Wild-type Plants Research Articles

Wheat TaTIFY3B and TaTIFY10A play roles in seed germination and abiotic stress responses in transgenic Arabidopsis and rice

BackgroundSeed germination is a key process in the plant life cycle that affects the vegetative and reproductive stages of plants. Although the JAZ gene family has been characterized in many plants, the relationship between the JAZ gene and seed germination is still unclear.ResultsWe identified two members of the JAZ family from wheat, TaTIFY3B and TaTIFY10A. TaTIFY3B and TaTIFY10A were localized in both the cell membrane and nucleus. Spatio-temporal expression analysis of TaTIFY3B and TaTIFY10A in wheat revealed that these genes are essential for the preharvest sprouting (PHS) stage of seed development, with expression levels significantly decreasing during the ripening period. Transgenic rice plants overexpressing wheat TaTIFY3B and TaTIFY10A improved seed germination rates. Transgenic Arabidopsis plants overexpressing wheat TaTIFY10A improved seed germination rates and promoted flowering. In addition, abscisic acid (ABA) and jasmonic acid (JA) were found to induce TaTIFY3B and TaTIFY10A expression. Under different ABA concentrations, the seed germination rates of transgenic rice and Arabidopsis overexpressing TaTIFY3B and TaTIFY10A are superior to wild-type (WT) and mutant plants, and the root lengths of Arabidopsis overexpressing TaTIFY3B and TaTIFY10A also change. Under different JA concentrations, there is no difference in the seed germination rate of rice overexpressing TaTIFY3B and TaTIFY10A compared to WT and mutant plants, but there is a significant difference in the seed germination rate and root length of overexpressing Arabidopsis compared to WT and mutant plants. Under different concentrations of salt and drought treatments, the seed germination rate and root length of overexpressing Arabidopsis of TaTIFY3B and TaTIFY10A are affected.ConclusionsThis study offers a novel perspective for understanding the molecular basis of pre-harvest sprouting and provides potential candidate genes for controlling wheat seed germination.

AtC3H3, an Arabidopsis Non-TZF Gene, Enhances Salt Tolerance by Increasing the Expression of Both ABA-Dependent and -Independent Stress-Responsive Genes.

Salinity causes widespread crop loss and prompts plants to adapt through changes in gene expression. In this study, we aimed to investigate the function of the non-tandem CCCH zinc-finger (non-TZF) protein gene AtC3H3 in response to salt stress in Arabidopsis. AtC3H3, a gene from the non-TZF gene family known for its RNA-binding and RNase activities, was up-regulated under osmotic stress, such as high salt and drought. When overexpressed in Arabidopsis, AtC3H3 improved tolerance to salt stress, but not drought stress. The expression of well-known abscisic acid (ABA)-dependent salt stress-responsive genes, namely Responsive to Desiccation 29B (RD29B), RD22, and Responsive to ABA 18 (RAB18), and representative ABA-independent salt stress-responsive genes, namely Dehydration-Responsive Element Binding protein 2A (DREB2A) and DREB2B, was significantly higher in AtC3H3-overexpressing transgenic plants (AtC3H3 OXs) than in wild-type plants (WT) under NaCl treatment, indicating its significance in both ABA-dependent and -independent signal transduction pathways. mRNA-sequencing (mRNA-Seq) analysis using NaCl-treated WT and AtC3H3 OXs revealed no potential target mRNAs for the RNase function of AtC3H3, suggesting that the potential targets of AtC3H3 might be noncoding RNAs and not mRNAs. Through this study, we conclusively demonstrated that AtC3H3 plays a crucial role in salt stress tolerance by influencing the expression of salt stress-responsive genes. These findings offer new insights into plant stress response mechanisms and suggest potential strategies for improving crop resilience to salinity stress.

Grain Lysine enrichment and improved stress tolerance in rice through protein engineering.

