroyed during acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) due to the apoptosis of alveolar epithelial cells (AECs). Therefore, treatments that block AEC apoptosis might be a therapeutic strategy to ameliorate ALI. Based on recent evidence, A2B adenosine receptor (A2BAR) plays an important role in ALI in several different animal models, but its exact function in AECs has not been clarified. We investigated the role of A2BAR in AEC apoptosis in a mouse model of oleic acid (OA)-induced ALI and in hydrogen peroxide (H2O2)-induced AEC (A549 cells and MLE-12 cells) injury. Mice treated with BAY60-6583, a selective A2BAR agonist, showed lower AEC apoptosis rates than mice treated with OA. However, the role of BAY60-6583 in OA-induced ALI was attenuated by a specific blocker of A2BAR, PSB1115. A2BAR activation decreased H2O2-induced cell apoptosis in vitro, as characterized by the translocation of apoptotic proteins, the release of cytochrome c, and the activation of caspase-3 and poly (ADP ribose) polymerase 1 (PARP-1). In addition, apoptosis was required for the phosphorylation of ERK1/2, p38, and JNK. Importantly, compared with cells transfected with the A2BAR-siRNA, an ERK inhibitor or p38 inhibitor exhibited decreased apoptotic ratios and cleaved caspase-9 and cleaved PARP-1 levels, whereas the JNK inhibitor displayed increases in these parameters. In conclusion, A2BAR activation effectively attenuated OA-induced ALI by inhibiting AEC apoptosis and mitigated H2O2-induced AEC injury by suppressing the p38 and ERK1/2-mediated mitochondrial apoptosis pathway.

A Novel NAC-Type Transcription Factor, NAC87, from Oilseed Rape Modulates Reactive Oxygen Species Accumulation and Cell Death.

Reactive oxygen species (ROS) are thought to play a dual role in plants by functioning as signaling molecules and toxic by-products of aerobic metabolism. The hypersensitive response (HR) is a typical feature of immune responses in plants and also a type of programmed cell death (PCD). How these two processes are regulated in oilseed rape (Brassica napus L.) at the transcriptional level remains largely unknown. In this study, we report that an oilseed rape (Brassica napus L.) NAM-ATAF-CUC (NAC)-type transcription factor NAC87 modulates ROS and cell death accompanied by typical changes at the morphological and cellular levels. The BnaNAC87 gene was induced by multiple stress and hormone treatments and was highly expressed in senescent leaves by quantitative reverse transcription-PCR (qRT-PCR). BnaNAC87 is located in nuclei and has transcriptional activation activity. Expression of BnaNAC87 promoted significant ROS production, cell death as well as death of protoplasts, as indicated by histological staining. In addition, putative downstream target genes of NAC87 were identified through both qRT-PCR and dual luciferase reporter assays. We found that genes implicated in ROS generation (RbohB), cell death (VPE1a, ZEN1), leaf senescence (WRKY6, ZAT12) and defense (PR2, PR5 and HIN1) were significantly induced. Through an electrophoretic mobility shift assay (EMSA), we confirmed that BnaNAC87 directly binds to the NACRS-containing promoter fragments of ZEN1, ZAT12, HIN1 and PR5 genes. From these results, we conclude that oilseed rape NAC87 is a novel NAC transcription factor that acts as a positive regulator of ROS metabolism and cell death.

ITRAQ-Based Proteomics Analysis of Acute Lung Injury Induced by Oleic Acid in Mice.

