OE Lines Research Articles

Fine-tuning the activities of β-KETOACYL-COA SYNTHASE 3 (KCS3) and KCS12 in Arabidopsis is essential for maintaining cuticle integrity.

The plant cuticle, consisting of wax and cutin, is involved in adaptations to various environments. β-Ketoacyl-CoA synthases (KCSs) usually serve as a component of the fatty acid elongation complex that participates in the production of very long-chain fatty acids and provides precursors for the synthesis of various lipids, including wax; however, we recently reported that KCS3 and KCS12 negatively regulate wax biosynthesis. In this current study, we observed that unlike KCS3-overexpressing (OE) lines, KCS12-OE lines had fused floral organs because of abnormal cuticle biosynthesis. This prompted us to compare the functions of KCS3 and KCS12 during cuticle formation. Mutation of KCS3 caused greater effects on wax production, whereas mutation of KCS12 exerted more severe effects on cutin synthesis. The double-mutant kcs3 kcs12 had significantly increased wax and cutin contents compared to either single-mutant, suggesting that KCS12 and KCS3 have additive effects on cuticle biosynthesis. Cuticle permeability was greater for the double-mutant than for the single mutants, which ultimately led to increased susceptibility to drought stress and floral-organ fusion. Taken together, our results demonstrate the regulatory roles of KCS3 and KCS12 during cuticle biosynthesis, and show that maintaining KCS3 and KCS12 expression at certain levels is essential for the formation of a functional cuticle layer.

Transcription Factor GmERF105 Negatively Regulates Salt Stress Tolerance in Arabidopsis thaliana.

The Ethylene Response Factor (ERF) transcription factors form a subfamily of the AP2/ERF family that is instrumental in mediating plant responses to diverse abiotic stressors. Herein, we present the isolation and characterization of the GmERF105 gene from Williams 82 (W82), which is rapidly induced by salt, drought, and abscisic acid (ABA) treatments in soybean. The GmERF105 protein contains an AP2 domain and localizes to the nucleus. GmERF105 was selectively bound to GCC-box by gel migration experiments. Under salt stress, overexpression of GmERF105 in Arabidopsis significantly reduced seed germination rate, fresh weight, and antioxidant enzyme activity; meanwhile, sodium ion content, malonic dialdehyde (MDA) content, and reactive oxygen species (ROS) levels were markedly elevated compared to the wild type. It was further found that the transcription levels of CSD1 and CDS2 of two SOD genes were reduced in OE lines. Furthermore, the GmERF105 transgenic plants displayed suppressed expression of stress response marker genes, including KIN1, LEA14, NCED3, RD29A, and COR15A/B, under salt treatment. Our findings suggest that GmERF105 can act as a negative regulator in plant salt tolerance pathways by affecting ROS scavenging systems and the transcription of stress response marker genes.

The transcription factor BnaA9.WRKY47 coordinates leaf senescence and nitrogen remobilization in Brassica napus.

Nitrogen (N) is an essential macronutrient for plants, and N remobilization is key for plant adaptation to N deficiency stress. However, there is a limited understanding of the regulatory mechanisms of N remobilization in Brassica napus. Here, we report a transcription factor, BnaA9.WRKY47, induced by N starvation. At the seedling stage, BnaA9.WRKY47-OE lines displayed earlier senescence of older leaves and preferential growth of juvenile leaves compared to the wild-type 'Westar 10' under N starvation. At the field scale, the seed yield was significantly increased in BnaA9.WRKY47-OE lines compared to 'Westar 10' grown under N deficiency conditions and, conversely, reduced in BnaA9.WRKY47-mutants. Biochemical analyses demonstrate that BnaA9.WRKY47 directly activates BnaC7.SGR1 to accelerate older leaf senescence. In line with leaf senescence, the amino acid concentration was elevated, and the N distribution was reduced in the older leaves of OE lines. This result is because BnaA9.WRKY47 activates the amino acid permease BnaA9.AAP1 and the nitrate transporter BnaA2.NRT1.7. Therefore, the expression of BnaA9.WRKY47 efficiently facilitates N remobilization from older to younger leaves or seeds. Taken together, the results of this study demonstrate that BnaA9.WRKY47 upregulates the expression of BnaC7.SGR1, BnaA2.NRT1.7 and BnaA9AAP1 thus promoting the remobilization of N in B. napus under N starvation.