Amino acids are a major source of nourishment for people living in regions where rice is a staple food. However, rice grain is deficient in essential amino acids, such as lysine. The activity of dihydrodipicolinate synthase (DHDPS) enzyme is crucial for lysine production in higher plants, but it is highly regulated through a feedback inhibition by its end product lysine, leading to its limited activity in the grain and resulting in low lysine accumulation. We identified lysine binding sites in the DHDPS enzyme and introduced key mutations to make it lysine feedback insensitive. Using in vivo analysis and functional complementation assays, we confirmed that protein engineering of the DHDPS renders it insensitive to lysine. Expression of mutated DHDPS resulted in 29 % higher lysine and 15 % higher protein accumulation in rice grains than the wild type. Importantly, the lysine content in transgenic grains was maintained in cooked rice. Further, the transgenic plants exhibited enhanced stress tolerance along with better antioxidant levels, improved photosynthesis, and higher grain yield compared to wild type plants. We have shown for the first time in rice that protein engineering of DHDPS can lead to accumulation of lysine in grains and impart abiotic stress tolerance. This approach could improve health in regions with nutrient deficiencies and environmental stressors that challenge food production and human health.

Members of WRKY Group III Transcription Factors Are Important in Mite Infestation in Strawberry (Fragaria × ananassa Duch.)

Strawberry is frequently attacked by mites, which directly affects the yield and quality of this fruit species. The WRKY Group III transcription factors (TFs) play an important role in plant tolerance to biotic sources of stress, such as pathogens and insect pests. In this study, six Group III WRKY TFs (FaWRKY25, FaWRKY31, FaWRKY32, FaWRKY43, FaWRKY44, and FaWRKY45) were identified in strawberry. A phylogenetic analysis showed that the six WRKY III TFs were divided into two clades and all had a conserved WRKYGQK domain and the C-X7-C-X23-H-T-C zinc finger motif. An interaction network analysis revealed that FaWRKY44 was co-expressing with FaWRKY25 and FaWRKY45. The expression patterns showed that the WRKY Group III genes responded to plant hormones and mite infestation in strawberry. To further verify the role of FaWRKY25 in plant resistance to mites, we cloned the FaWRKY25 gene and overexpressed it in transgenic plants. An in vivo subcellular localization analysis indicated that the FaWRKY25 protein was localized in the nucleus. Fewer mites were also detected on the wild-type plants than on FaWRKY25-overexpressing transgenic plants, suggesting that FaWRKY25 negatively regulates the resistance of strawberry to mites. The present study advances our understanding on a potential target that mites use to manipulate host plant defenses.

OsKANADI1 and OsYABBY5 regulate rice plant height by targeting GIBERELLIN 2-OXIDASE6.

Plant height is an important agronomic characteristic of rice (Oryza sativa L.). Map-based cloning analyses of a natural semi-dwarf rice mutant with inwardly curled leaves found in the field revealed that the defects were due to a mutation of a SHAQKYF-class MYB family transcription factor, OsKANADI1 (OsKAN1). OsKAN1 directly bound to the OsYABBY5 (OsYAB5) promoter to repress its expression and interacted with OsYAB5 to form a functional OsKAN1-OsYAB5 complex. GIBERELLIN 2-OXIDASE6 (OsGA2ox6), encoding an enzyme in the gibberellin (GA) catabolic pathway, was activated by OsYAB5. Furthermore, the OsKAN1-OsYAB5 complex suppressed the inhibitory effect of OsKAN1 toward OsYAB5 and inhibited OsYAB5-induced OsGA2ox6 expression. The proOsKAN1:OsYAB5 transgenic plants were taller than wild-type plants, whereas oskan1 proOsKAN1:OsYAB5 plants exhibited a severe dwarf phenotype due to the absence of the OsKAN1-OsYAB5 complex. The OsKAN1-OsYAB5 complex modulated OsGA2ox6 expression, thereby regulating the levels of bioactive gibberellins and, consequently, plant height. This study elucidated the mechanism underlying the effect of the OsKAN1-OsYAB5-OsGA2ox6 regulatory pathway on plant height at different positions in rice stems and provided insights on stem development and candidate genes for the aerial architecture improvement of crop plants.

