Wild-type Plants Research Articles

A plant-specific clade of serine/arginine-rich proteins regulates RNA splicing homeostasis and thermotolerance in tomato.

Global warming poses a threat for crops, therefore, the identification of thermotolerance mechanisms is a priority. In plants, the core factors that regulate transcription under heat stress (HS) are well described and include several HS transcription factors (HSFs). Despite the relevance of alternative splicing in HS response and thermotolerance, the core regulators of HS-sensitive alternative splicing have not been identified. In tomato, alternative splicing of HSFA2 is important for acclimation to HS. Here, we show that several members of the serine/arginine-rich family of splicing factors (SRSFs) suppress HSFA2 intron splicing. Individual-nucleotide resolution UV cross-linking and immunoprecipitation (iCLIP) combined with RNA-Seq revealed that RS2Z35 and RS2Z36, which make up a plant-specific clade of SR proteins, not only regulate HSFA2 but approximately 50% of RNAs that undergo HS-sensitive alternative splicing, with preferential binding to purine-rich RNA motifs. Single and double CRISPR rs2z mutant lines show a dysregulation of splicing and exhibit lower basal and acquired thermotolerance compared to wild type plants. Our results suggest that RS2Z35 and RS2Z36 have a central role in mitigation of the negative effects of HS on RNA splicing homeostasis, and their emergence might have contributed to the increased capacity of plants to acclimate to high temperatures.

ORANGE interplays with TCP7 to regulate endoreduplication and leaf size.

Leaf size is a crucial agronomic trait directly affecting crop yield, which is mainly determined by coordinated cell proliferation, growth, and differentiation. Although endoreduplication is known to be correlated with the onset of cell differentiation and leaf size, the underlying molecular mechanisms are largely unclear. The DnaJ-like zinc finger domain-containing protein ORANGE (OR) was initially demonstrated to confer the massive accumulation of carotenoids in cauliflower curds. However, the cauliflower or mutant also possesses other phenotypes such as smaller curds, smaller leaves with elongated petioles, and delayed flowering. Here, we demonstrated that OR physically interacts with the transcription factor TCP7, which promotes endoreduplication by inducing the expression of the cell cycle gene CYCLIN D 1;1 (CYCD1;1). Overexpression of OR resulted in smaller rosette leaves, whereas the OR-silencing plants had larger rosette leaves than wild-type plants. Our microscopic observations and flow cytometry analysis revealed that the variation in leaf size was a result of different endoreduplication levels. Genetic analyses showed that OR functions antagonistically with TCP7 in regulating the endoreduplication levels in leaf cells. While the expression of OR is induced by TCP7, OR represses the transactivation activity of TCP7 by affecting its binding capability to the TCP-binding motif in the promoter region of CYCD1;1. Through this interaction, OR negatively regulates the expression of CYCD1;1 and reduces the nuclear ploidy level in rosette leaf cells. Our findings provide new insights into the regulatory network of leaf size and also reveal a regulatory circuit controlling endoreduplication in leaf cells.

A dominant-negative Arabidopsis cation exchanger 1 (CAX1): N-terminal autoinhibition and membrane topology.

Calcium (Ca2+) is essential for plant growth and cellular homeostasis, with cation exchangers (CAXs) regulating Ca2+ transport into plant vacuoles. In Arabidopsis, multiple CAXs feature a common structural arrangement, comprising an N-terminal autoinhibitory domain followed by two pseudosymmetrical modules. Mutations in CAX1 enhance stress tolerance, notably tolerance to anoxia (a condition marked by oxygen depletion), crucial for flood resilience. Here we engineered a dominant-negative CAX1 variant, named ½N-CAX1, incorporating the autoinhibitory domain and the N-terminal pseudosymmetrical module, which, when expressed in wild-type Arabidopsis plants, phenocopied the anoxia tolerance of cax1. Physiological evaluations, yeast assays, and calcium imaging demonstrated that wild-type plants expressing ½N-CAX1 have phenotypes consistent with inhibition of CAX1, which is likely through direct interaction of ½N-CAX1 with CAX1. Eliminating segments within the N-terminal pseudosymmetrical module, as well as incorporating modules from other plant CAXs and expressing these variants into wild-type plants, failed to produce anoxia tolerance. This underscores the requirement for both the CAX1 autoinhibitory domain and the intact pseudosymmetrical module to produce the dominant-negative phenotype. Our study elucidates the interaction of this ½N-CAX1 variant with CAX1 and its impact on anoxia tolerance, offering insights into further approaches for engineering plant stress tolerance.

