The role of 14-3-3 proteins in plant growth and response to abiotic stress

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.

A clade of receptor-like cytoplasmic kinases and 14-3-3 proteins coordinate inositol hexaphosphate accumulation

Inositol hexaphosphate (InsP6) is the major storage form of phosphorus in seeds. Reducing seed InsP6 content is a breeding objective in agriculture, as InsP6 negatively impacts animal nutrition and the environment. Nevertheless, how InsP6 accumulation is regulated remains largely unknown. Here, we identify a clade of receptor-like cytoplasmic kinases (RLCKs), named Inositol Polyphosphate-related Cytoplasmic Kinases 1-6 (IPCK1-IPCK6), deeply involved in InsP6 accumulation. The InsP6 concentration is dramatically reduced in seeds of ipck quadruple (T-4m/C-4m) and quintuple (C-5m) mutants, accompanied with the obviously increase of phosphate (Pi) concentration. The plasma membrane-localized IPCKs recruit IPK1 involved in InsP6 synthesis, and facilitate its binding and activity via phosphorylation of GRF 14-3-3 proteins. IPCKs also recruit IPK2s and PI-PLCs required for InsP4/InsP5 and InsP3 biosynthesis respectively, to form a potential IPCK-GRF-PLC-IPK2-IPK1 complex. Our findings therefore uncover a regulatory mechanism of InsP6 accumulation governed by IPCKs, shedding light on the mechanisms of InsP biosynthesis in eukaryotes.

Construction of a Membrane Yeast Two-Hybrid Library and Screening of MsPYR1-Like Interacting Proteins in Malus sieversii

To investigate the biological effects of the ABA receptor pyrabactin resistance 1-like (PYR1-like) in Malus sieversii seeds, the proteins interacting with MsPYR1-like were screened by the membrane yeast two-hybrid library based on the split-ubiquitin system, and to construct the bait vector pBT3-SUC-PYR1 for Malus sieversii cDNA library, which had no self-activating effect on the yeast cells of the pPR3-N membrane yeast two-hybrid library. The library titer assay showed that it could meet the requirements for membrane yeast two-hybrid library screening. After sequencing, GenBank database blast, and yeast rotary validation, 28 candidate proteins interacting with MsPYR1-like were obtained, including ribosomal proteins, late embryogenesis abundant proteins, F-actin-capping proteins, phytochrome-interacting proteins, low-temperature-inducible 65 kDa protein-like, senescence-associated, PP2C and SnRK2 family members, and unknown proteins. Gene ontology analysis of the interaction proteins was related to plant hormone response and negative regulation of seed germination, overexpression of MsPYR1-like in Arabidopsis negatively regulates seed germination, and the study of the biological roles of MsPYR1-like interacting proteins lays the foundation for revealing the lifting of seed dormancy in Malus sieversii.

Should I stay or should I go? Trafficking of plant extra-nuclear transcription factors

At the heart of all biological processes lies the control of nuclear gene expression, which is primarily achieved through the action of transcription factors (TFs) that generally contain a nuclear localization signal (NLS) to facilitate their transport into the nucleus. However, some TFs reside in the cytoplasm in a transcriptionally inactive state and only enter the nucleus in response to specific signals, which in plants include biotic or abiotic stresses. These extra-nuclear TFs can be found in the cytosol or associated with various membrane systems, including the endoplasmic reticulum and plasma membrane. They may be integral proteins with transmembrane domains or associate peripherally with the lipid bilayer via acylation or membrane-binding domains. Although over 30 plant TFs, most of them involved in stress responses, have been experimentally shown to reside outside the nucleus, computational predictions suggest that this number is much larger. Understanding how extra-nuclear TFs are trafficked into the nucleus is essential for reconstructing transcriptional regulatory networks that govern major cellular pathways in response to biotic and abiotic signals. Here, we provide a perspective on what is known on plant extranuclear-nuclear TF retention, nuclear trafficking, and the post-translational modifications that ultimately enable them to regulate gene expression upon entering the nucleus.

Discovery of a Plant 14-3-3 Inhibitor Possessing Isoform Selectivity and In Planta Activity

Synthetic modulators of plant 14-3-3s are promising chemical tools both for understanding the 14-3-3-related signaling pathways and controlling plant physiology. Herein, we describe a novel small-molecule inhibitor for 14-3-3 proteins of Arabidopsis thaliana. The inhibitor was identified from unexpected products in a stock solution in dimethyl sulfoxide (DMSO) of an in-house chemical library. Mass spectroscopy, mutant-based analyses, fluorescence polarization assays, and thermal shift assays revealed that the inhibitor covalently binds to an allosteric site of 14-3-3 with isoform selectivity. Moreover, infiltration of the inhibitor to Arabidopsis leaves suppressed the stomatal aperture. The inhibitor should provide new insight into the design of potent and isoform-selective 14-3-3 modulators.