Modulation of the Arabidopsis Starch Metabolic Network by the Cytosolic Acetyl-CoA Pathway in the Context of the Diurnal Illumination Cycle

The starch metabolic network was investigated in relation to other metabolic processes by examining a mutant with altered single-gene expression of ATP citrate lyase (ACL), an enzyme responsible for generating cytosolic acetyl-CoA pool from citrate. Previous research has shown that transgenic antisense plants with reduced ACL activity accumulate abnormally enlarged starch granules. In this study, we explored the underlying molecular mechanisms linking cytosolic acetyl-CoA generation and starch metabolism under short-day photoperiods. We performed transcriptome and quantification of starch accumulation in the leaves of wild-type and antisense seedlings with reduced ACL activity. The antisense-ACLA mutant accumulated more starch than the wild type under short-day conditions. Zymogram analyses were conducted to compare the activities of starch-metabolizing enzymes with transcriptomic changes in the seedling. Differential expression between wild-type and antisense-ACLA plants was detected in genes implicated in starch and acetyl-CoA metabolism, and cell wall metabolism. These analyses revealed a strong correlation between the transcript levels of genes responsible for starch synthesis and degradation, reflecting coordinated regulation at the transcriptomic level. Furthermore, our data provide novel insights into the regulatory links between cytosolic acetyl-CoA metabolism and starch metabolic pathways.

Transcription factor PdMYB118 in poplar regulates lignin deposition and xylem differentiation in addition to anthocyanin synthesis through suppressing the expression of PagKNAT2/6b gene

R2R3-MYB transcription factors function as the master regulators of the phenylpropanoid pathway in which both lignin and anthocyanin are produced. In poplar, R2R3-MYB transcription factor PdMYB118 positively regulates anthocyanin production to change leaf color. However, the molecular mechanism by which it controls different branches of the phenylpropanoid pathway still remains poorly understood. Here, we reported that in addition to anthocyanin synthesis, lignin deposition and xylem differentiation were regulated by PdMYB118 through inhibiting PagKNAT2/6b gene expression. The transgenic poplar plants overexpressing PdMYB118 accumulated more xylem, lignin and anthocyanin. Transcriptome and reverse transcription quantitative PCR analyses revealed that the expression of PagKNAT2/6b gene which inhibited lignin deposition and xylem differentiation was significantly down-regulated in transgenic poplar plants. Subsequent dual-luciferase reporter and yeast-one-hybrid assays demonstrated that PdMYB118 directly inhibited the transcription of PagKNAT2/6b by binding to the AC elements in its promoter region. Further experiments with transgenic poplar plants overexpressing PagKNAT2/6b demonstrated that overexpression of PagKNAT2/6b in the PdMYB118 overexpression background rescued lignin accumulation and xylem width to the same level of wild type plants. The findings in this work suggest that PdMYB118 is involved in the lignin deposition and xylem differentiation via modulating the expression of PagKNAT2/6b, and the PdMYB118- PagKNAT2/6b model can be used for the genetic breeding of new woody tree with high lignin production.

TML1 AND TML2 SYNERGISTICALLY REGULATE NODULATION AND AFFECT ARBUSCULAR MYCORRHIZA IN MEDICAGO TRUNCATULA.

