Wild-type Plants Research Articles

OsMYB14, an R2R3-MYB transcription factor, regulates plant height through the control of hormone metabolism in rice

Plant growth must be regulated throughout the plant life cycle. The myeloblastosis (MYB) transcription factor (TF) family is one of the largest TF families and is involved in metabolism, lignin biosynthesis, and developmental processes. Here, we showed that OsMYB14, a rice R2R3-MYB TF, was expressed in leaves and roots, especially in rice culm and panicles, and that it localized to the nucleus. Overexpression of OsMYB14 (OsMYB14-ox) in rice resulted in a 30% reduction in plant height compared to that of the wild type (WT), while the height of the osmyb14-knockout (osmyb14-ko) mutant generated using the CRISPR/Cas9 system was not significantly different. Microscopic observations of the first internode revealed that the cell size did not differ significantly among the lines. RNA sequencing analysis revealed that genes associated with plant development, regulation, lipid metabolism, carbohydrate metabolism, and gibberellin (GA) and auxin metabolic processes were downregulated in the OsMYB14-ox line. Hormone quantitation revealed that inactive GA19 accumulated in OsMYB14-ox but not in the WT or knockout plants, suggesting that GA20 generation was repressed. Indole-3-acetic acid (IAA) and IAA-aspartate accumulated in OsMYB14-ox and osmyb14-ko, respectively. Indeed, real-time PCR analysis revealed that the expression of OsGA20ox1, encoding GA20 oxidase 1, and OsGH3-2, encoding IAA-amido synthetase, was downregulated in OsMYB14-ox and upregulated in osmyb14-ko. A protein-binding microarray revealed the presence of a consensus DNA-binding sequence, the ACCTACC-like motif, in the promoters of the OsGA20ox1 and GA20ox2 genes. These results suggest that OsMYB14 may act as a negative regulator of biological processes affecting plant height in rice by regulating GA biosynthesis and auxin metabolism.

Replacement of Arabidopsis H2A.Z with human H2A.Z orthologs reveals extensive functional conservation and limited importance of the N-terminal tail sequence for Arabidopsis development.

The incorporation of histone variants, distinct paralogs of core histones, into chromatin affects all DNA-templated processes in the cell, including the regulation of transcription. In recent years, much research has been focused on H2A.Z, an evolutionarily conserved H2A variant found in all eukaryotes. In order to investigate the functional conservation of H2A.Z histones during eukaryotic evolution we transformed h2a.z deficient plants with each of the three human H2A.Z variants to assess their ability to rescue the mutant defects. We discovered that human H2A.Z.1 and H2A.Z.2.1 fully complement the phenotypic abnormalities of h2a.z plants despite significant divergence in the N-terminal tail sequences of Arabidopsis and human H2A.Zs. In contrast, the brain-specific splice variant H2A.Z.2.2 has a dominant-negative effect in wild-type plants, mimicking an H2A.Z deficiency phenotype. Furthermore, H2A.Z.1 almost completely re-establishes normal H2A.Z chromatin occupancy in h2a.z plants and restores the expression of more than 84% of misexpressed genes. Finally, we used a series of N-terminal tail truncations of Arabidopsis HTA11 to reveal that the N-terminal tail of Arabidopsis H2A.Z is not necessary for normal plant development but does play an important role in mounting proper environmental stress responses.

Transgenic tobacco plants overexpressing a wheat salt stress root protein (TaSSRP) exhibit enhanced tolerance to heat stress.