LeGRXS14 Reduces Salt Stress Tolerance in Arabidopsis thaliana.

Salt stress represents a significant abiotic stressor for plants and poses a severe threat to agricultural productivity. Glutaredoxins (GRXs) are small disulfide reductases that can scavenge cellular reactive oxygen species and are crucial for plant growth and development, particularly under stressful circumstances. Although CGFS-type GRXs were found to be involved in various abiotic stresses, the intrinsic mechanism mediated by LeGRXS14, a tomato (Lycopersicon esculentum Mill.) CGFS-type GRX, is not yet fully understood. We discovered that LeGRXS14 is relatively conserved at the N-terminus and exhibits an increase in expression level under salt and osmotic stress conditions in tomatoes. The expression levels of LeGRXS14 in response to osmotic stress peaked relatively rapidly at 30 min, while the response to salt stress only peaked at 6 h. We constructed LeGRXS14 overexpression Arabidopsis thaliana (OE) lines and confirmed that LeGRXS14 is located on the plasma membrane, nucleus, and chloroplasts. In comparison to the wild-type Col-0 (WT), the OE lines displayed greater sensitivity to salt stress, resulting in a profound inhibition of root growth under the same conditions. Analysis of the mRNA levels of the WT and OE lines revealed that salt stress-related factors, such as ZAT12, SOS3, and NHX6, were downregulated. Based on our research, it can be concluded that LeGRXS14 plays a significant role in plant tolerance to salt. However, our findings also suggest that LeGRXS14 may act as a negative regulator in this process by exacerbating Na+ toxicity and the resulting oxidative stress.

SLs signal transduction gene CsMAX2 of cucumber positively regulated to salt, drought and ABA stress in Arabidopsis thaliana L.

Recent studies have demonstrated that strigolactones (SLs) participate in the regulation of stress adaptation, however, the mechanisms remain elusive. MAX2 (MORE AXILLARY GROWTH2) is the key gene in the signal transduction pathway of SLs. This study aimed to clone and functionally characterize the CsMAX2 gene of cucumber in Arabidopsis. The results showed that the expression levels of the CsMAX2 gene changed significantly after salt, drought, and ABA stresses in cucumber. Moreover, the overexpression of CsMAX2 promoted stress tolerance and increased the germination rate and root length of Arabidopsis thaliana. Meanwhile, the content of chlorophyll increased and malondialdehyde decreased in CsMAX2 OE lines under salt and drought stresses. Additionally, the expression levels of stress-related marker genes, especially AREB1 and COR15A, were significantly upregulated under salt stress, while the expression levels of all genes were upregulated under drought stress, except ABI4 and ABI5 genes. The level of NCED3 continued to rise under both salt and drought stresses. In addition, D10 and D27 gene expression level also showed a continuous increase under ABA stress. The result suggested the interaction between SL and ABA in the process of adapting to stress. Overall, CsMAX2 could positively regulate salt, drought, and ABA stress resistance, and this process correlated with ABA transduction.

Physiological responses induced by phospholipase C isoform 5 upon heat stress in Arabidopsis thaliana.

