A CBL-Interacting Protein Kinase TaCIPK2 Confers Drought Tolerance in Transgenic Tobacco Plants through Regulating the Stomatal Movement

Molecular Mechanisms of CBL-CIPK Signaling Pathway in Plant Abiotic Stress Tolerance and Hormone Crosstalk

Abiotic stressors, including drought, salt, cold, and heat, profoundly impact plant growth and development, forcing elaborate cellular responses for adaptation and resilience. Among the crucial orchestrators of these responses is the CBL-CIPK pathway, comprising calcineurin B-like proteins (CBLs) and CBL-interacting protein kinases (CIPKs). While CIPKs act as serine/threonine protein kinases, transmitting calcium signals, CBLs function as calcium sensors, influencing the plant's response to abiotic stress. This review explores the intricate interactions between the CBL-CIPK pathway and plant hormones such as ABA, auxin, ethylene, and jasmonic acid (JA). It highlights their role in fine-tuning stress responses for optimal survival and acclimatization. Building on previous studies that demonstrated the enhanced stress tolerance achieved by upregulating CBL and CIPK genes, we explore the regulatory mechanisms involving post-translational modifications and protein-protein interactions. Despite significant contributions from prior research, gaps persist in understanding the nuanced interplay between the CBL-CIPK system and plant hormone signaling under diverse abiotic stress conditions. In contrast to broader perspectives, our review focuses on the interaction of the pathway with crucial plant hormones and its implications for genetic engineering interventions to enhance crop stress resilience. This specialized perspective aims to contribute novel insights to advance our understanding of the potential of the CBL-CIPK pathway to mitigate crops' abiotic stress.

CRISPR/Cas as a Genome-Editing Technique in Fruit Tree Breeding

CRISPR (short for "Clustered Regularly Interspaced Short Palindromic Repeats") is a technology that research scientists use to selectively modify the DNA of living organisms. CRISPR was adapted for use in the laboratory from the naturally occurring genome-editing systems found in bacteria. In this work, we reviewed the methods used to introduce CRISPR/Cas-mediated genome editing into fruit species, as well as the impacts of the application of this technology to activate and knock out target genes in different fruit tree species, including on tree development, yield, fruit quality, and tolerance to biotic and abiotic stresses. The application of this gene-editing technology could allow the development of new generations of fruit crops with improved traits by targeting different genetic segments or even could facilitate the introduction of traits into elite cultivars without changing other traits. However, currently, the scarcity of efficient regeneration and transformation protocols in some species, the fact that many of those procedures are genotype-dependent, and the convenience of segregating the transgenic parts of the CRISPR system represent the main handicaps limiting the potential of genetic editing techniques for fruit trees. Finally, the latest news on the legislation and regulations about the use of plants modified using CRISPR/Cas systems has been also discussed.

Identification of loci associated with water use efficiency and symbiotic nitrogen fixation in soybean

Soybean (Glycine max) production is greatly affected by persistent and/or intermittent droughts in rainfed soybean-growing regions worldwide. Symbiotic N2 fixation (SNF) in soybean can also be significantly hampered even under moderate drought stress. The objective of this study was to identify genomic regions associated with shoot carbon isotope ratio (δ13C) as a surrogate measure for water use efficiency (WUE), nitrogen isotope ratio (δ15N) to assess relative SNF, N concentration ([N]), and carbon/nitrogen ratio (C/N). Genome-wide association mapping was performed with 105 genotypes and approximately 4 million single-nucleotide polymorphism markers derived from whole-genome resequencing information. A total of 11, 21, 22, and 22 genomic loci associated with δ13C, δ15N, [N], and C/N, respectively, were identified in two environments. Nine of these 76 loci were stable across environments, as they were detected in both environments. In addition to the 62 novel loci identified, 14 loci aligned with previously reported quantitative trait loci for different C and N traits related to drought, WUE, and N2 fixation in soybean. A total of 58 Glyma gene models encoding for different genes related to the four traits were identified in the vicinity of the genomic loci.