BACKGROUND/AIMS: This study was conducted to investigate the relationship between differentially expressed proteins (DEPs) and the pathogenesis of oleic acid (OA)-induced acute lung injury (ALI) in mice. METHODS: Eight-week-old male C57BL/6 mice were injected with OA through the tail vein and sacrificed 6 hours after OA administration to identify protein expression levels in lung tissue using isobaric tags for relative and absolute quantification (iTRAQ) technology. Then, DEPs such as antithrombin III (AT III), 12-lipoxygenase (12-LO), dedicator of cytokinesis 2 (DOCK2), polycystin-2 and plasminogen were identified by western blotting. Subsequently, we focused on investigating the effect of AT III on endothelial integrity using siRNA interference technology. The levels of IL-6, IL-1ß, TNF-α and TGF-ß expression were detected using an enzyme-linked immunosorbent assay (ELISA). Alterations in the tight junction component ZO-1 and the phosphorylation of myosin light chain (pMLC) were determined by western blotting. The stress fiber F-actin were also detected by immunofluorescence staining. In addition, endothelial permeability was determined via a transwell permeability assay. RESULTS: A total of 5152 proteins were found to be expressed in lung tissues from the OA-treated and saline-treated mice. Among these proteins, 849 were differentially expressed between the two groups, including 545 upregulated and 304 downregulated proteins. After AT III knockdown, the levels of inflammatory factors and endothelial permeability were elevated, the expression of ZO-1 was decreased, and the expression of F-actin and pMLC was increased. All these results illustrated that AT III knockdown exaggerated the disruption of endothelial integrity mediated by OA. CONCLUSION: These findings using iTRAQ technology demonstrate, for the first time, differences in the lung tissue expression levels of proteins between OA-treated mice and saline-treated mice. This study reveals that 12-LO, DOCK2 and especially AT III may be candidate biomarkers for OA-induced acute lung injury.

Oilseed rape NAC56 transcription factor modulates reactive oxygen species accumulation and hypersensitive response-like cell death.

The NAC (NAM, ATAF1/2, CUC2) transcription factor gene family is plant-specific and plays diverse roles in development and responses to abiotic stresses and pathogen challenge. Oilseed rape (Brassica napus) or canola is an important oil crop worldwide, however, the function of NAC genes in it remains largely elusive. In the present study, we identified and characterized the NAC56 gene isolated from oilseed rape. Expression of BnaNAC56 was induced by abscisic acid (ABA), jasmonic acid (JA), methyl viologen (MV) and a necrotrophic fungal pathogen Sclerotinia sclerotiorum, but repressed by cold. BnaNAC56 is a transcription activator and localized to nuclei. Overexpression of BnaNAC56 induced reactive oxygen species (ROS) accumulation and hypersensitive response (HR)-like cell death, with various physiological measurements supporting these. Furthermore, BnaNAC56 expression caused evident nuclear DNA fragmentation. Moreover, quantitative reverse transcription PCR (qRT-PCR) analysis identified that the expression levels of multiple genes regulating ROS homeostasis, cell death and defense response were significantly induced. Using a dual luciferase reporter assay, we further confirmed that BnaNAC56 could activate the expression of a few ROS- and cell death-related genes. In summary, our data demonstrate that BnaNAC56 functions as a stress-responsive transcriptional activator and plays a role in modulating ROS accumulation and cell death.

Functional characterization of NAC55 transcription factor from oilseed rape (Brassica napus L.) as a novel transcriptional activator modulating reactive oxygen species accumulation and cell death.

NAC transcription factors (TFs) are plant-specific and play important roles in development, responses to biotic and abiotic cues and hormone signaling. So far, only a few NAC genes have been reported to regulate cell death. In this study, we identified and characterized a NAC55 gene isolated from oilseed rape (Brassica napus L.). BnaNAC55 responds to multiple stresses, including cold, heat, abscisic acid (ABA), jasmonic acid (JA) and a necrotrophic fungal pathogen Sclerotinia sclerotiorum. BnaNAC55 has transactivation activity and is located in the nucleus. BnaNAC55 is able to form homodimers in planta. Unlike ANAC055, full-length BnaNAC55, but not either the N-terminal NAC domain or C-terminal regulatory domain, induces ROS accumulation and hypersensitive response (HR)-like cell death when expressed both in oilseed rape protoplasts and Nicotiana benthamiana. Furthermore, BnaNAC55 expression causes obvious nuclear DNA fragmentation. Moreover, quantitative reverse transcription PCR (qRT-PCR) analysis identified that the expression levels of multiple genes regulating ROS production and scavenging, defense response as well as senescence are significantly induced. Using a dual luciferase reporter assay, we further confirm that BnaNAC55 could activate the expression of a few ROS and defense-related gene expression. Taken together, our work has identified a novel NAC TF from oilseed rape that modulates ROS accumulation and cell death.

Identification and characterization of plant-specific NAC gene family in canola (Brassica napus L.) reveal novel members involved in cell death.