Heat stress is a detrimental abiotic stress that limits the development of many plant species and is linked to a variety of cellular and physiological problems. Heat stress affects membrane fluidity, which leads to negative effects on cell permeability and ion transport. Research reveals that heat stress causes severe damage to cells and leads to rapid accumulation of reactive oxygen species (ROS), which could cause programmed cell death. This current study aimed to validate the role of Triticum aestivum Salt Stress Root Protein (TaSSRP) in plants' tolerance to heat stress by modulating its expression in tobacco plants. The Relative Water Content (RWC), total chlorophyll content, and Membrane Stability Index (MSI) of the seven distinct transgenic lines (T0 - 2, T0 - 3, T0 - 6, T0 - 8, T0 - 9, T0 - 11, and T0 - 13), increased in response to heat stress. Despite the fact that the same tendency was detected in wild-type (WT) plants, changes in physio-biochemical parameters were greater in transgenic lines than in WT plants. The expression analysis revealed that the transgene TaSSRP expressed from 1.00 to 1.809 folds in different lines in the transgenic tobacco plants. The gene TaSSRP offered resistance to heat stress in Nicotiana tabacum, according to the results of the study. These findings could help to improve our knowledge and understanding of the mechanism underlying thermotolerance in wheat, and the novel identified gene TaSSRP could be used in generating wheat varieties with enhanced tolerance to heat stress.

The tomato WRKY-B transcription factor modulates lateral branching by targeting BLIND, PIN4, and IAA15.

Lateral branching is a crucial agronomic trait that impacts crop yield. In tomato ( Solanum lycopersicum ), excessive lateral branching is unfavorable and results in substantial labor and management costs. Therefore, optimizing lateral branching is a primary objective in tomato breeding. Although many genes related to lateral branching have been reported in tomato, the molecular mechanism underlying their network remains elusive. In this study, we found that the expression profile of a WRKY gene, WRKY-B (for WRKY-BRANCING), was associated with the auxin-dependent axillary bud development process. Wrky-b mutants generated by the CRISPR/Cas9 editing system presented fewer lateral branches, while WRKY-B overexpression lines presented more lateral branches than did wild-type plants. Furthermore, WRKY-B can directly target the well-known branching gene BLIND (BL) and the auxin efflux carrier gene PIN4 to activate their expression. Both the bl and pin4 mutants exhibited reduced lateral branching, similar to the wrky-b mutant. The IAA contents in the axillary buds of the wrky-b, bl, and pin4 mutant plants were significantly higher than those in the wild-type plants. In addition, WRKY-B can also directly target the AUX/IAA gene IAA15 and repress its expression. In summary, WRKY-B works upstream of BL, PIN4, and IAA15 to regulate the development of lateral branches in tomato.

The UDP-glycosyltransferase gene OsUGT706E2 negatively regulates rice tolerance to blast disease and abiotic stresses

Despite the crucial role of UDP-glycosyltransferases (UGTs) in various stress responses in plants, their biological functions in rice (Oryza sativa L.) remain poorly understood. In this study, we introduce a novel gene, OsUGT706E2, which is expressed at significantly higher levels in wild rice compared to cultivated rice. OsUGT706E2 is active in multiple tissues and localizes to both the nucleus and cytoplasm. Its transcription is notably up-regulated in response to cold stress, blast disease, and several hormone treatments. Overexpression of OsUGT706E2 markedly reduces seedling tolerance to blast disease, cold, and osmotic stress, whereas knocking out OsUGT706E2 enhances seedling tolerance to blast disease and osmotic stress. The expression levels of stress-related genes in OsUGT706E2 overexpressing plants were significantly lower compared to wild-type plants following stress treatment. Conversely, OsUGT706E2 knockout plants exhibited markedly higher expression levels of these genes than the control plants after stress treatment. Metabolome analysis further indicated that OsUGT760E2 influences metabolite content in rice. Specifically, OsUGT760E2-overexpressing seedlings had higher amino acid content and lower lipid content compared to wild-type seedlings, while OsUGT760E2-knockout seedlings showed lower amino acid content and higher lipid content than control seedlings. These findings suggest that OsUGT760E2 negatively regulates resistance to blast disease as well as tolerance to cold and osmotic stress in rice. As a result, OsUGT760E2 represents a promising target for enhancing rice stress tolerance through gene editing approaches.

Treatments with Diquat Reveal the Relationship between Protein Phosphatases (PP2A) and Oxidative Stress during Mitosis in Arabidopsis thaliana Root Meristems.