CBL-Interacting Protein Kinases 18 (CIPK18) Gene Positively Regulates Drought Resistance in Potato

Sensor-responder complexes comprising calcineurin B-like (CBL) proteins and CBL-interacting protein kinases (CIPKs) are plant-specific Ca²⁺ receptors, and the CBL-CIPK module is widely involved in plant growth and development and a large number of abiotic stress response signaling pathways. In this study, the potato cv. "Atlantic" was subjected to a water deficiency treatment and the expression of StCIPK18 gene was detected by qRT-PCR. The subcellular localization of StCIPK18 protein was observed by a confocal laser scanning microscope. The StCIPK18 interacting protein was identified and verified by yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC). StCIPK18 overexpression and StCIPK18 knockout plants were constructed. The phenotypic changes under drought stress were indicated by water loss rate, relative water content, MDA and proline contents, and CAT, SOD and POD activities. The results showed that StCIPK18 expression was upregulated under drought stress. StCIPK18 is localized in the cell membrane and cytoplasm. Y2H shows the interaction between StCIPK18 and StCBL1, StCBL4, StCBL6 and StCBL8. BiFC further verifies the reliability of the interaction between StCIPK18 and StCBL4. Under drought stress, StCIPK18 overexpression decreased the water loss rate and MDA, and increased RWC, proline contents and CAT, SOD and POD activities; however, StCIPK18 knockout showed opposite results, compared with the wild type, in response to drought stress. The results can provide information for the molecular mechanism of the StCIPK18 regulating potato response to drought stress.

Transcriptome-Wide Identification and Functional Characterization of CIPK Gene Family Members in Actinidia valvata under Salt Stress

Fruit plants are severely constrained by salt stress in the soil due to their sessile nature. Ca²⁺ sensors, which are known as CBL-interacting protein kinases (CIPKs), transmit abiotic stress signals to plants. Therefore, it is imperative to investigate the molecular regulatory role of CIPKs underlying salt stress tolerance in kiwifruit. In the current study, we have identified 42 CIPK genes from Actinidia. valvata (A.valvata). All the AvCIPKs were divided into four different phylogenetic groups. Moreover, these genes showed different conserved motifs. The expression pattern analysis showed that AvCIPK11 was specifically highly expressed under salt stress. The overexpression of AvCIPK11 in 'Hongyang' (a salt sensitive commercial cultivar from Actinidia chinensis) enhanced salt tolerance by maintaining K⁺/Na⁺ homeostasis in the leaf and positively improving the activity of POD. In addition, the salt-related genes AcCBL1 and AcNHX1 had higher expression in overexpression lines. Collectively, our study suggested that AvCIPK11 is involved in the positive regulation of salt tolerance in kiwifruit.

Contrasting a reference cranberry genome to a crop wild relative provides insights into adaptation, domestication, and breeding

Cranberry (Vaccinium macrocarpon) is a member of the Heath family (Ericaceae) and is a temperate low-growing woody perennial native to North America that is both economically important and has significant health benefits. While some native varieties are still grown today, breeding programs over the past 50 years have made significant contributions to improving disease resistance, fruit quality and yield. An initial genome sequence of an inbred line of the wild selection ‘Ben Lear,’ which is parent to multiple breeding programs, provided insight into the gene repertoire as well as a platform for molecular breeding. Recent breeding efforts have focused on leveraging the circumboreal V. oxycoccos, which forms interspecific hybrids with V. macrocarpon, offering to bring in novel fruit chemistry and other desirable traits. Here we present an updated, chromosome-resolved V. macrocarpon reference genome, and compare it to a high-quality draft genome of V. oxycoccos. Leveraging the chromosome resolved cranberry reference genome, we confirmed that the Ericaceae has undergone two whole genome duplications that are shared with blueberry and rhododendron. Leveraging resequencing data for ‘Ben Lear’ inbred lines, as well as several wild and elite selections, we identified common regions that are targets of improvement. These same syntenic regions in V. oxycoccos, were identified and represent environmental response and plant architecture genes. These data provide insight into early genomic selection in the domestication of a native North American berry crop.

