SNF1-related Protein Kinase Research Articles

Comprehensive identification and expression analyses of the SnRK gene family in Casuarina equisetifolia in response to salt stress

Sucrose nonfermenting-1 (SNF1)-related protein kinases (SnRKs) play crucial roles in plant signaling pathways and stress adaptive responses by activating protein phosphorylation pathways. However, there have been no comprehensive studies of the SnRK gene family in the widely planted salt-tolerant tree species Casuarina equisetifolia. Here, we comprehensively analyze this gene family in C. equisetifolia using genome-wide identification, characterization, and profiling of expression changes in response to salt stress. A total of 26 CeqSnRK genes were identified, which were divided into three subfamilies (SnRK1, SnRK2, and SnRK3). The intron-exon structures and protein‑motif compositions were similar within each subgroup but differed among groups. Ka/Ks ratio analysis indicated that the CeqSnRK family has undergone purifying selection, and cis-regulatory element analysis suggested that these genes may be involved in plant development and responses to various environmental stresses. A heat map was generated using quantitative real‑time PCR (RT-qPCR) data from 26 CeqSnRK genes, suggesting that they were expressed in different tissues. We also examined the expression of all CeqSnRK genes under exposure to different salt concentrations using RT-qPCR, finding that most CeqSnRK genes were regulated by different salt treatments. Moreover, co-expression network analysis revealed synergistic effects among CeqSnRK genes. Several CeqSnRK genes (CeqSnRK3.7, CeqSnRK3.16, CeqSnRK3.17) were up-regulated following salt treatment. Among them, CeqSnRK3.16 expression was significantly up-regulated under various salt treatments, identifying this as a candidate gene salt stress tolerance gene. In addition, CeqSnRK3.16 showed significant expression change correlations with multiple genes under salt stress, indicating that it might exhibit synergistic effects with other genes in response to salt stress. This comprehensive analysis will provide a theoretical reference for CeqSnRK gene functional verification and the role of these genes in salt tolerance.

SNF1-related protein kinase 1 represses Arabidopsis growth through post-translational modification of E2Fa in response to energy stress.

Cellular sugar starvation and/or energy deprivation serves as an important signaling cue for the live cells to trigger the necessary stress adaptation response. When exposed to cellular energy stress (ES) conditions, the plants reconfigure metabolic pathways and rebalance energy status while restricting vegetative organ growth. Despite the vital importance of this ES-induced growth restriction, the regulatory mechanism underlying the response remains largely elusive in plants. Using plant cell- and whole plant-based functional analyses coupled with extended genetic validation, we show that cellular ES-activated SNF1-related protein kinase 1 (SnRK1.1) directly interacts with and phosphorylates E2Fa transcription factor, a critical cell cycle regulator. Phosphorylation of E2Fa by SnRK1.1 leads to its proteasome-mediated protein degradation, resulting in S-phase repression and organ growth restriction. Our findings show that ES-dependently activated SnRK1.1 adjusts cell proliferation and vegetative growth for plants to cope with constantly fluctuating environments.

Wheat TaSnRK2.10 phosphorylates TaERD15 and TaENO1 and confers drought tolerance when overexpressed in rice.

Wheat (Triticum aestivum) is particularly susceptible to water deficit at the jointing stage of its development. Sucrose non-fermenting 1-related protein kinase 2 (SnRK2) acts as a signaling hub in the response to drought stress, but whether SnRK2 helps plants cope with water deficit via other mechanisms is largely unknown. Here, we cloned and characterized TaSnRK2.10, which was induced by multiple abiotic stresses and phytohormones. Ectopic expression of TaSnRK2.10 in rice (Oryza sativa) conferred drought tolerance, manifested by multiple improved physiological indices, including increased water content, cell membrane stability, and survival rates, as well as decreased water loss and accumulation of H2O2 and malonaldehyde. TaSnRK2.10 interacted with and phosphorylated early responsive to dehydration 15 (TaERD15) and enolase 1 (TaENO1) in vivo and in vitro. TaERD15 phosphorylated by TaSnRK2.10 was prone to degradation by the 26S proteasome, thereby mitigating its negative effects on drought tolerance. Phosphorylation of TaENO1 by TaSnRK2.10 may account for the substantially increased levels of phosphoenolpyruvate (PEP), a key metabolite of primary and secondary metabolism, in TaSnRK2.10-overexpressing rice, thereby enhancing its viability under drought stress. Our results demonstrate that TaSnRK2.10 not only regulated stomatal aperture and the expression of drought-responsive genes, but also enhanced PEP supply and promoted the degradation of TaERD15, all of which enhanced drought tolerance.