Integration of shoot-derived polypeptide signals by root TGA transcription factors is essential for survival under fluctuating nitrogen environments

Unlike plants in the field, which experience significant temporal fluctuations in environmental conditions, plants in the laboratory are typically grown in controlled, stable environments. Therefore, signaling pathways evolved for survival in fluctuating environments often remain functionally latent in laboratory settings. Here, we show that TGA1 and TGA4 act as hub transcription factors through which the expression of genes involved in high-affinity nitrate uptake are regulated in response to shoot-derived phloem mobile polypeptides, CEP DOWNSTREAM 1 (CEPD1), CEPD2 and CEPD-like 2 (CEPDL2) as nitrogen (N) deficiency signals, and Glutaredoxin S1 (GrxS1) to GrxS8 as N sufficiency signals. CEPD1/2/CEPDL2 and GrxS1-S8 competitively bind to TGA1/4 in roots, with the former acting as transcription coactivators that enhance the uptake of nitrate, while the latter function as corepressor complexes together with TOPLESS (TPL), TPL-related 1 (TPR1) and TPR4 to limit nitrate uptake. Arabidopsis plants deficient in TGA1/4 maintain basal nitrate uptake and exhibit growth similar to wild-type plants in a stable N environment, but are impaired in regulation of nitrate acquisition in response to shoot N demand, leading to defective growth under fluctuating N environments where rhizosphere nitrate ions switch periodically between deficient and sufficient states. TGA1/4 are crucial transcription factors that enable plants to survive under fluctuating and challenging N environmental conditions.

The tonoplast-localized OsTIP2;1 is involved in aluminum detoxification in rice

Aluminum (Al) stress is a significant issue in acidic soils, severely affecting crop growth and yield. Rice is notably resilient to Al toxicity, yet the internal tolerance mechanisms remain inadequately addressed. Here, we examined the role of OsTIP2;1, a tonoplast-bound intrinsic protein (TIP), in rice's internal Al detoxification. Our findings reveal that OsTIP2;1 expression was quickly and explicitly activated by Al ions in roots but not in shoots. The OsTIP2;1-GFP protein localizes to the tonoplast in plant and yeast cells. Non-functional ostip2;1 rice mutants were more vulnerable to Al toxicity. In the roots, the ostip2;1 mutants exhibited considerably lower levels of Al in the cell sap, primarily the vacuolar contents, than in the wild-type plant. Moreover, the ostip2;1 mutants showed reduced Al accumulation in the roots but increased translocation to the shoots. Heterologous expression of tonoplast-localized OsTIP2;1 in yeast led to enhanced Al tolerance, suggesting that OsTIP2;1 facilitates Al sequestration to the vacuole. These findings indicate that OsTIP2;1 mediates internal detoxification by transporting Al into the vacuole in the root and restricting its transport to above-ground tissues, thus contributing to Al resistance in rice.

The OsAGO2-OsNAC300-OsNAP module regulates leaf senescence in rice.

Leaves play a crucial role in the growth and development of rice (Oryza sativa) as sites for the production of photosynthesis. Early leaf senescence leads to substantial drops in rice yields. Whether and how DNA methylation regulates gene expression and affects leaf senescence remains elusive. Here, we demonstrate that mutations in rice ARGONAUTE 2 (OsAGO2) lead to premature leaf senescence, with chloroplasts in Osago2 having lower chlorophyll content and an abnormal thylakoid structure compared with those from wild-type plants. We show that OsAGO2 associates with a 24-nt microRNA and binds to the promoter region of OsNAC300, which causes DNA methylation and suppressed expression of OsNAC300. Overexpressing OsNAC300 causes the similar premature leaf senescence as Osago2 mutants and knocking out OsNAC300 in the Osago2 mutant background suppresses the early senescence of Osago2 mutants. Based on yeast one-hybrid, dual-luciferase, and electrophoresis mobility shift assays, we propose that OsNAC300 directly regulates transcription of the key rice aging gene NAC-like, activated by APETALA3/PISTILLATA (OsNAP) to control leaf senescence. Our results unravel a previously unknown epigenetic regulatory mechanism underlying leaf senescence in which OsAGO2-OsNAC300-OsNAP acts as a key regulatory module of leaf senescence to maintain leaf function.