Reversible protein phosphorylation regulates various cellular mechanisms in eukaryotes by altering the conformation, activity, localization, and stability of substrate proteins. In Arabidopsis thaliana root meristems, histone post-translational modifications are crucial for proper cell division, and they are also involved in oxidative stress signaling. To investigate the link between reactive oxygen species (ROS) and mitosis, we treated various Arabidopsis genotypes, including wild-types and mutants showing dysfunctional PP2A, with the ROS-inducing herbicide diquat (DQ). Studying the c3c4 double catalytic subunit mutant and fass regulatory subunit mutants of PP2A provided insights into phosphorylation-dependent mitotic processes. DQ treatment reduced mitotic activity in all genotypes and caused early mitotic arrest in PP2A mutants, likely due to oxidative stress-induced damage to essential mitotic processes. DQ had a minimal effect on reversible histone H3 phosphorylation in wild-type plants but significantly decreased phospho-histone H3 levels in PP2A mutants. Following drug treatment, the phosphatase activity decreased only in the stronger phenotype mutant plants (fass-5 and c3c4). Our findings demonstrate that (i) the studied PP2A loss-of-function mutants are more sensitive to increased intracellular ROS and (ii) DQ has indirect altering effects of mitotic activities and histone H3 phosphorylation. All these findings underscore the importance of PP2A in stress responses.

SlTDC modulates photosynthesis of senescent leaves in tomato

Melatonin (MT) is a key regulator in plants’ response to leaf senescence induced by aging or various abiotic stresses. Here, we demonstrated that darkness and leaf aging enhance endogenous MT levels by upregulating key genes involved in MT synthesis. Additionally, exogenous MT application significantly mitigated leaf senescence induced by darkness and leaf aging in tomato plants, leading to higher chlorophyll content and maximum photochemical efficiency (Fv/Fm) compared to the control. Using Solanum lycopersicum L. tryptophan decarboxylase (SlTDC)-overexpressed and -knockout transgenic tomato seedlings, we found that SlTDC overexpression increased endogenous MT content and suppressed mRNA levels of chlorophyll degradation-related genes: pheophorbide a oxygenase (PAO), pheophytinase (PPH), and non-yellow coloring1 like (NOL). Furthermore, SlTDC overexpression alleviated photosystem II complex (PSII) photoinhibition, increased ribulose-1,5-bisphosphate carboxylase (Rubisco) and Rubisco activase (RCA) activities and mRNA levels, and maintained higher photosynthetic efficiency in leaves under darkness and in leaves aged over 35 d compared to wild-type plants. Conversely, SlTDC knockout accelerated darkness- or leaf aging-induced leaf senescence in tomatoes. Our findings suggest that MT application or SlTDC overexpression can effectively alleviate leaf senescence by regulating photosynthesis in tomato plants.

AtSNU13 modulates pre-mRNA splicing of RBOHD and ALD1 to regulate plant immunity

Pre-mRNA splicing is a significant step for post-transcriptional modifications and functions in a wide range of physiological processes in plants. Human NHP2L binds to U4 snRNA during spliceosome assembly; it is involved in RNA splicing and mediates the development of human tumors. However, no ortholog has yet been identified in plants. Therefore, we report At4g12600 encoding the ortholog NHP2L protein, and AtSNU13 associates with the component of the spliceosome complex; the atsnu13 mutant showed compromised resistance in disease resistance, indicating that AtSNU13 is a positive regulator of plant immunity. Compared to wild-type plants, the atsnu13 mutation resulted in altered splicing patterns for defense-related genes and decreased expression of defense-related genes, such as RBOHD and ALD1. Further investigation shows that AtSNU13 promotes the interaction between U4/U6.U5 tri-snRNP-specific 27 K and the motif in target mRNAs to regulate the RNA splicing. Our study highlights the role of AtSNU13 in regulating plant immunity by affecting the pre-mRNA splicing of defense-related genes.

Two Calcium Sensor-Activated Kinases Function in Root Hair Growth.