Plant's perception of heat stress involves several pathways and signaling molecules, such as phosphoinositide, which is derived from structural membrane lipids phosphatidylinositol. Phospholipase C (PLC) is a well-known signaling enzyme containing many isoforms in different organisms. In the present study, Phospholipase C Isoform 5 (PLC5) was investigated for its role in thermotolerance in Arabidopsis thaliana. Two over-expressing lines and one knock-down mutant of PLC5 were first treated at a moderate temperature (37 °C) and left for recovery. Then again exposed to a high temperature (45 °C) to check the seedling viability and chlorophyll contents. Root behavior and changes in 32Pi labeled phospholipids were investigated after their exposure to high temperatures. Over-expression of PLC5 (PLC5 OE) exhibited quick and better phenotypic recovery with bigger and greener leaves followed by chlorophyll contents as compared to wild-type (Col-0) and PLC5 knock-down mutant in which seedling recovery was compromised. PLC5 knock-down mutant illustrated well-developed root architecture under controlled conditions but stunted secondary roots under heat stress as compared to over-expressing PLC5 lines. Around 2.3-fold increase in phosphatidylinositol 4,5-bisphosphate level was observed in PLC5 OE lines upon heat stress compared to wild-type and PLC5 knock-down mutant lines. A significant increase in phosphatidylglycerol was also observed in PLC5 OE lines as compared to Col-0 and PLC5 knock-down mutant lines. The results of the present study demonstrated that PLC5 over-expression contributes to heat stress tolerance while maintaining its photosynthetic activity and is also observed to be associated with primary and secondary root growth in Arabidopsis thaliana.

Cloning of TaeRF1 gene from Caucasian clover and its functional analysis responding to low-temperature stress.

Low temperature (LT) is an important threat to the normal growth of plants. In this study, based on the full-length transcriptome sequencing results, the cold resistance genes were cloned from Caucasian clover with strong cold resistance. We cloned the CDS of TaeRF1, which is 1311 bp in length and encodes 436 amino acids. The molecular weight of the protein is 48.97 kDa, which had no transmembrane structure, and its isoelectric point (pI) was 5.42. We predicted the structure of TaeRF1 and found 29 phosphorylation sites. Subcellular localization showed that TaeRF1 was localized and expressed in cell membrane and chloroplasts. The TaeRF1 gene was induced by stress due to cold, salt, alkali and drought and its expression level was higher in roots and it was more sensitive to LT. Analysis of transgenic A. thaliana plants before and after LT treatment showed that the TaeRF1 gene enhanced the removal of excess H2O2, and increased the activity of antioxidant enzymes, thus improving the plant's ability to resist stress. Additionally, the OE lines showed increased cold tolerance by upregulating the transcription level of cold-responsive genes (CBF1, CBF2, COR15B, COR47, ICE1, and RD29A). This study demonstrates that TaeRF1 is actively involved in the responses of plants to LT stress. We also provide a theoretical basis for breeding and a potential mechanism underlying the responses of Caucasian clover to abiotic stress.

Overexpression of a Cinnamyl Alcohol Dehydrogenase-Coding Gene, GsCAD1, from Wild Soybean Enhances Resistance to Soybean Mosaic Virus

Soybean mosaic virus (SMV) is the most prevalent soybean viral disease in the world. As a critical enzyme in the secondary metabolism of plants, especially in lignin synthesis, cinnamyl alcohol dehydrogenase (CAD) is widely involved in plant growth and development, and in defense against pathogen infestation. Here, we performed RNAseq-based transcriptome analyses of a highly SMV-resistant accession (BYO-15) of wild soybean (Glycine soja) and a SMV-susceptible soybean cultivar (Williams 82), also sequenced together with a resistant plant and a susceptible plant of their hybrid descendants at the F3 generation at 7 and 14 days post-inoculation with SMV. We found that the expression of GsCAD1 (from G. soja) was significantly up-regulated in the wild soybean and the resistant F3 plant, while the GmCAD1 from the cultivated soybean (G. max) did not show a significant and persistent induction in the soybean cultivar and the susceptible F3 plant, suggesting that GsCAD1 might play an important role in SMV resistance. We cloned GsCAD1 and overexpressed it in the SMV-susceptible cultivar Williams 82, and we found that two independent GsCAD1-overexpression (OE) lines showed significantly enhanced SMV resistance compared with the non-transformed wild-type (WT) control. Intriguingly, the lignin contents in both OE lines were higher than the WT control. Further liquid chromatography (HPLC) analysis showed that the contents of salicylic acid (SA) were significantly more improved in the OE lines than that of the wild-type (WT), coinciding with the up-regulated expression of an SA marker gene. Finally, we observed that GsCAD1-overexpression affected the accumulation of SMV in leaves. Collectively, our results suggest that GsCAD1 enhances resistance to SMV in soybeans, most likely by affecting the contents of lignin and SA.

