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Drought is a major environmental stress that threatens crop production. Therefore, identification of genes involved in drought stress response is of vital importance to decipher the molecular mechanism of stress signal transduction and breed drought tolerance crops, especially for maize. Clade A PP2C phosphatases are core abscisic acid (ABA) signaling components, regulating ABA signal transduction and drought response. However, the roles of other clade PP2Cs in drought resistance remain largely unknown. Here, we discovered a clade F PP2C, ZmPP84, that negatively regulates drought tolerance by screening a transgenic overexpression maize library. Quantitative RT-PCR indicates that the transcription of ZmPP84 is suppressed by drought stress. We identified that ZmMEK1, a member of the MAPKK family, interacts with ZmPP84 by immunoprecipitation and mass spectrometry analysis. Additionally, we found that ZmPP84 can dephosphorylate ZmMEK1 and repress its kinase activity on the downstream substrate kinase ZmSIMK1, while ZmSIMK1 is able to phosphorylate S-type anion channel ZmSLAC1 at S146 and T520 in vitro. Mutations of S146 and T520 to phosphomimetic aspartate could activate ZmSLAC1 currents in Xenopus oocytes. Taken together, our study suggests that ZmPP84 is a negative regulator of drought stress response that inhibits stomatal closure through dephosphorylating ZmMEK1, thereby repressing ZmMEK1-ZmSIMK1 signaling pathway.

Maintaining proper DNA methylation levels in the genome requires active demethylation of DNA. However, removing the methyl group from a modified cytosine is chemically difficult and therefore, the underlying mechanism of demethylation had remained unclear for many years. The discovery of the first eukaryotic DNA demethylase, Arabidopsis thaliana REPRESSOR OF SILENCING 1 (ROS1), led to elucidation of the 5-methylcytosine base excision repair mechanism of active DNA demethylation. In the 20 years since ROS1 was discovered, our understanding of this active DNA demethylation pathway, as well as its regulation and biological functions in plants, has greatly expanded. These exciting developments have laid the groundwork for further dissecting the regulatory mechanisms of active DNA demethylation, with potential applications in epigenome editing to facilitate crop breeding and gene therapy.

Repression of embryonic traits during the seed-to-seedling phase transition requires the inactivation of master transcription factors associated with embryogenesis. How the timing of such inactivation is controlled is unclear. Here, we report on a novel transcriptional co-repressor, Arabidopsis thaliana SDR4L, that forms a feedback inhibition loop with the master transcription factors LEC1 and ABI3 to repress embryonic traits post-imbibition. LEC1 and ABI3 regulate their own expression by inducing AtSDR4L during mid to late embryogenesis. AtSDR4L binds to sites upstream of LEC1 and ABI4, and these transcripts are upregulated in Atsdr4l seedlings. Atsdr4l seedlings phenocopy a LEC1 overexpressor. The embryonic traits of Atsdr4l can be partially rescued by impairing LEC1 or ABI3. The penetrance and expressivity of the Atsdr4l phenotypes depend on both developmental and external cues, demonstrating the importance of AtSDR4L in seedling establishment under suboptimal conditions.

While crop yields have historically increased, drought resistance has become a major concern in the context of global climate change. The trade-off between crop yield and drought resistance is a common phenomenon; however, the underlying molecular modulators remain undetermined. Through genome-wide association study, we revealed that three non-synonymous variants in a drought-resistant allele of ZmSRO1d-R resulted in plasma membrane localization and enhanced mono-ADP-ribosyltransferase activity of ZmSRO1d toward ZmRBOHC, which increased reactive oxygen species (ROS) levels in guard cells and promoted stomatal closure. ZmSRO1d-R enhanced plant drought resilience and protected grain yields under drought conditions, but it led to yield drag under favorable conditions. In contrast, loss-of-function mutants of ZmRBOHC showed remarkably increased yields under well-watered conditions, whereas they showed compromised drought resistance. Interestingly, by analyzing 189 teosinte accessions, we found that the ZmSRO1d-R allele was present in teosinte but was selected against during maize domestication and modern breeding. Collectively, our work suggests that the allele frequency reduction of ZmSRO1d-R in breeding programs may have compromised maize drought resistance while increased yields. Therefore, introduction of the ZmSRO1d-R allele into modern maize cultivars would contribute to food security under drought stress caused by global climate change.

