SNF1-related Protein Kinase Research Articles

A type-2C protein phosphatase (GhDRP1) participates in cotton (Gossypium hirsutum) response to drought stress.

GhDRP1 acts as a negatively regulator to participate in response to drought stress possibly by modulating ABA signaling pathway and flavonoid biosynthesis pathway which affects stomata movement and thus water loss, ROS scavenging enzymes, and proline accumulation in cotton. Type-2C protein phosphatases (PP2C) may play important roles in plant stress signal transduction. Here, we show the evidence that a cotton PP2C protein GhDRP1 participates in plant response to drought stress. GhDRP1 gene encodes an active type-2C protein phosphatase (PP2C) and its expression is significantly induced in cotton by drought stress. Compared with wild type, the GhDRP1 overexpression (OE) transgenic cotton and Arabidopsis displayed reduced drought tolerance, whereas GhDRP1-silenced (RNAi) cotton showed enhanced drought tolerance. Under drought stress, malondialdehyde content was lower, whereas superoxide dismutase and peroxidase activities, proline content, stomata closure and relative water content were higher in GhDRP1 RNAi plants compared with those in wild type. In contrast, GhDRP1 OE plants showed the opposite phenotype under the same conditions. Expression levels of some stress-related and flavonoid biosynthesis-related genes were altered in GhDRP1 transgenic plants under drought stress. Additionally, GhDRP1 protein could interact with other proteins such as PYLs, SNF1-related protein kinase and GLK1-like protein. Collectively, these data suggest that GhDRP1 participates in plant response to drought stress possibly by modulating ABA signaling pathway and flavonoid biosynthesis pathway which affects stomata movement and thus water loss, ROS scavenging enzymes, and proline accumulation in cotton.

Embryogenic Calli Induction and Salt Stress Response Revealed by RNA-Seq in Diploid Wild Species Gossypium sturtianum and Gossypium raimondii.

Wild cotton species can contribute to a valuable gene pool for genetic improvement, such as genes related to salt tolerance. However, reproductive isolation of different species poses an obstacle to produce hybrids through conventional breeding. Protoplast fusion technology for somatic cell hybridization provides an opportunity for genetic manipulation and targeting of agronomic traits. Transcriptome sequencing analysis of callus under salt stress is conducive to study salt tolerance genes. In this study, calli were induced to provide materials for extracting protoplasts and also for screening salt tolerance genes. Calli were successfully induced from leaves of Gossypium sturtianum (C1 genome) and hypocotyls of G. raimondii (D5 genome), and embryogenic calli of G. sturtianum and G. raimondii were induced on a differentiation medium with different concentrations of 2, 4-D, KT, and IBA, respectively. In addition, embryogenic calli were also induced successfully from G. raimondii through suspension cultivation. Transcriptome sequencing analysis was performed on the calli of G. raimondii and G. sturtianum, which were treated with 200 mM NaCl at 0, 6, 12, 24, and 48 h, and a total of 12,524 genes were detected with different expression patterns under salt stress. Functional analysis showed that 3,482 genes, which were differentially expressed in calli of G. raimondii and G. sturtianum, were associated with biological processes of nucleic acid binding, plant hormone (such as ABA) biosynthesis, and signal transduction. We demonstrated that DEGs or TFs which related to ABA metabolism were involved in the response to salt stress, including xanthoxin dehydrogenase genes (ABA2), sucrose non-fermenting 1-related protein kinases (SnRK2), NAM, ATAT1/2, and CUC2 transcription factors (NAC), and WRKY class of zinc-finger proteins (WRKY). This research has successfully induced calli from two diploid cotton species and revealed new genes responding to salt stress in callus tissue, which will lay the foundation for protoplast fusion for further understanding of salt stress responses in cotton.

Ethephon-Induced Ethylene Enhances Starch Degradation and Sucrose Transport with an Interactive Abscisic Acid-Mediated Manner in Mature Leaves of Oilseed rape (Brassica napus L.).

