WT Plants Research Articles

Vegetative and Fecundity Fitness Benefit Found in a Glyphosate-Resistant Eleusine indica Population Caused by 5-Enolpyruvylshikimate-3-Phosphate Synthase Overexpression.

Fitness is an important trait in weed species that have developed herbicide resistance, including resistance to the popular herbicide glyphosate. Fitness cost is commonly found in weeds with glyphosate resistance, which is caused by target-site mutations. In this study, the vegetative and fecundity fitness traits in a glyphosate-resistant (GR) Eleusine indica population caused by 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) overexpression were investigated under glyphosate-free conditions. The results showed that the resistance index of the population resistant (R) to glyphosate compared with that of the population susceptible (WT) to it was approximately 4.0. Furthermore, EPSPS expression level in the R plants was 20.1–82.7 times higher than that in the WT plants. The dry weight of the R population was significantly higher than that of the WT population at the later growth stage after planting; a similar trend was observed for leaf area. In addition, seed production in the R population was 1.4 times higher than that in the WT population. The R and WT populations showed similar maximum germination rates and T50 values. UPLC-MS/MS was performed for the metabolic extracts prepared from the leaves of R and WT populations to address changes in the metabolome. A total of 121 differential metabolites were identified between R and WT individuals. The levels of 6-hydroxy-1H-indole-3-acetamide and indole acetaldehyde, which are associated with auxin synthesis, were significantly higher in plants of the R population than in those of the WT population. However, some secondary metabolite levels were slightly lower in the R population than in the WT population. To conclude, in this study, vegetative and fecundity fitness benefits were found in the GR E. indica population. The results of metabolome analysis indicate that the increase in 6-hydroxy-1H-indole-3-acetamide and indole acetaldehyde levels may be the result of fitness benefit. Further studies should be conducted to confirm the functions of these metabolites.

The bHLH transcription factor AhbHLH112 improves the drought tolerance of peanut

BackgroundBasic helix-loop-helix (bHLH) transcription factors (TFs) are one of the largest gene families in plants. They regulate gene expression through interactions with specific motifs in target genes. bHLH TFs are not only universally involved in plant growth but also play an important role in plant responses to abiotic stress. However, most members of this family have not been functionally characterized.ResultsHere, we characterized the function of a bHLH TF in the peanut, AhHLH112, in response to drought stress. AhHLH112 is localized in the nucleus and it was induced by drought stress. The overexpression of this gene improves the drought tolerance of transgenic plants both in seedling and adult stages. Compared to wild-type plants, the transgenic plants accumulated less reactive oxygen species (ROS), accompanied by increased activity and transcript levels of antioxidant enzymes (superoxide dismutase, peroxidase and catalase). In addition, the WT plants demonstrated higher MDA concentration levels and higher water loss rate than the transgenic plants under drought treatment. The Yeast one-hybrid result also demonstrates that AhbHLH112 directly and specifically binds to and activates the promoter of the peroxidase (POD) gene. Besides, overexpression of AhHLH112 improved ABA level under drought condition, and elevated the expression of genes associated with ABA biosynthesis and ABA responding, including AtNCED3 and AtRD29A.ConclusionsDrawing on the results of our experiments, we propose that, by improving ROS-scavenging ability, at least in part through the regulation of POD -mediated H2O2 homeostasis, and possibly participates in ABA-dependent stress-responding pathway, AhbHLH112 acts as a positive factor in drought stress tolerance.

Aldehyde dehydrogenase 3I1 gene is recruited in conferring multiple abiotic stress tolerance in plants.