A comprehensive meta-QTL analysis for yield-related traits of durum wheat (Triticum turgidum L. var. durum) grown under different water regimes

Abiotic stress strongly affects yield-related traits in durum wheat, in particular drought is one of the main environmental factors that have effect on grain yield and plant architecture. In order to obtain new genotypes well adapted to stress conditions, the highest number of desirable traits needs to be combined in the same genotype. In this context, hundreds of quantitative trait loci (QTL) have been identified for yield-related traits in different genetic backgrounds and environments. Meta-QTL (MQTL) analysis is a useful approach to combine data sets and for creating consensus positions for the QTL detected in independent studies for the reliability of their location and effects. MQTL analysis is a useful method to dissect the genetic architecture of complex traits, which provide an extensive allelic coverage, a higher mapping resolution and allow the identification of putative molecular markers useful for marker-assisted selection (MAS). In the present study, a complete and comprehensive MQTL analysis was carried out to identify genomic regions associated with grain-yield related traits in durum wheat under different water regimes. A total of 724 QTL on all 14 chromosomes (genomes A and B) were collected for the 19 yield-related traits selected, of which 468 were reported under rainfed conditions, and 256 under irrigated conditions. Out of the 590 QTL projected on the consensus map, 421 were grouped into 76 MQTL associated with yield components under both irrigated and rainfed conditions, 12 genomic regions containing stable MQTL on all chromosomes except 1A, 4A, 5A, and 6B. Candidate genes associated to MQTL were identified and an in-silico expression analysis was carried out for 15 genes selected among those that were differentially expressed under drought. These results can be used to increase durum wheat grain yields under different water regimes and to obtain new genotypes adapted to climate change.

The CaCIPK3 gene positively regulates drought tolerance in pepper

Drought stress is a major agricultural problem restricting the growth, development, and productivity of plants. Calcineurin B-like proteins (CBLs) and CBL-interacting protein kinases (CIPKs) significantly influence the plant response to different stresses. However, the molecular mechanisms of CBL-CIPK in the drought stress response of pepper are still unknown. Here, the function of CaCIPK3 in the regulation of drought stress in pepper (Capsicum annuum L.) was explored. Transcriptomic data and quantitative real-time PCR (qRT-PCR) analysis revealed that CaCIPK3 participates in the response to multiple stresses. Knockdown of CaCIPK3 in pepper increased the sensitivity to mannitol and methyl jasmonate (MeJA). Transient overexpression of CaCIPK3 improved drought tolerance by enhancing the activities of the antioxidant system and positively regulating jasmonate (JA)-related genes. Ectopic expression of CaCIPK3 in tomato also improved drought and MeJA resistance. As the CaCIPK3-interacting partner, CaCBL2 positively influenced drought resistance. Additionally, CaWRKY1 and CaWRKY41 directly bound the CaCIPK3 promoter to influence its expression. This study shows that CaCIPK3 acts as a positive regulator in drought stress resistance via the CBL-CIPK network to regulate MeJA signaling and the antioxidant defense system.

Drought and High Temperature Stress in Sorghum: Physiological, Genetic, and Molecular Insights and Breeding Approaches

Sorghum is one of the staple crops for millions of people in Sub-Saharan Africa (SSA) and South Asia (SA). The future climate in these sorghum production regions is likely to have unexpected short or long episodes of drought and/or high temperature (HT), which can cause significant yield losses. Therefore, to achieve food and nutritional security, drought and HT stress tolerance ability in sorghum must be genetically improved. Drought tolerance mechanism, stay green, and grain yield under stress has been widely studied. However, novel traits associated with drought (restricted transpiration and root architecture) need to be explored and utilized in breeding. In sorghum, knowledge on the traits associated with HT tolerance is limited. Heat shock transcription factors, dehydrins, and genes associated with hormones such as auxin, ethylene, and abscisic acid and compatible solutes are involved in drought stress modulation. In contrast, our understanding of HT tolerance at the omic level is limited and needs attention. Breeding programs have exploited limited traits with narrow genetic and genomic resources to develop drought or heat tolerant lines. Reproductive stages of sorghum are relatively more sensitive to stress compared to vegetative stages. Therefore, breeding should incorporate appropriate pre-flowering and post-flowering tolerance in a broad genetic base population and in heterotic hybrid breeding pipelines. Currently, more than 240 QTLs are reported for drought tolerance-associated traits in sorghum prospecting discovery of trait markers. Identifying traits and better understanding of physiological and genetic mechanisms and quantification of genetic variability for these traits may enhance HT tolerance. Drought and HT tolerance can be improved by better understanding mechanisms associated with tolerance and screening large germplasm collections to identify tolerant lines and incorporation of those traits into elite breeding lines. Systems approaches help in identifying the best donors of tolerance to be incorporated in the SSA and SA sorghum breeding programs. Integrated breeding with use of high-throughput precision phenomics and genomics can deliver a range of drought and HT tolerant genotypes that can improve yield and resilience of sorghum under drought and HT stresses.