Plant pollen tubes and root hairs typical polarized tip growth. It is well established that calcium ions (Ca2+) play essential roles in maintaining cell polarity and guiding cell growth orientation. Ca2+ signals are encoded by Ca2+ channels and transporters and are decoded by a variety of Ca2+-binding proteins often called Ca2+ sensors, in which calcineurin B-like protein (CBL) proteins function by interacting with and activating a group of kinases, activate CBL-interacting protein kinases (CIPKs). Some CBL-CIPK complexes, such as CBL2/3-CIPK12/19, act as crucial regulators of pollen tube growth. Whether these calcium decoding components regulate the growth of root hairs, another type of plant cell featuring Ca2+-regulated polarized growth, remains unknown. In this study, we identified CIPK13 and CIPK18 as genes specifically expressed in Arabidopsis (Arabidopsis thaliana) root hairs. The cipk13 cipk18 double mutants showed reduced root hair length and lower growth rates. The calcium oscillations at the root hair tip were attenuated in the cipk13 cipk18 mutants as compared to the wild-type plants. Through yeast two-hybrid screens, CBL2 and CBL3 were identified as interacting with CIPK13 and CIPK18. cbl2 cbl3 displayed a shortened root hair phenotype similar to cipk13 cipk18. This genetic analysis, together with biochemical assays showing activation of CIPK13/18 by CBL2/3, supported the conclusion that CBL2/3 and CIPK13/18 may work as Ca2+-decoding modules in controlling root hair growth. Thus, the findings that CIPK12/19 and CIPK13/18 function in pollen tube and root hair growth, respectively, illustrate a molecular mechanism in which the same CBLs recruit distinct CIPKs in regulating polarized tip growth in different types of plant cells.

Overexpression of RpKTI2 from Robinia pseudoacacia Affects the Photosynthetic Physiology and Endogenous Hormones of Tobacco.

Kunitz trypsin inhibitor genes play important roles in stress resistance. In this study, we investigated RpKTI2 cloned from Robinia pseudoacacia and its effect on tobacco. RpKTI2 was introduced into the tobacco cultivar NC89 using Agrobacterium-mediated transformation. Six RpKTI2-overexpressing lines were obtained. Transgenic and wild-type tobacco plants were then compared for photosynthetic characteristics and endogenous hormone levels. Transgenic tobacco showed minor changes in chlorophyll content, fluorescence, and photosynthetic functions. However, the maximum photochemical efficiency (Fv/Fm) increased significantly while intercellular CO2 concentration (Ci) decreased significantly. Stomatal size and hormone content (indole-3-acetic acid, zeatin riboside, gibberellin, and indole-3-propionic acid) were reduced, while brassinosteroid content increased. Random forest regression revealed that RpKTI2 overexpression had the biggest impact on carotenoid content, initial fluorescence, Ci, stomatal area, and indole-3-acetic acid. Overall, RpKTI2 overexpression minimally affected chlorophyll synthesis and photosynthetic system characteristics but influenced stomatal development and likely enhanced the antioxidant capacity of tobacco. These findings provide a basis for future in-depth research on RpKTI2.

Integrated analysis of DNA methylome and transcriptome revealing epigenetic regulation of CRIR1-promoted cold tolerance

BackgroundDNA methylation contributes to the epigenetic regulation of nuclear gene expression, and is associated with plant growth, development, and stress responses. Compelling evidence has emerged that long non-coding RNA (lncRNA) regulates DNA methylation. Previous genetic and physiological evidence indicates that lncRNA-CRIR1 plays a positive role in the responses of cassava plants to cold stress. However, it is unclear whether global DNA methylation changes with CRIR1-promoted cold tolerance.ResultsIn this study, a comprehensive comparative analysis of DNA methylation and transcriptome profiles was performed to reveal the gene expression and epigenetic dynamics after CRIR1 overexpression. Compared with the wild-type plants, CRIR1-overexpressing plants present gained DNA methylation in over 37,000 genomic regions and lost DNA methylation in about 16,000 genomic regions, indicating a global decrease in DNA methylation after CRIR1 overexpression. Declining DNA methylation is not correlated with decreased/increased expression of the DNA methylase/demethylase genes, but is associated with increased transcripts of a few transcription factors, chlorophyll metabolism and photosynthesis-related genes, which could contribute to the CRIR1-promoted cold tolerance.ConclusionsIn summary, a first set of transcriptome and epigenome data was integrated in this study to reveal the gene expression and epigenetic dynamics after CRIR1 overexpression, with the identification of several TFs, chlorophyll metabolism and photosynthesis-related genes that may be involved in CRIR1-promoted cold tolerance. Therefore, our study has provided valuable data for the systematic study of molecular insights for plant cold stress response.