SnRK2.4-mediated phosphorylation of ABF2 regulates ARGININE DECARBOXYLASE expression and putrescine accumulation under drought stress.

Arginine decarboxylase (ADC)-mediated putrescine (Put) biosynthesis plays an important role in plant abiotic stress response. SNF1-related protein kinases 2s (SnRK2s) and abscisic acid (ABA)-response element (ABRE)-binding factors (ABFs), are core components of the ABA signaling pathway involved in drought stress response. We previously reported that ADC of Poncirus trifoliata (PtrADC) functions in drought tolerance. However, whether and how SnRK2 and ABF regulate PtrADC to modulate putrescine accumulation under drought stress remains largely unclear. Herein, we employed a set of physiological, biochemical, and molecular approaches to reveal that a protein complex composed of PtrSnRK2.4 and PtrABF2 modulates putrescine biosynthesis and drought tolerance by directly regulating PtrADC. PtrABF2 was upregulated by dehydration in an ABA-dependent manner. PtrABF2 activated PtrADC expression by directly and specifically binding to the ABRE core sequence within its promoter and positively regulated drought tolerance via modulating putrescine accumulation. PtrSnRK2.4 interacts with and phosphorylates PtrABF2 at Ser93. PtrSnRK2.4-mediated PtrABF2 phosphorylation is essential for the transcriptional regulation of PtrADC. Besides, PtrSnRK2.4 was shown to play a positive role in drought tolerance by facilitating putrescine synthesis. Taken together, this study sheds new light on the regulatory module SnRK2.4-ABF2-ADC responsible for fine-tuning putrescine accumulation under drought stress, which advances our understanding on transcriptional regulation of putrescine synthesis.

Characterization and expression analysis of key abscisic acid signal transduction genes during kiwifruit development

To characterise the regulation of abscisic acid (ABA) signal transduction during fruit development and ripening, we investigated the key genes involved in the ABA signalling pathway in kiwifruit (Actinidia chinensis), including 18 AcPYLs genes encoding ABA receptors, 7 AcPP2Cs genes encoding type 2C protein phosphatases, and 7 AcSnRK2s genes encoding members of the SNF1-related protein kinases 2 family identified in the kiwifruit reference genome. AcPYLs, AcPP2Cs, and AcSnRK2s from kiwifruit are putative homologues of the corresponding Arabidopsis and tomato proteins. Phylogenetic analysis revealed that AcPYLs and AcSnRK2s clustered into three subfamilies. Transcript levels indicated that the expression pattern of AcNCED4 was consistent with the ABA content of the pulp during kiwifruit development. Furthermore, the ABA content of the axile placenta was higher than that of the sarcocarp in kiwi pulp, and the expression of most ABA signal transduction genes, including AcPYLs, AcPP2Cs, and AcSnRK2s, was more predominant in the axile placenta. Moreover, AcPP2C3 was localised in the nucleus and could interact with all AcPYLs and AcSnRK2s in an ABA-independent manner, as revealed by subcellular localisation and yeast two-hybrid assays. These findings enhance our understanding of ABA signal transduction genes in kiwis, and provide the necessary background for further exploration of the molecular mechanisms at play during kiwifruit development.

Targeted in vivo mutagenesis of a sensor histidine kinase playing an essential role in ABA signaling of the moss Physcomitrium patens

Land plants exhibit various adaptation responses to unfavorable water environments, such as drought and flooding. The phytohormone abscisic acid (ABA) and ethylene play essential roles in plant adaptation to drought and flooding, respectively. It remains largely unknown how plants integrate environmental information for water availability. In the moss Physcomitrium patens, we recently reported that not only ethylene/flooding signaling but also ABA/osmostress signaling are mediated by ethylene receptor-related sensor histidine kinases (ETR-HKs). Subfamily I ETR-HKs of this moss were found to interact with a RAF kinase (ARK) and were required for ABA-dependent activation of SNF1-related protein kinase 2 (SnRK2) via ARK activation. To elucidate the mechanisms of ARK regulation by ETR-HKs, here we employed targeted in vivo mutagenesis of PpHK5, a member of subfamily I ETR-HKs. Analyses of ABA-insensitive Pphk5 mutants indicated that PpHK5 mutations affecting the interaction with ARK resulted in loss of PpHK5 function to activate ABA signaling. We also identified a PpHK5 mutation that does not affect ARK interaction but resulted in loss of PpHK5 function. These results suggest that physical interaction between ETR-HK and ARK is essential but not sufficient for the regulation of ARK activity, and the C-terminal response regulator domain is involved in regulating ARK activation.