Plant growth and productivity is restricted by a multitude of abiotic stresses. These stresses negatively affect physiological and metabolic pathways, leading to the production of many harmful substances like ROS, lipid peroxides and aldehydes. This study was conducted to investigate the role of Arabidopsis ALDH3I1 gene in multiple abiotic stress tolerance. Transgenic tobacco plants were generated that overexpress the ALDH3I1 gene driven by the CaMV35S promoter and evaluated under different abiotic stresses, namely salt, drought, cold and oxidative stress. Tolerance to stress was evaluated based on responses of various growth and physiological traits under stress condition. Transgenic plants displayed elevated ALDH3I1 transcript levels compared to WT plants. The constitutive ectopic expression of ALDH3I1 conferred increased tolerance to salt, drought, cold and oxidative stresses in transgenic plants, along with improved plant growth. Transgenic plants overexpressing ALDH3I1 had higher chlorophyll content, photosynthesis rate and proline, and less accumulation of ROS and malondialdehyde compared to the WT, which contributed to stress tolerance in transgenic plants. Our results further revealed that ALDH3I1 had a positive effect on CO2 assimilation rate in plants under abiotic stress conditions. Overall, this study revealed that ALDH3I1 positively regulates abiotic stress tolerance in plants, and has future implications in producing transgenic cereal and horticultural plants tolerant to abiotic stresses.

A Cold-Shock Protein from the South Pole-Dwelling Soil Bacterium Arthrobacter sp. Confers Cold Tolerance to Rice.

Low temperature is a critical environmental factor restricting the physiology of organisms across kingdoms. In prokaryotes, cold shock induces the expression of various genes and proteins involved in cellular processes. Here, a cold-shock protein (ArCspA) from the South Pole-dwelling soil bacterium Arthrobacter sp. A2-5 was introduced into rice, a monocot model plant species. Four-week-old 35S:ArCspA transgenic rice plants grown in a cold chamber at 4 °C survived for 6 days. Cold stress significantly decreased the chlorophyll content in WT plants after 4 days compared with that in 35S:ArCspA transgenic plants. RNA-seq analysis was performed on WT and 35S:ArCspA transgenic rice with/without cold stress. GO terms such as “response to stress (GO:0006950)”, “response to cold (GO:0009409)”, and “response to heat (GO:0009408)” were significantly enriched among the upregulated genes in the 35S:ArCspA transgenic rice under normal conditions, even without cold-stress treatment. The expression of five cold stress-related genes, Rab16B (Os11g0454200), Rab21 (Os11g0454300), LEA22 (Os01g0702500), ABI5 (Os01 g0859300), and MAPK5 (Os03g0285800), was significantly upregulated in the transgenic rice compared with the WT rice. These results indicate that the ArCspA gene might be involved in the induction of cold-responsive genes and provide cold tolerance.

MdVQ37 overexpression reduces basal thermotolerance in transgenic apple by affecting transcription factor activity and salicylic acid homeostasis

High temperature (HT) is one of the most important environmental stress factors and seriously threatens plant growth, development, and production. VQ motif-containing proteins are transcriptional regulators that have been reported to regulate plant growth and developmental processes, including responses to biotic and abiotic stresses. However, the relationships between VQ motif-containing proteins and HT stress have not been studied in depth in plants. In this study, transgenic apple (Malus domestica) plants overexpressing the apple VQ motif-containing protein-coding gene (MdVQ37) were exposed to HT stress, and the transgenic lines exhibited a heat-sensitive phenotype. In addition, physiological and biochemical studies revealed that, compared with WT plants, transgenic lines had lower enzymatic activity and photosynthetic capacity and lower amounts of nonenzymatic antioxidant system metabolites under HT stress. Transcriptome analysis revealed 1379 genes whose expression differed between the transgenic lines and WT plants. GO and KEGG pathway analyses showed that transcription factor activity and plant hormone signaling pathways were differentially influenced and enriched in the transgenic lines. Salicylic acid (SA) content analysis indicated that overexpression of MdVQ37 reduced the content of endogenous SA by regulating the expression of SA catabolism-related genes, which ultimately resulted in disruption of the SA-dependent signaling pathway under HT stress. The application of SA slightly increased the survival rate of the transgenic lines under HT stress. Taken together, our results indicate that apple MdVQ37 has a regulatory function in basal thermotolerance by modulating the activity of transcription factors and SA homeostasis. Overall, this study provides novel insights that improve our understanding of the various functions of VQ motif-containing proteins.