Ultraviolet‐B Stress Increases Epidermal UV‐Screening Effectiveness and Alters Growth and Cell‐Wall Constituents of the Brown Midrib bmr6 and bmr12 Mutants of Sorghum bicolor

ABSTRACTThe brown midrib bmr6 and bmr12 mutants of sorghum (Sorghum bicolor) have alterations to the phenylpropanoid pathway impairing the activity of cinnamyl alcohol dehydrogenase (CAD) and/or caffeate5/hydroxyferulate O‐methyl transferase (COMT) enzymes, which inhibit lignin synthesis. Interestingly, these phenylpropanoids can also act as sunscreen compounds in plants and potentially attenuate ultraviolet radiation. We examined the effects of ultraviolet‐B (UV‐B; 280–320 nm) exclusion on growth, cell‐wall constituents and UV‐screening abilities of bmr6, bmr12, a double mutant (bmr6 bmr12; dm) and wild‐type (WT) genotypes of S. bicolor. Plants were grown in a UV‐transparent greenhouse under filters that either transmitted 2.8% (Mylar) or 90% (Aclar) of UV‐B. The greenhouse experiment was a 2 × 4 (UV treatment × genotype) complete factorial design. Sorghum grown under reduced UV were 23% taller and had 22% fewer leaves. Among genotypes, the WT plants were 5%–12% taller than the bmr6, bmr12 and dm mutants. The near‐ambient UV‐B treatment group was more effective at UV screening and had a 16% higher UV‐screening effectiveness than those under reduced UV‐B. Sorghum plants with the bmr6 and dm genotypes had 8%–19% higher UV‐shield than the bmr12 and WT. Plants grown under the reduced UV‐B treatment had 5% less hemicellulose and 6% more cellulose in their cell walls. There were no overall treatment effects on bulk soluble phenolics, chlorophyll fluorescence (Fv/Fm) or lignin concentrations. These results are a possible indication that the bmr mutants of S. bicolor have a varied response to UV‐B exclusion due to alterations in the phenylpropanoid pathway leading to redistribution of metabolites.

A putative Na+/H+ antiporter BpSOS1 contributes to salt tolerance in birch

White birch (Betula platyphylla Suk.) is an important pioneer tree which plays a critical role in maintaining ecosystem stability and forest regeneration. The growth of birch is dramatically inhibited by salt stress, especially the root inhibition. Salt Overly Sensitive 1 (SOS1) is the only extensively characterized Na+ efflux transporter in multiple plant species. The salt-hypersensitive mutant, sos1, display significant inhibition of root growth by NaCl. However, the role of SOS1 in birch responses to salt stress remains unclear. Here, we characterized a putative Na+/H+ antiporter BpSOS1 in birch and generated the loss-of-function mutants of the birch BpSOS1 by CRISPR/Cas9 approach. The bpsos1 mutant exhibit exceptional increased salt sensitivity which links to excessive Na+ accumulation in root, stem and old leaves. We observed a dramatic reduction of K+ contents in leaves of the bpsos1 mutant plants under salt stress. Furthermore, the Na+/K+ ratio of roots and leaves is significant higher in the bpsos1 mutants than the wild-type plants under salt stress. The ability of Na+ efflux in the root meristem zone is found to be impaired which might result the imbalance of Na+ and K+ in the bpsos1 mutants. Our findings indicate that the Na+/H+ exchanger BpSOS1 plays a critical role in birch salt tolerance by maintaining Na+ homeostasis and provide evidence for molecular breeding to improve salt tolerance in birch and other trees.