Genome-Wide Identification, Expression and Interaction Analysis of GmSnRK2 and Type A PP2C Genes in Response to Abscisic Acid Treatment and Drought Stress in Soybean Plant.

As a typical ancient tetraploid, soybean (Glycine max) is an important oil crop species and plays a crucial role in supplying edible oil, plant protein and animal fodder worldwide. As global warming intensifies, the yield of soybean in the field is often strongly restricted by drought stress. SNF1-related protein kinase 2 (SnRK2) and type A protein phosphatase 2C (PP2C-A) family members are core components of the abscisic acid (ABA) signal transduction pathway in plants and have been suggested to play important roles in increasing plant tolerance to drought stress, but genetic information supporting this idea is still lacking in soybean. Here, we cloned the GmSnRK2s and GmPP2C-A family genes from the reference genome of Williams 82 soybean. The results showed that the expression patterns of GmSnRK2s and GmPP2C-As are spatiotemporally distinct. The expression of GmSnRK2s in response to ABA and drought signals is not strictly the same as that of Arabidopsis SnRK2 homologous genes. Moreover, our results indicated that the duplicate pairs of GmSnRK2s and GmPP2C-As have similar expression patterns, cis-elements and relationships. GmSnRK2.2 may have a distinct function in the drought-mediated ABA signaling pathway. Furthermore, the results of yeast two-hybrid (Y2H) assays between GmSnRK2s and GmPP2C-As revealed that GmSnRK2.17, GmSnRK2.18, GmSnRK2.22, GmPP2C5, GmPP2C7, GmPP2C10 and GmPP2C17 may play central roles in the crosstalk among ABA signals in response to drought stress. Furthermore, GmPP2C-As and GmSnRKs were targeted by miRNA and validated by degradome sequencing, which may play multiple roles in the crosstalk between ABA and drought signals and other stress signals. Taken together, these results indicate that GmSnRK2s and GmPP2C-As may play a variety of roles in the drought-mediated ABA signaling pathway.

Identification and characteristics of SnRK genes and cold stress-induced expression profiles in Liriodendron chinense

BackgroundThe sucrose non-fermenting 1 (SNF1)-related protein kinases (SnRKs) play a vivid role in regulating plant metabolism and stress response, providing a pathway for regulation between metabolism and stress signals. Conducting identification and stress response studies on SnRKs in plants contributes to the development of strategies for tree species that are more tolerant to stress conditions.ResultsIn the present study, a total of 30 LcSnRKs were identified in Liriodendron chinense (L. chinense) genome, which was distributed across 15 chromosomes and 4 scaffolds. It could be divided into three subfamilies: SnRK1, SnRK2, and SnRK3 based on phylogenetic analysis and domain types. The LcSnRK of the three subfamilies shared the same Ser/Thr kinase structure in gene structure and motif composition, while the functional domains, except for the kinase domain, showed significant differences. A total of 13 collinear gene pairs were detected in L. chinense and Arabidopsis thaliana (A. thaliana), and 18 pairs were detected in L. chinense and rice, suggesting that the LcSnRK family genes may be evolutionarily more closely related to rice. Cis-regulation element analysis showed that LcSnRKs were LTR and TC-rich, which could respond to different environmental stresses. Furthermore, the expression patterns of LcSnRKs are different at different times under low-temperature stress. LcSnRK1s expression tended to be down-regulated under low-temperature stress. The expression of LcSnRK2s tended to be up-regulated under low-temperature stress. The expression trend of LcSnRK3s under low-temperature stress was mainly up-or down-regulated.ConclusionThe results of this study will provide valuable information for the functional identification of the LcSnRK gene in the future.

NUCLEAR PORE ANCHOR and EARLY IN SHORT DAYS 4 negatively regulate abscisic acid signaling by inhibiting Snf1-related protein kinase2 activity and stability in Arabidopsis.