Insights into drought stress response mechanism of tobacco during seed germination by integrated analysis of transcriptome and metabolome

Drought stress inhibits seed germination, plant growth and development of tobacco, and seriously affects the yield and quality of tobacco leaves. However, the molecular mechanism underlying tobacco drought stress response remains largely unknown. In this study, integrated analysis of transcriptome and metabolome was performed on the germinated seeds of a cultivated variety K326 and its EMS mutagenic mutant M28 with great drought tolerance. The result showed that drought stress inhibited seed germination of the both varieties, while the germination rate of M28 was faster than that of K326 under drought stress. Besides, the levels of phytohormone ABA, GA19, and zeatin were increased by drought stress in M28. Five vital pathways were identified through integrated transcriptomic and metabolomic analysis, including zeatin biosynthesis, aspartate and glutamate synthesis, phenylamine metabolism, glutathione metabolism, and phenylpropanoid synthesis. Furthermore, 20 key metabolites in the above pathways were selected for further analysis of gene modular-trait relationship, and then four highly correlated modules were found. Then analysis of gene expression network was carried out of Top30 hub gene of these four modules, and 9 key candidate genes were identified, including HSP70s, XTH16s, APX, PHI-1, 14-3-3, SCP, PPO. In conclusion, our study uncovered some key drought-responsive pathways and genes of tobacco during seeds germination, providing new insights into the regulatory mechanisms of tobacco drought stress response.

Investigation of two-pore K+ (TPK) channels in Triticum aestivum L. suggests their role in stress response

Two-pore K+ (TPK) channels are voltage-independent and involved in stress response in plants. Herein, we identified 12 TaTPK genes located on nine chromosomes in the Triticum aestivum genome. The majority of TaTPK genes comprised two exons. Each TaTPK channel comprised four transmembrane (TM) helices, N- and C-terminal ion-channel domains, two EF-hand domains and one 14-3-3 binding site. Additionally, highly conserved 'GYGD' motif responsible for K+ ion specificity, was found in between the TMs in both the ion-channel domains. Nine TaTPK channels were predicted to be localised at the plasma membrane, while three were vacuolar. The protein-protein and protein-chemical interactions indicated the coordinated functioning of the TaTPK channels with the other K+ transporters and their possible interaction with the Ca2+-signaling pathway. Expression studies suggested their importance in both vegetative and reproductive tissues development. Significantly modulated expression of various TaTPK genes during heat, drought, combined heat and drought and salt stresses, and after fungal infestation, depicted their function in stress responses. The miRNAs and transcription factors interaction analyses suggested their role in the hormone, light, growth and development-related, and stress-responsive signaling cascades. The current study suggested vital functions of various TaTPK genes, especially in stress response, and would provide an opportunity for their detailed characterization in future studies.

Potato virus Y viral protein 6K1 inhibits the interaction between defense proteins during virus infection

14-3-3 proteins play vital roles in plant defense against various pathogen invasions. To date, how 14-3-3 affects virus infections in plants remains largely unclear. In this study, we found that Nicotiana benthamiana 14-3-3h interacts with TRANSLATIONALLY CONTROLLED TUMOR PROTEIN (TCTP), a susceptibility factor of potato virus Y (PVY). Silencing of Nb14-3-3h facilitates PVY accumulation, whereas overexpression of Nb14-3-3h inhibits PVY replication. The antiviral activities of 3 Nb14-3-3h dimerization defective mutants are significantly decreased, indicating that dimerization of Nb14-3-3h is indispensable for restricting PVY infection. Our results also showed that the mutant Nb14-3-3hE16A, which is capable of dimerizing but not interacting with NbTCTP, has reduced anti-PVY activity; the mutant NbTCTPI65A, which is unable to interact with Nb14-3-3h, facilitates PVY replication compared with the wild-type NbTCTP, indicating that dimeric Nb14-3-3h restricts PVY infection by interacting with NbTCTP and preventing its proviral function. As a counter-defense, PVY 6K1 interferes with the interaction between Nb14-3-3h and NbTCTP by competitively binding to Nb14-3-3h and rescues NbTCTP to promote PVY infection. Our results provide insights into the arms race between plants and potyviruses.