PagbHLH35 Enhances Salt Tolerance through Improving ROS Scavenging in Transgenic Poplar.

The bHLH transcription factor family plays crucial roles in plant growth and development and their responses to adversity. In this study, a highly salt-induced bHLH gene, PagbHLH35 (Potri.018G141600), was identified from Populus alba × P. glandullosa (84K poplar). PagbHLH35 contains a highly conserved bHLH domain within the region of 52-114 amino acids. A subcellular localization result confirmed its nuclear localization. A yeast two-hybrid assay indicated PagbHLH35 lacks transcriptional activation activity, while a yeast one-hybrid assay indicated it could specifically bind to G-box and E-box elements. The expression of PagbHLH35 reached its peak at 12 h and 36 h time points under salt stress in the leaves and roots, respectively. A total of three positive transgenic poplar lines overexpressing PagbHLH35 were generated via Agrobacterium-mediated leaf disk transformation. Under NaCl stress, the transgenic poplars exhibited significantly enhanced morphological and physiological advantages such as higher POD activity, SOD activity, chlorophyll content, and proline content, and lower dehydration rate, MDA content and hydrogen peroxide (H2O2) content, compared to wild-type (WT) plants. In addition, histological staining showed that there was lower ROS accumulation in the transgenic poplars under salt stress. Moreover, the relative expression levels of several antioxidant genes in the transgenic poplars were significantly higher than those in the WT. All the results indicate that PagbHLH35 can improve salt tolerance by enhancing ROS scavenging in transgenic poplars.

Genome-wide identification and expression analysis of the BZR gene family in Zanthoxylum armatum DC and functional analysis of ZaBZR1 in drought tolerance.

In this study, six ZaBZRs were identified in Zanthoxylum armatum DC, and all the ZaBZRs were upregulated by abscisic acid (ABA) and drought. Overexpression of ZaBZR1 enhanced the drought tolerance of transgenic Nicotiana benthamian. Brassinosteroids (BRs) are a pivotal class of sterol hormones in plants that play a crucial role in plant growth and development. BZR (brassinazole resistant) is a crucial transcription factor in the signal transduction pathway of BRs. However, the BZR gene family members have not yet been identified in Zanthoxylum armatum DC. In this study, six members of the ZaBZR family were identified by bioinformatic methods. All six ZaBZRs exhibited multiple phosphorylation sites. Phylogenetic and collinearity analyses revealed a closest relationship between ZaBZRs and ZbBZRs located on the B subgenomes. Expression analysis revealed tissue-specific expression patterns of ZaBZRs in Z. armatum, and their promoter regions contained cis-acting elements associated with hormone response and stress induction. Additionally, all six ZaBZRs showed upregulation upon treatment after abscisic acid (ABA) and polyethylene glycol (PEG), indicating their participation in drought response. Subsequently, we conducted an extensive investigation of ZaBZR1. ZaBZR1 showed the highest expression in the root, followed by the stem and terminal bud. Subcellular localization analysis revealed that ZaBZR1 is present in the cytoplasm and nucleus. Overexpression of ZaBZR1 in transgenic Nicotiana benthamiana improved seed germination rate and root growth under drought conditions, reducing water loss rates compared to wild-type plants. Furthermore, ZaBZR1 increased proline content (PRO) and decreased malondialdehyde content (MDA), indicating improved tolerance to drought-induced oxidative stress. The transgenic plants also showed a reduced accumulation of reactive oxygen species. Importantly, ZaBZR1 up-regulated the expression of drought-related genes such as NbP5CS1, NbDREB2A, and NbWRKY44. These findings highlight the potential of ZaBZR1 as a candidate gene for enhancing drought resistance in transgenic N. benthamiana and provide insight into the function of ZaBZRs in Z. armatum.