To test the hypothesis that elevated plasma levels of homocysteine (Hcy) and lipoprotein (a) (LPA) contribute to diabetic retinopathy (DR) associated with dysregulated lipid profile, dyslipidaemia, and kidney function.A total of 83 patients with type 2 diabetes mellitus (T2DM) were enrolled in this prospective case-control study. Patients were categorized into those with no DR (DM), non-proliferative DR (NPDR), and proliferative DR (PDR). Age and sex-matched individuals with no diabetes were included in the control group. Biochemical tests, including fasting blood glucose (FBG), glycated hemoglobin (HbA1c), Hcy, LPA, lipid profile, and urine microalbumin (UMA), were evaluated.Hcy was negatively correlated with high-density lipoprotein-cholesterol (HDL-C) (p 0.05), but positively correlated with [total cholesterol (TC)-HDL-C)/HDL-C] (p 0.05), low-density lipoprotein cholesterol (LDL-C)/HDL-C (p 0.05), and UMA (p 0.05). Traditional risk factors, Hcy, arteriosclerosis-associated plasma indices, and UMA, resulted as the independent risk factors for the occurrence of DM and DR. After controlling for age, sex, duration of DM, and FBG, a multiple ordinal logistic regression model showed that LPA [OR = 2.90, 95% confidence interval (95% CI) 1.16-7.23, p = 0.023)], LDL-C (OR = 4.28, 95% CI 1.24-14.79, p = 0.021), and (TC-HDL-C)/HDL-C (OR = 1.92, 95% CI 1.05-3.53, p = 0.035) were risk factors for DM and DR.Hcy and LPA contributed to DM and DR. Hcy was positively correlated with kidney dysfunction and the ratios of lipid profiles, and negatively with HDL-C, LPA, LDL-C, and (TC-HDL-C)/HDL-C resulted as predictors of the occurrence of DM and severity of DR.

The mechanisms that balance plant growth and stress responses are poorly understood, but they appear to involve abscisic acid (ABA) signaling mediated by protein kinases. Here, to explore these mechanisms, we examined the responses of Arabidopsis thaliana protein kinase mutants to ABA treatment. We found that mutants of BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED RECEPTOR KINASE 1 (BAK1) were hypersensitive to the effects of ABA on both seed germination and primary root growth. The kinase OPEN STOMATA 1 (OST1) was more highly activated by ABA in bak1 mutant than the wild type. BAK1 was not activated by ABA treatment in the dominant negative mutant abi1-1 or the pyr1 pyl4 pyl5 pyl8 quadruple mutant, but it was more highly activated by this treatment in the abi1-2 abi2-2 hab1-1 loss-of-function triple mutant than the wild type. BAK1 phosphorylates OST1 T146 and inhibits its activity. Genetic analyses suggested that BAK1 acts at or upstream of core components in the ABA signaling pathway, including PYLs, PP2Cs, and SnRK2s, during seed germination and primary root growth. Although the upstream brassinosteroid (BR) signaling components BAK1 and BR INSENSITIVE 1 (BRI1) positively regulate ABA-induced stomatal closure, mutations affecting downstream components of BR signaling, including BRASSINOSTEROID-SIGNALING KINASEs (BSKs) and BRASSINOSTEROID-INSENSITIVE 2 (BIN2), did not affect ABA-mediated stomatal movement. Thus, our study uncovered an important role of BAK1 in negatively regulating ABA signaling during seed germination and primary root growth, but positively modulating ABA-induced stomatal closure, thus optimizing the plant growth under drought stress.

Manganese (Mn) is an essential micronutrient for all living organisms. However, excess supply of Mn as occurring in acid or waterlogged soils has toxic effects on plant physiology and development. Although a variety of Mn transporter families has been characterized, our understanding of how these transporters are regulated to uphold and adjust Mn homeostasis in plants remains rudimentary. Here, we identify two calcineurin-B-like proteins, CBL2/3, and their interacting kinases, CIPK3/9/26, as key regulators for plant Mn homeostasis. We found that Arabidopsis mutants lacking CBL2 and 3 or their interacting protein kinases CIPK3/9/26 exhibit remarkable high-Mn tolerance. Intriguingly, CIPK3/9/26 interact with and phosphorylate the tonoplast-localized Mn and iron (Fe) transporter MTP8 primarily at Ser35, which is conserved among MTP8 proteins from various species. Mn transport complementation assays in yeast combined with multiple physiological assays indicate that CBL-CIPK-mediated phosphorylation of MTP8 negatively regulates its transport activity from the cytoplasm to the vacuole. Moreover, we report that sequential phosphorylation of MTP8 initially at Ser31/32 by the calcium-dependent protein kinases CPK5 and subsequently by CIPK26 at Ser35 provides an activation/deactivation fine-tuning mechanism for differential Mn transport regulation. Collectively, our studies define a two-tiered calcium-controlled mechanism for dynamically orchestrating Mn homeostasis under conditions of fluctuating Mn supply.