Calmodulin-Domain Protein Kinase PiCDPK1 Interacts with the 14-3-3-like Protein NtGF14 to Modulate Pollen Tube Growth

Calcium-mediated signaling pathways are known to play important roles in the polar growth of pollen tubes. The calcium-dependent protein kinase, PiCDPK1, has been shown to be involved in regulating this process through interaction with a guanine dissociation inhibitor, PiRhoGDI1. To more fully understand the role of PiCDPK1 in pollen tube extension, we designed a pull-down study to identify additional substrates of this kinase. These experiments identified 123 putative interactors. Two of the identified proteins were predicted to directly interact with PiCDPK1, and this possibility was investigated in planta. The first, NtGF14, a 14-3-3-like protein, did not produce a noticeable phenotype when overexpressed in pollen alone but partially rescued the spherical tube phenotype caused by PiCDPK1 over-expression when co-over-expressed with the kinase. The second, NtREN1, a GTPase activating protein (GAP), severely inhibited pollen tube germination when over-expressed, and its co-over-expression with PiCDPK1 did not substantially affect this phenotype. These results suggest a novel in vivo interaction between NtGF14 and PiCDPK1 but do not support the direct interaction between PiCDPK1 and NtREN1. We demonstrate the utility of the methodology used to identify potential protein interactions while confirming the necessity of additional studies to confirm their validity. Finally, additional support was found for intersection between PiCDPK1 and RopGTPase pathways to control polar growth at the pollen tube tip.

Molecular evolution and interaction of 14-3-3 proteins with H+-ATPases in plant abiotic stresses

Environmental stresses severely affect plant growth and crop productivity. Regulated by 14-3-3 proteins (14-3-3s), H+-ATPases (AHAs) are important proton pumps that can induce diverse secondary transport via channels and co-transporters for the abiotic stress response of plants. Many studies demonstrated the roles of 14-3-3s and AHAs in coordinating the processes of plant growth, phytohormone signaling, and stress responses. However, the molecular evolution of 14-3-3s and AHAs has not been summarized in parallel with evolutionary insights across multiple plant species. Here, we comprehensively review the roles of 14-3-3s and AHAs in cell signaling to enhance plant responses to diverse environmental stresses. We analyzed the molecular evolution of key proteins and functional domains that are associated with 14-3-3s and AHAs in plant growth and hormone signaling. The results revealed evolution, duplication, contraction, and expansion of 14-3-3s and AHAs in green plants. We also discussed the stress-specific expression of those 14-3-3and AHA genes in a eudicotyledon (Arabidopsis thaliana), a monocotyledon (Hordeum vulgare), and a moss (Physcomitrium patens) under abiotic stresses. We propose that 14-3-3s and AHAs respond to abiotic stresses through many important targets and signaling components of phytohormones, which could be promising to improve plant tolerance to single or multiple environmental stresses.

The 14-3-3 Protein BdGF14a Increases the Transcriptional Regulation Activity of BdbZIP62 to Confer Drought and Salt Resistance in Tobacco

BdGF14a, a 14-3-3 gene from Brachypodium distachyon, induced by salt, H2O2, and abscisic acid (ABA), improved tolerance to drought and salt in tobacco, with a higher survival rate and longer roots under these stresses. Additionally, physiological index analyses showed that the heterologous expression of BdGF14a induced higher expression levels of antioxidant enzymes and their activities, leading to lighter DAB and NBT staining, denoting decreased H2O2 content. Additionally, the lower MDA content and ion leakage indicated enhanced cell membrane stability. Moreover, exogenous ABA resulted in shorter roots and a lower stomatal aperture in BdGF14a transgenic plants. BdGF14a interacted with NtABF2 and regulated the expression of stress-related genes. However, adding an ABA biosynthesis inhibitor suppressed most of these changes. Furthermore, similar salt and drought resistance phenotypes and physiological indicators were characterized in tobacco plants expressing BdbZIP62, an ABRE/ABF that interacts with BdGF14a. And Y1H and LUC assays showed that BdGF14a could enhance the transcription regulation activity of NtABF2 and BdbZIP62, targeting NtNECD1 by binding to the ABRE cis-element. Thus, BdGF14a confers resistance to drought and salinity through interaction with BdbZIP62 and enhances its transcriptional regulation activity via an ABA-mediated signaling pathway. Therefore, this work offers novel target genes for breeding salt- and drought-tolerant plants.

Systematic thermal analysis of the Arabidopsis proteome: Thermal tolerance, organization, and evolution

Understanding the thermal stability of the plant proteome in the context of the native cellular environment would aid the design of crops with high thermal tolerance, but only limited such data are available. Here, we applied quantitative mass spectrometry to profile the thermal stability of the Arabidopsis proteome and identify thermo-sensitive and thermo-resilient protein networks in Arabidopsis, providing a basis for understanding heat-induced damage. We also show that the similarities of the protein-melting curves can be used as a proxy to evaluate system-wide protein-protein interactions in non-engineered plants and enable the identification of transient interactions exhibited by metabolons in the context of the cellular environment. Finally, we report a systematic comparison of the thermal stability of paralogs in Arabidopsis to aid the investigation and understanding of gene duplication and protein evolution. Taken together, our results could have broad implications for the fields of plant thermal tolerance, plant protein assemblies, and evolution.