Arabidopsis thaliana Genes Associated with Cucumber mosaic virus Virulence and Their Link to Virus Seed Transmission

Virulence, the effect of pathogen infection on progeny production, is a major determinant of host and pathogen fitness as it affects host fecundity and pathogen transmission. In plant-virus interactions, ample evidence indicates that virulence is genetically controlled by both partners. However, the host genetic determinants are poorly understood. Through a genome-wide association study (GWAS) of 154 Arabidopsis thaliana genotypes infected by Cucumber mosaic virus (CMV), we identified eight host genes associated with virulence, most of them involved in response to biotic stresses and in cell wall biogenesis in plant reproductive structures. Given that virulence is a main determinant of the efficiency of plant virus seed transmission, we explored the link between this trait and the genetic regulation of virulence. Our results suggest that the same functions that control virulence are also important for CMV transmission through seeds. In sum, this work provides evidence of a novel role for some previously known plant defense genes and for the cell wall metabolism in plant virus interactions.

CIPK11: a calcineurin B-like protein-interacting protein kinase from Nitraria tangutorum, confers tolerance to salt and drought in Arabidopsis

BACKGROUND

The CIPKs are a group of plant-specific Ser/Thr protein kinases acting in response to calcium signaling, which plays an important role in the physiological and developmental adaptation of plants to adverse environments. However, the functions of halophyte-derived CIPKs are still poorly understood, that limits a potential application of CIPKs from halophytes for improving the tolerance of glycophytes to abiotic stresses.

RESULTS

In this study, we characterized the NtCIPK11 gene from the halophyte Nitraria tangutorum and subsequently analyzed its role in salt and drought stress tolerance, using Arabidopsis as a transgenic model system. NtCIPK11 expression was upregulated in N. tangutorum root, stem and blade tissues after salt or drought treatment. Overexpressing NtCIPK11 in Arabidopsis improved seed germination on medium containing different levels of NaCl. Moreover, the transgenic plants grew more vigorously under salt stress and developed longer roots under salt or drought conditions than the WT plants. Furthermore, NtCIPK11 overexpression altered the transcription of genes encoding key enzymes involved in proline metabolism in Arabidopsis exposed to salinity, however, which genes showed a relatively weak expression in the transgenic Arabidopsis undergoing mannitol treatment, a situation that mimics drought stress. Besides, the proline significantly accumulated in NtCIPK11-overexpressing plants compared with WT under NaCl treatment, but that was not observed in the transgenic plants under drought stress caused by mannitol application.

CONCLUSIONS

We conclude that NtCIPK11 promotes plant growth and mitigates damage associated with salt stress by regulating the expression of genes controlling proline accumulation. These results extend our understanding on the function of halophyte-derived CIPK genes and suggest that NtCIPK11 can serve as a candidate gene for improving the salt and drought tolerance of glycophytes through genetic engineering.

The kinase CIPK11 functions as a positive regulator in cadmium stress response in Arabidopsis

Cadmium (Cd) pollution in agricultural soil has always been a knotty problem, which made it necessary to find the mechanism related to Cd transport in plant. In this study, we found a novel character of the CIPK11 modulating the transport of Cd in Arabidopsis thaliana. Over-expression of CIPK11 (CIPK11OE#1-7, CIPK11OE#8-5) resulted in the increased tolerance to Cd stress, which embodied in higher fresh weight, lower Cd enrichment and reactive oxygen species (ROS) than the wild-type (WT) plants. qRT-PCR results showed a collective down-regulation of the expression of IRT1 and transcription factor genes FIT, bHLH039 in the CIPK11-overexpression plants after Cd stress. Overexpression of CIPK11 significantly increased the expression of ABA marker genes in Arabidopsis after Cd stress. With different concentrations of ABA treatment, the root length differences caused by Cd stress could be recovered. However the transcription levels of FIT and bHLH039 decreased in WT and cipk11 mutant when treated with ABA which indicated that ABA can inhibit the transcription of IRT1 by repressing FIT and bHLH039 expression. Taken together, our results demonstrated that the kinase CIPK11 responses to Cd stress by ABA signaling pathway.