Minichromosome Maintenance protein 10 (MCM10) is essential for DNA replication initiation and DNA elongation in yeasts and animals. Although the functions of MCM10 in DNA replication and repair have been well documented, the detail mechanisms for MCM10 in these processes are not well known. Here, we identified AtMCM10 gene through a forward genetic screening for releasing a silenced marker gene. Although plant MCM10 possesses a similar crystal structure as animal MCM10, AtMCM10 is not essential for plant growth or development in Arabidopsis. AtMCM10 can directly binds to histone H3-H4 and promotes nucleosome assembly in vitro. The nucleosome density is decreased in Atmcm10, and most of the nucleosome density decreased regions in Atmcm10 are also regulated by newly synthesized histone chaperone Chromatin Assembly Factor-1 (CAF-1). Loss of both AtMCM10 and CAF-1 is embryo lethal, indicating that AtMCM10 and CAF-1 are indispensable for replication-coupled nucleosome assembly. AtMCM10 interacts with both new and parental histones. Atmcm10 mutants have lower H3.1 abundance and reduced H3K27me1/3 levels with releasing some silenced transposons. We propose that AtMCM10 deposit new and parental histones during nucleosome assembly, maintaining proper epigenetic modifications and genome stability during DNA replication. This article is protected by copyright. All rights reserved.

Water uptake is crucial for crop growth and development and drought stress tolerance. The water channels aquaporins play important roles in plant water uptake. Here, we discovered that a jasmonic acid analog, coronatine (COR), enhanced maize (Zea mays) root water uptake capacity under artificial water deficiency conditions. COR treatment induced the expression of the aquaporin gene Plasma membrane intrinsic protein 2;5 (ZmPIP2;5). In vivo and in vitro experiments indicated that COR also directly acts on ZmPIP2;5 to improve water uptake in maize and Xenopus oocytes. The leaf water potential and hydraulic conductivity of roots growing under hyperosmotic conditions were higher in ZmPIP2;5-overexpression lines and lower in the zmpip2;5 knockout mutant, compared to wild-type plants. Based on a comparison between ZmPIP2;5 and other PIP2s, we predicted that COR may bind to the functional site in loop E of ZmPIP2;5. We confirmed this prediction by surface plasmon resonance technology and a microscale thermophoresis assay, and showed that deleting the binding motif greatly reduced COR binding. We identified the N241 residue as the COR-specific binding site, which may activate the channel of the aquaporin tetramer and increase water transport activity, which may facilitate water uptake under hyperosmotic stress. This article is protected by copyright. All rights reserved.

CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1), a well-characterized E3 ubiquitin ligase, is a central repressor of seedling photomorphogenic development in darkness. However, whether COP1 is involved in modulating abscisic acid (ABA) signaling in darkness remains largely obscure. Here, we report that COP1 is a positive regulator of ABA signaling during Arabidopsis seedling growth in the dark. COP1 mediates ABA-induced accumulation of ABI5, a transcription factor playing a key role in ABA signaling, through transcriptional and post-translational regulatory mechanisms. We further show that COP1 physically interacts with ABA-hypersensitive DCAF1 (ABD1), a substrate receptor of the CUL4-DDB1 E3 ligase targeting ABI5 for degradation. Accordingly, COP1 directly ubiquitinates ABD1 in vitro, and negatively regulates ABD1 protein abundance in vivo in the dark but not in the light. Therefore, COP1 promotes ABI5 protein stability post-translationally in darkness by destabilizing ABD1 in response to ABA. Interestingly, we reveal that ABA induces the nuclear accumulation of COP1 in darkness, thus enhancing its activity in propagating the ABA signal. Together, our study uncovers that COP1 modulates ABA signaling during seedling growth in darkness by mediating ABA-induced ABI5 accumulation, demonstrating that plants adjust their ABA signaling mechanisms according to their light environment.