Transcriptional and post-translational regulation of plant autophagy

In response to changing environmental conditions, plants activate cellular responses to enable them to adapt. One such response is autophagy, in which cellular components, for example proteins and organelles, are delivered to the vacuole for degradation. Autophagy is activated by a wide range of conditions, and the regulatory pathways controlling this activation are now being elucidated. However, key aspects of how these factors may function together to properly modulate autophagy in response to specific internal or external signals are yet to be discovered. In this review we discuss mechanisms for regulation of autophagy in response to environmental stress and disruptions in cell homeostasis. These pathways include post-translational modification of proteins required for autophagy activation and progression, control of protein stability of the autophagy machinery, and transcriptional regulation, resulting in changes in transcription of genes involved in autophagy. In particular, we highlight potential connections between the roles of key regulators and explore gaps in research, the filling of which can further our understanding of the autophagy regulatory network in plants.

MdGRF11-MdARF19-2 module acts as a positive regulator of drought resistance in apple rootstock

14-3-3 proteins play an important role in the response of plants to drought resistance. In this study, 14-3-3 protein MdGRF11 was cloned from Malus xiaojinensis, and its positive regulation of drought resistance was verified using Orin calli and M. xiaojinensis plants. The transcription factor MdARF19-2 was further screened for interaction with this protein in vitro and in vivo. We also conducted experiments using Orin calli and found that the overexpression of MdARF19-2 decreased the level of reactive oxygen species (ROS) and increased the activity of enzymes that scavenge ROS in plant materials. This indicates that MdARF19-2 is a positive regulator in the drought resistance of plants. The drought tolerance was further improved by the overexpression of both MdGRF11 and MdARF19-2 in the calli. In addition, we examined several genes related to ROS scavenging with auxin response factor binding elements in their promoters and found that their level of expression was regulated by the MdGRF11-MdARF19-2 module. In conclusion, the enhancement of plant drought resistance by MdGRF11 could be owing to its accumulation at the protein level in response to drought, which then combined with MdARF19-2, affecting the expression of MdARF19-2 downstream genes. Thus, it scavenges ROS, which ultimately improves the resistance of plant to drought stress.

Drought stress in maize: stress perception to molecular response and strategies for its improvement

Given the future demand for food crops, increasing crop productivity in drought-prone rainfed areas has become essential. Drought-tolerant varieties are warranted to solve this problem in major crops, with drought tolerance as a high-priority trait for future research. Maize is one such crop affected by drought stress, which limits production, resulting in substantial economic losses. It became a more serious issue due to global climate change. The most drought sensitive among all stages of maize is the reproductive stages and the most important for overall maize production. The exact molecular basis of reproductive drought sensitivity remains unclear due to genes' complex regulation of drought stress. Understanding the molecular biology and signaling of the unexplored area of reproductive drought tolerance will provide an opportunity to develop climate-smart drought-tolerant next-generation maize cultivars. In recent decades, significant progress has been made in maize to understand the drought tolerance mechanism. However, improving maize drought tolerance through breeding is ineffective due to the complex nature and multigenic control of drought traits. With the help of advanced breeding techniques, molecular genetics, and a precision genome editing approach like CRISPR-Cas, candidate genes for drought-tolerant maize can be identified and targeted. This review summarizes the effects of drought stress on each growth stage of maize, potential genes, and transcription factors that determine drought tolerance. In addition, we discussed drought stress sensing, its molecular mechanisms, different approaches to developing drought-resistant maize varieties, and how molecular breeding and genome editing will help with the current unpredictable climate change.

14-3-3 Proteins and the Plasma Membrane H+-ATPase Are Involved in Maize (Zea mays) Magnetic Induction

The geomagnetic field (GMF) is a natural component of the biosphere, and, during evolution, all organisms experienced its presence while some evolved the ability to perceive magnetic fields (MF). We studied the response of 14-3-3 proteins and the plasma membrane (PM) proton pump H+-ATPase to reduced GMF values by lowering the GMF intensity to a near-null magnetic field (NNMF). Seedling morphology, H+-ATPase activity and content, 14-3-3 protein content, binding to PM and phosphorylation, gene expression, and ROS quantification were assessed in maize (Zea mays) dark-grown seedlings. Phytohormone and melatonin quantification were also assessed by LG-MS/MS. Our results suggest that the GMF regulates the PM H+-ATPase, and that NNMF conditions alter the proton pump activity by reducing the binding of 14-3-3 proteins. This effect was associated with both a reduction in H2O2 and downregulation of genes coding for enzymes involved in ROS production and scavenging, as well as calcium homeostasis. These early events were followed by the downregulation of IAA synthesis and gene expression and the increase in both cytokinin and ABA, which were associated with a reduction in root growth. The expression of the homolog of the MagR gene, ZmISCA2, paralleled that of CRY1, suggesting a possible role of ISCA in maize magnetic induction. Interestingly, melatonin, a widespread molecule present in many kingdoms, was increased by the GMF reduction, suggesting a still unknown role of this molecule in magnetoreception.