Abscisic acid (ABA) is a key regulator of plant responses to abiotic stresses, such as drought. Abscisic acid receptors and coreceptors perceive ABA to activate Snf1-related protein kinase2s (SnRK2s) that phosphorylate downstream effectors, thereby activating ABA signaling and the stress response. As stress responses come with fitness penalties for plants, it is crucial to tightly control SnRK2 kinase activity to restrict ABA signaling. However, how SnRK2 kinases are inactivated remains elusive. Here, we show that NUCLEAR PORE ANCHOR (NUA), a nuclear pore complex (NPC) component, negatively regulates ABA-mediated inhibition of seed germination and post-germination growth, and drought tolerance in Arabidopsis thaliana. The role of NUA in response to ABA depends on SnRK2.2 and SnRK2.3 for seed germination and on SnRK2.6 for drought. NUA does not directly inhibit the phosphorylation of these SnRK2s or affects their abundance. However, the NUA-interacting protein EARLY IN SHORT DAYS 4 (ESD4), a SUMO protease, negatively regulates ABA signaling by directly interacting with and inhibiting SnRK2 phosphorylation and protein levels. More importantly, we demonstrated that SnRK2.6 can be SUMOylated in vitro, and ESD4 inhibits its SUMOylation. Taken together, we identified NUA and ESD4 as SnRK2 kinase inhibitors that block SnRK2 activity, and reveal a mechanism whereby NUA and ESD4 negatively regulate plant responses to ABA and drought stress possibly through SUMOylation-dependent regulation of SnRK2s.

Later Growth Cessation and Increased Freezing Tolerance Potentially Result in Later Dormancy in Evergreen Iris Compared with Deciduous Iris.

Winter dormancy is a protective survival strategy for plants to resist harsh natural environments. In the context of global warming, the progression of dormancy has been significantly affected in perennials, which requires further research. Here, a systematic study was performed to compare the induction of dormancy in two closely related iris species with an ecodormancy-only process, the evergreen Iris japonica Thunb. and the deciduous Iris tectorum Maxim. under artificial conditions. Firstly, morphological and physiological observations were evaluated to ensure the developmental status of the two iris species. Furthermore, the expression patterns of the genes involved in key pathways related to plant winter dormancy were determined, and correlation analyses with dormancy marker genes were conducted. We found that deciduous iris entered dormancy earlier than evergreen iris under artificial dormancy induction conditions. Phytohormones and carbohydrates play roles in coordinating growth and stress responses during dormancy induction in both iris species. Moreover, dormancy-related MADS-box genes and SnRKs (Snf1-related protein kinase) might represent a bridge between carbohydrate and phytohormone interaction during iris dormancy. These findings provide a hypothetical model explaining the later dormancy in evergreen iris compared with deciduous iris under artificial dormancy induction conditions and reveal some candidate genes. The findings of this study could provide new insights into the research of dormancy in perennial plants with an ecodormancy-only process and contribute to effectively managing iris production, postharvest storage, and shipping.

Identification and expression profile analysis of the SnRK2 gene family in cucumber.

The sucrose non-fermenting-1-related protein kinase 2 (SnRK2) is a plant-specific type of serine/threonine protein kinase that plays an important role in the physiological regulation of stress. The objective of this study was to identify and analyze the members of the SnRK2 gene family in cucumber and lay a foundation for further exploration of the mechanism of CsSnRK2 resistance to stress. Here, 12 SnRK2 genes were isolated from cucumber and distributed on five chromosomes, phylogenetic clustering divided these into three well-supported clades. In addition, collinearity analysis showed that the CsSnRK2 gene family underwent purifying selection pressure during evolution. CsSnRK2 genes of the same group have similar exons and conserved motifs, and intron length may be a specific imprint for the evolutionary amplification of the CsSnRK2 gene family. By predicting cis elements in the promoter, we found that the promoter region of CsSnRK2 gene members had various cis-regulatory elements in response to hormones and stress. Relative expression analysis showed that CsSnRK2.11 (group II) and CsSnRK2.12 (group III) were strongly induced by ABA, NaCl and PEG stress; whereas CsSnRK2.2 (group III) was not activated by any treatment. The response of group I CsSnRK2 to ABA, NaCl and PEG was weak. Furthermore, protein interaction prediction showed that multiple CsSnRK2 proteins interacted with four proteins including protein phosphatase 2C (PP2C), and it is speculated that the CsSnRK2 genes may also an independent role as a third messenger in the ABA signaling pathway. This study provides a reference for analyzing the potential function of CsSnRK2 genes in the future research.