Two symbiotic processes, nodulation and arbuscular mycorrhiza, are primarily controlled by the plant's need for nitrogen (N) and phosphorus (P), respectively. Autoregulation of Nodulation (AON) and Autoregulation of Mycorrhization (AOM) both negatively regulate their respective processes and share multiple components - plants that make too many nodules usually have higher AM fungal root colonization. The protein TML (TOO MUCH LOVE) was shown to function in roots to maintain susceptibly to rhizobial infection under low N conditions and control nodule number through AON in Lotus japonicus . M. truncatula has two sequence homologs: Mt TML1 and Mt TML2. We report the generation of stable single and double mutants harboring multiple allelic variations in MtTML1 and MtTML2 using CRISPR-Cas9 targeted mutagenesis and screening of a transposon mutagenesis library. Plants containing single mutations in Mt TML1 or Mt TML2 produced 2-3 times the nodules of wild-type plants whereas plants containing mutations in both genes displayed a synergistic effect, forming 20x more nodules compared to wild type plants. Examination of expression and heterozygote effects suggest genetic compensation may play a role in the observed synergy. Plants with mutations in both TMLs only showed mild increases in AM fungal root colonization at later timepoints in our experiments, suggesting these genes may also play a minor role in AM symbiosis regulation. The mutants created will be useful tools to dissect the mechanism of synergistic action of Mt TML1 and Mt TML2 in M. truncatula symbiosis with beneficial microbes.

Exploring the Relationship Between Gene Expression and Low-Frequency Somatic Mutations in Arabidopsis with Duplex Sequencing.

Intragenomic mutation rates can vary dramatically due to transcription-associated mutagenesis or transcription-coupled repair, which vary based on local epigenomic modifications that are nonuniformly distributed across genomes. One feature associated with decreased mutation is higher expression level, which depends on environmental cues. To understand the magnitude of expression-dependent mutation rate variation, we perturbed expression through a heat treatment in Arabidopsis thaliana. We quantified gene expression to identify differentially expressed genes, which we then targeted for mutation detection using duplex sequencing. This approach provided a highly accurate measurement of the frequency of rare somatic mutations in vegetative plant tissues, which has been a recent source of uncertainty. Somatic mutations in plants may be useful for understanding drivers of DNA damage and repair in the germline since plants experience late germline segregation and both somatic and germline cells share common repair machinery. We included mutant lines lacking mismatch repair (MMR) and base excision repair (BER) capabilities to understand how repair mechanisms may drive biased mutation accumulation. We found wild-type (WT) and BER mutant mutation frequencies to be very low (mean variant frequency 1.8 × 10-8 and 2.6 × 10-8, respectively), while MMR mutant frequencies were significantly elevated (1.13 × 10-6). Interestingly, in the MMR mutant lines, there was no difference in the somatic mutation frequencies between temperature treatments or between highly versus lowly expressed genes. The extremely low somatic variant frequencies in WT plants indicate that larger datasets will be needed to address fundamental evolutionary questions about whether environmental change leads to gene-specific changes in mutation rate.

Elucidating the downstream pathways triggered by H2S signaling in Arabidopsis thaliana under drought stress via transcriptome analysis

ABSTRACT Hydrogen sulfide (H2S) is a crucial signaling molecule in plants. Recent studies have shown that H2S plays an equally important role as nitric oxide (NO) and hydrogen peroxide (H2O2) in plant signaling. Previous studies have demonstrated the involvement of H2S in regulating drought and other stressful environmental conditions, but the exact downstream molecular mechanisms activated by the H2S signaling molecule remain unclear. In this study, we conducted a comprehensive genome-wide transcriptomic analysis of both wild type (WT) and double mutant (lcd/des1). Arabidopsis thaliana plants were exposed to 40% polyethylene glycol (PEG) to induce drought stress and 20 µM sodium hydrosulfide (NaHS). The resulting transcriptome data were analyzed for differentially significant genes and their statistical enrichments in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The results indicated significant upregulation of genes related to photosynthesis, carbon fixation, plant secondary metabolite biosynthesis, inositol and phosphatidylinositol signaling pathways, and stress-responsive pathways in mutant plants under drought stress. Mutant plants with impaired H2S signaling mechanisms displayed greater susceptibility to drought stress compared to wild-type plants. In summary, all findings highlight the pivotal role of H2S signaling in stimulating other drought-responsive signaling pathways.