The leaf senescence process is characterized by the degradation of macromolecules in mature leaves and the remobilization of degradation products via phloem transport. The phytohormone ethylene mediates leaf senescence. This study aimed to investigate the ethephon-induced ethylene effects on starch degradation and sucrose remobilization through their interactive regulation with other hormones. Ethephon (2-chloroethylphosphonic acid) was used as an ethylene-generating agent. Endogenous hormonal status, carbohydrate compounds, starch degradation-related gene expression, sucrose transporter gene expression, and phloem sucrose loading were compared between the ethephon-treated plants and controls. Foliar ethephon spray enhanced the endogenous ethylene concentration and accelerated leaf senescence, as evidenced by reduced chlorophyll content and enhanced expression of the senescence-related gene SAG12. Ethephon-enhanced ethylene prominently enhanced the endogenous abscisic acid (ABA) level. accompanied with upregulation of ABA synthesis gene 9-cis-epoxycarotenoid dioxygenase (NCED3), ABA receptor gene pyrabactin resistance 1 (PYR1), and ABA signaling genes sucrose non-fermenting 1 (Snf1)-related protein kinase 2 (SnRK2), ABA-responsive element binding 2 (AREB2), and basic-helix-loop-helix (bHLH) transcription factor (MYC2).) Ethephon treatment decreased starch content by enhancing expression of the starch degradation-related genes α-amylase 3 (AMY3) and β-amylase 1 (BAM1), resulting in an increase in sucrose content in phloem exudates with enhanced expression of sucrose transporters, SUT1, SUT4, and SWEET11. These results suggest that a synergistic interaction between ethylene and ABA might account for sucrose accumulation, mainly due to starch degradation in mature leaves and sucrose phloem loading in the ethephon-induced senescent leaves.

Dynamic Nutrient Signaling Networks in Plants.

Nutrients are vital to life through intertwined sensing, signaling, and metabolic processes. Emerging research focuses on how distinct nutrient signaling networks integrate and coordinate gene expression, metabolism, growth, and survival. We review the multifaceted roles of sugars, nitrate, and phosphate as essential plant nutrients in controlling complex molecular and cellular mechanisms of dynamic signaling networks. Key advances in central sugar and energy signaling mechanisms mediated by the evolutionarily conserved master regulators HEXOKINASE1 (HXK1), TARGET OF RAPAMYCIN (TOR), and SNF1-RELATED PROTEIN KINASE1 (SNRK1) are discussed. Significant progress in primary nitrate sensing, calcium signaling, transcriptome analysis, and root-shoot communication to shape plant biomass and architecture are elaborated. Discoveries on intracellular and extracellular phosphate signaling and the intimate connections with nitrate and sugar signaling are examined. This review highlights the dynamic nutrient, energy, growth, and stress signaling networks that orchestrate systemwide transcriptional, translational, and metabolic reprogramming, modulate growth and developmental programs, and respond to environmental cues.

Tudor staphylococcal nuclease is a docking platform for stress granule components and is essential for SnRK1 activation in Arabidopsis

Tudor staphylococcal nuclease (TSN; also known as Tudor‐SN, p100, or SND1) is a multifunctional, evolutionarily conserved regulator of gene expression, exhibiting cytoprotective activity in animals and plants and oncogenic activity in mammals. During stress, TSN stably associates with stress granules (SGs), in a poorly understood process. Here, we show that in the model plant Arabidopsis thaliana, TSN is an intrinsically disordered protein (IDP) acting as a scaffold for a large pool of other IDPs, enriched for conserved stress granule components as well as novel or plant‐specific SG‐localized proteins. While approximately 30% of TSN interactors are recruited to stress granules de novo upon stress perception, 70% form a protein–protein interaction network present before the onset of stress. Finally, we demonstrate that TSN and stress granule formation promote heat‐induced activation of the evolutionarily conserved energy‐sensing SNF1‐related protein kinase 1 (SnRK1), the plant orthologue of mammalian AMP‐activated protein kinase (AMPK). Our results establish TSN as a docking platform for stress granule proteins, with an important role in stress signalling.