NUA and ESD4 negatively regulate ABA signaling during seed germination

The phytohormone abscisic acid (ABA) plays important roles in plant growth, development and adaptative responses to abiotic stresses. SNF1-related protein kinase 2s (SnRK2) are key components that activate the ABA core signaling pathway. NUCLEAR PORE ANCHOR (NUA) is a component of the nuclear pore complex (NPC) that involves in deSUMOylation through physically interacting with the EARLY IN SHORT DAYS 4 (ESD4) SUMO protease. However, it is not clear how NUA functions with SnRK2 and ESD4 to regulate ABA signaling. In our study, we found that nua loss-of-function mutants exhibited pleiotropic ABA-hypersensitive phenotype. We also found that ABA-responsive genes remarkably up-regulated in nua by exogenous ABA. The nua snrk2.2 snrk2.3 triple mutant and nua abi5 double mutant partially rescued the ABA-hypersensitive phenotype of nua, thereby suggesting that NUA is epistatic to SnRK2s. Additionally, we observed that esd4-3 mutant was also ABA-hypersensitive. NUA and ESD4 were further demonstrated to physically interact with SnRK2s and negatively regulate ABA signaling by reducing SnRK2s stability. Taken together, our findings uncover a new regulatory mechanism that can modulate ABA signaling.

Dynamic modeling of ABA-dependent expression of the Arabidopsis RD29A gene.

The abscisic acid (ABA) signaling pathway is the key defense mechanism against drought stress in plants. In the pathway, signal transduction among four core proteins, pyrabactin resistance (PYR), protein phosphatase 2C (PP2C), sucrose-non-fermenting-1-related protein kinase 2 (SnRK2), and ABRE binding factor (ABF) leads to altered gene expression kinetics that is driven by an ABA-responsive element (ABRE). A most recent and comprehensive study provided data suggesting that ABA alters the expression kinetics in over 6,500 genes through the ABF-ABRE associations in Arabidopsis. Of these genes, termed ABA gene regulatory network (GRN), over 50% contain a single ABRE within 4 kb of the gene body, despite previous findings suggesting that a single copy of ABRE is not sufficient to drive the gene expression. To understand the expression system of the ABA GRN by the single ABRE, a dynamic model of the gene expression for the desiccation 29A (RD29A) gene was constructed with ordinary differential equations. Parameter values of molecular-molecular interactions and enzymatic reactions in the model were implemented from the data obtained by previously conducted in vitro experiments. On the other hand, parameter values of gene expression and translation were determined by comparing the kinetics of gene expression in the model to the expression kinetics of RD29A in real plants. The optimized model recapitulated the trend of gene expression kinetics of RD29A in ABA dose–response that were previously investigated. Further analysis of the model suggested that a single ABRE controls the time scale and dynamic range of the ABA-dependent gene expression through the PP2C feedback regulation even though an additional cis-element is required to drive the expression. The model construed in this study underpins the importance of a single ABRE in the ABA GRN.

To grow or not to grow under nutrient scarcity: Target of rapamycin-ethylene is the question

To cope with nutrient scarcity, plants generally follow two main complementary strategies. On the one hand, they can slow down growing, mainly shoot growth, to diminish the demand of nutrients. We can call this strategy as “stop growing.” On the other hand, plants can develop different physiological and morphological responses, mainly in their roots, aimed to facilitate the acquisition of nutrients. We can call this second strategy as “searching for nutrients.” Both strategies are compatible and can function simultaneously but the interconnection between them is not yet well-known. In relation to the “stop growing” strategy, it is known that the TOR (Target Of Rapamycin) system is a central regulator of growth in response to nutrients in eukaryotic cells. TOR is a protein complex with kinase activity that promotes protein synthesis and growth while some SnRK (Sucrose non-fermenting 1-Related protein Kinases) and GCN (General Control Non-derepressible) kinases act antagonistically. It is also known that some SnRKs and GCNs are activated by nutrient deficiencies while TOR is active under nutrient sufficiency. In relation to the “searching for nutrients” strategy, it is known that the plant hormone ethylene participates in the activation of many nutrient deficiency responses. In this Mini Review, we discuss the possible role of ethylene as the hub connecting the “stop growing” strategy and the “searching for nutrients” strategy since very recent results also suggest a clear relationship of ethylene with the TOR system.