Cryptochrome 1a of tomato modulates nutritional deficiency responses

The blue light photoreceptor cryptochromes are involved in nutritional response pathways in plants. Evidence shows that cryptochromes mediate the control of genes related to nutrients accumulation in plants. However, nothing is known about the role of cryptochrome 1a (cry1a) in tomato (Solanum lycopersicum L.) nutritional stress responses. Thus, this study aims to evaluate the importance of cry1a photoreceptors in plant responses to nutrient deficiency. To this end, we proposed the use of a tomato mutant carrying a lesion in a gene encoding the blue light photoreceptor cry1a (cry1a) and its wild type (WT; cv. Moneymaker). Both genotypes (20-day-old plants) were grown under treatments consisting of a complete nutrient solution and the individual omission of each nutrient (–N, –P, –K, –Ca, or –S) from a balanced nutrient solution. Subsequently, we measured the growth, pigmentation, oxidative stress, and nutrient accumulation, as well as uptake efficiency, transport efficiency, and use efficiency of nutrients in all treated plants. The cry1a plants had greater shoot extension growth than WT plants in all tested growth conditions, although the shoot biomass accumulation with cry1a was greater than in the WT only under Ca omission. Except in the –N and –Ca conditions, the cry1a plants accumulated less root biomass than WT plants. In addition, leaf pigments (chlorophyll a+b and carotenoids) were reduced in the mutant plants compared to WT plants grown under CS, –P, and –S conditions. Thus, considering that WT plants have the full functions of cry1a photoreceptor, here we showed that cry1a plays an important role in the nutrient deficiency responses in tomato, particularly, mediating growth and development of stressed plants through changes in plant growth and oxidative stress, as well as the nutrient contents and efficiencies of transport use.

Identification of BR biosynthesis genes in cotton reveals that GhCPD-3 restores BR biosynthesis and mediates plant growth and development.

Brassinosteroid (BR) synthesis genes in different cotton species was comprehensively identified, and the participation of GhCPD-3 in the BR synthesis signaling pathway for regulating plant development was verified. Brassinosteroid is a natural steroidal phytohormone that plays fundamental roles in plant growth and development. In cotton, detailed characterization and functional validation of BR biosynthesis genes remain rare. Here, 16, 8 and 9 BR biosynthesis genes were identified in Gossypium hirsutum, Gossypium raimondii and Gossypium arboreum, respectively, and their phylogenetic relationships, gene structures, conserved motifs of the encoded proteins, chromosomal locations were determined and a synteny analysis was performed. Gossypium hirsutum and Arabidopsis BR biosynthesis genes closely clustered in the phylogenetic tree and fragment duplication was likely the primary cause promoting gene family expansion in G. hirsutum. Gene Ontology (GO) and KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis showed their relevance as BR biosynthesis genes. GhCPD-3 was highly expressed in roots and stems and the loci of single nucleotide polymorphisms (SNPs) were significantly associated with these traits.Ectopic overexpression of GhCPD-3 in the cpd91 Arabidopsis mutant rescued the mutant phenotype by increasing plant height and leaf size in comparison to those of cpd91 and WT plants. Moreover, overexpressed GhCPD-3 in cpd91 mutants showed greater hypocotyl and root lengths than those of cpd91 and WT plants under light and dark conditions, respectively, indicating that BR actively promotes hypocotyl and root growth. Similar to CPD (CONSTITUTIVE PHOTOMORPHOGENIC DWARF), GhCPD-3 restores BR biosynthesis thereby mediating plant growth and development.

Enhancing plant growth and biomass production by overexpression of GA20ox gene under control of a root preferential promoter.

