IDD10-NAC079 transcription factor complex regulates sheath blight resistance by inhibiting ethylene signaling in rice.

INTRODUCTION: Rhizoctonia solani Kühn is a pathogen causing rice sheath blight (ShB). Ammonium transporter 1 (AMT1) promotes resistance of rice to ShB by activating ethylene signaling. However, how AMT1 activates ethylene signaling remains unclear. OBJECTIVE: In this study, the indeterminate domain 10 (IDD10)-NAC079 interaction model was used to investigate whether ethylene signaling is modulated downstream of ammonium signaling and modulates ammonium-mediated ShB resistance. METHODS: RT-qPCR assay was used to identify the relative expression levels of nitrogen and ethylene related genes. Yeast two-hybrid assays, Bimolecular fluorescence complementation (BiFC) and Co-immunoprecipitation (Co-IP) assay were conducted to verify the IDD10-NAC079-calcineurin B-like interacting protein kinase 31 (CIPK31) transcriptional complex. Yeast one-hybrid assay, Chromatin immunoprecipitation (ChIP) assay, and Electrophoretic mobility shift assay (EMSA) were used to verify whether ETR2 was activated by IDD10 and NAC079. Ethylene quantification assay was used to verify ethylene content in IDD10 transgenic plants. Genetic analysis is used to detect the response of IDD10, NAC079 and CIPK31 to ShB infestation. RESULTS: IDD10-NAC079 forms a transcription complex that activates ETR2 to inhibit the ethylene signaling pathway to negatively regulating ShB resistance. CIPK31 interacts and phosphorylates NAC079 to enhance its transcriptional activation activity. In addition, AMT1-mediated ammonium absorption and subsequent N assimilation inhibit the expression of IDD10 and CIPK31 to activate the ethylene signaling pathway, which positively regulates ShB resistance. CONCLUSION: The study identified the link between ammonium and ethylene signaling and improved the understanding of the rice resistance mechanism.

The 14-3-3 protein nt GF14e interacts with CIPK2 and increases low potassium stress in tobacco.

Potassium (K+) plays a role in enzyme activation, membrane transport, and osmotic regulation processes. An increase in potassium content can significantly improve the elasticity and combustibility of tobacco and reduce the content of harmful substances. Here, we report that the expression analysis of Nt GF14e, a 14-3-3 gene, increased markedly after low-potassium treatment (LK). Then, chlorophyll content, POD activity and potassium content, were significantly increased in overexpression of Nt GF14e transgenic tobacco lines compared with those in the wild type plants. The net K+ efflux rates were severely lower in the transgenic plants than in the wild type under LK stress. Furthermore, transcriptome analysis identified 5708 upregulated genes and 2787 downregulated genes between Nt GF14e overexpressing transgenic tobacco plants. The expression levels of some potassium-related genes were increased, such as CBL-interacting protein kinase 2 (CIPK2), Nt CIPK23, Nt CIPK25, H+-ATPase isoform 2 a (AHA2a), Nt AHA4a, Stelar K+ outward rectifier 1(SKOR1), and high affinity K+ transporter 5 (HAK5). The result of yeast two-hybrid and luciferase complementation imaging experiments suggested Nt GF14e could interact with CIPK2. Overall, these findings indicate that NtGF14e plays a vital roles in improving tobacco LK tolerance and enhancing potassium nutrition signaling pathways in tobacco plants.

Flooding Tolerance of Rice: Regulatory Pathways and Adaptive Mechanisms.

Rice is a major food crop for more than half of the world's population, while its production is seriously threatened by flooding, a common environmental stress worldwide. Flooding leads to oxygen deficiency, which is a major problem for submerged plants. Over the past three decades, significant progress has been made in understanding rice adaptation and molecular regulatory mechanisms in response to flooding. At the seed germination and seedling establishment stages, the CIPK15-SnRK1A-MYBS1 signaling cascade plays a central role in determining rice submergence tolerance. However, from seedlings to mature plants for harvesting, SUB1A- and SK1/SK2-regulated pathways represent two principal and opposite regulatory mechanisms in rice. In addition, phytohormones, especially gibberellins, induce adaptive responses to flooding throughout the rice growth period. This review summarizes the significant adaptive traits observed in flooded rice varieties and updates the molecular genetics and mechanisms of submergence tolerance in rice.