Triose phosphate export from chloroplasts and cellular sugar content regulate anthocyanin biosynthesis during high light acclimation

Plants have evolved multiple strategies to cope with rapid changes in the environment. During high light (HL) acclimation, the biosynthesis of photoprotective flavonoids, such as anthocyanins, is induced. However, the exact nature of the signal and downstream factors for HL induction of flavonoid biosynthesis (FB) is still under debate. Here, we show that carbon fixation in chloroplasts, subsequent export of photosynthates by triose phosphate/phosphate translocator (TPT), and rapid increase in cellular sugar content permit the transcriptional and metabolic activation of anthocyanin biosynthesis during HL acclimation. In combination with genetic and physiological analysis, targeted and whole-transcriptome gene expression studies suggest that reactive oxygen species and phytohormones play only a minor role in rapid HL induction of the anthocyanin branch of FB. In addition to transcripts of FB, sugar-responsive genes showed delayed repression or induction in tpt-2 during HL treatment, and a significant overlap with transcripts regulated by SNF1-related protein kinase 1 (SnRK1) was observed, including a central transcription factor of FB. Analysis of mutants with increased and repressed SnRK1 activity suggests that sugar-induced inactivation of SnRK1 is required for HL-mediated activation of anthocyanin biosynthesis. Our study emphasizes the central role of chloroplasts as sensors for environmental changes as well as the vital function of sugar signaling in plant acclimation.

Screening of salt stress in the overexpressed type of Arabidopsis thaliana (L.) Heynh. for the identification of significant hub genes using a systems biology approach

Worldwide, it is known that abiotic and biotic stresses can affect the production of crops by a declining trend. To control the situation, SnRK2 (a subfamily 2 of SNF1-related protein kinase) overexpression levels can induce salt tolerance. This study used a dataset for 2 types of Arabidopsis thaliana including the wild and PtSnRK2.7 overexpressed in mock and salt conditions to compare and identify the salt stress-responsive genes. A computational systems biology approach was employed to identify the differentially expressed genes and determine their mechanisms in terms of molecular functionalities, cellular components, KEGG enrichment pathways and plant ontology analyses. The results indicate that the 15 genes identified for PtSnRK2.7 overexpressed type in mock against salt conditions were upregulated (AT1G19180 and AT2G23150 were downregulated) and related to various environmental stresses. Furthermore, 8 out of 15 identified genes were downregulated for the wild type exposed to salt stress and the rest were upregulated. And, the only upregulated gene found differentially expressed between wild and overexpressed types in salt stress conditions was AT4G15110. In contrast, the other two AT1G15010 and AT4G19430 were downregulated and involved in transient stress and inactivation of chloroplast, respectively. Taken together, it has been shown that A. thaliana PtSnRK2.7 overexpressed type can resist salt stress. Finally, more experimental studies and computational systems biology methodologies are needed to reveal and confirm the responsive gene for salt stress in A. thaliana.

Genome-Wide Identification and Expression Analysis of SnRK2 Gene Family in Dormant Vegetative Buds of Liriodendron chinense in Response to Abscisic Acid, Chilling, and Photoperiod.

Protein kinases play an essential role in plants’ responses to environmental stress signals. SnRK2 (sucrose non-fermenting 1-related protein kinase 2) is a plant-specific protein kinase that plays a crucial role in abscisic acid and abiotic stress responses in some model plant species. In apple, corn, rice, pepper, grapevine, Arabidopsis thaliana, potato, and tomato, a genome-wide study of the SnRK2 protein family was performed earlier. The genome-wide comprehensive investigation was first revealed to categorize the SnRK2 genes in the Liriodendron chinense (L. chinense). The five SnRK2 genes found in the L. chinense genome were highlighted in this study. The structural gene variants, 3D structure, chromosomal distributions, motif analysis, phylogeny, subcellular localization, cis-regulatory elements, expression profiles in dormant buds, and photoperiod and chilling responses were all investigated in this research. The five SnRK2 genes from L. chinense were grouped into groups (I–IV) based on phylogeny analysis, with three being closely related to other species. Five hormones-, six stress-, two growths and biological process-, and two metabolic-related responsive elements were discovered by studying the cis-elements in the promoters. According to the expression analyses, all five genes were up- and down-regulated in response to abscisic acid (ABA), photoperiod, chilling, and chilling, as well as photoperiod treatments. Our findings gave insight into the SnRK2 family genes in L. chinense and opened up new study options.