NAC transcription factors are plant-specific and play important roles in plant development processes, response to biotic and abiotic cues and hormone signaling. However, to date, little is known about the NAC genes in canola (or oilseed rape, Brassica napus L.). In this study, a total of 60 NAC genes were identified from canola through a systematical analysis and mining of expressed sequence tags. Among these, the cDNA sequences of 41 NAC genes were successfully cloned. The translated protein sequences of canola NAC genes with the NAC genes from representative species were phylogenetically clustered into three major groups and multiple subgroups. The transcriptional activities of these BnaNAC proteins were assayed in yeast. In addition, by quantitative real-time RT-PCR, we further observed that some of these BnaNACs were regulated by different hormone stimuli or abiotic stresses. Interestingly, we successfully identified two novel BnaNACs, BnaNAC19 and BnaNAC82, which could elicit hypersensitive response-like cell death when expressed in Nicotiana benthamiana leaves, which was mediated by accumulation of reactive oxygen species. Overall, our work has laid a solid foundation for further characterization of this important NAC gene family in canola.

Identification, expression and interaction analyses of calcium-dependent protein kinase (CPK) genes in canola (Brassica napus L.).

BACKGROUND: Canola (Brassica napus L.) is one of the most important oil-producing crops in China and worldwide. The yield and quality of canola is frequently threatened by environmental stresses including drought, cold and high salinity. Calcium is a well-known ubiquitous intracellular secondary messenger in plants. Calcium-dependent protein kinases (CPKs) are Ser/Thr protein kinases found only in plants and some protozoans. CPKs are Ca2+ sensors that have both Ca2+ sensing function and kinase activity within a single protein and play crucial roles in plant development and responses to various environmental stresses. RESULTS: In this study, we mined the available expressed sequence tags (ESTs) of B. napus and identified a total of 25 CPK genes, among which cDNA sequences of 23 genes were successfully cloned from a double haploid cultivar of canola. Phylogenetic analysis demonstrated that they could be clustered into four subgroups. The subcellular localization of five selected BnaCPKs was determined using green fluorescence protein (GFP) as the reporter. Furthermore, the expression levels of 21 BnaCPK genes in response to salt, drought, cold, heat, abscisic acid (ABA), low potassium (LK) and oxidative stress were studied by quantitative RT-PCR and were found to respond to multiple stimuli, suggesting that canola CPKs may be convergence points of different signaling pathways. We also identified and cloned five and eight Clade A basic leucine zipper (bZIP) and protein phosphatase type 2C (PP2C) genes from canola and, using yeast two-hybrid and bimolecular fluorescence complementation (BiFC), determined the interaction between individual BnaCPKs and BnabZIPs or BnaPP2Cs (Clade A). We identified novel, interesting interaction partners for some of the BnaCPK proteins. CONCLUSION: We present the sequences and characterization of CPK gene family members in canola for the first time. This work provides a foundation for further crop improvement and improved understanding of signal transduction in plants.

Arabidopsis CIPK14 positively regulates glucose response.

Calcium is a ubiquitous intracellular secondary messenger in plants. Calcineurin B-like proteins (CBLs), which contain four Ca(2+)-binding EF hand motifs, are Ca(2+) sensors and regulate a group of Ser/Thr protein kinases called CBL-interacting protein kinases (CIPKs). Although the CBL-CIPK network has been demonstrated to play crucial roles in plant development and responses to various environmental stresses in Arabidopsis, little is known about their function in glucose signaling. In the present study, we identified CIPK14 gene from Arabidopsis that play a role in glucose signaling. The subcellular localization of CIPK14 was determined using green fluorescence protein (GFP) as the reporter. Furthermore, the expression levels of CIPK14 in response to salt, drought, cold, heat, ABA, methyl viologen (MV) and glucose treatments were examined by quantitative RT-PCR and it was found to respond to multiple stimuli, suggesting that CIPK14 may be a point of convergence for several different signaling pathways. Moreover, knock-out mutation of CIPK14 rendered it more sensitive to glucose treatment. Yeast two-hybrid assay demonstrated that CIPK14 interacted with three CBLs and also with two key kinases, sucrose non-fermenting 1-related kinase (SnRK) 1.1 and SnRK1.2 implicated in glucose signaling. This is the first report to demonstrate that CIPK also plays a role in glucose signaling.