MsWRKY44 regulates Mg-K homeostasis of shoots and promotes alfalfa sensitivities to acid and Al stresses.

Mg-K homeostasis is essential for plant response to abiotic stress, but its regulation remains largely unknown. MsWRKY44 cloned from alfalfa was highly expressed in leaves and petioles. Overexpression of it inhibited alfalfa growth, and promoted leaf senescence and alfalfa sensitivities to acid and Al stresses. The leaf tips, margins and interveins of old leaves occurred yellow spots in MsWRKY44-OE plants under pH4.5 and pH4.5 +Al conditions. Meanwhile, Mg-K homeostasis was substantially changed with reduction of K accumulation and increases of Mg as well as Al accumulation in shoots of MsWRKY44-OE plants. Further, MsWRKY44 was found to directly bind to the promoters of MsMGT7 and MsCIPK23, and positively activated their expression. Transiently overexpressed MsMGT7 and MsCIPK23 in tobacco leaves increased the Mg and Al accumulations but decreased K accumulation. These results revealed a novel regulatory module MsWRKY44-MsMGT7/MsCIPK23, which affects the transport and accumulation of Mg and K in shoots, and promotes alfalfa sensitivities to acid and Al stresses.

The role of CBL-CIPK signaling in plant responses to biotic and abiotic stresses.

Plants have a variety of regulatory mechanisms to perceive, transduce, and respond to biotic and abiotic stress. One such mechanism is the calcium-sensing CBL-CIPK system responsible for the sensing of specific stressors, such as drought or pathogens. CBLs perceive and bind Calcium (Ca2+) in response to stress and then interact with CIPKs to form an activated complex. This leads to the phosphorylation of downstream targets, including transporters and ion channels, and modulates transcription factor levels and the consequent levels of stress-associated genes. This review describes the mechanisms underlying the response of the CBL-CIPK pathway to biotic and abiotic stresses, including regulating ion transport channels, coordinating plant hormone signal transduction, and pathways related to ROS signaling. Investigation of the function of the CBL-CIPK pathway is important for understanding plant stress tolerance and provides a promising avenue for molecular breeding.

TORC: latest addition to the K+ signaling league.

Potassium (K) is an essential macronutrient for plant development. Although the low-K+-responsive calcium (Ca2+) signaling pathway is known, its regulator remained elusive. Li et al. recently demonstrated that the target of rapamycin complex (TORC) and Ca2+ signaling pathways show reciprocal regulation of K+-responsive growth in plants.

Overexpression of Calcineurin B-like Interacting Protein Kinase 31 Promotes Lodging and Sheath Blight Resistance in Rice.

A breakthrough "Green Revolution" in rice enhanced lodging resistance by using gibberellin-deficient semi-dwarf varieties. However, the gibberellic acid (GA) signaling regulation on rice disease resistance remains unclear. The resistance test showed that a positive GA signaling regulator DWARF1 mutant d1 was more susceptible while a negative GA signaling regulator Slender rice 1 (SLR1) mutant was less susceptible to sheath blight (ShB), one of the major rice diseases, suggesting that GA signaling positively regulates ShB resistance. To isolate the regulator, which simultaneously regulates rice lodging and ShB resistance, SLR1 interactors were isolated. Yeast two-hybrid (Y2H), bimolecular fluorescence complementation (BiFC), and Co-IP assay results indicate that SLR1 interacts with Calcineurin B-like-interacting protein kinase 31 (CIPK31). cipk31 mutants exhibited normal plant height, but CIPK31 OXs showed semi-dwarfism. In addition, the SLR1 level was much higher in CIPK31 OXs than in the wild-type, suggesting that CIPK31 OX might accumulate SLR1 to inhibit GA signaling and thus regulate its semi-dwarfism. Recently, we demonstrated that CIPK31 interacts and inhibits Catalase C (CatC) to accumulate ROS, which promotes rice disease resistance. Interestingly, CIPK31 interacts with Vascular Plant One Zinc Finger 2 (VOZ2) in the nucleus, and expression of CIPK31 accumulated VOZ2. Inoculation of Rhizoctonia solani AG1-IA revealed that the voz2 mutant was more susceptible to ShB. Thus, these data prove that CIPK31 promotes lodging and ShB resistance by regulating GA signaling and VOZ2 in rice. This study provides a valuable reference for rice ShB-resistant breeding.