Differential roles of SNAC4 and SNAC9 in ABA-mediated softening during tomato fruit ripening

Previous study suggested that SNAC4 (NM_001279348.2) and SNAC9 (NM_001365397.1) have opposite effects on carotenoid biosynthesis and softening in tomato (Solanum lycopersicum L.) fruit ripening. Here, we use an overexpressing system to explore the regulatory mechanism of SNAC4/9 in tomato fruit ripening and softening. Our results showed that the overexpression of SNAC4 and SNAC9 (OE-SNAC4/9) accelerated fruit ripening, promoted ethylene biosynthesis and carotenoid accumulation, but showed different functions on ABA content and fruit firmness. Genes related to ABA and fruit softening were up-regulated in OE-SNAC4, while down-regulated in OE-SNAC9. The structures of cell wall and peel were also different in these two OE lines. These data verified that SNAC4 and SNAC9 exhibit different regulation modes on fruit softening. Thus, we propose a working model that SNAC4/9 regulates fruit ripening and softening through three layers including cell wall modification-related genes, ethylene and ABA signaling. Our findings provide new insight into NACs involved in regulating fruit ripening.

Phenylalanine Ammonia Lyase GmPAL1.1 Promotes Seed Vigor under High-Temperature and -Humidity Stress and Enhances Seed Germination under Salt and Drought Stress in Transgenic Arabidopsis

Seed vigor is an important agronomic attribute, essentially associated with crop yield. High-temperature and humidity (HTH) stress directly affects seed development of plants, resulting in the decrease of seed vigor. Therefore, it is particularly important to discover HTH-tolerant genes related to seed vigor. Phenylalanine ammonia lyase (PAL, EC 4.3.1.24) is the first rate-limiting enzyme in the phenylpropanoid biosynthesis pathway and a key enzyme involved in plant growth and development and environmental adaptation. However, the biological function of PAL in seed vigor remains unknown. Here, GmPAL1.1 was cloned from soybean, and its protein was located in the cytoplasm and cell membrane. GmPAL1.1 was significantly induced by HTH stress in developing seeds. The overexpression of GmPAL1.1 in Arabidopsis (OE) accumulated lower level of ROS in the developing seeds and in the leaves than the WT at the physiological maturity stage under HTH stress, and the activities of SOD, POD, and CAT and flavonoid contents were significantly increased, while MDA production was markedly reduced in the leaves of the OE lines than in those of the WT. The germination rate and viability of mature seeds of the OE lines harvested after HTH stress were higher than those of the WT. Compared to the control, the overexpression of GmPAL1.1 in Arabidopsis enhanced the tolerance to salt and drought stresses during germination. Our results suggested the overexpression of GmPAL1.1 in Arabidopsis promoted seed vigor at the physiological maturation period under HTH stress and increased the seeds' tolerance to salt and drought during germination.

LAMP3/CD63 Expression in Early and Late Endosomes in Human Vaginal Epithelial Cells Is Associated with Enhancement of HSV-2 Infection.