Plants cannot move, so they must endure abiotic stresses such as drought, salinity and extreme temperatures. These stressors greatly limit the distribution of plants, alter their growth and development, and reduce crop productivity. Recent progress in our understanding of the molecular mechanisms underlying the responses of plants to abiotic stresses emphasizes their multilevel nature; multiple processes are involved, including sensing, signalling, transcription, transcript processing, translation and post-translational protein modifications. This improved knowledge can be used to boost crop productivity and agricultural sustainability through genetic, chemical and microbial approaches.

Exposure to cold triggers a spike in cytosolic calcium (Ca 2+ ) that often leads to transcriptional reprogramming in plants. However, how this Ca 2+ signal is perceived and relayed to the downstream cold signaling pathway remains unknown. Here, we show that the CALCIUM-DEPENDENT PROTEIN KINASE 28 (CPK28) initiates a phosphorylation cascade to specify transcriptional reprogramming downstream of cold-induced Ca 2+ signal. Plasma membrane (PM)–localized CPK28 is activated rapidly upon cold shock within 10 seconds in a Ca 2+ -dependent manner. CPK28 then phosphorylates and promotes the nuclear translocation of NIN-LIKE PROTEIN 7 (NLP7), a transcription factor that specifies the transcriptional reprogramming of cold-responsive gene sets in response to Ca 2+ , thereby positively regulating plant response to cold stress. This study elucidates a previously unidentified mechanism by which the CPK28-NLP7 regulatory module integrates cold-evoked Ca 2+ signal and transcriptome and thus uncovers a key strategy for the rapid perception and transduction of cold signals from the PM to the nucleus.

Manganese (Mn) is an essential micronutrient in plants. However, excessive Mn absorption in acidic and waterlogged soils can lead to Mn toxicity. Despite their essential roles in Mn homeostasis, transcriptional and post-transcriptional modifications of Mn transporters remain poorly understood. Here, we demonstrated that high-Mn stress induces an obvious Ca2+ signature in Arabidopsis. We identified four calcium-dependent protein kinases, CPK4/5/6/11, that interact with the tonoplast-localized Mn and iron (Fe) transporter MTP8 in vitro and in vivo. The cpk4/5/6/11 quadruple mutant displayed a dramatic high-Mn-sensitive phenotype similar to that of the mtp8 mutant. CPKs phosphorylated the N-terminal domain of MTP8 primarily at the Ser31 and Ser32 residues. Transport assays combined with multiple physiological experiments on phospho-dead variant MTP8S31/32A and phospho-mimetic variant MTP8S31/32D plants under different Mn and Fe conditions suggested that Ser31 and Ser32 are crucial for MTP8 function. In addition, genetic analysis showed that CPKs functioned upstream of MTP8. In summary, we identified a tonoplast-associated calcium signaling cascade that orchestrates Mn homeostasis and links Mn toxicity, Ca2+ signaling, and Mn transporters. These findings provide new insight into Mn homeostasis mechanisms and Ca2+ signaling pathways in plants, providing potential targets for engineering heavy metal toxicity-tolerant plants.

Potassium (K+) is one of the essential macronutrients for plant growth and development. However, the available K+ concentration in soil is relatively low. Plant roots can perceive low K+ (LK) stress, then enhance high-affinity K+ uptake by activating H+-ATPases in root cells, but the mechanisms are still unclear. Here, we identified the receptor-like protein kinase Brassinosteroid Insensitive 1-Associated Receptor Kinase 1 (BAK1) that is involved in LK response by regulating the Arabidopsis (Arabidopsis thaliana) plasma membrane H+-ATPase isoform 2 (AHA2). The bak1 mutant showed leaf chlorosis phenotype and reduced K+ content under LK conditions, which was due to the decline of K+ uptake capacity. BAK1 could directly interact with the AHA2 C terminus and phosphorylate T858 and T881, by which the H+ pump activity of AHA2 was enhanced. The bak1 aha2 double mutant also displayed a leaf chlorosis phenotype that was similar to their single mutants. The constitutively activated form AHA2Δ98 and phosphorylation-mimic form AHA2T858D or AHA2T881D could complement the LK sensitive phenotypes of both aha2 and bak1 mutants. Together, our data demonstrate that BAK1 phosphorylates AHA2 and enhances its activity, which subsequently promotes K+ uptake under LK conditions.