Arabidopsis group C Raf-like protein kinases negatively regulate abscisic acid signaling and are direct substrates of SnRK2

The phytohormone abscisic acid (ABA) plays a major role in abiotic stress responses in plants, and subclass III SNF1-related protein kinase 2 (SnRK2) kinases mediate ABA signaling. In this study, we identified Raf36, a group C Raf-like protein kinase in Arabidopsis, as a protein that interacts with multiple SnRK2s. A series of reverse genetic and biochemical analyses revealed that 1) Raf36 negatively regulates ABA responses during postgermination growth, 2) the N terminus of Raf36 is directly phosphorylated by SnRK2s, and 3) Raf36 degradation is enhanced in response to ABA. In addition, Raf22, another C-type Raf-like kinase, functions partially redundantly with Raf36 to regulate ABA responses. A comparative phosphoproteomic analysis of ABA-induced responses of wild-type and raf22raf36-1 plants identified proteins that are phosphorylated downstream of Raf36 and Raf22 in planta. Together, these results support a model in which Raf36/Raf22 function mainly under optimal conditions to suppress ABA responses, whereas in response to ABA, the SnRK2 module promotes Raf36 degradation as a means of alleviating Raf36-dependent inhibition and allowing for heightened ABA signaling to occur.

Growth Promotion or Osmotic Stress Response: How SNF1-Related Protein Kinase 2 (SnRK2) Kinases Are Activated and Manage Intracellular Signaling in Plants.

Reversible phosphorylation is a major mechanism for regulating protein function and controls a wide range of cellular functions including responses to external stimuli. The plant-specific SNF1-related protein kinase 2s (SnRK2s) function as central regulators of plant growth and development, as well as tolerance to multiple abiotic stresses. Although the activity of SnRK2s is tightly regulated in a phytohormone abscisic acid (ABA)-dependent manner, recent investigations have revealed that SnRK2s can be activated by group B Raf-like protein kinases independently of ABA. Furthermore, evidence is accumulating that SnRK2s modulate plant growth through regulation of target of rapamycin (TOR) signaling. Here, we summarize recent advances in knowledge of how SnRK2s mediate plant growth and osmotic stress signaling and discuss future challenges in this research field.

CaADIP1‐dependent CaADIK1‐kinase activation is required for abscisic acid signalling and drought stress response in Capsicum annuum

Induction of the abscisic acid (ABA) signalling network is associated with various stress conditions, including cold, high salinity and drought. As core ABA signalling components, group A type 2C protein phosphatases (PP2Cs) interact with and inhibit snf1-related protein kinase2s. Here, we isolated and characterised the pepper mitogen-activated protein kinase kinase kinase CaADIK1, which interacts with the group A PP2C CaADIP1. CaADIK1 transcripts were induced by abiotic stresses, and CaADIK1 localised in the nucleus and cytoplasm. We verified that CaADIP1 inhibits the autokinase activity of CaADIK1; moreover, the kinase activity of CaADIK1 is enhanced by drought stress. We performed genetic analysis using CaADIK1-silenced pepper and CaADIK1-overexpressing (OX) Arabidopsis plants. CaADIK1-silenced pepper plants showed drought-sensitive phenotypes, whereas CaADIK1-OX Arabidopsis plants showed ABA-sensitive and drought-tolerant phenotypes. In CaADIK1K32N -OX Arabidopsis plants mutated at the ATP-binding site, the ABA-insensitive and drought-sensitive phenotypes were restored. Taken together, our findings show that CaADIK1 positively regulates the ABA-dependent drought stress response and is inhibited by CaADIP1.

Persulfidation-induced structural change in SnRK2.6 establishes intramolecular interaction between phosphorylation and persulfidation

Post-translational modifications (PTMs), including phosphorylation and persulfidation, regulate the activity of SNF1-RELATED PROTEIN KINASE2.6 (SnRK2.6). Here, we report how persulfidations and phosphorylations of SnRK2.6 influence each other. The persulfidation of cysteine C131/C137 alters SnRK2.6 structure and brings the serine S175 residue closer to the aspartic acid D140 that acts as ATP-γ-phosphate proton acceptor, thereby improving the transfer efficiency of phosphate groups to S175 to enhance the phosphorylation level of S175. Interestingly, we predicted that S267 and C137 were predicted to lie in close proximity on the protein surface and found that the phosphorylation status of S267 positively regulates the persulfidation level at C137. Analyses of the responses of dephosphorylated and depersulfidated mutants to abscisic acid and the H2S-donor NaHS during stomatal closure, water loss, gas exchange, Ca2+ influx, and drought stress revealed that S175/S267-associated phosphorylation and C131/137-associated persulfidation are essential for SnRK2.6 function in vivo. In light of these findings, we propose a mechanistic model in which certain phosphorylations facilitate persulfidation, thereby changing the structure of SnRK2.6 and increasing its activity.