Overexpression of GA20 oxidase gene has been a recent trend for improving plant growth and biomass. Constitutive expression of GA20ox has successfully improved plant growth and biomass in several plant species. However, the constitutive expression of this gene causes side-effects, such as reduced leaf size and stem diameter, etc. To avoid these effects, we identified and employed different tissue-specific promoters for GA20ox overexpression. In this study, we examined the utility of At1g promoter to drive the expression of GUS (β-glucuronidase) reporter and AtGA20ox genes in tobacco and Melia azedarach. Histochemical GUS assays and quantitative real-time-PCR results in tobacco showed that At1g was a root-preferential promoter whose expression was particularly strong in root tips. The ectopic expression of AtGA20ox gene under the control of At1g promoter showed improved plant growth and biomass of both tobacco and M. azedarach transgenic plants. Stem length as well as stem and root fresh weight increased by up to 1.5-3 folds in transgenic tobacco and 2 folds in transgenic M. azedarach. Both tobacco and M. azedarach transgenic plants showed increases in root xylem width with xylem to phloem ratio over 150-200% as compared to WT plants. Importantly, no significant difference in leaf shape and size was observed between At1g::AtGA20ox transgenic and WT plants. These results demonstrate the great utility of At1g promoter, when driving AtGA20ox gene, for growth and biomass improvements in woody plants and potentially some other plant species.

Overexpression of nicotinamidase 3 (NIC3) gene and the exogenous application of nicotinic acid (NA) enhance drought tolerance and increase biomass in Arabidopsis.

Overexpressing Nicotinamidase 3 gene, and the exogenous application of its metabolite nicotinic acid (NA), enhance drought stress tolerance and increase biomass in Arabidopsis thaliana. With progressive global climatic changes, plant productivity is threatened severely by drought stress. Deciphering the molecular mechanisms regarding genes responsible for balancing plant growth and stress amelioration could imply multiple possibilities for future sustainable goals. Nicotinamide adenine dinucleotide (NAD) biosynthesis and recycling/ distribution is a crucial feature for plant growth. The current study focuses on the functional characterization ofnicotinamidase 3(NIC3) gene, which is involved in the biochemical conversion of nicotinamide (NAM) to nicotinic acid (NA) in the salvage pathway of NAD biosynthesis. Our data show that overexpression of NIC3geneenhances drought stress tolerance and increases plant growth. NIC3-OX plants accumulated more NA as compared to WT plants. Moreover, the upregulation of several genes related to plant growth/stress tolerance indicates that regulating the NAD salvage pathway could significantly enhance plant growth and drought stress tolerance. The exogenous application of nicotinic acid (NA) showed a similar phenotype as the effect of overexpressing NIC3gene. In short, we contemplated the role of NIC3gene and NA application in drought stress tolerance and plant growth. Our results would be helpful in engineering plants with enhanced drought stress tolerance and increased growth potential.

A type 2 metallothionein (SbMT-2) gene cloned from Salicornia brachiata confers enhanced Zn stress-tolerance in transgenic tobacco by transporting Zn2+ and maintaining photosynthesis efficacy

Metallothioneins are cysteine-rich proteins, which play key roles in metal detoxification, intracellular ion homeostasis maintenance, and protection against intracellular oxidative damage. This study reports the characterization of SbMT-2 cloned from Salicornia brachiata concerning physiology, molecular, and photosynthesis efficiency. Overexpression of SbMT-2 conferred enhanced tolerance to Zn stress in transgenic tobacco supported by increased photosynthesis efficiency and crop quality compared to wild-type. The growth of transgenic and WT plants was comparable in control conditions; transgenic plants showed better growth than WT plants under stress (20 mM ZnSO4 for 30 days). After 30 days of stress, transgenic plants completed their life cycle with early maturation, whereas the WT plants did not and matured very late. About 35 pods with a total weight of 3.5 g per plant were measured in transgenic compared to WT (about 19 pods with total weight 2.5 g). Further, gas exchange and fluorescence measurements established that the SbMT-2 gene improved the photosynthetic efficiency of the transgenic line compared to WT plants during stress conditions. In addition, SbMT-2 might be involved in the selective translocation of Zn2+ under long-term stress condition. Microarray analysis showed that the expression of many Zn transporters, Zn-binding proteins, and Zn-associated proteins encoding genes was up-regulated 4–6 (log2) fold. However the expression of genes encoding other metal-binding proteins, metal metabolism-associated enzymes, and metal-inducible transcription factors were down-regulated. Furthermore, transcript expression analysis elucidated that overexpression of the SbMT-2 gene may regulate the expression pattern of metal transporter encoding genes under stress conditions. Thus, SbMT-2 is an important gene, which plays a positive role by detoxifying reactive oxygen species and maintaining photosynthesis efficiency under Zn stress conditions.