Background：Gut microbiota play major roles in host nutrition and metabolism, but can also cause serious diseases among animals and humans. Recent studies have focused on gut bacterial diversity in migratory waterbirds; however, little information about their gut fungal communities has been reported.Results: In this study, we investigated the gut fungal communities of Anser erythropus wintering at either Shengjin Lake or Caizi Lake, China, using high-throughput sequencing of the internal transcribed spacer (ITS) gene region. The operational taxonomic units (OTUs) from the Shengjin Lake geese represented seven phyla and 27 classes; those from the Caizi Lake geese comprised seven phyla and 28 classes. Ascomycota, Basidiomycota, Zygomycota, and Rozellomycota were the dominant gut fungal phyla. Gut fungal community composition showed dramatic differences between the two populations. The Shengjin Lake geese ate mainly Poaceae spp., whereas the Caizi Lake geese ate mainly Carex spp., suggesting that different diets may induce variation in gut fungal communities between these populations. Additionally, nine potentially pathogenic species were identified across all samples, and their relative abundances were significantly higher in the Shengjin Lake samples than the Caizi Lake samples.Conclusions: The results indicated that gut fungal community were significant differences between Anser erythropus wintering at Shengjin and Caizi Lakes. Between Caizi Lake and Shengjin Lake, the geese in our study group consumed food that differed in type and quality maybe lead the gut fungi varied markedly between the geese from each lake. These findings expand our knowledge of gut fungi in waterbirds and suggest that the gut fungal communities differed in two wintering populations of the same species. This study provides basic data for the composition and structure of gut fungi of wintering waterbirds, and we argue that more attention should be paid to investigating the pathogenic gut species of migratory waterbirds, which may increase disease risks for sympatric poultry as well as humans.

Protein kinases are major players in various signal transduction pathways. Understanding the molecular mechanisms behind plant responses to biotic and abiotic stresses has become critical for developing and breeding climate-resilient crops. In this review, we summarize recent progress on understanding plant drought, salt, and cold stress responses, with a focus on signal perception and transduction by different protein kinases, especially sucrose nonfermenting1 (SNF1)-related protein kinases (SnRKs), mitogen-activated protein kinase (MAPK) cascades, calcium-dependent protein kinases (CDPKs/CPKs), and receptor-like kinases (RLKs). We also discuss future challenges in these research fields.

Plant root architecture flexibly adapts to changing nitrate (NO

Plants adapt to their ever-changing environment via positive and negative signals induced by environmental stimuli. Drought stress, for instance, induces accumulation of the plant hormone abscisic acid (ABA), triggering ABA signal transduction. However, the molecular mechanisms for switching between plant growth promotion and stress response remain poorly understood. Here we report that RAF (rapidly accelerated fibrosarcoma)-LIKE MITOGEN-ACTIVATED PROTEIN KINASE KINASE KINASE 22 (RAF22) in Arabidopsis thaliana physically interacts with ABA INSENSITIVE 1 (ABI1) and phosphorylates ABI1 at Ser416 residue to enhance its phosphatase activity. Interestingly, ABI1 can also enhance the activity of RAF22 through dephosphorylation, reciprocally inhibiting ABA signaling and promoting the maintenance of plant growth under normal conditions. Under drought stress, however, the ABA-activated OPEN STOMATA1 (OST1) phosphorylates the Ser81 residue of RAF22 and inhibits its kinase activity, restraining its enhancement of ABI1 activity. Taken together, our study reveals that RAF22, ABI1, and OST1 form a dynamic regulatory network that plays crucial roles in optimizing plant growth and environmental adaptation under drought stress.