Overexpression of peanut (Arachis hypogaea L.) AhGRFi gene enhanced root growth inhibition under exogenous NAA treatment in Arabidopsis thaliana

The 14-3-3 protein is a kind of evolutionary ubiquitous protein family highly conserved in eukaryotes. Initially, 14-3-3 proteins were reported in mammalian nervous tissues, but in the last decade, their role in various metabolic pathways in plants established the importance of 14-3-3 proteins. In the present study, a total of 22 14-3-3 genes, also called general regulatory factors (GRF), were identified in the peanut (Arachis hypogaea) genome, out of which 12 belonged to the ε group, whereas 10 of them belonged to the non- ε-group. Tissue-specific expression of identified 14-3-3 genes were studied using transcriptome analysis. The peanut AhGRFi gene was cloned and transformed into Arabidopsis thaliana. The investigation of subcellular localization indicated that AhGRFi is localized in the cytoplasm. Overexpression of the AhGRFi gene in transgenic Arabidopsis showed that under exogenous 1-naphthaleneacetic acid (NAA) treatment, root growth inhibition in transgenic plants was enhanced. Further analysis indicated that the expression of auxin-responsive genes IAA3, IAA7, IAA17, and SAUR-AC1 was upregulated and GH3.2 and GH3.3 were downregulated in transgenic plants, but the expression of GH3.2, GH3.3, and SAUR-AC1 showed opposite trends of change under NAA treatment. These results suggest that AhGRFi may be involved in auxin signaling during seedling root development. An in-depth study of the molecular mechanism of this process remains to be further explored.

Evolution of the 14-3-3 gene family in monocotyledons and dicotyledons and validation of MdGRF13 function in transgenic Arabidopsis thaliana

KEY MESSAGE

The 14-3-3 family is more highly conserved among monocotyledons, and overexpression of MdGRF13 improved drought and salt tolerance in transgenic Arabidopsis thaliana. The 14-3-3 are highly conserved regulatory proteins found in eukaryotes and play an essential role in plant growth, development and stress response. However, the 14-3-3 gene family evolution in monocotyledons and dicotyledons and the biological functions of the MdGRF13 under abiotic stress remain unknown. In our study, 195 members of the 14-3-3 family were identified from 12 species and divided into ε group and the Non-ε group. Synteny analysis within the 14-3-3 family indicated that segmental duplication events contributed to the expansion of the family. Selective pressure analysis indicated that purifying selection was a vital force in the 14-3-3 genes evolution, and monocotyledons had a lower million years ago (Mya) mean values than dicotyledons. Meanwhile, the codon adaptation index (CAI) and frequency of optical codons (FOP) are higher and the effective number of codons (Nc) is lower in monocotyledons 14-3-3 genes compared to dicotyledons. Moreover, the yeast two-hybrid (Y2H) demonstrated that MdGRF13 interacts with MdRD22, MdLHP1a and MdMORF1. Significantly, the malondialdehyde (MDA) content and relative conductivity were decreased, while the superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities were increased in transgenic Arabidopsis compared to the wild type (WT) under drought and salt stress. These results suggest that overexpression of MdGRF13 significantly improved the tolerance to drought and salt stress in transgenic Arabidopsis. Thus, our results provide a theoretical basis for exploring the evolution and function of the 14-3-3 gene family in monocotyledons and dicotyledons.

Genome-wide identification and characterization of tomato 14-3-3 (SlTFT) genes and functional analysis of SlTFT6 under heat stress

The plant 14-3-3 proteins are essential for many biological processes and responses to abiotic stress. We performed genome-wide identification and analysis of the 14-3-3 family genes in tomato. To explore the properties of the thirteen Sl14-3-3 found in the tomato genome, their chromosomal location, phylogenetic, and syntenic relationships were analyzed. The Sl14-3-3 promoters were found to have a number of growth-, hormone-, and stress-responsive cis-regulatory elements. Moreover, the qRT-PCR assay revealed that Sl14-3-3 genes are responsive to heat and osmotic stress. Subcellular localization experiments evidenced that the SlTFT3/6/10 proteins occur in the nucleus and cytoplasm Additional analysis on Sl14-3-3 putative interactor proteins revealed a number of prospective clients that potentially participate in stress reactions and developmental processes. Furthermore, overexpression of an Sl14-3-3 family gene, SlTFT6, improved tomato plants thermotolerance. Taken together, the study provides basic information on tomato 14-3-3 family genes in plant growth and abiotic stress response (high temperature stress), which can be helpful to further study the underlying molecular mechanisms.