CaCBL1 Acts as a Positive Regulator in Pepper Response to Ralstonia solanacearum

Bacterial wilt caused by Ralstonia solanacearum is an important disease of pepper (Capsicum annuum), an economically important solanaceous vegetable worldwide, in particular, under high temperature (HT) conditions. However, the molecular mechanism underlying pepper immunity against bacterial wilt remains poorly understood. Herein, CaCBL1, a putative calcineurin B-like protein, was functionally characterized in the pepper response to R. solanacearum inoculation (RSI) under HT (RSI/HT). CaCBL1 was significantly upregulated by RSI at room temperature (RSI/RT), HT, or RSI/HT. CaCBL1-GFP fused protein targeted to whole epidermal cells of Nicotiana benthamiana when transiently overexpressed. CaCBL1 silencing by virus-induced gene silencing significantly enhanced pepper susceptibility to RSI under RT or HT, while its transient overexpression triggered hypersensitive response mimic cell death and upregulation of immunity-associated marker genes, including CabZIP63, CaWRKY40, and CaCDPK15, the positive regulators in the pepper response to RSI or HT found in our previous studies. In addition, by chromatin immunoprecipitation PCR and electrophoretic mobility shift assay, CaCBL1 was found to be directly targeted by CaWRKY40, although not by CaWRKY27 or CaWRKY58, via the W-box-2 within its promoter, and its transcription was found to be downregulated by silencing of CaWRKY40 while it was enhanced by its transient overexpression. These results suggest that CaCBL1 acts as a positive regulator in pepper immunity against R. solanacearum infection, constituting a positive feedback loop with CaWRKY40.

Genome-Wide Association Study of Wood Anatomical and Morphological Traits in Populus trichocarpa

To understand the genetic mechanisms underlying wood anatomical and morphological traits in Populus trichocarpa, we used 869 unrelated genotypes from a common garden in Clatskanie, Oregon that were previously collected from across the distribution range in western North America. Using GEMMA mixed model analysis, we tested for the association of 25 phenotypic traits and nine multitrait combinations with 6.741 million SNPs covering the entire genome. Broad-sense trait heritabilities ranged from 0.117 to 0.477. Most traits were significantly correlated with geoclimatic variables suggesting a role of climate and geography in shaping the variation of this species. Fifty-seven SNPs from single trait GWAS and 11 SNPs from multitrait GWAS passed an FDR threshold of 0.05, leading to the identification of eight and seven nearby candidate genes, respectively. The percentage of phenotypic variance explained (PVE) by the significant SNPs for both single and multitrait GWAS ranged from 0.01% to 6.18%. To further evaluate the potential roles of candidate genes, we used a multi-omic network containing five additional data sets, including leaf and wood metabolite GWAS layers and coexpression and comethylation networks. We also performed a functional enrichment analysis on coexpression nearest neighbors for each gene model identified by the wood anatomical and morphological trait GWAS analyses. Genes affecting cell wall composition and transport related genes were enriched in wood anatomy and stomatal density trait networks. Signaling and metabolism related genes were also common in networks for stomatal density. For leaf morphology traits (leaf dry and wet weight) the networks were significantly enriched for GO terms related to photosynthetic processes as well as cellular homeostasis. The identified genes provide further insights into the genetic control of these traits, which are important determinants of the suitability and sustainability of improved genotypes for lignocellulosic biofuel production.

The Kinase CIPK11 Functions as a Negative Regulator in Drought Stress Response in Arabidopsis