Functional analysis on the role of HvHKT1.4 in barley (Hordeum vulgare L.) salinity tolerance

High-affinity potassium transporters (HKTs) are well known proteins that govern the partitioning of Na+ between roots and shoots. Six HvHKTs were identified in barley and designated as HvHKT1.1, HvHKT1.3, HvHKT1.4, HvHKT1.5, HvHKT2.1 and HvHKT2.2 according to their similarity to previously reported OsHKTs. Among these HvHKTs, HvHKT1.4 was highly up-regulated under salinity stress in both leaves and roots of Golden Promise. Subcellular localization analysis showed that HvHKT1.4 is a plasma-membrane–localized protein. The knockout mutants of HvHKT1.4 showed greater salinity sensitivity and higher Na+ concentration in leaves than wild-type plants. Haplotype analysis of HvHKT1.4 in 344 barley accessions showed 15 single nucleotide substitutions in the CDS region, belonging to five haplotypes. Significant differences in mean salinity damage scores, leaf Na+ contents and Na+/K+ were found between Hap5 and other haplotypes with Hap5 showing better salinity tolerance. The results indicated that HvHKT1.4 can be an effective target in improving salinity tolerance through ion homeostasis.

Identification and Expression Analysis of Sulfate Transporter Genes Family and Function Analysis of GmSULTR3;1a from Soybean.

Sulfate transporters (SULTRs) are essential for the transport and absorption of sulfate in plants and serve as critical transport proteins within the sulfur metabolism pathway, significantly influencing plant growth, development, and stress adaptation. A bioinformatics analysis of SULTR genes in soybean was performed, resulting in the identification and classification of twenty-eight putative GmSULTRs into four distinct groups. In this study, the characteristics of the 28 GmSULTR genes, including those involved in collinearity, gene structure, protein motifs, cis-elements, tissue expression patterns, and the response to abiotic stress and plant hormone treatments, were systematically analyzed. This study focused on conducting a preliminary functional analysis of the GmSULTR3;1a gene, wherein a high expression level of GmSULTR3;1a in the roots, stems, and leaves was induced by a sulfur deficiency and GmSULTR3;1a improved the salt tolerance. A further functional characterization revealed that GmSULTR3;1a-overexpressing soybean hairy roots had higher SO42-, GSH, and methionine (Met) contents compared with the wild-type (WT) plant. These results demonstrate that the overexpression of GmSULTR3;1a may promote the sulfur assimilation metabolism and increase the content of sulfur-containing amino acids in plants.

Arabidopsis VQ motif-containing proteins VQ1 and VQ10 interact with plastidial 1-deoxy-D-xylulose-5-phosphate synthase

VQ1 and VQ10 are largely unstructured homologous proteins with a significant potential for protein–protein interactions. Yeast two-hybrid (Y2H) analysis confirmed that both proteins interact not only with themselves and each other but also with other VQ and WRKY proteins. Screening an Arabidopsis Y2H library with VQ1 as bait identified 287 interacting proteins. Validation of the screening confirmed that interactions with VQ1 also occurred with VQ10, supporting their functional homology. Although VQ1 or VQ10 proteins do not localize in plastids, 47 VQ1-targets were found to be plastidial proteins. In planta interaction with the isoprenoid biosynthetic enzyme 1-deoxy-D-xylulose-5-phosphate synthase (DXS) was confirmed by co-immunoprecipitation. DXS oligomerizes through redox-regulated intermolecular disulfide bond formation, and the interaction with VQ1 or VQ10 do not involve their unique C residues. The VQ-DXS protein interaction did not alter plastid DXS localization or its oligomerization state. Although plants with enhanced or reduced VQ1 and VQ10 expression did not exhibit significantly altered levels of isoprenoids compared to wild-type plants, they did display significantly improved or diminished photosynthesis efficiency, respectively.

Overexpression of the ribosome-inactivating protein OsRIP1 modulates the jasmonate signaling pathway in rice.