SlSTOP1-regulated SlHAK5 expression confers Al tolerance in tomato by facilitating citrate secretion from roots.

SENSITIVE TO PROTON RHIZOTOXICITY 1 (STOP1) is a core transcription factor that regulates the expression of aluminum (Al) resistance genes to manage Al toxicity in plants. However, the genome-wide roles of SlSTOP1 in the Al stress response of tomato (Solanum lycopersicum) remain largely unknown. Here, we report that SlSTOP1 is crucial for Al tolerance in tomato, as loss-of-function mutants of SlSTOP1 displayed hypersensitivity to Al stress. Aluminum stress had no effect on SlSTOP1 mRNA expression, but promoted accumulation of SlSTOP1 protein in the nucleus. Through integrated DNA affinity purification sequencing and RNA sequencing analysis, we identified 39 SlSTOP1-targeted Al-responsive genes, some of which are homologous to known Al resistance genes in other plant species, suggesting that these SlSTOP1-targeted genes play essential roles in Al resistance in tomato. Furthermore, using peak enrichment analysis of SlSTOP1-targeted sequences, we identified a cis-acting element bound by SlSTOP1 and validated this finding via dual-luciferase reporter and electrophoretic mobility shift assay (EMSA). Additionally, we demonstrated SlHAK5 is one of direct targets of SlSTOP1 and functionally characterized it in terms of Al stress tolerance. Compared with wild-type plants, Slhak5 mutants developed by CRISPR/Cas9 technology presented increased sensitivity to Al stress, which was associated with reduced citrate secretion from the roots. Together, our findings demonstrate that SlSTOP1 directly interacts with cis-acting elements located in the promoters of target genes involved in diverse pathways contributing to Al resistance in tomato.

Comprehensive analysis of ankyrin repeat gene family revealed SbANK56 confers drought tolerance in sorghum

Ankyrin repeat (ANK) proteins are crucial for cell growth, development, and response to hormones and environmental stress. However, there has been little research done to clarify the roles of ANK proteins in sorghum. In this study, 142 ANK genes of sorghum were identified and classified into 12 subfamilies according to the conserved domains. The cis-elements analysis revealed a substantial presence of stress-responsive elements within the promoter region of SbANK genes. After treated with drought, salt, and abscisic acid, SbANK56 showed the highest expression levels among family members by using quantitative real-time PCR (qRT-PCR) analysis. The survival rate was significantly improved by the overexpression of SbANK56 compared to wild type (WT) under drought conditions. SbANK56 overexpressing plants displayed lower malondialdehyde and higher proline contents compared to WT plants under drought conditions. Additionally, the expression levels of drought-associated genes were significantly increased in SbANK56 transgenic plants. Importantly, the analysis of natural variation in SbANK56 revealed a significant positive correlation between SbANK56Hap4 and both its differential expression and drought stress tolerance. Taken together, our results provide some evidence for improving drought tolerance in sorghum through breeding initiatives while also advancing our knowledge of the evolutionary trends and functional mechanisms underlying ANK genes.

The transcription factor TaNF-YB4 overexpression in wheat increases plant vigor and yield

Ensuring food security is a priority in developing countries. This study aimed to improve wheat yield by overexpressing the TaNF-YB4 transcription factor, which is involved in carbon assimilation and stress tolerance. An expression cassette for TaNF-YB4 was developed in a modified wheat transformation vector (pSB219) and examined through transient expression in Nicotiana tabacum, followed by Agrobacterium-mediated transformation of wheat variety FSD-2008. T0 transgenic plants were propagated to obtain T3 generation PCR-positive plants. Transgene expression was assessed in PCR-verified T2 plants using RT-PCR and qRT-PCR at six weeks post-germination. qRT-PCR analysis using the ΔΔCT method indicated higher TaNF-YB4 expression in transgenic lines than in the wild-type control plants. Improved agronomic and phenotypic traits were observed with a 6-36% increase in 1000-grain weight in the selected transgenic lines. Root architecture assessments demonstrated enhanced root length, surface area, and projected area in transgenic lines compared with wild-type plants. Additionally, notable variances in total chlorophyll, protein, and sugar content levels were observed between the transgenic lines and control plants, demonstrating statistical significance with a p-value ≤ 0.05. This study indicates that low-level constitutive expression of TaNF-YB4 can enhance wheat yield, presenting a viable strategy for improving wheat productivity.