Stomatal regulation: Role of H2S-induced persulfidation in ABA signaling

Stomatal regulation: Role of H2S-induced persulfidation in ABA signaling

Transcriptome and MiRNAomics Analyses Identify Genes Associated with Cytoplasmic Male Sterility in Cotton (Gossypium hirsutum L.).

Cytoplasmic male sterility (CMS) is important for large-scale hybrid seed production. Rearrangements in the mitochondrial DNA (mtDNA) for the cotton (Gossypium hirsutum L.) CMS line J4A were responsible for pollen abortion. However, the expression patterns of nuclear genes associated with pollen abortion and the molecular basis of CMS for J4A are unknown, and were the objectives of this study by comparing J4A with the J4B maintainer line. Cytological evaluation of J4A anthers showed that microspore abortion occurs during meiosis preventing pollen development. Changes in enzyme activity of mitochondrial respiratory chain complex IV and mitochondrial respiratory chain complex V and the content of ribosomal protein and ATP during anther abortion were observed for J4A suggesting insufficient synthesis of ATP hindered pollen production. Additionally, levels of sucrose, starch, soluble sugar, and fructose were significantly altered in J4A during the meiosis stage, suggesting reduced sugar metabolism contributed to sterility. Transcriptome and miRNAomics analyses identified 4461 differentially expressed mRNAs (DEGs) and 26 differentially expressed microRNAs (DEMIs). Pathway enrichment analysis indicated that the DEMIs were associated with starch and sugar metabolism. Six deduced target gene regulatory pairs that may participate in CMS were identified, ghi-MIR7484-10/mitogen-activated protein kinase kinase 6 (MAPKK6), ghi-undef-156/agamous-like MADS-box protein AGL19 (AGL19), ghi-MIR171-1-22/SNF1-related protein kinase regulatory subunit gamma-1 and protein trichome birefringence-like 38, and ghi-MIR156-(8/36)/WRKY transcription factor 28 (WRKY28). Overall, a putative CMS mechanism involving mitochondrial dysfunction, the ghi-MIR7484-10/MAPKK6 network, and reduced glucose metabolism was suggested, and ghi-MIR7484-10/MAPKK6 may be related to abnormal microspore meiosis and induction of excessive sucrose accumulation in anthers.

Genome-wide identification of sucrose nonfermenting-1-related protein kinase (SnRK) genes in barley and RNA-seq analyses of their expression in response to abscisic acid treatment

BackgroundSucrose nonfermenting-1 (SNF1)-related protein kinases (SnRKs) play important roles in regulating metabolism and stress responses in plants, providing a conduit for crosstalk between metabolic and stress signalling, in some cases involving the stress hormone, abscisic acid (ABA). The burgeoning and divergence of the plant gene family has led to the evolution of three subfamilies, SnRK1, SnRK2 and SnRK3, of which SnRK2 and SnRK3 are unique to plants. Therefore, the study of SnRKs in crops may lead to the development of strategies for breeding crop varieties that are more resilient under stress conditions. In the present study, we describe the SnRK gene family of barley (Hordeum vulgare), the widespread cultivation of which can be attributed to its good adaptation to different environments.ResultsThe barley HvSnRK gene family was elucidated in its entirety from publicly-available genome data and found to comprise 50 genes. Phylogenetic analyses assigned six of the genes to the HvSnRK1 subfamily, 10 to HvSnRK2 and 34 to HvSnRK3. The search was validated by applying it to Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa) genome data, identifying 50 SnRK genes in rice (four OsSnRK1, 11 OsSnRK2 and 35 OsSnRK3) and 39 in Arabidopsis (three AtSnRK1, 10 AtSnRK2 and 26 AtSnRK3). Specific motifs were identified in the encoded barley proteins, and multiple putative regulatory elements were found in the gene promoters, with light-regulated elements (LRE), ABA response elements (ABRE) and methyl jasmonate response elements (MeJa) the most common. RNA-seq analysis showed that many of the HvSnRK genes responded to ABA, some positively, some negatively and some with complex time-dependent responses.ConclusionsThe barley HvSnRK gene family is large, comprising 50 members, subdivided into HvSnRK1 (6 members), HvSnRK2 (10 members) and HvSnRK3 (34 members), showing differential positive and negative responses to ABA.