Herpes simplex virus 2 (HSV-2) is a lifelong sexually transmitted virus that disproportionately infects women through heterosexual transmission in the vaginal tract. The vaginal epithelium is known to be highly susceptible to HSV-2 infection; however, the cellular mechanism of HSV-2 uptake and replication in vaginal epithelium has not been extensively studied. Previously, we observed that lysosomal-associated membrane protein-3 (LAMP3/CD63) was among the highly upregulated genes during HSV-2 infection of human vaginal epithelial cell line VK2, leading us to posit that LAMP3/CD63 may play a role in HSV-2 infection. Consequently, we generated two gene-altered VK2-derived cell lines, a LAMP3-overexpressed (OE) line and a LAMP3 knockout (KO) line. The wild-type VK2 and the LAMP3 OE and KO cell lines were grown in air-liquid interface (ALI) cultures for 7 days and infected with HSV-2. Twenty-four hours postinfection, LAMP3 OE cells produced and released significantly higher numbers of HSV-2 virions than wild-type VK2 cells, while virus production was greatly attenuated in LAMP3 KO cells, indicating a functional association between LAMP3/CD63 expression and HSV-2 replication. Fluorescence microscopy of HSV-2-infected cells revealed that HSV-2 colocalized with LAMP3 in both early endosomes and lysosomal compartments. In addition, blocking endosomal maturation or late endosomal/lysosomal fusion using specific inhibitors resulted in reduced HSV-2 replication in VK2 cells. Similarly, LAMP3 KO cells exhibited very low viral entry and association with endosomes, while LAMP3 OE cells demonstrated large amounts of virus that colocalized with LAMP3/CD63 in endosomes and lysosomes. IMPORTANCE Collectively, these results showed that HSV-2 is taken up by human vaginal epithelial cells through an endosomal-lysosomal pathway in association with LAMP3, which plays a crucial role in the enhancement of HSV-2 replication. These findings provide the basis for the future design of antiviral agents for prophylactic measures against HSV-2 infection.

The Poplar (Populus trichocarpa) Dehydrin Gene PtrDHN-3 Enhances Tolerance to Salt Stress in Arabidopsis.

Dehydrin (DHN), a member of the late embryogenesis abundant protein (LEA) family, was recently found to play a role in physiological responses to salt and drought stress. In this study, we identified and cloned the PtrDHN-3 gene from Populus trichocarpa. The PtrDHN-3 protein encoded 226 amino acids, having a molecular weight of 25.78 KDa and an isoelectric point of 5.18. It was identified as a SKn-type DHN and was clustered with other resistance-related DHN proteins. Real-time fluorescent quantitative PCR showed that transcription levels of PtrDHN-3 were induced by mannitol stress, and more significantly by salt stress. Meanwhile, in a yeast transgenic assay, salt tolerance increased in the PtrDHN-3 transgenic yeast, while the germination rate, fresh weight and chlorophyll content increased in PtrDHN-3-overexpressing transgenic Arabidopsis plants (OE) under salt stress. Significant increases in expression levels of six antioxidant enzymes genes, and SOD and POD enzyme activity was also observed in the OE lines, resulting in a decrease in O2- and H2O2 accumulation. The proline content also increased significantly compared with the wild-type, along with expression of proline synthesis-related genes P5CS1 and P5CS2. These findings suggest that PtrDHN-3 plays an important role in salt resistance in plants.

A soybean GmDREB3 gene contributes to drought tolerance in wheat

AbstractDREB transcription factor can significantly improve the plant resistance to drought, high salt, low temperature, high temperature, and other abiotic stress. A previous study showed that DREB transcription factor gene GmDREB3 from soybean can improve drought resistance in tobacco, however, whether it can improve drought resistance in wheat needs to be further investigated. In the present study, GmDREB3 was transferred to a wheat variety, Shi366 and two positive lines of the T5 generation were obtained by additive culture and molecular identification. GmDREB3‐OE (overexpression) lines conferred drought tolerance characteristics, including higher survival rates, lower malondialdehyde (MDA) content, lower relative conductivity, higher chlorophyll content, and higher proline content than Shi366 wheat plants under drought stress. The SPAD, Fv/Fm, panicle number, and grain yield of GmDREB3‐OE lines were increased but the transpiration rate was decreased, compared to the Shi366 plants in the field condition under drought stress. Significant differences in the stress indices were observed between the GmDREB3–OE lines and Shi366 wheat plants, which suggested that the GmDREB3 significantly improved wheat tolerance to drought stress. In addition, RT‐qPCR analysis indicated that GmDREB3 could enhance the expression of drought‐related genes in wheat. Therefore, GmDREB3 significantly increased drought tolerance in wheat plants along with improved physiological and agronomic traits and grain yield.