RNAi-mediated suppression of the abscisic acid catabolism gene OsABA8ox1 increases abscisic acid content and tolerance to saline–alkaline stress in rice (Oryza sativa L.)

Saline–alkaline (SA) stress is characterized by high salinity and high alkalinity (high pH), which severely inhibit plant growth and cause huge losses in crop yields worldwide. Here we show that a moderate elevation of endogenous abscisic acid (ABA) levels by RNAi-mediated suppression of OsABA8ox1 (OsABA8ox1-kd), a key ABA catabolic gene, significantly increased tolerance to SA stress in rice plants. We produced OsABA8ox1-kd lines in two different japonica cultivars, Dongdao 4 and Nipponbare. Compared with non-transgenic control plants (WT), the OsABA8ox1-kd seedlings accumulated 25.9%–55.7% higher levels of endogenous ABA and exhibited reduced plasmalemma injury, ROS accumulation and Na+/K+ ratio, and higher survival rates, under hydroponic alkaline conditions simulated by 10, 15, and 20 mmol L−1 of Na2CO3. In pot trials using SA field soils of different alkali levels (pH 7.59, 8.86, and 9.29), OsABA8ox1–kd plants showed markedly higher seedling survival rates and more vigorous plant growth, resulting in significantly higher yield components including panicle number (85.7%–128.6%), spikelets per panicle (36.9%–61.9%), branches (153.9%–236.7%), 1000–kernel weight (20.0%–28.6%), and percentage of filled spikelets (96.6%–1340.8%) at harvest time. Under severe SA soil conditions (pH = 9.29, EC = 834.4 μS cm−1), OsABA8ox1-kd lines showed an 194.5%–1090.8% increase in grain yield per plant relative to WT plants. These results suggest that suppression of OsABA8ox1 to increase endogenous ABA levels provides a new molecular approach for improving rice yield in SA paddies.

GmDREB6, a soybean transcription factor, notably affects the transcription of the NtP5CS and NtCLC genes in transgenic tobacco under salt stress conditions.

Soil is contaminated with salinity, which inhibits plant growth and development and reduces crop yields. The DREB (dehydration responsive element binding protein) gene responds to salt stresses through enhanced transcriptional expression and activation of genes involved in plant salinity resistance. In this study, we present the results of the analysis of the expression of the GmDREB6 transgene, a gene that encodes the soybean DREB6 transcription factor, regulating the transcription of the NtP5CS and NtCLC genes in transgenic tobacco under salt stress conditions. The transcription of GmDREB6, NtP5CS, and NtCLC in transgenic tobacco lines was confirmed by qRT-PCR. Under salt stress conditions, the GmDREB6 gene transcription levels in the transgenic tobacco lines L1 and L9 had increased from 2.40- to 3.22- fold compared with the condition without salinity treatment. Two transgenic lines, L1 and L9, had transcription levels of the P5CS gene that had increased from 1.24- to 3.60- fold compared with WT plants. For the NtCLC gene, under salt stress conditions, the transgenic lines had transcription levels that had increased by 3.65–4.54 (fold) compared with WT plants (P < 0.05). The L1-transgenic tobacco line showed simultaneous expression of both the GmDREB6 transgene and two intrinsic genes, the NtP5CS and NtCLC genes. This study demonstrated that expression of the GmDREB6 gene from soybean increases the transcription levels of the NtP5CS and NtCLC genes in transgenic tobacco plants under salt stress conditions. The analysis results have suggested that the GmDREB6 gene is a potential candidate for improving the salt tolerance of plants, opening up research and development opportunities for salt stress-tolerant crops to respond to climate change and the rise in sea levels.