SnRK2.6 interacts with phytochrome B and plays a negative role in red light-induced stomatal opening

ABSTRACT Light is an important environmental factor for plant growth and development. Phytochrome B (phyB), a classical red/far-red light receptor, plays vital role in controlling plant photomorphogenesis and light-induced stomatal opening. Phytohormone abscisic acid (ABA) accumulates rapidly and triggers a series of physiological and molecular events during the responses to multiple abiotic stresses. Recent studies showed that phyB mutant synthesizes more ABA and exhibits improved tolerance to salt and cold stress, suggesting that a crosstalk exists between light and ABA signaling pathway. However, whether ABA signaling components mediate responses to light remains unclear. Here, we showed that SnRK2.6 (Sucrose Nonfermenting 1-Related Protein Kinase 2.6), a key regulator in ABA signaling, interacts with phyB and participates in light-induced stomatal opening. First, we checked the interaction between phyB and SnRK2s, and found that SnRK2.2/2.3/2.6 kinases physically interacted with phyB in yeast and in vitro. We also performed co-IP assay to support that SnRK2.6 interacts with phyB in plant. To investigate the role of SnRK2.6 in red light-induced stomatal opening, we obtained the snrk2.6 mutant and overexpression lines, and found that snrk2.6 mutant exhibited a significantly larger stomatal aperture under red light treatment, while the two independent overexpression lines showed significantly smaller stomatal aperture, indicative of a negative role for SnRK2.6 in red light-induced stomatal opening. The interaction of SnRK2.6 with red light receptor and the negative role of SnRK2.6 in red light-induced stomatal opening provide new evidence for the crosstalk between ABA and red light in guard cell signaling.

Cellular Phosphorylation Signaling and Gene Expression in Drought Stress Responses: ABA-Dependent and ABA-Independent Regulatory Systems.

Drought is a severe and complex abiotic stress that negatively affects plant growth and crop yields. Numerous genes with various functions are induced in response to drought stress to acquire drought stress tolerance. The phytohormone abscisic acid (ABA) accumulates mainly in the leaves in response to drought stress and then activates subclass III SNF1-related protein kinases 2 (SnRK2s), which are key phosphoregulators of ABA signaling. ABA mediates a wide variety of gene expression processes through stress-responsive transcription factors, including ABA-RESPONSIVE ELEMENT BINDING PROTEINS (AREBs)/ABRE-BINDING FACTORS (ABFs) and several other transcription factors. Seed plants have another type of SnRK2s, ABA-unresponsive subclass I SnRK2s, that mediates the stability of gene expression through the mRNA decay pathway and plant growth under drought stress in an ABA-independent manner. Recent research has elucidated the upstream regulators of SnRK2s, RAF-like protein kinases, involved in early responses to drought stress. ABA-independent transcriptional regulatory systems and ABA-responsive regulation function in drought-responsive gene expression. DEHYDRATION RESPONSIVE ELEMENT (DRE) is an important cis-acting element in ABA-independent transcription, whereas ABA-RESPONSIVE ELEMENT (ABRE) cis-acting element functions in ABA-responsive transcription. In this review article, we summarize recent advances in research on cellular and molecular drought stress responses and focus on phosphorylation signaling and transcription networks in Arabidopsis and crops. We also highlight gene networks of transcriptional regulation through two major regulatory pathways, ABA-dependent and ABA-independent pathways, that ABA-responsive subclass III SnRK2s and ABA-unresponsive subclass I SnRK2s mediate, respectively. We also discuss crosstalk in these regulatory systems under drought stress.

Regulation of Flowering Timing by ABA-NnSnRK1 Signaling Pathway in Lotus

The lotus produces flower buds at each node, yet most of them are aborted because of unfavorable environmental changes and the mechanism remains unclear. In this work, we proposed a potential novel pathway for ABA-mediated flower timing control in the lotus, which was explored by combining molecular, genetic, transcriptomic, biochemical, and pharmacologic approaches. We found that the aborting flower buds experienced extensive programmed cell death (PCD). The hormonal changes between the normal and aborting flower buds were dominated by abscisic acid (ABA). Seedlings treated with increasing concentrations of ABA exhibited a differential alleviating effect on flower bud abortion, with a maximal response at 80 μM. Transcriptome analysis further confirmed the changes of ABA content and the occurrence of PCD, and indicated the importance of PCD-related SNF1-related protein kinase 1 (NnSnRK1). The NnSnRK1-silenced lotus seedlings showed stronger flowering ability, with their flower:leaf ratio increased by 40%. When seedlings were treated with ABA, the expression level and protein kinase activity of NnSnRK1 significantly decreased. The phenotype of NnSnRK1-silenced seedlings could also be enhanced by ABA treatment and reversed by tungstate treatment. These results suggested that the decline of ABA content in lotus flower buds released its repression of NnSnRK1, which then initiated flower bud abortion.