Calcium-dependent protein kinase CDPK16 phosphorylates serine-856 of glutamate receptor-like GLR3.6 protein leading to salt-responsive root growth in Arabidopsis. FRONTIERS IN PLANT SCIENCE 2023;14:1093472. [PMID: 36818849 PMCID: PMC9935832 DOI: 10.3389/fpls.2023.1093472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Calcium-permeable channels in the plasma membrane play vital roles in plant growth, development, and response to environmental stimuli. Arabidopsis possesses 20 glutamate receptor-like proteins that share similarities with animal ionotropic glutamate receptors and mediate Ca²⁺ influx in plants. Calcium-dependent protein kinases (CDPKs) phosphorylate serine (Ser)-860 of glutamate receptor-like (GLR)3.7 protein, which interacts with 14-3-3ω and plays an essential role in salt and abscisic acid response in Arabidopsis by modulating Ca²⁺ signaling. However, the significance of CDPK- mediated phosphorylation status of Ser residues of GLR3.6 with regard to the functioning of GLR3.6 remains to be elucidated. In this study, we performed an in vitro kinase assay using CDPK16 and peptides containing the 14-3-3ω interacting domain of GLR3.6. We showed that Ser861/862 of GLR3.6 are required for the interaction with 14-3-3ω and that Ser856 of GLR3.6 is specifically phosphorylated by CDPK16 but not by CDPK3 and CDPK34. In addition, the expression of GLR3.6 was quickly downregulated by salt stress, and plants of glr3.6 mutants and GLR3.6-overexpression lines presented shorter and longer root lengths, respectively, under normal growth conditions than Col. Overexpression of the GLR3.6-Ser856 to Ala mutation resulted in a less sensitive phenotype in response to salt stress similar to glr3.6. Our results indicated that the Ser861/862 residues of GLR3.6 are required for interaction with 14-3-3ω. Additionally, the phosphorylation status of Ser856 residue of GLR3.6, which is mediated specifically by CDPK16, regulates root growth in normal and salt stress and conditions.

Genome-Wide Identification of 14-3-3 gene family reveals their diverse responses to abiotic stress by interacting with StABI5 in Potato (Solanum tuberosum L.)

The 14-3-3 genes are widely present in plants and participate in a wide range of cellular and physiological processes. In the current study, twelve 14-3-3s were identified from potato genome. According to phylogenetic evolutionary analysis, potato 14-3-3s were divided into ϵ and non-ϵ groups. Conserved motif and gene structure analysis displayed a distinct class-specific divergence between the ϵ group and non-ϵ group. Multiple sequence alignments and three-dimensional structure analysis of 14-3-3 proteins indicated all the members contained nine conservative antiparallel α-helices. The majority of 14-3-3s had transcript accumulation in each detected potato tissue, implying their regulatory roles across all stages of potato growth and development. Numerous cis-acting elements related to plant hormones and abiotic stress response were identified in the promoter region of potato 14-3-3s, and the transcription levels of these genes fluctuated to different degrees under exogenous ABA, salt and drought stress, indicating that potato 14-3-3s may be involved in different hormone signaling pathways and abiotic stress responses. In addition, eight potato 14-3-3s were shown to interact with StABI5, which further demonstrated that potato 14-3-3s were involved in the ABA-dependent signaling pathway. This study provides a reference for the identification of the 14-3-3 gene family in other plants, and provides important clues for cloning potential candidates in response to abiotic stresses in potato.

Genome-Wide Identification and Expression Analysis of the 14-3-3 (TFT) Gene Family in Tomato, and the Role of SlTFT4 in Salt Stress

The 14-3-3 proteins, which are ubiquitous and highly conserved in eukaryotic cells, play an essential role in various areas of plant growth, development, and physiological processes. The tomato is one of the most valuable vegetable crops on the planet. The main objective of the present study was to perform genome-wide identification and analysis of the tomato 14-3-3 (SlTFT) family to investigate its response to different abiotic stresses and phytohormone treatments in order to provide valuable information for variety improvement. Here, 13 SlTFTs were identified using bioinformatics methods. Characterization showed that they were categorized into ε and non-ε groups with five and eight members, accounting for 38.5% and 61.5%, respectively. All the SlTFTs were hydrophilic, and most of them did not contain transmembrane structural domains. Meanwhile, the phylogeny of the SlTFTs had a strong correlation with the gene structure, conserved domains, and motifs. The SlTFTs showed non-random chromosomal distribution, and the promoter region contained more cis-acting elements related to abiotic stress tolerance and phytohormone responses. The results of the evolutionary analysis showed that the SlTFTs underwent negative purifying selection during evolution. Transcriptional profiling and gene expression pattern analysis showed that the expression levels of the SlTFTs varied considerably in different tissues and periods, and they played a specific role under various abiotic stresses and phytohormone treatments. Meanwhile, the constructed protein-based interaction network systematically broadens our understanding of SlTFTs. Finally, the virus-induced gene silencing of SlTFT4 affected the antioxidant and reactive oxygen species defense systems, increased the degree of cellular damage, and reduced salt resistance in tomatoes.