Drought is a major limiting factor for plant growth and crop productivity. Many Calcineurin B-like interacting protein kinases (CIPKs) play crucial roles in plant adaptation to environmental stresses. It is particularly essential to find the phosphorylation targets of CIPKs and to study the underlying molecular mechanisms. In this study, we demonstrate that CIPK11 acts as a novel component to modulate drought stress in plants. The overexpression of CIPK11 (CIPK11OE) in Arabidopsis resulted in the decreased tolerance of plant to drought stress. When compared to wild type plants, CIPK11OE plants exhibited higher leaf water loss and higher content of reactive oxygen species (ROS) after drought treatment. Additionally, a yeast two hybrid screening assay by using CIPK11 as a bait captures Di19-3, a Cys2/His2-type zinc-finger transcription factor that is involved in drought stress, as a new interactor of CIPK11. Biochemical analysis revealed that CIPK11 interacted with Di19-3 in vivo and it was capable of phosphorylating Di19-3 in vitro. Genetic studies revealed that the function of CIPK11 in regulating drought stress was dependent on Di19-3. The transcripts of stress responsive genes, such as RAB18, RD29A, RD29B, and DREB2A were down-regulated in the CIPK11OE plants. Whereas overexpression of CIPK11 in di19-3 mutant background, expression levels of those marker genes were not significantly altered. Taken together, our results demonstrate that CIPK11 partly mediates the drought stress response by regulating the transcription factor Di19-3.

TaCIPK10 interacts with and phosphorylates TaNH2 to activate wheat defense responses to stripe rust

Calcineurin B-like interacting protein kinase (CIPKs) has been shown to be required for biotic stress tolerance of plants in plant-pathogen interactions. However, the roles of CIPKs in immune signalling of cereal crops and an in-depth knowledge of substrates of CIPKs in response to biotic stress are under debate. In this study, we identified and cloned a CIPK homologue gene TaCIPK10 from wheat. TaCIPK10 was rapidly induced by Puccinia striiformis f. sp. tritici (Pst) inoculation and salicylic acid (SA) treatment. In vitro phosphorylation assay demonstrated that the kinase activity of TaCIPK10 is regulated by Ca²⁺ and TaCBL4. Knockdown TaCIPK10 significantly reduced wheat resistance to Pst, whereas TaCIPK10 overexpression resulted in enhanced wheat resistance to Pst by the induction of defense response in different aspects, including hypersensitive cell death, ROS accumulation and pathogenesis-relative genes expression. Moreover, TaCIPK10 physically interacted with and phosphorylated TaNH2, which was homologous to AtNPR3/4. Silencing of TaNH2 in wheat resulted in enhanced susceptibility to the avirulent Pst race, CYR23, indicating its positive role in wheat resistance. Our results demonstrate that TaCIPK10 positively regulate wheat resistance to Pst as molecular links between of Ca²⁺ and downstream components of defense response and TaCIPK10 interacts with and phosphorylates TaNH2 to regulate wheat resistance to Pst.

An apple sucrose transporter MdSUT2.2 is a phosphorylation target for protein kinase MdCIPK22 in response to drought

Sugars increase with drought stress in plants and accumulate in the vacuole. However, the exact molecular mechanism underlying this process is not clear yet. In this study, protein interaction and phosphorylation experiments were conducted for sucrose transporter and CIPK kinase in apple. The specific phosphorylation site of sucrose transporter was identified with mass spectrometry. Transgenic analyses were performed to characterize their biological function. It was found that overexpression of sucrose transporter gene MdSUT2.2 in apple plants promoted sugar accumulation and drought tolerance. MdSUT2.2 protein was phosphorylated at Ser³⁸¹ site in response to drought. A DUALmembrane system using MdSUT2.2 as bait through an apple cDNA library got a protein kinase MdCIPK22. Bimolecular fluorescence complementary (BiFC), pull-down and co-immunoprecipitation (Co-IP) assays further demonstrated that MdCIPK22 interacted with MdSUT2.2. A series of transgenic analysis showed that MdCIPK22 was required for the drought-induced phosphylation at Ser³⁸¹ site of MdSUT2.2 protein, and that it enhanced the stability and transport activity of MdSUT2.2 protein. Finally, it was found that MdCIPK22 overexpression promoted sugar accumulation and improved drought tolerance in an MdSUT2.2-dependent manner in transgenic apple plants. MdCIPK22-MdSUT2.2 regulatory module shed light on the molecular mechanism by which plant accumulates sugars and enhances tolerance in response to drought stress.