Genome-wide identification, expression analysis, and abiotic stress response of the CBL and CIPK gene families in Artocarpus nanchuanensis.

Artocarpus nanchuanensis, the northernmost species in the jackfruit genus, has great economic and horticultural value due to its nutritious fruit and beautiful tree shape. Calcineurin B-like proteins (CBLs) act as plant-specific Ca2+ sensors and participate in regulating plant responses to various abiotic stresses by interacting with CBL-interacting protein kinases (CIPKs). However, the characteristics and functions of the CBL and CIPK genes in A. nanchuanensis are still unclear. Here, we identified 14 CBL and 33 CIPK genes from the A. nanchuanensis genome, and based on phylogenetic analysis, they were divided into 4 and 7 clades, respectively. Gene structure and motif analysis indicated that the AnCBL and AnCIPK genes were relatively conserved. Colinear analysis showed that segmental duplication contributed to the expansion of the AnCBL and AnCIPK gene families. Expression analysis showed that AnCBL and AnCIPK genes were widely expressed in various tissues of A. nanchuanensis and exhibited tissue-specific expression. In addition, three genes (AnCBL6, AnCIPK7/8) may play important roles in response to salt, cold, and drought stresses. In summary, this study lays an important foundation for the improvement of stress resistance in A. nanchuanensis and provides new insight for the functional research on CBL and CIPK gene families.

Potato calcium sensor modules StCBL3-StCIPK7 and StCBL3-StCIPK24 negatively regulate plant immunity.

BACKGROUND: Potato late blight, caused by Phytophthora infestans, is the most devastating disease on potato. Dissecting critical immune components in potato will be supportive for engineering P. infestans resistance. Upon pathogens attack, plant Ca2+ signature is generated and decoded by an array of Ca2+ sensors, among which calcineurin B-like proteins (CBLs) coupled with plant specific CBL-interacting protein kinases (CIPKs) are much less explored in plant immunity. RESULTS: In this study, we identified that two differential potato CBL-CIPK modules regulate plant defense responses against Phytophthora and ROS production, respectively. By deploying virus-induced gene silencing (VIGS) system-based pathogen inoculation assays, StCBL3 was shown to negatively regulate Phytophthora resistance. Consistently, StCBL3 was further found to negatively regulate PTI and ETI responses in Nicotiana benthamiana. Furthermore, StCIPK7 was identified to act together with StCBL3 to negatively regulate Phytophthora resistance. StCIPK7 physically interacts with StCBL3 and phosphorylates StCBL3 in a Ca2+-dependent manner. StCBL3 promotes StCIPK7 kinase activity. On the other hand, another StCBL3-interacting kinase StCIPK24 negatively modulating flg22-triggered accumulation of reactive oxygen species (ROS) by interacting with StRBOHB. CONCLUSIONS: Together, these findings demonstrate that the StCBL3-StCIPK7 complex negatively modulates Phytophthora resistance and StCBL3-StCIPK24 complex negatively regulate ROS production. Our results offer new insights into the roles of potato CBL-CIPK in plant immunity and provide valuable gene resources to engineer the disease resistance potato in the future.