HcLEA113, a late embryogenesis abundant protein gene, positively regulates drought-stress responses in kenaf.

Late embryogenesis abundant (LEA) proteins have been widely recognized for their role in various abiotic stress responses in higher plants. Nevertheless, the specific mechanism responsible for the function of LEA proteins in plants has not yet been explored. This research involved the isolation and characterization of HcLEA113 from kenaf, revealing a significant increase in its expression in response to drought stress. When HcLEA113 was introduced into yeast, it resulted in an improved survival rate under drought conditions. Furthermore, the overexpression of HcLEA113 in tobacco plants led to enhanced tolerance to drought stress. Specifically, HcLEA113-OE plants exhibited higher germination rates, longer root lengths, greater chlorophyll content, and higher relative water content under drought stress compared to wild-type (WT) plants, while their relative conductivity was significantly lower than that of WT plants. Further physiological measurements revealed that the proline content, soluble sugars, and antioxidant activities of WT and HcLEA113-OE tobacco leaves increased significantly under drought stress, with greater changes in HcLEA113-OE plants than WT. The increase in hydrogen peroxide (H2O2), superoxide anions (O2 -), and malondialdehyde (MDA) content was significantly lower in HcLEA113-OE lines than in WT plants. Additionally, HcLEA113-OE plants can activate reactive oxygen species (ROS)- and osmotic-related genes in response to drought stress. On the other hand, silencing the HcLEA113 gene through virus-induced gene silencing (VIGS) in kenaf plants led to notable growth suppression when exposed to drought conditions, manifesting as decreased plant height and dry weight. Meanwhile, antioxidant enzymes' activity significantly decreased and the ROS content increased. This study offers valuable insights for future research on the genetic engineering of drought resistance in plants.

OsUVR8b, rather than OsUVR8a, plays a predominant role in rice UVR8-mediated UV-B response.

UV RESISTANCE LOCUS 8 (UVR8) has been identified in Arabidopsis thaliana as the receptor mediating responses to UV-B radiation. However, UVR8-mediated UV-B signaling pathways in rice, which possesses two proteins (UVR8a and UVR8b) with high identities to AtUVR8, remain largely unknown. Here, UVR8a/b were found to be predominantly expressed in rice leaves and leaf sheaths, while the levels of UVR8b transcript and UVR8b protein were both higher than those of UVR8a. Compared to wild-type (WT) plants, uvr8b and uvr8a uvr8b rice mutants exposed to UV-B showed reduced UV-B-induced growth inhibition and upregulation of CHS and HY5 transcripts alongside UV-B acclimation. However, uvr8a mutant was similar to WT plants and exhibited changes comparable with WT. Overexpressing OsUVR8a/b enhanced UV-B-induced growth inhibition and acclimation to UV-B. UV-B was able to enhance the interaction between E3 ubiquitin ligase OsCOP1 and OsUVR8a/b, whereas the interaction of the homologous protein of Arabidopsis REPRESSOR OF UV-B PHOTOMORPHOGENESIS2 (AtRUP2) in rice with OsUVR8a/b was independent of UV-B. Additionally, OsUVR8a/b proteins were also found in the nucleus and cytoplasm even in the absence of UV-B. The abundance of OsUVR8 monomer showed an invisible change in the leaves of rice seedlings transferred from white light to that supplemented with UV-B, even though UV-B was able to weaken the interactions between OsUVR8a and OsUVR8b homo and heterodimers. Therefore, both OsUVR8a and OsUVR8b, which have different localization and response patterns compared with AtUVR8, function in the response of rice to UV-B radiation, whereas OsUVR8b plays a predominant role in this process.

Autophagy is suppressed by low temperatures and is dispensable for cold acclimation in Arabidopsis.