A heat shock transcription factor gene (HaHSFA1) from a desert shrub, Haloxylon ammodendron, elevates salt tolerance in Arabidopsis thaliana

Haloxylon ammodendron is a typical desert xerophyte with worthy genetic resources, therefore, it is necessary to explore the resistance genes of H. ammodendron , and to improve the stress tolerance of other plant species through genetic engineering. In this study, a heat shock transcription factor gene, HaHSFA1 , was firstly cloned from H. ammodendron and overexpressed in Arabidopsis thaliana . The sensitivity of transgenic plants to exogenous ABA, osmotic stress and salt stress were analyzed; the effects of overexpression of HaHSFA1 in Arabidopsis on salt tolerance were deeply investigated. The results indicated that overexpression of HaHSFA1 increased chlorophyll content in Arabidopsis, and the growth of plants was promoted. The leaf soluble sugar and proline contents in OE lines were significantly increased compared with those in WT. OE lines maintained lower osmotic potential and higher shoot water content. Overexpression of HaHSFA1 in Arabidopsis also enhanced antioxidant activity, which may be important for protecting plasma membrane integrity in cells. Overexpression of HaHSFA1 in Arabidopsis improved root activity and increased selective absorption and transport capacity for K + over Na + , which was of great significance to reduce the toxic effect of Na + . This study indicated that overexpression of HaHSFA1 from H. ammodendron significantly elevates the salt tolerance of Arabidopsis, and HaHSFA1 has potential application values in improving abiotic stress tolerance in crops by genetic engineering. • HaHSFA1 was firstly cloned from a desert shrub, Haloxylon ammodendron . • Overexpression of HaHSFA1 enhanced osmotic adjustment and ROS scavenging ability in Arabidopsis. • Overexpression of HaHSFA1 maintained higher selectivity of absorption and transport for K + over Na + in Arabidopsis.

Genome-wide characterization of chalcone synthase genes in sweet cherry and functional characterization of CpCHS1 under drought stress.

Cherries are one of the important fruit trees. The growth of cherry is greatly affected by abiotic stresses such as drought, which hinders its development. Chalcone synthase (CHS, EC 2.3.1.74) is a crucial rate-limiting enzyme in the flavonoid biosynthetic pathway that plays an important role in regulating plant growth, development, and abiotic stress tolerance. In the current study, three genes encoding chalcone synthase were identified in the genome of sweet cherry (Prunus avium L.). The three genes contained fewer introns and showed high homology with CHS genes of other Rosaceae members. All members are predicted to localize in the cytoplasm. The conserved catalytic sites may be located at the Cys163, Phe214, His302, and Asn335 residues. These genes were differentially expressed during flower bud dormancy and fruit development. The total flavonoid content of Chinese cherry (Cerasus pseudocerasus Lindl.) was highest in the leaves and slightly higher in the pulp than in the peel. No significant difference in total flavonoid content was detected between aborted kernels and normally developing kernels. Overexpression of Chinese cherry CpCHS1 in tobacco improved the germination frequency of tobacco seeds under drought stress, and the fresh weight of transgenic seedlings under drought stress was higher than that of the wild type, and the contents of SOD, POD, CAT, and Pro in OE lines were significantly increased and higher than WT under drought stress. These results indicate cherry CHS genes are conserved and functionally diverse and will assist in elucidating the functions of flavonoid synthesis pathways in cherry and other Rosaceae species under drought stress.