Capsicum annuum NAC4 (CaNAC4) Is a Transcription Factor with Roles in Biotic and Abiotic Stresses.

Transcription factors (TFs) regulate gene expression by binding to DNA. The NAC gene family in plants consists of crucial TFs that influence plant development and stress responses. The whole genome of Capsicum annuum shows over 100 NAC genes (CaNAC). Functional characteristics of the most CaNAC TFs are unknown. In this study, we identified CaNAC4, a novel NAC TF in C. annuum. CaNAC4 expression increased after inoculation with the pathogens, Xanthomonas axonopodis pv. vesicatoria race 3 and X. axonopodis pv. glycines 8ra, and following treatment with the plant hormones, salicylic acid and abscisic acid. We investigated the functional characteristics of the CaNAC4 gene and its roles in salt tolerance and anti-pathogen defense in transgenic Nicotiana benthamiana. For salt stress analysis, the leaf discs of wild-type and CaNAC4-transgenic N. benthamiana plants were exposed to different concentrations of sodium chloride. Chlorophyll loss was more severe in salt stress-treated wild-type plants than in CaNAC4-transgenic plants. To analyze the role of CaNAC4 in anti-pathogen defense, a spore suspension of Botrytis cinerea was used to infect the leaves. The disease caused by B. cinerea gradually increased in severity, and the symptoms were clearer in the CaNAC4-transgenic lines. We also investigated hypersensitive response (HR) in CaNAC4-transgenic plants. The results showed a stronger HR in wild-type plants after infiltration with the apoptosis regulator, BAX. In conclusion, our results suggest that CaNAC4 may enhance salt tolerance and act as a negative regulator of biotic stress in plants.

Arabidopsis GDH1 and GDH2 genes double knock-out results in a stay-green phenotype during dark-induced senescence.

Yellowing is the first visually observable sign of plant leaf senescence. We found that Arabidopsis double knockout mutant gdh1gdh2 for genes of NAD(H)-dependent glutamate dehydrogenase retains green color of the leaves (stay-green phenotype) during a dark-induced senescence, in contrast to wild-type plants, whose leaves turn yellow. When the gdh1gdh2 plants are exposed to the dark more than four days, they demonstrate slower chlorophyll degradation than in the wild-type plants under the same conditions, as well as dysregulation of chlorophyll breakdown genes encoding chlorophyll b reductase, Mg-dechelatase, pheophytinase and pheophorbide a oxygenase. The slowed degradation of chlorophyll b in gdh1gdh2 plants significantly alters the chlorophyll a/b ratio. Ion leakage in the mutant plants increases significantly from four to eight days in the darkness, correlating with their premature death during this period. The discovered facts suggest a functional connection between activity of NAD(H)-dependent glutamate dehydrogenase and dark-induced senescence progress in Arabidopsis.

The GhEB1C gene mediates resistance of cotton to Verticillium wilt.