Ribosome-inactivating proteins (RIPs) are plant enzymes that target the rRNA. The cytoplasmic RIP, called OsRIP1, plays a crucial role in regulating jasmonate, a key plant hormone. Understanding the role of OsRIP1 can provide insights into enhancing stress tolerance and optimizing growth of rice. Transcription profiling by mRNA sequencing was employed to measure the changes in gene expression in rice plants in response to MeJA treatment. Compared to wild type (WT) plants, OsRIP1 overexpressing rice plants showed a lower increase in mRNA transcripts for genes related to jasmonate responses when exposed to MeJA treatment for 3 h. After 24 h of MeJA exposure, the mRNA transcripts associated with the gibberellin pathway occurred in lower levels in OsRIP1 overexpressing plants compared to WT plants. We hypothesize that the mechanism underlying OsRIP1 antagonization of MeJA-induced shoot growth inhibition involves cytokinin-mediated leaf senescence and positive regulation of cell cycle processes, probably via OsRIP1 interaction with 40S ribosomal protein S5 and α-tubulin. Moreover, the photosystem II 10kDa polypeptide was identified to favorably bind to OsRIP1, and its involvement may be attributed to the reduction of photosynthesis in OsRIP1-overexpressing plants subjected to MeJA at the early timepoint (3 h).

A P450 superfamily member NtCYP82C4 promotes nicotine biosynthesis in Nicotiana tabacum

In plants, cytochrome P450s are monooxygenase that play key roles in the synthesis and degradation of intracellular substances. In tobacco, the majority of studies examining the P450 superfamily have concentrated on the CYP82E subfamily, where multiple family members function as demethylases, facilitating the synthesis of nornicotine. In this study, NtCYP82C4, a tobacco P450 superfamily member, was identified from a gene-edited tobacco mutant that nicotine biosynthesis in tobacco leaves is evidently reduced. Compared to the wild-type plants, the knockout of NtCYP82C4 resulted in a significantly lower nicotine content and biomass in tobacco leaves. Transcriptome and metabolome analyses indicated that the knockout of NtCYP82C4 inhibites secondary metabolic processes in tobacco plants, leading to the accumulation of some important precursors in the nicotine synthesis process, including aspartic acid and nicotinic acid, and increases nitrogen partitioning associated with those processes such as amino acid synthesis and utilization. It is speculated that NtCYP82C4 may function as an important catalase downstream of the nicotine synthesis. Currently, most of the steps and enzymes involved in the nicotine biosynthesis process in tobacco have been elucidated. Here, our study deepens the current understanding of nicotine biosynthesis process and provides new enzyme targets for nicotine synthesis in tobacco plants.

Identification of CKX gene family in Morusindica cv K2 and functional characterization of MiCKX4 during abiotic stress

Cytokinin oxidase/dehydrogenase (CKX) is the key enzyme that has been observed to catalyze irreversible inactivation of cytokinins and thus modulate cytokinin levels in plants. CKX gene family is known to have few members which are, expanded in the genome mainly due to duplication events. A total of nine MiCKXs were identified in Morus indica cv K2 with almost similar gene structures and conserved motifs and domains. The cis-elements along with expression analysis of these MiCKXs revealed their contrasting and specific role in plant development across different developmental stages. The localization of these enzymes in ER and Golgi bodies signifies their functional specification and property of getting modified post-translationally to carry out their activities. The overexpression of MiCKX4, an ortholog of AtCKX4, displayed longer primary root and higher number of lateral roots. Under ABA stress also the transgenic lines showed higher number of lateral roots and tolerance against drought stress as compared to wild-type plants. In this study, the CKX gene family members were analyzed bioinformatically for their roles under abiotic stresses.