Overexpression of sugarcane SoTUA gene enhances cold tolerance in transgenic sugarcane

AbstractAlpha (α)–tubulin (TUA) is a primary unit of cytoskeleton microtubules. In recent years, more frequent frosts have caused considerable yield loss in sugarcane (Saccharum spp. hybrid) production. Temperature is one of the most influential abiotic factors affecting the microtubule polymerization state in plants. In this research, we developed overexpressing SoTUA transgenic sugarcane lines from the cold‐susceptible cultivar ROC22. The transgene was confirmed by polymerase chain reaction (PCR) and quantificational real‐time polymerase chain reaction (qRT–PCR) analysis, while the relative expression of SoTUA protein was verified by Western blot. Compared with the nontransformed control plants (wild type [WT]), the transgenic lines showed higher relative protein expression than the WT at 25 °C, which indicates the overexpression of SoTUA protein. The contents of soluble protein and sugar and the activity of peroxidase (POD) were higher while the content of maleicdialdehyde was lower in the transgenic plants than the WT plants under the chilling treatment. Meanwhile, the expression levels of cold‐defense related genes (P5CS, WRKY, Cu/Zn–SOD, and POD1) were higher in the transgenic lines than in the WT. These results suggest that the SoTUA protein plays an important role in protecting plants during chilling stress. This positive effect is not affected by transgenic plant generations.

Stress-inducible expression of chalcone isomerase2 gene improves accumulation of flavonoids and imparts enhanced abiotic stress tolerance to rice

Analysis of rice microarray data indicated that a gene encoding for chalcone isomerase2 (OsCHI2) showed upregulation in response to abiotic stress. Hence, we isolated OsCHI2 from a popular drought tolerant upland rice variety Nagina22 and developed transgenic plants of a drought stress sensitive rice cv. Pusa Sugandh 2 expressing OsCHI2 under the control of stress inducible promoter AtRd29A and further studied their response to different abiotic stresses. Stable chromosomal integration of transgene was confirmed in the transgenic plants through PCR, Southern hybridization and expression analysis. Physio-biochemical studies revealed that the Rd29A::OsCHI2 transgenic rice plants upheld higher relative water content, more photosynthetic pigments and proline with lower relative electrolyte leakage and less malondialdehyde content as compared to WT plants under abiotic stresses. Quantitative RT-PCR analysis demonstrated that the expression level of the transgene in the OsCHI2 transgenic lines was higher than WT plants under stress conditions. Stress-inducible expression of OsCHI2 also enhanced transcript abundance of structural genes of flavonoids biosynthesis pathway leading to higher production of flavonoids under abiotic stresses in the transgenic plants. In brief, our results demonstrated that OsCHI2 is not only capable of modulating flavonoid metabolism but also can impart enhanced adaptation to different abiotic stresses other than heat stress.

CCCH protein-PvCCCH69 acted as a repressor for leaf senescence through suppressing ABA-signaling pathway