Drought Intensity-Responsive Salicylic Acid and Abscisic Acid Crosstalk with the Sugar Signaling and Metabolic Pathway in Brassica napus.

The aim of this study was to characterize hormonal crosstalk with the sugar signaling and metabolic pathway based on a time course analysis of drought intensity. Drought intensity-responsive changes in the assimilation of newly fixed carbon (C) into soluble sugar, the content of sugar and starch, and expression of genes involved in carbohydrate metabolism were interpreted as being linked to endogenous abscisic acid (ABA) and salicylic acid (SA) levels and their signaling genes. The ABA and SA levels in the drought-stressed leaves increased together during the early drought period (days 0–6), and additional ABA accumulation occurred with depressed SA during the late period (days 6–14). Although drought treatment decreased the assimilation of newly fixed C into soluble sugar, representing a 59.9%, 33.1%, and 62.9% reduction in 13C-glucose, 13C-fructose, and 13C-sucrose on day 14, respectively, the drought-responsive accumulation of soluble sugars was significant. During the early period, the drought-responsive accumulation of hexose and sucrose was concurrent with the upregulated expression of hexokinase 1 (HXK1), which, in turn, occurred parallel to the upregulation of ABA synthesis gene 9-sis-epoxycarotenoid dioxygenase (NCED3) and SA-related genes (isochorismate synthase 1 (ICS1) and non-expressor of pathogenesis-related gene (NPR1)). During the late period, hexose accumulation, sucrose phloem loading, and starch degradation were dominant, with a highly enhanced expression of the starch degradation-related genes β-amylase 1 (BAM1) and α-amylase 3 (AMY3), which were concomitant with the parallel enhancement of sucrose non-fermenting−1 (Snf1)-related protein kinase 2 (SnRK2).2 and ABA-responsive element binding 2 (AREB2) expression in an ABA-dependent manner. These results indicate that the drought-responsive accumulation of sugars (especially SA-mediated sucrose accumulation) is part of the acclamatory process during the early period. Conversely, ABA-responsive hexose accumulation and sucrose phloem loading represent severe drought symptoms during the late drought period.

Genome-wide identification and expression pattern of SnRK gene family under several hormone treatments and its role in floral scent emission in Hedychium coronarium.

The SnRK (Snf1-Related protein Kinase) gene family plays crucial roles in various plant signaling pathways and stress-adaptive responses including biotic and abiotic stresses via activating protein phosphorylation pathways. However, there is no information available on the role of the SnRK gene family in Hedychium coronarium. H. coronarium is an important crop widely cultivated as an ornamental plant, herb, spice, or condiment. In this study, 60 HcSnRK genes were identified from the H. coronarium genomic and transcriptome data. Phylogenetic and gene structure analysis showed that the HcSnRK genes were divided into three groups (HcSnRK1, HcSnRK2 and HcSnRK3) and among them HcSnRK3 subfamily was further subdivided into two clades according to the number of introns. Chromosome localization analysis showed that HcSnRK genes were unevenly mapped onto all chromosomes, and the Ka/Ks ratio of 24 paralogues includes four tandems and 20 segmental duplications indicated that the HcSnRK gene family underwent a purifying selection. Cis-regulatory elements analysis suggested that the HcSnRK genes respond to multiple hormones and other stresses. The responsiveness of HcSnRK genes to several hormones was analyzed by quantitative real-time PCR. Based on the different transcriptome data, two candidates HcSnRK genes (HcSnRK2.2 and HcSnRK2.9) were screened out for further characterization . The subcellular localization experiment revealed that both genes were located in the nucleus and cytoplasm. Moreover, virus-induced gene silencing (VIGS) of HcSnRK2.2 and HcSnRK2.9 significantly reduced the floral volatile contents by suppressing the expression of terpene synthase genes (HcTPS1, HcTPS3, and HcTPS5), indicating that HcSnRK2.2 and HcSnRK2.9 genes play an important role in the regulatory mechanism of floral aroma. These results will provide novel insights into the functional dissection of H. coronarium SnRK gene family.