Solanum tuberosum Microtuber Development under Darkness Unveiled through RNAseq Transcriptomic Analysis

Potato microtuber (MT) development through in vitro techniques are ideal propagules for producing high quality potato plants. MT formation is influenced by several factors, i.e., photoperiod, sucrose, hormones, and osmotic stress. We have previously developed a protocol of MT induction in medium with sucrose (8% w/v), gelrite (6g/L), and 2iP as cytokinin under darkness. To understand the molecular mechanisms involved, we performed a transcriptome-wide analysis. Here we show that 1715 up- and 1624 down-regulated genes were involved in this biological process. Through the protein-protein interaction (PPI) network analyses performed in the STRING database (v11.5), we found 299 genes tightly associated in 14 clusters. Two major clusters of up-regulated proteins fundamental for life growth and development were found: 29 ribosomal proteins (RPs) interacting with 6 PEBP family members and 117 cell cycle (CC) proteins. The PPI network of up-regulated transcription factors (TFs) revealed that at least six TFs-MYB43, TSF, bZIP27, bZIP43, HAT4 and WOX9-may be involved during MTs development. The PPI network of down-regulated genes revealed a cluster of 83 proteins involved in light and photosynthesis, 110 in response to hormone, 74 in hormone mediate signaling pathway and 22 related to aging.

Identification of the 14-3-3 Gene Family in Bamboo and Characterization of Pe14-3-3b Reveals Its Potential Role in Promoting Growth

The 14-3-3 protein family plays an important role in regulating plant growth and development. The genes of the 14-3-3 family have been reported in multiple species. However, little is known about the 14-3-3 gene family in bamboo. In this study, a total of 58 genes belonging to the 14-3-3 family were identified in three representative bamboo species, i.e., Olyra latifolia, Phyllostachys edulis, and Bonia amplexicaulis, whose encoding proteins were grouped into ε and non-ε groups by phylogeny analysis with 14-3-3 proteins from Arabidopsis thaliana and Oryza sativa. The 14-3-3s had diverse gene structures and motif characteristics among the three bamboo species. Collinearity analysis suggested that the genes of the 14-3-3 family in bamboo had undergone a strong purification selection during evolution. Tissue-specific expression analysis showed the expression of Pe14-3-3s varied in different tissues of P. edulis, suggesting that they had functional diversity during growth and development. Co-expression analysis showed that four Pe14-3-3s co-expressed positively with eight ribosomal genes. Yeast two-hybrid (Y2H) assays showed that Pe14-3-3b/d could interact with Pe_ribosome-1/5/6, and qPCR results demonstrated that Pe14-3-3b/d and Pe_ribosome-1/5/6 had similar expression trends with the increase in shoot height, which further confirmed that they would work together to participate in the shoot growth and development of bamboo. Additionally, the transgenic Arabidopsis plants overexpressing Pe14-3-3b had longer roots, a larger stem diameter, an earlier bolting time and a faster growth rate than wild-type Arabidopsis, indicating that Pe14-3-3b acted as a growth promoter. Our results provide comprehensive information on 14-3-3 genes in bamboo and highlight Pe14-3-3b as a potential target for bamboo improvement.

Proteomic Changes in Paspalum fasciculatum Leaves Exposed to Cd Stress

(1) Background: Cadmium is a toxic heavy metal that is widely distributed in water, soil, and air. It is present in agrochemicals, wastewater, battery waste, and volcanic eruptions. Thus, it can be absorbed by plants and enter the trophic chain. P. fasciculatum is a plant with phytoremediation capacity that can tolerate Cd stress, but changes in its proteome related to this tolerance have not yet been identified. (2) Methods: We conducted a quantitative analysis of the proteins present in P. fasciculatum leaves cultivated under greenhouse conditions in mining soils doped with 0 mg kg−1 (control), 30 mg kg−1, or 50 mg kg−1. This was carried out using the label-free shotgun proteomics technique. In this way, we determined the changes in the proteomes of the leaves of these plants, which allowed us to propose some tolerance mechanisms involved in the response to Cd stress. (3) Results: In total, 329 variable proteins were identified between treatments, which were classified into those associated with carbohydrate and energy metabolism; photosynthesis; structure, transport, and metabolism of proteins; antioxidant stress and defense; RNA and DNA processing; and signal transduction. (4) Conclusions: Based on changes in the differences in the leaf protein profiles between treatments, we hypothesize that some proteins associated with signal transduction (Ras-related protein RABA1e), HSPs (heat shock cognate 70 kDa protein 2), growth (actin-7), and cellular development (actin-1) are part of the tolerance response to Cd stress.