Finding Balance in Adversity: Nitrate Signaling as the Key to Plant Growth, Resilience, and Stress Response.

To effectively adapt to changing environments, plants must maintain a delicate balance between growth and resistance or tolerance to various stresses. Nitrate, a significant inorganic nitrogen source in soils, not only acts as an essential nutrient but also functions as a critical signaling molecule that regulates multiple aspects of plant growth and development. In recent years, substantial advancements have been made in understanding nitrate sensing, calcium-dependent nitrate signal transmission, and nitrate-induced transcriptional cascades. Mounting evidence suggests that the primary response to nitrate is influenced by environmental conditions, while nitrate availability plays a pivotal role in stress tolerance responses. Therefore, this review aims to provide an overview of the transcriptional and post-transcriptional regulation of key components in the nitrate signaling pathway, namely, NRT1.1, NLP7, and CIPK23, under abiotic stresses. Additionally, we discuss the specificity of nitrate sensing and signaling as well as the involvement of epigenetic regulators. A comprehensive understanding of the integration between nitrate signaling transduction and abiotic stress responses is crucial for developing future crops with enhanced nitrogen-use efficiency and heightened resilience.

A straight-forward gene mining strategy to identify TaCIPK19 as a new regulator of drought tolerance in wheat.

Drought stress is one of the most impactful abiotic stresses to global wheat production. Therefore, identifying key regulators such as the calcineurin B-like protein interacting protein kinase (CIPK) in the signaling cascades known to coordinate developmental cues and environmental stimuli represents a useful approach to improve drought tolerance. However, functional studies have been very limited partly due to the difficulties in prioritizing candidate genes from the large TaCIPK family. To address this issue, we demonstrate a straight-forward strategy by analyzing gene expression patterns in response to phytohormones or stresses and identified TaCIPK19 as a new regulator to improve drought tolerance. The effects of TaCIPK19 on drought tolerance were evaluated in both tobacco and wheat through transgenic approach. Ectopic expression of TaCIPK19 in tobacco greatly improves drought tolerance with enhanced ABA biosynthesis/signaling and ROS scavenging capacity. TaCIPK19 overexpression in wheat also confers the drought tolerance at both seedling and mature stages with enhanced ROS scavenging capacity. Additionally, potential CBL partners interacting with TaCIPK19 were investigated. Collectively, our finding exemplifies a straight-forward approach to facilitate reverse genetics related to abiotic stress improvement and demonstrates TaCIPK19 as a new candidate gene to improve ROS scavenging capacity and drought tolerance, which is useful for genetic improvement and breeding application in wheat.

Integrative gene duplication and genome-wide analysis as an approach to facilitate wheat reverse genetics: An example in the TaCIPK family.

INTRODUCTION: Reverse genetic studies conducted in the plant with a complex or polyploidy genome enriched with large gene families (like wheat) often meet challenges in identifying the key candidate genes related to important traits and prioritizing the genes for functional experiments. OBJECTIVE: To overcome the above-mentioned challenges of reverse genetics, this work aims to establish an efficient multi-species strategy for genome-wide gene identification and prioritization of the key candidate genes. METHODS: We established the integrative gene duplication and genome-wide analysis (iGG analysis) as a strategy for pinpointing key candidate genes deserving functional research. The iGG captures the evolution, and the expansion/contraction of large gene families across phylogeny-related species and integrates spatial-temporal expression information for gene function inference. Transgenic approaches were also employed to functional validation. RESULTS: As a proof-of-concept for the iGG analysis, we took the wheat calcineurin B-like protein-interacting protein kinases (CIPKs) family as an example. We identified CIPKs from seven monocot species, established the orthologous relationship of CIPKs between rice and wheat, and characterized Triticeae-specific CIPK duplicates (e.g., CIPK4 and CIPK17). Integrated with our analysis of CBLs and CBL-CIPK interaction, we revealed that divergent expressions of TaCBLs and TaCIPKs could play an important role in keeping the stoichiometric balance of CBL-CIPK. Furthermore, we validated the function of TaCIPK17-A2 in the regulation of drought tolerance by using transgenic approaches. Overexpression of TaCIPK17 enhanced antioxidant capacity and improved drought tolerance in wheat. CONCLUSION: The iGG analysis leverages evolutionary and comparative genomics of crops with large genomes to rapidly highlight the duplicated genes potentially associated with speciation, domestication and/or particular traits that deserve reverse-genetic functional studies. Through the identification of Triticeae-specific TaCIPK17 duplicates and functional validation, we demonstrated the effectiveness of the iGG analysis and provided a new target gene for improving drought tolerance in wheat.