Identification and analysis of gibberellin 2-oxidase (GA2ox) members in Cunninghamia lanceolate and the negative regulatory character of ClGA2ox12 in tree stature and xylem lignin deposits

Cunninghamia lanceolata (Lamb.) Hook (C. lanceolate) is a fast-growing evergreen coniferous tree species with high wood yield and fantabulous timber quality. To date, numerous studies have revealed that gibberellins (GAs) regulate the formation of plant wood (secondary xylem). Moreover, GA 2-oxidases (GA2oxs) are known as the major enzymes that deactivate GAs. However, a small or no number of the GA2oxs involved in xylem development and lignin biosynthesis mediated by the GA pathway in woody plants have been identified previously. In this study, 5 GA2oxs members were identified in C. lanceolate, including 4 ClGA2ox12s and one ClGA2ox8-like. Exogenous gibberellin not only promoted lignin deposition in the stem of C. lanceolate but also up-regulated the expression of the lignin biosynthesis gene ClCAD1 by 2–3 folds and one of ClGA2ox12s (designated ClGA2ox12) by 4 folds, suggesting that ClGA2ox12 may be involved in the modulation of lignin deposition by the gibberellin signaling pathway in C. lanceolate. Furthermore, transgenic Populus tomentosa overexpressing ClGA2ox12 exhibited growth retardation and a typical dwarfing phenotype, with a reduction of approximately 40 % in the number of xylem cell layers and a decrease of approximately 16.7 %-26.9 % in lignin content relative to wild-type plants. At the same time, the expression level of lignin biosynthetic genes and lignin content were down-regulated in transgenic plants. Together, these results suggested that ClGA2ox12 functioned as a GA 2oxs catabolic enzyme that plays pivotal roles in plant growth processes, xylem development, and lignin biosynthesis, which gives insights into producing dwarf and low-lignin varieties of C. lanceolate.

Decoding the role of OsPRX83 in enhancing osmotic stress tolerance in rice through ABA-dependent pathways and ROS scavenging

ABSTRACT Plant Class III peroxidases have diverse roles in controlling root hair growth, anther development, and abiotic and biotic stress responses. However, their abiotic stress response mechanism in rice remains elusive. Here, we identified a peroxidase precursor gene, OsPRX83, and investigated its role in enhancing osmotic stress tolerance in rice. We used OsPRX83 overexpression and CRISPR-Cas9-generated mutant lines to elucidate OsPRX83‘s function and expression patterns under stress conditions. The expression of OsPRX83 was induced by H2O2, PEG, NaCl, and ABA treatments. Using qRT-PCR, RNA sequencing, and physiological assays, we demonstrated that overexpression of OsPRX83 enhanced the osmotic and oxidative stress tolerance as compared to the wild-type and mutant seedlings, as evident from the higher survival rates, enhanced peroxidase (POD) and ascorbate peroxidase (APX) activities, and increased ABA sensitivity compared with mutants and wild-type plants. Transcriptome analysis further supported the involvement of OsPRX83 in the ROS scavenging, by modulating the expression of OsDREB1B, OsDREB1E, OsDREB1F, OsDREB1G in response to osmotic treatment. In summary, our study suggests that OsPRX83 plays a pivotal role in enhancing stress tolerance in rice through ABA-dependent pathways and ROS scavenging. Therefore, this study elucidates the function of a novel abiotic stress response gene in rice, thereby may contribute to a new genetic engineering resource for engineering drought-resistant rice varieties.

BRASSINOSTEROID-SIGNALING KINASE 1 modulates OPEN STOMATA 1 phosphorylation and contributes to stomatal closure and plant immunity.

Stomatal movement plays a critical role in plant immunity by limiting the entry of pathogens. OPEN STOMATA 1 (OST1) is a key component that mediates stomatal closure in plants, however, how OST1 functions in response to pathogens is not well understood. RECEPTOR-LIKE KINASE 902 (RLK902) phosphorylates BRASSINOSTEROID-SIGNALING KINASE 1 (BSK1) and positively modulates plant resistance. In this study, by a genome-wide phosphorylation analysis, we found that the phosphorylation of BSK1 and OST1 was missing in the rlk902 mutant compared with the wild-type plants, indicating a potential connection between the RLK902-BSK1 module and OST1-mediated stomatal closure. We showed that RLK902 and BSK1 contribute to stomatal immunity, as the stomatal closure induced by the bacterial pathogen Pto DC3000 was impaired in rlk902 and bsk1-1 mutants. Stomatal immunity mediated by RLK902 was dependent on BSK1 phosphorylation at Ser230, a key phosphorylation site for BSK1 functions. Several phosphorylation sites of OST1 were important for RLK902- and BSK1-mediated stomatal immunity. Interestingly, the phosphorylation of Ser171 and Ser175 in OST1 contributed to the stomatal immunity mediated by RLK902 but not by BSK1, while phosphorylation of OST1 at Ser29 and Thr176 residues was critical for BSK1-mediated stomatal immunity. Taken together, these results indicate that RLK902 and BSK1 contribute to disease resistance via OST1-mediated stomatal closure. This work revealed a new function of BSK1 in activating stomatal immunity, and the role of RLK902-BSK1 and OST1 module in regulating pathogen-induced stomatal movement.