CCCH is a subfamily of zinc finger proteins involved in plant growth, development, and stresses response. The function of CCCH in regulating leaf senescence, especially its roles in abscisic acid (ABA)-mediated leaf senescence is largely unknown. The objective of this study was to determine functions and mechanisms of CCCH gene in regulating leaf senescence in switchgrass (Panicum virgatum). A CCCH gene, PvCCCH69 (PvC3H69), was cloned from switchgrass. Overexpressing PvC3H69 in rice suppressed both natural senescence with leaf aging and dark-induced leaf senescence. Endogenous ABA content, ABA biosynthesis genes (NCED3, NCED5, and AAO3), and ABA signaling-related genes (SnRKs, ABI5, and ABF2/3/4) exhibited significantly lower levels in senescencing leaves of PvC3H69-OE plants than those in WT plants. PvC3H69-suppression of leaf senescence was associated with transcriptional upregulation of genes mainly involved in the light-dependent process of photosynthesis, including light-harvesting complex proteins, PSI proteins, and PSII proteins and downregulation of ABA biosynthesis and signaling genes and senescence-associated genes. PvC3H69 could act as a repressor for leaf senescence via upregulating photosynthetic proteins and repressing ABA synthesis and ABA signaling pathways.

CaFtsH06, A Novel Filamentous Thermosensitive Protease Gene, Is Involved in Heat, Salt, and Drought Stress Tolerance of Pepper (Capsicum annuum L.).

Harsh environmental factors have continuous negative effects on plant growth and development, leading to metabolic disruption and reduced plant productivity and quality. However, filamentation temperature-sensitive H protease (FtsH) plays a prominent role in helping plants to cope with these negative impacts. In the current study, we examined the transcriptional regulation of the CaFtsH06 gene in the R9 thermo-tolerant pepper (Capsicum annuum L.) line. The results of qRT-PCR revealed that CaFtsH06 expression was rapidly induced by abiotic stress treatments, including heat, salt, and drought. The CaFtsH06 protein was localized to the mitochondria and cell membrane. Additionally, silencing CaFtsH06 increased the accumulation of malonaldehyde content, conductivity, hydrogen peroxide (H2O2) content, and the activity levels of superoxide dismutase and superoxide (·O2−), while total chlorophyll content decreased under these abiotic stresses. Furthermore, CaFtsH06 ectopic expression enhanced tolerance to heat, salt, and drought stresses, thus decreasing malondialdehyde, proline, H2O2, and ·O2− contents while superoxide dismutase activity and total chlorophyll content were increased in transgenic Arabidopsis. Similarly, the expression levels of other defense-related genes were much higher in the transgenic ectopic expression lines than WT plants. These results suggest that CaFtsH06 confers abiotic stress tolerance in peppers by interfering with the physiological indices through reducing the accumulation of reactive oxygen species, inducing the activities of stress-related enzymes and regulating the transcription of defense-related genes, among other mechanisms. The results of this study suggest that CaFtsH06 plays a very crucial role in the defense mechanisms of pepper plants to unfavorable environmental conditions and its regulatory network with other CaFtsH genes should be examined across variable environments.

Development and Yield Traits Indicate That the Constitutive Wound Response Phenotype of Prosystemin Overexpressing Tomato Plants Entails No Fitness Penalty

Systemin is a peptide hormone that regulates the wound response in tomato plants. Consequently, the overexpression of its prosystemin (ProSys) precursor protein leads to a resource-demanding constitutive activation of tomato’s wound-response. According to the growth vs. defense resource allocation premise, ProSys overexpression should negatively affect the physiological fitness of tomato plants. The present study was performed to explore why the opposite effect was steadily observed, instead. It was based on the premise that a better understanding of this unexpected outcome could help establish improved wound and related defense responses without negatively affecting crop productivity. To this effect, an experimental strategy was deployed to measure various physiological, biochemical and molecular parameters associated with either development, productivity, defense or in combination in untransformed (WT) and ProSys overexpressing (ProSys-OE) tomato plants. Thus, the chlorophyll fluorescence data obtained from plants grown under greenhouse experiments indicated that photosynthetic performance was not affected in ProSys-OE plants which also grew 7–14% taller than WT plants. Moreover, they showed accelerated flowering and yielded fruits of increased size (7–16% taller and wider) and weight (16–58% heavier), with modified fruit quality in terms of firmness (28% higher), titratable acidity (27–32% higher) and chemical composition. These findings suggest two complementary possibilities: (i) systemin is able to modulate both the wound response and plant development through the activation of jasmonic acid biosynthesis and signaling, and (ii) ProSys, an intrinsically disordered protein, acts as a signaling hub to regulate development and defense programs. These results shed light on the understanding of this plant regulatory mechanism and further suggest that systemin/ProSys-based regulation is central to control the defense-development balance in tomato. This knowledge could eventually lead to improved and more environmentally sound agricultural production practices.