Canola (Brassica napus L.) NAC103 transcription factor gene is a novel player inducing reactive oxygen species accumulation and cell death in plants.

NAC transcription factors are plant-specific and play important roles in many processes including plant development, response to biotic and abiotic stresses and hormone signaling. So far, only a few NAC genes have been identified to mediate cell death. In this study, we identified a novel NAC gene from canola (Brassica napus L.), BnaNAC103 which induces reactive oxygen species (ROS) accumulation and cell death in Nicotianabenthamiana leaves. We found that BnaNAC103 responded to multiple signalings, including cold, salicylic acid (SA) and a fungal pathogen Sclerotinia sclerotiorum. BnaNAC103 is located in the nucleus. Expression of full-length BnaNAC103, but not either the N-terminal NAC domain or C-terminal regulatory domain, was identified to induce hypersensitive response (HR)-like cell death when expressed in N. benthamiana. The cell death triggered by BnaNAC103 is preceded by accumulation of ROS, with diaminobenzidine (DAB) staining supporting this. Moreover, quantification of ion leakage and malondialdehyde (MDA) of leaf discs indicates significant cell membrane breakage and lipid peroxidation induced by BnaNAC103 expression. Taken together, our work has identified a novel NAC transcription factor gene modulating ROS level and cell death in plants.

Identification and functional analysis of mitogen-activated protein kinase kinase kinase (MAPKKK) genes in canola (Brassica napus L.).

Mitogen-activated protein kinase (MAPK) signalling cascades, consisting of three types of reversibly phosphorylated kinases (MAPKKK, MAPKK, and MAPK), are involved in important processes including plant immunity and hormone responses. The MAPKKKs comprise the largest family in the MAPK cascades, yet only a few of these genes have been associated with physiological functions, even in the model plant Arabidopsis thaliana. Canola (Brassica napus L.) is one of the most important oilseed crops in China and worldwide. To explore MAPKKK functions in biotic and abiotic stress responses in canola, 66 MAPKKK genes were identified and 28 of them were cloned. Phylogenetic analysis of these canola MAPKKKs with homologous genes from representative species classified them into three groups (A-C), comprising four MAPKKKs, seven ZIKs, and 17 Raf genes. A further 15 interaction pairs between these MAPKKKs and the downstream BnaMKKs were identified through a yeast two-hybrid assay. The interactions were further validated through bimolecular fluorescence complementation (BiFC) analysis. In addition, by quantitative real-time reverse transcription-PCR, it was further observed that some of these BnaMAPKKK genes were regulated by different hormone stimuli, abiotic stresses, or fungal pathogen treatments. Interestingly, two novel BnaMAPKKK genes, BnaMAPKKK18 and BnaMAPKKK19, which could elicit hypersensitive response (HR)-like cell death when transiently expressed in Nicotiana benthamiana leaves, were successfully identified. Moreover, it was found that BnaMAPKKK19 probably mediated cell death through BnaMKK9. Overall, the present work has laid the foundation for further characterization of this important MAPKKK gene family in canola.

Multilayered regulation and implication of flowering time in plants.

Initiation of flowering is a key switch for plants to shift from the vegetative growth to the phase of reproductive growth. This critical phase is essential not only for achieving successful reproduction, but also for facilitating environmental adaptation and maximizing yield potential. In the past decades, the environmental factors and genetic pathways that control flowering time have undergone extensive investigation in both model plant Arabidopsis and various crop species. The impact of environmental factors on plant flowering time is well documented. This paper focuses on the multilayered modulation of flowering time. Recent multi-omics approaches, and genetic screens have revealed additional components that modulate flowering time across various levels, encompassing chromatin modification, transcriptional and post-transcriptional control, as well as translational and post-translational regulation. The interplay between these various layers of regulation creates a finely-tuned system that can respond to a wide variety of inputs and allows plants to adjust flowering time in response to changing environmental conditions. In this review, we present a comprehensive overview of the recent progress made in understanding the intricate regulation of flowering time in plants, emphasizing the pivotal molecular components and their intricate interactions. Additionally, we provide an exhaustive list of key genes implicated in the intricate modulation of flowering time and offer a detailed summary of regulators of FLOWERING LOCUS T (FT) and FLOWERING LOCUS (FLC). We also discuss the implications of this knowledge for crop improvement and adaptation to changing environments.