Function of the NAC1 Gene from Fraxinus mandshurica in Cold Resistance and Growth Promotion in Tobacco

To elucidate the function of the cold-resistance regulatory gene FmNAC1 from Fraxinus mandshurica Rupr., this study identified the role that overexpression of the FmNAC1 gene plays in tobacco growth and cold-stress regulation. The cloned FmNAC1 gene from F. mandshurica is 891 bp in length and encodes 296 amino acids. Our subcellular localization analysis confirmed that FmNAC1 is primarily located in the nucleus and functions as a transcription factor. FmNAC1 is responsive to cold and NaCl stress, as well as to the induction of IAA, GA, and ABA hormone signals. To further elucidate its function in cold resistance, four transgenic tobacco lines expressing FmNAC1 (FmNAC1-OE) were generated through tissue culture after the Agrobacterium-mediated transformation of wild-type (WT) Nicotiana tabacum L.. These FmNAC1-OE plants exhibited accelerated growth after transplantation. When exposed to low-temperature conditions at −5 °C for 24 h, the rates of wilting and yellowing of the FmNAC1-OE plants were significantly lower than those of the WT tobacco plants. Additionally, the membrane integrity, osmotic regulation, and reactive oxygen species (ROS)-scavenging abilities of the FmNAC1-OE tobacco lines were better than those of the WT plants, indicating the potential of the FmNAC1 gene to improve plant cold resistance. The gene expression results further revealed that the FmNAC1 transcription factor exhibits regulatory interactions with growth-related genes such as IAA and AUX1; cold-resistance-related genes such as ICE, DREB, and CBF1; and genes involved in the clearance of reactive oxygen species (ROS), such as CAT and SOD. All of this evidence shows that the FmNAC1 transcription factor from F. mandshurica plays a key role in contributing to the enhancement of growth, cold resistance, and ROS clearance in transgenic tobacco plants.

Stable early heading in photoperiod-insensitive rice varieties results from an extremely short photoperiod-sensitive phase and weak temperature sensitivity

The transition from vegetative to reproductive growth in rice (Oryza sativa) is mainly regulated by photoperiod and temperature; however, it remains unclear how photoperiod-insensitive (photo-In) early heading rice varieties make this transition. Vegetative growth consists of a basic vegetative phase (BVP) and a photoperiod-sensitive phase (PSP). A certain duration of the BVP is required prior to the PSP, which varies according to daylength conditions. PSP duration is conventionally used as a parameter of photoperiod sensitivity, but this is not applicable to photo-In rice varieties. Here, we aimed to characterize the PSP in photo-In rice varieties. We examined four photo-In varieties and photoperiod-sensitive (photo-Se) varieties grown in four controlled environments, evaluating the lengths of their growth phases based on the turning point of the interval of leaf emergence and panicle initiation (PI). The photo-In varieties had an extremely short PSP, regardless of daylength, compared with the photo-Se varieties. Low temperature uniformly prolonged all growth stages in the photo-In varieties but led to a much longer PSP in the photo-Se varieties. The photo-In varieties, each carrying a non-functional allele of Ghd7, lost the ability to suppress PI, resulting in early heading. Hemi-knockout plants at the Ghd7 locus demonstrated the earlier heading than the wild-type plant due to shortening of PSP. Our results suggest that the photo-In varieties begin PI immediately after the end of the BVP, but their flowering is not a temperature-dependent process.

Overexpression of Potato PYL16 Gene in Tobacco Enhances the Transgenic Plant Tolerance to Drought Stress.