Phosphorylation by CIPK23 regulates the high-affinity Mn transporter NRAMP1 in Arabidopsis.

Manganese (Mn) is essential for plants but is toxic when taken up in excess. To maintain Mn homeostasis, the root Mn transporter natural resistance associated macrophage protein 1 (NRAMP1) cycles from the plasma membrane to endosomes upon phosphorylation. To identify the kinase involved, a split-luciferase screening was carried out between NRAMP1 and kinases of the CIPK family and identified CIPK23 as a partner of NRAMP1. The interaction was confirmed by split-mCitrine bimolecular fluorescence complementation and co-immunoprecipitation assays. In vitro phosphorylation assays pinpointed two CIPK23 target residues in NRAMP1, among which serine 20, important for endocytosis. Interestingly, Mn-induced internalization of NRAMP1 was unaffected by cipk23 mutation suggesting a potential redundancy between CIPK23 and other kinase(s). How CIPK23 could regulate NRAMP1 in response to Mn availability is discussed.

Overexpression of CdtCIPK21 from triploid bermudagrass reduces salt and drought tolerance but increases chilling tolerance in transgenic rice.

Calcineurin B-like-interacting protein kinase (CIPK) is a serine/threonine kinase, which transmits the Ca2+ signal sensed by CBL proteins. A CdtCIPK21 showing highly identical to OsCIPK21 in rice was isolated from triploid bermudagrass (Cynodon dactylon × Cynodon transvaalensis). CdtCIPK21 transcript could be detected in roots, rhizomes, stems, stolons, and leaves, with highest level in roots. It was induced by salinity, dehydration and chilling, but reduced by ABA treatment. Transgenic rice plants overexpressing CdtCIPK21 had decreased salt and drought tolerance as well as ABA sensitivity but increased chilling tolerance. Lower SOD and CAT activities was observed in transgenic lines under salinity and drought stress conditions, but higher levels under chilling stress. Similarly, lower levels of proline concentration and P5CS1 and P5CS2 transcripts were maintained in transgenic lines under salinity and drought stresses, and higher levels were maintained under chilling. In addition, transgenic lines had lower transcript levels of ABA-independent genes (OsDREB1A, OsDREB1B, and OsDREB2A) and ABA responsive genes (OsLEA3, OsLIP9, and OsRAB16A) under salinity and drought but higher levels under chilling compared with WT. The results suggest that CdtCIPK21 regulates salt and drought tolerance negatively and chilling tolerance positively, which are associated with the altered ABA sensitivity, antioxidants, proline accumulation and expression of ABA-dependent and ABA-independent stress responsive genes.

OsCBL5-CIPK1-PP23 module enhances rice grain size and weight through the gibberellin pathway.