Stomatal opening is largely promoted by light-activated plasma membrane-localized proton ATPases (PM H+-ATPases), while their closure is mainly modulated by abscisic acid (ABA) signaling during drought stress. It is unknown whether PM H+-ATPases participate in ABA-induced stomatal closure. We established that BRI1-ASSOCIATED RECEPTOR KINASE 1 (BAK1) interacts with, phosphorylates and activates the major PM Arabidopsis H+-ATPase isoform 2 (AHA2). Detached leaves from aha2-6 single mutant Arabidopsis thaliana plants lost as much water as bak1-4 single and aha2-6 bak1-4 double mutants, with all three mutants losing more water than the wild-type (Columbia-0 [Col-0]). In agreement with these observations, aha2-6, bak1-4, and aha2-6 bak1-4 mutants were less sensitive to ABA-induced stomatal closure than Col-0, whereas the aha2-6 mutation did not affect ABA-inhibited stomatal opening under light conditions. ABA-activated BAK1 phosphorylated AHA2 at Ser-944 in its C-terminus and activated AHA2, leading to rapid H+ efflux, cytoplasmic alkalinization, and reactive oxygen species (ROS) accumulation, to initiate ABA signal transduction and stomatal closure. The phosphorylation-mimicking mutation AHA2S944D driven by its own promoter could largely compensate for the defective phenotypes of water loss, cytoplasmic alkalinization, and ROS accumulation in both aha2-6 and bak1-4 mutants. Our results uncover a crucial role of AHA2 in cytoplasmic alkalinization and ABA-induced stomatal closure during the plant’s response to drought stress.

Abiotic stresses and soil nutrient limitations are major environmental conditions that reduce plant growth, productivity and quality. Plants have evolved mechanisms to perceive these environmental challenges, transmit the stress signals within cells as well as between cells and tissues, and make appropriate adjustments in their growth and development in order to survive and reproduce. In recent years, significant progress has been made on many fronts of the stress signaling research, particularly in understanding the downstream signaling events that culminate at the activation of stress- and nutrient limitation-responsive genes, cellular ion homeostasis, and growth adjustment. However, the revelation of the early events of stress signaling, particularly the identification of primary stress sensors, still lags behind. In this review, we summarize recent work on the genetic and molecular mechanisms of plant abiotic stress and nutrient limitation sensing and signaling and discuss new directions for future studies.

RNA splicing and spliceosome assembly in eukaryotes occur mainly during transcription. However, co-transcriptional splicing has not yet been explored in plants. Here, we built transcriptomes of nascent chromatin RNAs in Arabidopsis thaliana and showed that nearly all introns undergo co-transcriptional splicing, which occurs with higher efficiency for introns in protein-coding genes than for those in noncoding RNAs. Total intron number and intron position are two predominant features that correlate with co-transcriptional splicing efficiency, and introns with alternative 5′ or 3′ splice sites are less efficiently spliced. Furthermore, we found that mutations in genes encoding trans-acting proteins lead to more introns with increased splicing defects in nascent RNAs than in mature RNAs, and that introns with increased splicing defects in mature RNAs are inefficiently spliced at the co-transcriptional level. Collectively, our results not only uncovered widespread co-transcriptional splicing in Arabidopsis but also identified features that may affect or be affected by co-transcriptional splicing efficiency.

The phytohormone abscisic acid (ABA) and the Polycomb group proteins have key roles in regulating plant growth and development; however, their interplay and underlying mechanisms are not fully understood. Here, we identified an Arabidopsis (Arabidopsis thaliana) nodulin homeobox (AtNDX) protein as a negative regulator in the ABA signaling pathway. AtNDX mutants are hypersensitive to ABA, as measured by inhibition of seed germination and root growth, and the expression of AtNDX is downregulated by ABA. AtNDX interacts with the Polycomb Repressive Complex1 (PRC1) core components AtRING1A and AtRING1B in vitro and in vivo, and together, they negatively regulate the expression levels of some ABA-responsive genes. We identified ABA-INSENSITIVE (ABI4) as a direct target of AtNDX. AtNDX directly binds the downstream region of ABI4 and deleting this region increases the ABA sensitivity of primary root growth. Furthermore, ABI4 mutations rescue the ABA-hypersensitive phenotypes of ndx mutants and ABI4-overexpressing plants are hypersensitive to ABA in primary root growth. Thus, our work reveals the critical functions of AtNDX and PRC1 in some ABA-mediated processes and their regulation of ABI4.

Plants cannot move, so they must endure abiotic stresses such as drought, salinity and extreme temperatures. These stressors greatly limit the distribution of plants, alter their growth and development, and reduce crop productivity. Recent progress in our understanding of the molecular mechanisms underlying the responses of plants to abiotic stresses emphasizes their multilevel nature; multiple processes are involved, including sensing, signalling, transcription, transcript processing, translation and post-translational protein modifications. This improved knowledge can be used to boost crop productivity and agricultural sustainability through genetic, chemical and microbial approaches.