SNF1-related protein kinase 1: the many-faced signaling hub regulating developmental plasticity in plants.

The Snf1-related protein kinase 1 (SnRK1) is the plant homolog of the heterotrimeric AMP-activated protein kinase/sucrose non-fermenting 1 (AMPK/Snf1), which works as a major regulator of growth under nutrient-limiting conditions in eukaryotes. Along with its conserved role as a master regulator of sugar starvation responses, SnRK1 is involved in controlling the developmental plasticity and resilience under diverse environmental conditions in plants. In this review, through mining and analyzing the interactome and phosphoproteome data of SnRK1, we are highlighting its role in fundamental cellular processes such as gene regulation, protein synthesis, primary metabolism, protein trafficking, nutrient homeostasis, and autophagy. Along with the well-characterized molecular interaction in SnRK1 signaling, our analysis highlights several unchartered regions of SnRK1 signaling in plants such as its possible communication with chromatin remodelers, histone modifiers, and inositol phosphate signaling. We also discuss potential reciprocal interactions of SnRK1 signaling with other signaling pathways and cellular processes, which could be involved in maintaining flexibility and homeostasis under different environmental conditions. Overall, this review provides a comprehensive overview of the SnRK1 signaling network in plants and suggests many novel directions for future research.

Genomic Characterization and Expression Analysis of the SnRK Family Genes in Dendrobium officinale Kimura et Migo (Orchidaceae).

Sucrose non-fermenting1-related protein kinases (SnRKs) are a type of Ser/Thr protein kinases, and they play an important role in plant life, especially in metabolism and responses to environmental stresses. However, there is limited information on SnRK genes in Dendrobium officinale. In the present research, a total of 36 DoSnRK genes were identified based on genomic data. These DoSnRKs could be grouped into three subfamilies, including 1 member of DoSnRK1, 7 of DoSnRK2, and 28 of DoSnRK3. The gene structure analysis of DoSnRK genes showed that 17 members had no introns, while 16 members contained six or more introns. The conserved domains and motifs were found in the same subfamily. The various cis-elements present in the promoter regions showed that DoSnRK genes could respond to stresses and hormones. Furthermore, the expression patterns of DoSnRK genes in eight tissues were investigated according to RNA sequencing data, indicating that multiple DoSnRK genes were ubiquitously expressed in these tissues. The transcript levels of DoSnRK genes after drought, MeJA, and ABA treatments were analyzed by quantitative real-time PCR and showed that most DoSnRK genes could respond to these stresses. Therefore, genomic characterization and expression analyses provide valuable information on DoSnRK genes for further understanding the functions of SnRKs in plants.

Abscisic acid signaling negatively regulates nitrate uptake via phosphorylation of NRT1.1 by SnRK2s in Arabidopsis.

Nitrogen (N) is a limiting nutrient for plant growth and productivity. The phytohormone abscisic acid (ABA) has been suggested to play a vital role in nitrate uptake in fluctuating N environments. However, the molecular mechanisms underlying the involvement of ABA in N deficiency responses are largely unknown. In this study, we demonstrated that ABA signaling components, particularly the three subclass III SUCROSE NON-FERMENTING1 (SNF1)-RELATED PROTEIN KINASE 2S (SnRK2) proteins, function in root foraging and uptake of nitrate under N deficiency in Arabidopsis thaliana. The snrk2.2snrk2.3snrk2.6 triple mutant grew a longer primary root and had a higher rate of nitrate influx and accumulation compared with wild-type plants under nitrate deficiency. Strikingly, SnRK2.2/2.3/2.6 proteins interacted with and phosphorylated the nitrate transceptor NITRATE TRANSPORTER1.1 (NRT1.1) in vitro and in vivo. The phosphorylation of NRT1.1 by SnRK2s resulted in a significant decrease of nitrate uptake and impairment of root growth. Moreover, we identified NRT1.1Ser585 as a previously unknown functional site: the phosphomimetic NRT1.1S585D was impaired in both low- and high-affinity transport activities. Taken together, our findings provide new insight into how plants fine-tune growth via ABA signaling under N deficiency.