Grain size is a key factor in determining rice (Oryza sativa) yield, and exploring new pathways to regulate grain size has immense potential to improve yield. In this study, we report that OsCBL5 encodes a calcineurin B subunit protein that significantly promotes grain size and weight. oscbl5 plants produced obviously smaller and lighter seeds. We further revealed that OsCBL5 promotes grain size by affecting cell expansion in the spikelet hull. Biochemical analyses demonstrated that CBL5 interacts with CIPK1 and PP23. Furthermore, double and triple mutations were induced using CRISPR/Cas9 (cr) to analyze the genetic relationship. It was found that the cr-cbl5/cipk1 phenotype was similar to that of cr-cipk1 and that the cr-cbl5/pp23, cr-cipk1/pp23, and cr-cbl5/cipk1/pp23 phenotype was similar to that of cr-pp23, indicating that OsCBL5, CIPK1, and PP23 act as a molecular module influencing seed size. In addition, the results show that both CBL5 and CIPK1 are involved in the gibberellic acid (GA) pathway and significantly affect the accumulation of endogenous active GA4 . PP23 participates in GA signal transduction. In brief, this study identified a new module that affects rice grain size, OsCBL5-CIPK1-PP23, which could potentially be targeted to improve rice yield.

AtCIPK16, a CBL-interacting protein kinase gene, confers salinity tolerance in transgenic wheat.

Globally, wheat is the major source of staple food, protein, and basic calories for most of the human population. Strategies must be adopted for sustainable wheat crop production to fill the ever-increasing food demand. Salinity is one of the major abiotic stresses involved in plant growth retardation and grain yield reduction. In plants, calcineurin-B-like proteins form a complicated network with the target kinase CBL-interacting protein kinases (CIPKs) in response to intracellular calcium signaling as a consequence of abiotic stresses. The AtCIPK16 gene has been identified in Arabidopsis thaliana and found to be significantly upregulated under salinity stress. In this study, the AtCIPK16 gene was cloned in two different plant expression vectors, i.e., pTOOL37 having a UBI1 promoter and pMDC32 having a 2XCaMV35S constitutive promoter transformed through the Agrobacterium-mediated transformation protocol, in the local wheat cultivar Faisalabad-2008. Based on their ability to tolerate different levels of salt stress (0, 50, 100, and 200 mM), the transgenic wheat lines OE1, OE2, and OE3 expressing AtCIPK16 under the UBI1 promoter and OE5, OE6, and OE7 expressing the same gene under the 2XCaMV35S promoter performed better at 100 mM of salinity stress as compared with the wild type. The AtCIPK16 overexpressing transgenic wheat lines were further investigated for their K+ retention ability in root tissues by utilizing the microelectrode ion flux estimation technique. It has been demonstrated that after 10 min of 100 mM NaCl application, more K+ ions were retained in the AtCIPK16 overexpressing transgenic wheat lines than in the wild type. Moreover, it could be concluded that AtCIPK16 functions as a positive elicitor in sequestering Na+ ions into the cell vacuole and retaining more cellular K+ under salt stress to maintain ionic homeostasis.

The Effect of Stress Hormones, Ultraviolet C, and Stilbene Precursors on Expression of Calcineurin B-like Protein (CBL) and CBL-Interacting Protein Kinase (CIPK) Genes in Cell Cultures and Leaves of Vitis amurensis Rupr.

Calcium serves as a crucial messenger in plant stress adaptation and developmental processes. Plants encode several multigene families of calcium sensor proteins with diverse functions in plant growth and stress responses. Several studies indicated that some calcium sensors may be involved in the regulation of secondary metabolite production in plant cells. The present study aimed to investigate expression of calcineurin B-like proteins (CBL) and CBL-interacting protein kinase (CIPK) in response to conditions inducting biosynthesis of stilbenes in grapevine. We investigated CBL and CIPK gene expression in wild-growing grapevine Vitis amurensis Rupr., known as a rich stilbene source, in response to the application of stilbene biosynthesis-inducing conditions, including application of stress hormones (salicylic acid or SA, methyl jasmonate or MeJA), phenolic precursors (p-coumaric acids or CA), and ultraviolet irradiation (UV-C). The influence of these effectors on the levels of 13 VaCBL and 27 VaCIPK mRNA transcripts as well as on stilbene production was analyzed by quantitative real-time RT-PCR in the leaves and cell cultures of V. amurensis. The data revealed that VaCBL4-1 expression considerably increased after UV-C treatment in both grapevine cell cultures and leaves. The expression of VaCIPK31, 41-1, and 41-2 also increased, but this increase was mostly detected in cell cultures of V. amurensis. At the same time, expression of most VaCBL and VaCIPK genes was markedly down-regulated both in leaves and cell cultures of V. amurensis, which may indicate that the CBLs and CIPKs are involved in negative regulation of stilbene accumulation (VaCBL8, 10a-2, 10a-4, 11, 12, VaCIPK3, 9-1, 9-2, 12, 21-1, 21-2, 33, 34, 35, 36, 37, 39, 40, 41-3, 41-4). The results obtained provide new information of CBL and CIPK implication in the regulation of plant secondary metabolism in response to stress hormones, metabolite precursors, and UV-C irradiation.