Mining the Roles of Wheat (Triticum aestivum) SnRK Genes in Biotic and Abiotic Responses.

Sucrose non-fermenting-1-related protein kinases (SnRKs) play vital roles in plant growth and stress responses. However, little is known about the SnRK functions in wheat. In this study, 149 TaSnRKs (wheat SnRKs) were identified and were divided into three subfamilies. A combination of public transcriptome data and real-time reverse transcription-polymerase chain reaction (qRT-PCR) analysis revealed the distinct expression patterns of TaSnRKs under various abiotic and biotic stresses. TaSnRK2.4-B, a member of SnRK2s, has different expression patterns under polyethylene glycol (PEG), sodium chloride (NaCl) treatment, and high concentrations of abscisic acid (ABA) application. Yeast two-hybrid assay indicated that TaSnRK2.4-B could interact with the SnRK2-interacting calcium sensor (SCS) in wheat and play a role in the ABA-dependent pathway. Moreover, TaSnRK2.4-B might be a negative regulator in wheat against pathogen infection. The present study provides valuable information for understanding the functions of the TaSnRK family and provides recommendations for future genetic improvement in wheat stress resistance.

Genome-Wide Identification and Expression Analysis of SnRK Gene Family under Abiotic Stress in Cucumber (Cucumis sativus L.)

Sucrose non-fermenting 1-related protein kinases (SnRKs) are a kind of plant-specific serine/threonine (Ser/Thr) protein kinase, which play an important role in plant stress resistance. However, the scale analysis of SnRK in the cucumber genome is currently unclear. In the study, a total of 30 CsSnRK genes were identified from genomic data. They were distributed on six chromosomes, including 1 CsSnRK1, 10 CsSnRK2s and 19 CsSnRK3s. According to the analysis of gene structure and motif composition, CsSnRKs showed obvious differences among the three subfamilies. The ratio of synonymous (Ks) and nonsynonymous (Ka) nucleotide substitutions (Ka/Ks) of three paralogues indicates that the CsSnRK gene family undergoes a purifying selection. The analysis of cis-acting elements shows that the promoter region of each CsSnRK gene contained different classes of hormone and stress-related cis-acting elements. Furthermore, based on RNA-sequencing data from the Short Read Archive (SRA) database of NCBI, the expression patterns of CsSnRK genes in six tissues were investigated, indicating that the expression of multiple CsSnRK genes was prevalent in these tissues. Transcription levels of CsSnRK genes after drought, methyl jasmonate (MeJA) and abscisic acid (ABA) treatments were analyzed by quantitative RT-PCR, and the results show that most of the CsSnRK genes responded to these stresses. However, under different treatments, individual genes played a major role. For example, under ABA treatment, CsSnRK2.2 and CsSnRK2.3 played a major role in the response to ABA. These results provide clear evidence that CsSnRKs may be involved in cucumber growth, development and stress response, and provide valuable information for future functional studies of CsSnRKs.

Energy homeostasis mediated by the LcSnRK1α-LcbZIP1/3 signaling pathway modulates litchi fruit senescence.

Cellular energy status is a key factor deciding the switch-on of the senescence of horticultural crops. Despite the established significance of the conserved energy master regulator sucrose non-fermenting 1 (SNF1)-related protein kinase 1 (SnRK1) in plant development, its working mechanism and related signaling pathway in the regulation of fruit senescence remain enigmatic. Here, we demonstrate that energy deficit accelerates fruit senescence, whereas exogenous ATP treatment delays it. The transient suppression of LcSnRK1α in litchi (Litchi chinensis Sonn.) fruit inhibited the expression of energy metabolism-related genes, while its ectopic expression in tomato (Solanum lycopersicum) promoted ripening and a high energy level. Biochemical analyses revealed that LcSnRK1α interacted with and phosphorylated the transcription factors LcbZIP1 and LcbZIP3, which directly bound to the promoters to activate the expression of DARK-INDUCIBLE 10 (LcDIN10), ASPARAGINE SYNTHASE 1 (LcASN1), and ANTHOCYANIN SYNTHASE (LcANS), thereby fine-tuning the metabolic reprogramming to ensure energy and redox homeostasis. Altogether, these observations reveal a post-translational modification mechanism by which LcSnRK1α-mediated phosphorylation of LcbZIP1 and LcbZIP3 regulates the expression of metabolic reprogramming-related genes, consequently modulating litchi fruit senescence.