The GhEB1C gene of the EB1 protein family functions as microtubule end-binding protein and may be involved in the regulation of microtubule-related pathways to enhance resistance to Verticillium wilt. The expression of GhEB1C is induced by SA, also contributing to Verticillium wilt resistance. Cotton, as a crucial cash and oil crop, faces a significant threat from Verticillium wilt, a soil-borne disease induced by Verticillium dahliae, severely impacting cotton growth and development. Investigating genes associated with resistance to Verticillium wilt is paramount. We identified and performed a phylogenetic analysis on members of the EB1 family associated with Verticillium wilt in this work. GhEB1C was discovered by transcriptome screening and was studied for its function in cotton defense against V. dahliae. The RT-qPCR analysis revealed significant expression of the GhEB1C gene in cotton leaves. Subsequent localization analysis using transient expression demonstrated cytoplasmic localization of GhEB1C. VIGS experiments indicated that silencing of the GhEB1C gene significantly increased susceptibility of cotton to V. dahliae. Comparative RNA-seq analysis showed that GhEB1C silenced plants exhibited altered microtubule-associated protein pathways and flavonogen-associated pathways, suggesting a role for GhEB1C in defense mechanisms. Overexpression of tobacco resulted in enhanced resistance to V. dahliae as compared to wild-type plants. Furthermore, our investigation into the relationship between the GhEB1C gene and plant disease resistance hormones salicylic axid (SA) and jasmonic acid (JA) revealed the involvement of GhEB1C in the regulation of the SA pathway. In conclusion, our findings demonstrate that GhEB1C plays a crucial role in conferring immunity to cotton against Verticillium wilt, providing valuable insights for further research on plant adaptability to pathogen invasion.

Genome-wide identification and expression analysis of the SWEET gene family in sweet sorghum (Sorghum dochna) and the role of SdSWEET01 in sugar transport

The SWEET sugar transporter plays a fundamental role in plant growth and development. In this study, 18 SWEET genes were identified from sweet sorghum (Sorghum dochna), encoding proteins with 231–336 amino acids, molecular weights from 25.15 to 35.69 kDa, and isoelectric points ranging between 6.41 and 9.69. Phylogenetic analysis categorized these proteins into four distinct subgroups. Examination of spatial expression patterns demonstrated that SdSWEET genes were expressed in a tissue-specific manner. Furthermore, their involvement in responses to various abiotic stresses, including cold, heat, drought, and salinity was observed. A yeast complementation assay verified that SdSWEET01, located on the plasma membrane, selectively transported glucose, sucrose, and galactose, while excluding fructose. Transgenic Arabidopsis expressing SdSWEET01 exhibited enhanced sugar absorption compared to wild-type plants, resulting in increased sensitivity and growth inhibition under high-sugar conditions. The study provides a detailed functional characterization of SdSWEET genes and emphasizes the critical role of SdSWEET01 in regulating sugar transport.

Functional characterization of Arabidopsis hydroxynitrile lyase in response to abiotic stress and the regulation of flowering time.

Hydroxynitrile lyases (HNLs) are a class of hydrolytic enzymes from a wide range of sources, which play crucial roles in the catalysis of the reversible conversion of carbonyl compounds derived from cyanide and free cyanide in cyanogenic plant species. HNLs were also discovered in non-cyanogenic plants, such as Arabidopsis thaliana, and their roles remain unclear even during plant growth and reproduction. The pattern of expression of the HNL in A. thaliana (AtHNL) in different tissues, as well as under abiotic stresses and hormone treatments, was examined by real-time quantitative reverse transcription PCR (qRT-PCR) and an AtHNL promoter-driven histochemical β-glucuronidase (GUS) assay. AtHNL is highly expressed in flowers and siliques, and the expression of AtHNL was dramatically affected by abiotic stresses and hormone treatments. The overexpression of AtHNL resulted in transgenic A. thaliana seedlings that were more tolerance to mannitol and salinity. Moreover, transgenic lines of A. thaliana that overexpressed this gene were less sensitive to abscisic acid (ABA). Altered expression of ABA/stress responsive genes was also observed in hnl mutant and AtHNL-overexpressing plants, suggesting AtHNL may play functional roles on regulating Arabidopsis resistance to ABA and abiotic stresses by affecting ABA/stress responsive gene expression. In addition, the overexpression of AtHNL resulted in earlier flowering, whereas the AtHNL mutant flowered later than the wild type (WT) plants. The expression of the floral stimulators CONSTANS (CO), SUPPRESSOR OF OVER EXPRESSION OF CO 1 (SOC1) and FLOWERING LOCUS T (FT) was upregulated in plants that overexpressed AtHNL when compared with the WT plants. In contrast, expression of the floral repressor FLOWERING LOCUS C (FLC) was upregulated in AtHNL mutants and downregulated in plants that overexpressed AtHNL compared to the WT plants. This study revealed that AtHNL can be induced under abiotic stresses and ABA treatment, and genetic analysis showed that AtHNL could also act as a positive regulator of abiotic stress and ABA tolerance, as well as flowering time.