Morpho-Physiological Testing of NaCl Sensitivity of Tobacco Plants Overexpressing Choline Oxidase Gene.

In this study the transgenic lines (TLs) of tobacco (Nicotiana tabacum L.), which overexpress the heterologous gene encoding the bacterial enzyme choline oxidase were evaluated. The goal of our work is to study the effect of choline oxidase gene expression on the sensitivity of plant tissues to the action of NaCl. The regenerative capacity, rhizogenesis, the amount of photosynthetic pigments and osmotically active compounds (proline and glycine betaine) were assessed by in vitro cell culture methods using biochemical and morphological parameters. Transgenic lines with confirmed expression were characterized by high regeneration capacity from callus in the presence of 200 mmol NaCl, partial retention of viability at 400 mmol NaCl. These data correlated with the implicit response of regenerants and whole plants to the harmful effects of salinity. They turned out to be less sensitive to the presence of 200 mmol NaCl in the cultivation medium, in contrast to the WT plants.

In Arabidopsis thaliana Cd differentially impacts on hormone genetic pathways in the methylation defective ddc mutant compared to wild type

DNA methylation plays an important role in modulating plant growth plasticity in response to stress, but mechanisms involved in such control need further investigation. We used drm1 drm2 cmt3 mutant of Arabidopsis thaliana, defective in DNA methylation, to explore metabolic pathways downstream epigenetic modulation under cadmium (Cd) stress. To this aim, a transcriptomic analysis was performed on ddc and WT plants exposed to a long-lasting (21 d) Cd treatment (25/50 µM), focusing on hormone genetic pathways. Growth parameters and hormones amount were also estimated. Transcriptomic data and hormone quantification showed that, under prolonged Cd treatment, level and signalling of growth-sustaining hormones (auxins, CKs, GAs) were enhanced and/or maintained, while a decrease was detected for stress-related hormones (JA, ABA, SA), likely as a strategy to avoid the side effects of their long-lasting activation. Such picture was more effective in ddc than WT, already at 25 µM Cd, in line with its better growth performance. A tight relationship between methylation status and the modulation of hormone genetic pathways under Cd stress was assessed. We propose that the higher genome plasticity conferred to ddc by DNA hypomethylated status underlies its prompt response to modulate hormones genetic pathways and activity and assure a flexible growth.

Overexpression of GhMPK3 from Cotton Enhances Cold, Drought, and Salt Stress in Arabidopsis

Cotton production is hampered by a variety of abiotic stresses that wreak havoc on the growth and development of plants, resulting in significant financial losses. According to reports, cotton production areas have declined around the world as a result of the ongoing stress. Therefore, plant breeding programs are concentrating on abiotic stress-tolerant cotton varieties. Mitogen-activated protein kinase (MAPK) cascades are involved in plant growth, stress responses, and the hormonal signaling pathway. In this research, three abiotic stresses (cold, drought, and salt) were analyzed on GhMPK3 transformed Arabidopsis plants. The transgenic plant’s gene expression and morphologic analysis were studied under cold, drought, and salt stress. Physiological parameters such as relative leaf water content, excised leaf water loss, chlorophyll content, and ion leakage showed that overexpressed plants possess more stable content under stress conditions compared with the WT plants. Furthermore, GhMPK3 overexpressed plants had greater antioxidant activities and weaker oxidant activities. Silencing GhMPK3 in cotton inhibited its tolerance to drought stress. Our research findings strongly suggest that GhMPK3 can be regarded as an essential gene for abiotic stress tolerance in cotton plants.