Inhibition of SlSKOR by SlCIPK23-SlCBL1/9 uncovers CIPK-CBL-target network rewiring in land plants.

Transport of K+ to the xylem is a key process in the mineral nutrition of the shoots. Although CIPK-CBL complexes have been widely shown to regulate K+ uptake transport systems, no information is available about the xylem ones. Here, we studied the physiological roles of the voltage-gated K+ channel SlSKOR and its regulation by the SlCIPK23-SlCBL1/9 complexes in tomato plants. We phenotyped gene-edited slskor and slcipk23 tomato knockout mutants and carried out two-electrode voltage-clamp (TEVC) and BiFC assays in Xenopus oocytes as key approaches. SlSKOR was preferentially expressed in the root stele and was important not only for K+ transport to shoots but also, indirectly, for that of Ca2+ , Mg2+ , Na+ , NO3 - , and Cl- . Surprisingly, the SlCIPK23-SlCBL1/9 complexes turned out to be negative regulators of SlSKOR. Inhibition of SlSKOR by SlCIPK23-SlCBL1/9 was observed in Xenopus oocytes and tomato plants. Regulation of SKOR-like channels by CIPK23-CBL1 complexes was also present in Medicago, grapevine, and lettuce but not in Arabidopsis and saltwater cress. Our results provide a molecular framework for coordinating root K+ uptake and its translocation to the shoot by SlCIPK23-SlCBL1/9 in tomato plants. Moreover, they evidenced that CIPK-CBL-target networks have evolved differently in land plants.

Comprehensive Analysis of Calcium Sensor Families, CBL and CIPK, in Aeluropus littoralis and Their Expression Profile in Response to Salinity.

Plants have acquired sets of highly regulated and complex signaling pathways to respond to unfavorable environmental conditions during evolution. Calcium signaling, as a vital mechanism, enables plants to respond to external stimuli, including abiotic and biotic stresses, and coordinate the basic processes of growth and development. In the present study, two calcium sensor families, CBL and CIPK, were investigated in a halophyte plant, Aeluropus littoralis, with a comprehensive analysis. Here, six AlCBL genes, and twenty AlCIPK genes were studied. The analysis of the gene structure and conserved motifs, as well as physicochemical properties, showed that these genes are highly conserved during evolution. The expression levels of AlCBL genes and AlCIPK genes were evaluated under salt stress in leaf and root tissue. Based on the real-time RT-PCR results, the AlCIPK gene family had a higher variation in mRNA abundance than the AlCBL gene family. AlCIPK genes were found to have a higher abundance in leaves than in roots. The results suggest that the correlation between AlCBL genes and AlCIPK is tissue-specific, and different correlations can be expected in leaves and roots. Based on these correlations, AlCIPK3.1-AlCBL4.1 and AlCIPK1.2-AlCBL4.4 can be co-expressed in the root tissue, while AlCBL10 has the potential to be co-expressed with AlCIPK5, AlCIPK26, and AlCIPK12.3 in the leaf tissue. Our findings reveal valuable information on the structure and function of calcium sensor families in A. littoralis, a halophyte plant, that can be used in future research on the biological function of CBLs and CIPKs on salt stress resistance.

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.