The gut microbiota play major roles in host nutrition and metabolism, and even potential to cause serious disease for animals and human, however, the knowledge of waterbirds’ gut fungal communities are quite limited at present. In this paper, the gut fungal communities and infer the potential pathogens isolated from the feces of Anser erythropus wintering at Shengjin Lake (SJ) and Caizi Lake (CZ) were investigated based on ITS gene region by using high-throughput sequencing. 1,302,562 valid tags corresponding to 2,102 OTUs were retained from 20 fecal samples, including 10 samples per lake. The OTUs from SJ geese represented seven phyla and 27 classes, seven phyla and 28 classes were identified from CZ samples. Ascomycota, Basidiomycota, Zygomycota and Rozellomycota were the dominant gut fungal phyla in this study, accounted for 61.60%, 35.60%, 1.84%, and 0.30% of the OTUs, respectively. The alpha diversity indices showed significantly different between the geese from SJ and CZ. The Anser erythropus mainly ate Poaceae spp. at SJ, while Carex spp. component was identified at CZ, suggesting that the variations in fungal community between the two lake geese might be induced by different diets. We also observed a fungal pattern with a higher number of significant correlations to bacterial genus, and Ceratobasidium, Tomentella, Paurocotylis, Tuber, Podospora and Mortierella were core fungal genus in the two lake geese. Nine potential pathogenic species were identified in the guts across all samples of Anser erythropus at SJ and CZ, it also showed the relative abundance of potential pathogen was significantly higher from SJ samples than that from CZ samples. These findings expanded our knowledge on the gut fungi for waterbirds, indicating the fungi are highly sensitive to diet at two lakes and should pay more attention to the potential pathogenic species of Anser erythropus.

Cold acclimation in Arabidopsis thaliana triggers a significant transcriptional reprogramming altering the expression patterns of thousands of cold-responsive (COR) genes. Essential to this process is the C-repeat binding factor (CBF)-dependent pathway, involving the activity of AP2/ERF (APETALA2/ethylene-responsive factor)-type CBF transcription factors required for plant cold acclimation. In this study, we performed chromatin immunoprecipitation assays followed by deep sequencing (ChIP-seq) to determine the genome-wide binding sites of the CBF transcription factors. Cold-induced CBF proteins specifically bind to the conserved C-repeat (CRT)/dehydration-responsive elements (CRT/DRE; G/ACCGAC) of their target genes. A Gene Ontology enrichment analysis showed that 1,012 genes are targeted by all three CBFs. Combined with a transcriptional analysis of the cbf1,2,3 triple mutant, we define 146 CBF regulons as direct CBF targets. In addition, the CBF-target genes are significantly enriched in functions associated with hormone, light, and circadian rhythm signaling, suggesting that the CBFs act as key integrators of endogenous and external environmental cues. Our findings not only define the genome-wide binding patterns of the CBFs during the early cold response, but also provide insights into the role of the CBFs in regulating multiple biological processes of plants.

Protein phosphorylation and dephosphorylation have been reported to play important roles in plant cold responses. In addition, phospho-regulatory feedback is a conserved mechanism for biological processes and stress responses in animals and plants. However, it is less well known that a regulatory feedback loop is formed by the protein kinase and the protein phosphatase in plant responses to cold stress. Here, we report that OPEN STOMATA 1 (OST1) and PROTEIN PHOSPHATASE 2C G GROUP 1 (PP2CG1) reciprocally regulate the activity during the cold stress response. The interaction of PP2CG1 and OST1 is inhibited by cold stress, which results in the release of OST1 at the cytoplasm and nucleus from suppression by PP2CG1. Interestingly, cold-activated OST1 phosphorylates PP2CG1 to suppress its phosphatase activity, thereby amplifying cold signaling in plants. Mutations of PP2CG1 and its homolog PP2CG2 enhance freezing tolerance, whereas overexpression of PP2CG1 decreases freezing tolerance. Moreover, PP2CG1 negatively regulates protein levels of C-REPEAT BINDING FACTORs (CBFs) under cold stress. Our results uncover a phosphor/dephosphor-regulatory feedback loop mediated by PP2CG1 phosphatase and OST1 protein kinase in plant cold responses.