Effect of arbuscular mycorrhizal fungi and phosphorus on drought-induced oxidative stress and 14-3-3 proteins gene expression of Populus cathayana

The application of arbuscular mycorrhizal fungi (AM fungi) and phosphorus (P) can improve plant growth under drought stress by upregulating the antioxidant system and osmotic accumulation. The 14-3-3 protein can respond to different abiotic stresses such as low P and drought. The purpose of this experiment was to study the effects of AM fungi (Rhizophagus intraradices) inoculation on reactive oxygen species (ROS) homeostasis, P metabolism, and 14-3-3 gene expression of Populus cathayana at different P levels and drought stress (WW: well-watered and WD: water deficit). Under WD conditions, AM fungi inoculation significantly increased the P content in leaves and roots, but the benefit in roots is limited by the level of P addition, and the roots may have more alkaline phosphatase and phytase under P stress, and these activities in the rhizosphere soil inoculated with AM fungi were stronger. Under WD conditions, the activities of catalase (leaf and root) and peroxidase (root) inoculated with AM fungi were significantly higher than those without inoculation and decreased with P addition. 14-3-3 genes, PcGRF10 and PcGRF11, have a positive correlation with the antioxidant system, osmotic regulation, and P metabolism, which may be more significant after inoculation with AM fungi. Our results provide new insights into the mechanism of ROS homeostasis and P metabolism in mycorrhizal plants under drought stress.

PheGRF4e initiated auxin signaling during moso bamboo shoot development

BACKGROUND

As a ubiquitous acid-regulating protein family in eukaryotes, general regulatory factors (GRFs) are active in various life activities of plants. However, detailed investigations of the GRFs gene family in moso bamboo are scarce.

METHODS AND RESULTS

Genome-wide characteristics of the GRF gene family in moso bamboo were analyzed using the moso bamboo genome. GRF phylogeny, gene structure, conserved domains, cis-element promoters, and gene expression were systematically analyzed. A total of 20 GRF gene family members were identified in the moso bamboo genome. These genes were divided into ε and non-ε groups. qRT-PCR (real-time quantitative reverse transcription polymerase chain reaction) showed that PheGRF genes responded to auxin and gibberellin treatment. To further study PheGRF gene functions, a yeast two-hybrid experiment was performed and verified by a bimolecular fluorescence complementation experiment. The results showed that PheGRF4e could interact with PheIAA30 (auxin/indole-3-acetic acid, an Aux/IAA family gene), and both were found to act mainly on the root tip meristem and vascular bundle cells of developing shoots by in situ hybridization assay.

CONCLUSIONS

This study revealed that PheGRF genes were involved in hormone response during moso bamboo shoot development, and the possible regulatory functions of PheGRF genes were enriched by the fact that PheGRF4e initiated auxin signaling by binding to PheIAA30.

Arbuscular Mycorrhizal Fungi Enhanced Drought Resistance of Populus cathayana by Regulating the 14-3-3 Family Protein Genes

Plants can improve their resistance to a variety of stresses by forming mutualistic relationships with arbuscular mycorrhizal fungi (AMF). The 14-3-3 protein is a major regulator of the plant stress response. However, the regulation mechanism of 14-3-3 family protein genes (14-3-3s) of mycorrhizal plants coping with stress during AMF symbiosis remains unclear. Here, we analyzed the physiological changes and 14-3-3 expression profiles of Populus cathayana inoculated with AMF under different water conditions. The results showed that good colonization and symbiotic relationships with plants were formed under all water conditions (63.00% to 83.67%). Photosynthesis, peroxidase (POD) activity, and Mg and Ca content were significantly affected by drought and AMF. In addition, thirteen 14-3-3 protein genes (PcGRF1-PcGRF13) were identified by quantitative real-time PCR (qRT-PCR), of which the expression levels of PcGRF10 and PcGRF11 induced by AMF were significantly positively correlated with superoxide dismutase (SOD), POD, and sugar content, indicating that the 14-3-3s of mycorrhizal symbiotic plants may respond to drought through antioxidant and osmotic regulation. This is the first study on 14-3-3s in the symbiosis system of forest arbor plants and AMF, and it may help to further study the effects of 14-3-3s during AMF symbiosis on stresses and provide new ideas for improving mycorrhizal seedling cultivation under stress.

IMPORTANCE The 14-3-3 protein may regulate many biochemical and physiological processes under abiotic stress. Studies have shown that the 14-3-3 protein gene of AMF is not only upregulated under drought stress, but also enhances the regulation of AMF on plant drought tolerance by regulating plant signal pathways and drought response genes; however, knowledge about the biological relevance of these interactions remains limited and controversial. The precise functions of Populus cathayana 14-3-3s under drought stress remain poorly resolved and the mechanisms of action of these genes in mycorrhizae-induced drought stress are still unknown. Thus, studying the drought-resistance mechanism of the AMF symbiotic plant 14-3-3 gene is of special significance to improving the drought tolerance of the plant. Further systematic study is needed to probe the mechanism by which AMF regulates different 14-3-3 genes and their subsequent physiological effects on drought.