PYR/PYL/RCAR proteins are abscisic acid (ABA) receptors that play a crucial role in plant responses to abiotic stresses. However, there have been no research reports on potato PYL so far. In this study, a potato PYL gene named StPYL16 was identified based on transcriptome data under drought stress. Molecular characteristics analysis revealed that the StPYL16 protein possesses an extremely conserved PYL family domain. The tissue expression results indicated that the StPYL16 is predominantly expressed at high levels in the underground parts, particularly in tubers. Abiotic stress response showed that StPYL16 has a significant response to drought treatment. Further research on the promoter showed that drought stress could enhance the activation activity of the StPYL16 promoter on the reporter gene. Then, transient and stable expression of StPYL16 in tobacco enhanced the drought resistance of transgenic plants, resulting in improved plant height, stem thickness, and root development. In addition, compared with wild-type plants, StPYL16 transgenic tobacco exhibited lower malondialdehyde (MDA) content, higher proline accumulation, and stronger superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities. Meanwhile, StPYL16 also up-regulated the expression levels of stress-related genes (NtSOD, NtCAT, NtPOD, NtRD29A, NtLEA5, and NtP5CS) in transgenic plants under drought treatment. These findings indicated that the StPYL16 gene plays a positive regulatory role in potato responses to drought stress.

Dominant-negative chaperonin mutation ptCPN60α1S57F uncovers redundancy in chloroplast rRNA processing.

The biogenesis of functional forms of chloroplast ribosomal RNAs (rRNAs) is crucial for the translation of chloroplast mRNAs into polypeptides. However, the molecular mechanisms underlying the proper processing and maturation of chloroplast rRNA species are poorly understood. Through a genetic approach, we isolated and characterized an Arabidopsis mutant, α1-4, harboring a missense mutation in the plastid chaperonin-60α1 gene. Using allelism tests and transgenic manipulation, we determined functional redundancy among ptCPN60 subunits. The ptCPN60α1S57F mutation caused specific defects in the formation of chloroplast rRNA species, including 23S, 5S, and 4.5S rRNAs, but not 16S rRNAs. Allelism tests suggested that the dysfunctional ptCPN60α1S57F competes with other members of the ptCPN60 family. Indeed, overexpression of the ptCPN60α1S57F protein in wild-type plants mimicked the phenotypes observed in the α1-4 mutant, while increasing the endogenous transcriptional levels of ptCPN60α2, β1, β2, and β3 in the α1-4 mutant partially mitigated the abnormal fragmentation processing of chloroplast 23S, 5S, and 4.5S rRNAs. Furthermore, we demonstrated functional redundancy between ptCPN60β1 and ptCPN60β2 in chloroplast rRNA processing through double-mutant analysis. Collectively, our data reveal a novel physiological role of ptCPN60 subunits in generating the functional rRNA species of the large 50S ribosomal subunit in Arabidopsis chloroplasts.

Expression of Foxtail Millet bZIP Transcription Factor SibZIP67 Enhances Drought Tolerance in Arabidopsis.

Foxtail millet is a drought-tolerant cereal and forage crop. The basic leucine zipper (bZIP) gene family plays important roles in regulating plant development and responding to stresses. However, the roles of bZIP genes in foxtail millet remain largely uninvestigated. In this study, 92 members of the bZIP transcription factors were identified in foxtail millet and clustered into ten clades. The expression levels of four SibZIP genes (SibZIP11, SibZIP12, SibZIP41, and SibZIP67) were significantly induced after PEG treatment, and SibZIP67 was chosen for further analysis. The studies showed that ectopic overexpression of SibZIP67 in Arabidopsis enhanced the plant drought tolerance. Detached leaves of SibZIP67 overexpressing plants had lower leaf water loss rates than those of wild-type plants. SibZIP67 overexpressing plants improved survival rates under drought conditions compared to wild-type plants. Additionally, overexpressing SibZIP67 in plants displayed reduced malondialdehyde (MDA) levels and enhanced activities of antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) under drought stress. Furthermore, the drought-related genes, such as AtRD29A, AtRD22, AtNCED3, AtABF3, AtABI1, and AtABI5, were found to be regulated in SibZIP67 transgenic plants than in wild-type Arabidopsis under drought conditions. These data suggested that SibZIP67 conferred drought tolerance in transgenic Arabidopsis by regulating antioxidant enzyme activities and the expression of stress-related genes. The study reveals that SibZIP67 plays a beneficial role in drought response in plants, offering a valuable genetic resource for agricultural improvement in arid environments.