Light and temperature are two key environmental factors that coordinately regulate plant growth and development. Although the mechanisms that integrate signaling mediated by cold and red light have been unraveled, the roles of the blue light photoreceptors cryptochromes in plant responses to cold remain unclear. In this study, we demonstrate that the CRYPTOCHROME2 (CRY2)-COP1-HY5-BBX7/8 module regulates blue light-dependent cold acclimation in Arabidopsis thaliana. We show that phosphorylated forms of CRY2 induced by blue light are stabilized by cold stress and that cold-stabilized CRY2 competes with the transcription factor HY5 to attenuate the HY5–COP1 interaction, thereby allowing HY5 to accumulate at cold temperatures. Furthermore, our data demonstrate that B-BOX DOMAIN PROTEIN7 (BBX7) and BBX8 function as direct HY5 targets that positively regulate freezing tolerance by modulating the expression of a set of cold-responsive genes, which mainly occurs independently of the C-repeat-binding factor pathway. Our study uncovers a mechanistic framework by which CRY2-mediated blue-light signaling enhances freezing tolerance, shedding light on the molecular mechanisms underlying the crosstalk between cold and light signaling pathways in plants.

Verticillium wilt is a severe plant disease that causes massive losses in multiple crops. Increasing the plant resistance to Verticillium wilt is a critical challenge worldwide. Here, we report that the hemibiotrophic Verticillium dahliae (V. dahliae)-secreted Asp f2-like protein VDAL causes leaf wilting when applied to cotton leaves in vitro, but enhances the resistance to V. dahliae when overexpressed in Arabidopsis or cotton without affecting the plant growth and development. VDAL protein interacts with Arabidopsis E3 ligases PUB25 and PUB26 (PUBs) and is ubiquitinated by PUBs in vitro. However, VDAL is not degraded by PUB25 or PUB26 in planta. Besides, the pub25 pub26 double mutant shows higher resistance to V. dahliae than the wild type. PUBs interact with the transcription factor MYB6 in a yeast two-hybrid screen. MYB6 promotes plant resistance to Verticillium wilt while PUBs ubiquitinate MYB6 and mediate its degradation. VDAL competes with MYB6 for binding to PUBs, and the role of VDAL in increasing Verticillium wilt resistance depends on MYB6. Taken together, these results suggest that plants evolute a strategy to utilize the invaded effector protein VDAL to resist the V. dahliae infection without causing a hypersensitive response (HR), Alternatively, in order to take nutrients from host cells, hemibiotrophic pathogens may use some effectors to keep plant cells alive during its infection in order to take nutrients from host cells. This study provides the molecular mechanism for plants increasing disease resistance when overexpressing some effector proteins without inducing HR, and may promote searching for more genes from pathogenic fungi or bacteria to engineer plant disease resistance.One-sentence summaryEctopically expressed VDAL in Arabidopsis alleviates the degradation of a positive disease response factor MYB6 through its interaction with PUB25/26 E3 ligases.

Verticillium wilt is a severe plant disease that causes massive losses in multiple crops. Increasing the plant resistance to Verticillium wilt is a critical challenge worldwide. Here, we report that the hemibiotrophic Verticillium dahliae-secreted Asp f2-like protein VDAL causes leaf wilting when applied to cotton leaves in vitro but enhances the resistance to V. dahliae when overexpressed in Arabidopsis or cotton without affecting the plant growth and development. VDAL protein interacts with Arabidopsis E3 ligases plant U-box 25 (PUB25) and PUB26 and is ubiquitinated by PUBs in vitro. However, VDAL is not degraded by PUB25 or PUB26 in planta. Besides, the pub25 pub26 double mutant shows higher resistance to V. dahliae than the wild-type. PUBs interact with the transcription factor MYB6 in a yeast two-hybrid screen. MYB6 promotes plant resistance to Verticillium wilt while PUBs ubiquitinate MYB6 and mediate its degradation. VDAL competes with MYB6 for binding to PUBs, and the role of VDAL in increasing Verticillium wilt resistance depends on MYB6. Taken together, these results suggest that plants evolute a strategy to utilize the invaded effector protein VDAL to resist the V. dahliae infection without causing a hypersensitive response (HR); alternatively, hemibiotrophic pathogens may use some effectors to keep plant cells alive during its infection in order to take nutrients from host cells. This study provides the molecular mechanism for plants increasing disease resistance when overexpressing some effector proteins without inducing HR, and may promote searching for more genes from pathogenic fungi or bacteria to engineer plant disease resistance.