Picea wilsonii Transcription Factor PwNAC38 Promotes Drought and Salt Tolerance in Transgenic Arabidopsis and Apple Calli

The mechanism of Picea wilsonii adapting to abiotic stress remains largely unknown. NAC (NAM, ATAF and CUC) transcription factors play significant roles in plant response to adverse environments. In this study, based on our previous RNA-seq, we analyzed the expression patterns of PwNAC38, and revealed its functions in the process of PwNAC38-mediated stress responses. An open-reading frame, encoding PwNAC38 protein with 330 amino acids, was isolated from the cDNA library, a process which can be induced by drought, salt and ABA treatment. Subcellular localization and yeast experiments showed that PwNAC38 was a nuclear-localized transcription factor, and could form homodimers. The full length of PwNAC38 showed transcriptional activity, while the truncated segments, C-PwNAC38 (156–330 aa) and N-PwNAC38 (1–156 aa), did not. The constitutive expression of PwNAC38 (OE lines) in Arabidopsis did not exert influence on the growth of transgenic plants under normal conditions, whereas transgenic seedlings showed higher survival rates, and the seeds had stronger vigor and a higher germination rate under drought and salt stress. The seed germination and root growth of PwNAC38 OE lines were significantly inhibited in the presence of ABA, suggesting the hypersensitivity of PwNAC38 to ABA treatment. Physiological assays showed that the activity of antioxidant enzymes, such as SOD and POD, increased, and that the accumulation of superoxide anion decreased, in OE lines under stress conditions. Moreover, overexpression of PwNAC38 significantly improved drought and salt tolerance in apple calli. A qRT-PCR assay showed that overexpression of PwNAC38 in Arabidopsis promoted the expression of drought or ABA-responsive genes ATHB-7, ANAC019, ERD1, DREB2A, RD29A, ABI5 and NCED3. Taken together, our results revealed that PwNAC38 is positively involved in plants’ response to drought and salt stress by enhancing ROS scavenging efficiency, and is partially dependent on the ABA signaling pathway.

Transcription Factor AtOFP1 Involved in ABA-Mediated Seed Germination and Root Growth through Modulation of ROS Homeostasis in Arabidopsis.

Ovate family proteins (OFPs) are valued as a family of transcription factors that are unique to plants, and they play a pluripotent regulatory role in plant growth and development, including secondary-cell-wall synthesis, DNA repair, gibberellin synthesis, and other biological processes, via their interaction with TALE family proteins. In this study, CHIP-SEQ was used to detect the potential target genes of AtOFP1 and its signal-regulation pathways. On the other hand, Y2H and BIFC were employed to prove that AtOFP1 can participate in ABA signal transduction by interacting with one of the TALE family protein called AtKNAT3. ABA response genes are not only significantly upregulated in the 35S::HAOFP1 OE line, but they also show hypersensitivity to ABA in terms of seed germination and early seedling root elongation. In addition, the AtOFP1-regulated target genes are mainly mitochondrial membranes that are involved in the oxidative–phosphorylation pathway. Further qRT-PCR results showed that the inefficient splicing of the respiratory complex I subunit genes NAD4 and NAD7 may lead to ROS accumulation in 35S::HA-AtOFP1 OE lines. In conclusion, we speculated that the overexpression of AtOFP1 may cause the ABA hypersensitivity response by increasing the intracellular ROS content generated from damage to the intima systems of mitochondria.