The calcium sensor TaCBL4 and its interacting protein TaCIPK5 are required for wheat resistance to stripe rust fungus

Calcineurin B-like proteins (CBLs) act as Ca2+ sensors to activate specific protein kinases, namely CBL-interacting protein kinases (CIPKs). Recent research has demonstrated that the CBL-CIPK complex is not only required for abiotic stress signaling, but is also probably involved in biotic stress perception. However, the role of this complex in immune signaling, including pathogen perception, is unknown. In this study, we isolated one signaling component of the TaCBL-TaCIPK complex (TaCBL4-TaCIPK5) and characterized its role in the interaction between wheat (Triticum aestivum) and Puccinia striiformis f. sp. tritici (Pst, stripe rust fungus). Among all TaCBLs in wheat, TaCBL4 mRNA accumulation markedly increased after infection by Pst. Silencing of TaCBL4 resulted in enhanced susceptibility to avirulent Pst infection. In addition, screening determined that TaCIPK5 physically interacted with TaCBL4 in planta and positively contributed to wheat resistance to Pst. Moreover, the disease resistance phenotype of TaCBL4 and TaCIPK5 co-silenced plants was consistent with that of single-knockdown plants. The accumulation of reactive oxygen species (ROS) was significantly altered in all silenced plants during Pst infection. Together these findings demonstrate that the TaCBL4-TaCIPK5 complex positively modulates wheat resistance in a ROS-dependent manner, and provide new insights into the roles of CBL-CIPK in wheat.

Expression of a populus histone deacetylase gene 84KHDA903 in tobacco enhances drought tolerance

Histone deacetylases (HDACs) play a key role in regulating plant growth, development and stress responses. However, functions of HDACs in woody plants are largely unknown. In this study, a novel gene encoding a RPD3/HDA1-type histone deacetylase was cloned from 84K poplar (Populus alba×Populus glandulosa) and designated as 84KHDA903. The 84KHDA903 encodes a protein composed of 500 amino acid residues, which contains a conserved HDAC domain. Transient expression of 84KHDA903 in onion epidermal cells suggested that it was exclusively localized in nucleus. The 84KHDA903 exhibited different expression patterns under drought, salt and ABA treatments. The expression of 84KHDA903 was responsive to drought and ABA but not to salt. To understand the function of 84KHDA903 in stress responses, the 84KHDA903 gene was transformed into tobacco. The expression of 84KHDA903 in tobacco increased the tolerance of transgenic seeds to mannitol but not to salt. In adult stage, the 84KHDA903-expressing tobacco exhibited drought tolerance and showed strong capacity to recover after drought. During the recovery period, the stress-responsive genes including NtDREB4, NtDREB3 and NtLEA5 were induced to be highly expressed in the 84KHDA903 transgenic plants in contrast to wild-type plants. Taken together, for the first time, we reported a RPD3/HDA1-type histone deacetylase from poplar, 84KHDA903, which acted as a positive regulator in drought stress responses.

BdCIPK31, a Calcineurin B-Like Protein-Interacting Protein Kinase, Regulates Plant Response to Drought and Salt Stress

Calcineurin B-like protein interacting protein kinases (CIPKs) are vital elements in plant abiotic stress signaling pathways. However, the functional mechanism of CIPKs has not been understood clearly, especially in Brachypodium distachyon, a new monocot model plant. In this study, BdCIPK31, a CIPK gene from B. distachyon was characterized. BdCIPK31 was downregulated by polyethylene glycol, NaCl, H2O2, and abscisic acid (ABA) treatments. Transgenic tobacco plants overexpressing BdCIPK31 presented improved drought and salt tolerance, and displayed hypersensitive response to exogenous ABA. Further investigations revealed that BdCIPK31 functioned positively in ABA-mediated stomatal closure, and transgenic tobacco exhibited reduced water loss under dehydration conditions compared with the controls. BdCIPK31 also affected Na+/K+ homeostasis and root K+ loss, which contributed to maintain intracellular ion homeostasis under salt conditions. Moreover, the reactive oxygen species scavenging system and osmolyte accumulation were enhanced by BdCIPK31 overexpression, which were conducive for alleviating oxidative and osmotic damages. Additionally, overexpression of BdCIPK31 could elevate several stress-associated gene expressions under stress conditions. In conclusion, BdCIPK31 functions positively to drought and salt stress through ABA signaling pathway. Overexpressing BdCIPK31 functions in stomatal closure, ion homeostasis, ROS scavenging, osmolyte biosynthesis, and transcriptional regulation of stress-related genes.