Plants have evolved various mechanisms to adapt to the ever-changing external environment. Autophagy is one such mechanism and has been suggested to play a key role in responding to and adapting to abiotic stresses in plants. However, the role of autophagy in adaptation to cold and freezing stresses remains to be characterized in detail. Here, we investigated the role of autophagy in the low-temperature response of Arabidopsis using atg mutants. Both the atg5-1 and atg10-1 mutants exhibited normal freezing tolerance, regardless of cold acclimation. A comparison of fresh weights indicated that the difference in growth between the wild-type and atg plants under cold conditions was rather small compared with that under normal conditions. Analysis of COLD-REGULATED gene expression showed no significant differences between the atg mutants and wild type. Treatment with 3-methyladenine, an inhibitor of autophagy, did not impair the induction of COR15Apro::LUC expression upon exposure to low temperature. Evaluation of autophagic activity using transgenic plants expressing RBCS-mRFP demonstrated that autophagy was rarely induced by cold exposure, even in the dark. Taken together, these data suggest that autophagy is suppressed by low temperatures and is dispensable for cold acclimation and freezing tolerance in Arabidopsis.

Genome-wide analysis of soybean hypoxia inducible gene domain containing genes: a functional investigation of GmHIGD3.

The response of Hypoxia Inducible Gene Domain (HIGD) proteins to hypoxia plays a crucial role in plant development. However, the research on this gene family in soybean has been lacking. In this study, we aimed to identify and comprehensively analyze soybean HIGD genes using the Glycine max genome database. As a result, six GmHIGD genes were successfully identified, and their phylogeny, gene structures, and putative conserved motifs were analyzed in comparison to Arabidopsis and rice. Collinearity analysis indicated that the HIGD gene family in soybean has expanded to some extent when compared to Arabidopsis. Additionally, the cis-elements in the promoter regions of GmHIGD and the transcription factors potentially binding to these regions were identified. All GmHIGD genes showed specific responsiveness to submergence and hypoxic stresses. Expression profiling through quantitative real-time PCR revealed that these genes were significantly induced by PEG treatment in root tissue. Co-expressed genes of GmHIGD were primarily associated with oxidoreductase and dioxygenase activities, as well as peroxisome function. Notably, one of GmHIGD genes, GmHIGD3 was found to be predominantly localized in mitochondria, and its overexpression in Arabidopsis led to a significantly reduction in catalase activity compared to wild-type plants. These results bring new insights into the functional role of GmHIGD in terms of subcellular localization and the regulation of oxidoreductase activity.

ZmWRKY30 modulates drought tolerance in maize by influencing myo-inositol and reactive oxygen species homeostasis.

Maize (Zea mays L.) is an important food crop with a wide range of uses in both industry and agriculture. Drought stress during its growth cycle can greatly reduce maize crop yield and quality. However, the molecular mechanisms underlying maize responses to drought stress remain unclear. In this work, a WRKY transcription factor-encoding gene, ZmWRKY30, from drought-treated maize leaves was screened out and characterized. ZmWRKY30 gene expression was induced by dehydration treatments. The ZmWRKY30 protein localized to the nucleus and displayed transactivation activity in yeast. Compared with wild-type (WT) plants, Arabidopsis lines overexpressing ZmWRKY30 exhibited a significantly enhanced drought stress tolerance, as evidenced by the improved survival rate, increased antioxidant enzyme activity by superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), elevated proline content, and reduced lipid peroxidation recorded after drought stress treatment. In contrast, the mutator (Mu)-interrupted ZmWRKY30 homozygous mutant (zmwrky30) was more sensitive to drought stress than its null segregant (NS), characterized by the decreased survival rate, reduced antioxidant enzyme activity (SOD, POD, and CAT) and proline content, as well as increased malondialdehyde accumulation. RNA-Seq analysis further revealed that, under drought conditions, the knockout of the ZmWRKY30 gene in maize affected the expression of genes involved in reactive oxygen species (ROS), proline, and myo-inositol metabolism. Meanwhile, the zmwrky30 mutant exhibited significant downregulation of myo-inositol content in leaves under drought stress. Combined, our results suggest that ZmWRKY30 positively regulates maize responses to water scarcity. This work provides potential target genes for the breeding of drought-tolerant maize.