Over-expression of TaDWF4 increases wheat productivity under low and sufficient nitrogen through enhanced carbon assimilation

There is a strong pressure to reduce nitrogen (N) fertilizer inputs while maintaining or increasing current cereal crop yields. We show that overexpression of TaDWF4-B, the dominant shoot expressed homoeologue of OsDWF4, in wheat can increase plant productivity by up to 105% under a range of N levels on marginal soils, resulting in increased N use efficiency (NUE). We show that a two to four-fold increase in TaDWF4 transcript levels enhances the responsiveness of genes regulated by N. The productivity increases seen were primarily due to the maintenance of photosystem II operating efficiency and carbon assimilation in plants when grown under limiting N conditions and not an overall increase in photosynthesis capacity. The increased biomass production and yield per plant in TaDWF4 OE lines could be linked to modified carbon partitioning and changes in expression pattern of the growth regulator Target Of Rapamycin, offering a route towards breeding for sustained yield and lower N inputs.

Alternative oxidase plays a role in minimizing ROS and RNS produced under salinity stress in Arabidopsis thaliana.

Under stress conditions, the overproduction of different reactive oxygen species (ROS) and reactive nitrogen species (RNS) causes imbalance in the redox homeostasis of the cell leading to nitro-oxidative stress in plants. Alternative oxidase (AOX) is a conserving terminal oxidase of the mitochondrial electron transport chain, which can minimize the ROS. Still, the role of AOX in the regulation of RNS during nitro-oxidative stress imposed by salinity stress is not known. Here, we investigated the role of AOX in minimizing ROS and RNS induced by 150 mM NaCl in Arabidopsis using transgenic plants overexpressing (AOX OE) and antisense lines (AOX AS) of AOX. Imposing NaCl treatment leads to a 4-fold enhanced expression of AOX accompanied by enhanced AOX capacity in WT Col-0. Further AOX-OE seedlings displayed enhanced growth compared with the AOX-AS line under stress. Examination of NO levels by DAF-FM fluorescence and chemiluminescence revealed that AOX overexpression leads to reduced levels of NO. The total NR activity was elevated under NaCl, but no significant change was observed in wild-type (WT), AOX OE, and AS lines. The total ROS, superoxide, H2 O2 levels, and lipid peroxidation were higher in the AOX-AS line than in WT and AOX-OE lines. The peroxynitrite levels were also higher in the AOX-AS line than in WT and AOX-OE lines; further, the expression of antioxidant genes was elevated in AOX-AS. Taken together, our results suggest that AOX plays an important role in the mitigation of ROS and RNS levels and enhances plant growth, thus providing tolerance against nitro-oxidative stress exerted by NaCl.

Overexpression of the tyrosine decarboxylase gene MdTyDC in apple enhances long-term moderate drought tolerance and WUE

Drought stress affects the apple yield and quality. Tyrosine decarboxylase (TyDC) plays a fundamental role in many secondary metabolite reactions in higher plants (including those involving dopamine). Our aims of this study are: 1) to identify the role of TyDC in dopamine derivative biosynthesis and its function in long-term moderate drought conditions; and 2) to explore the role of MdTyDC in plant growth and development as well as the drought stress response. Wild type and three independently apple plants overexpression of MdTyDC were treated for long-term moderate drought stress. The growth and physiological parameters of apple plant, photosynthetic capacity, antioxidant enzymes activity, water use efficiency (WUE), stomatal behavior, amino acid content and dopamine content were detected under long-term moderate drought stress. Overexpression of MdTyDC (OE) in apple showed better growth performance, higher photosynthetic capacity and higher capacity for photochemical reactions than wild type lines (WT). Under long-term moderate drought stress, OE lines showed higher WUE, increased ABA content, decreased stomatal aperture, higher antioxidant activity, lower accumulation of ROS and increases in amino acids, such as proline, phenylalanine and lysine. In addition, qRT-PCR revealed higher gene expression of MdTyDC and dopamine content in OE compared with WT lines under long-term moderate drought stress. These results indicate that MdTyDC confers long-term moderate drought tolerance by improving photosynthetic capacity, WUE, antioxidant activity, dopamine content and changing the contents of amino acids (such as proline accumulation).