Regulation of photosystems II and I depending on N partitioning to Rubisco in rice leaves: a study using Rubisco-antisense transgenic plants.

We have previously suggested that in rice (Oryza sativa L.) leaves of different ages and N nutrition statuses, photosystems II and I (PSII and PSI, respectively) are regulated depending on N partitioning to Rubisco, which can determine the magnitude of unutilized light energy. The robustness of this mechanism was tested using Rubisco-antisense transgenic rice plants, in which reduced N partitioning to Rubisco markedly increases unutilized light energy. In wild-type plants, N partitioning to Rubisco tended to be smaller in the leaves at lower positions owing to leaf senescence. In the transgenic plants, N partitioning to Rubisco was generally smaller than in the wild-type plants and was relatively constant among leaf positions. The quantum efficiency of PSII [Y(II)] and quantum yield of non-photochemical quenching [Y(NPQ)] correlated positively and negatively, respectively, with N partitioning to Rubisco irrespective of leaf position or genotype. The oxidation levels of the reaction center chlorophyll of PSI (P700) [Y(ND)] negatively correlated with N partitioning to Rubisco. However, in mature and early senescent leaves of the transgenic plants, Y(ND) was markedly lower than expected from N partitioning to Rubisco. These results suggest that in the transgenic plants, the regulation depending on N partitioning to Rubisco is robust for PSII but fails for PSI in mature and early senescing leaves. In these leaves, the magnitudes of P700 oxidation were found to be less than expected from the Y(II) and Y(NPQ) values. The mechanistic reasons and physiological implications of these phenomena are discussed.

Functional analysis of LdPMAT1, a positive regulator that promotes drought tolerance in Lilium distic hum nakai

Abiotic stress has become a major challenge for lily crop growth, development, yield and quality under irregular climate and precipitation trends. Molecular breeding is one of the most effective methods for developing highly stress-resistant cultivars. Previous studies revealed that miR396b and its target gene LdPMAT1 are involved in drought resistance, and in lily silencing miR396b significantly enhances drought resistance and LdPMAT1 expression. However, the function of LdPMAT1 in the lily response to abiotic stress is unclear. In this study, GUS activity tests and dual luciferase reporter gene assays (LUC) confirmed that LdPMAT1 is a novel miR396b target. The LdPMAT1 transcription level was greater in the roots and leaves and increased significantly within 7 days of drought stress. Stable LdPMAT1 overexpression significantly reduced leaf wilting and enhanced cell membrane stability by affecting osmoregulatory substance accumulation, improving plant drought resistance. Additionally, LdPMAT1 overexpression significantly increased the expression levels of LdCAT3 and SOD2, which encode superoxide dismutase (SOD) and catalase (CAT), respectively, as well as SOD and CAT enzyme activities. In contrast, reactive oxygen species (ROS) accumulated at high levels in the leaves and roots of the silenced plants, and the degree of damage was significantly greater than that in the wild type plants. Under conditions of 1% NaCl and 42 °C, plants overexpressing LdPMAT1 exhibited similar characteristic s of high stress resistance, with less wilting and lower ROS accumulation. This study provides a theoretical basis for cultivating new highly resistant lily cultivars and accelerating germplasm innovation to produce high-quality lilies worldwide.