Wild-type Wheat Research Articles

Deciphering High-Temperature-Induced Lignin Biosynthesis in Wheat through Comprehensive Transcriptome Analysis.

This study systematically investigated the physiological and molecular responses of the wheat mutant 'XC-MU201' under high-temperature stress through comprehensive transcriptome analysis and physiological measurements. RNA sequencing of 21 samples across seven different treatment groups revealed, through Weighted Gene Co-expression Network Analysis (WGCNA), 13 modules among 9071 genes closely related to high-temperature treatments. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses showed significant enrichment of lignin biosynthesis-related modules under high-temperature conditions, especially at the H-10DAT, H-20DAT, and H-30DAT time points. Experimental results demonstrated a significant increase in lignin content in high-temperature-treated samples, confirmed by tissue staining methods, indicating wheat's adaptation to heat damage through lignin accumulation. The phenylalanine ammonia-lyase gene (TaPAL33) was significantly upregulated under high-temperature stress, peaking at H-30DAT, suggesting its critical role in cellular defense mechanisms. Overexpression of TaPAL33 in the wheat variety 'Xinchun 11' enhanced lignin synthesis but inhibited growth. Subcellular localization of GFP-labeled TaPAL33 in tobacco cells showed its distribution mainly in the cytoplasm and cell membrane. Transgenic wheat exhibited higher PAL enzyme activity, enhanced antioxidant defense, and reduced oxidative damage under high-temperature stress, outperforming wild-type wheat. These results highlight TaPAL33's key role in improving wheat heat tolerance and provide a genetic foundation for future research and applications.

TabZIP60 is involved in the regulation of ABA synthesis-mediated salt tolerance through interacting with TaCDPK30 in wheat (Triticum aestivum L.).

TabZIP60 is found to interact with TaCDPK30 and act as a positive regulator of ABA synthesis-mediated salt tolerance in wheat. Wheat basic leucine zipper (bZIP) transcription factor (TabZIP60) was previously found to act as a positive regulator of salt resistance. However, its molecular mechanism in response to salt stress in wheat is still unclear. In this study, TabZIP60 was found to interact with wheat calcium-dependent protein kinase (TaCDPK30), which belonged to group III of CDPK family, and was induced by salt, polyethylene glycol, and abscisic acid (ABA) treatments. This mutation of serine 110 in TabZIP60 resulted in no interaction with TaCDPK30. Moreover, TaCDPK30 was involved in interactions with wheat protein phosphatase 2C clade A (TaPP2CA116/TaPP2CA121). TabZIP60-overexpressing wheat plants showed increased salt tolerance, as exhibited by better growth status, higher soluble sugar, and lower malonaldehyde contents of transgenic plants than wild-type wheat cv. Kenong 199 under salt stress. Moreover, transgenic lines showed high ABA content by upregulating ABA synthesis-related gene expression levels. TabZIP60 protein could bind and interact with the promoter of the wheat nine-cis epoxycarotenoid dioxygenase (TaNCED2) gene. Furthermore, TabZIP60 upregulated several stress response gene expression levels, which could also increase the plant's ability to resist salt stress. Thus, these results suggest that TabZIP60 could function as a regulator of ABA synthesis-mediated salt tolerance through interacting with TaCDPK30 in wheat.

Overexpression of TaLBD16-4D alters plant architecture and heading date in transgenic wheat.

Lateral organ boundaries domain (LBD) proteins, a class of plant-specific transcription factors with a special domain of lateral organ boundaries (LOB), play essential roles in plant growth and development. However, there is little known about the functions of these genes in wheat to date. Our previous study demonstrated that TaLBD16-4D is conducive to increasing lateral root number in wheat. In the present work, we further examined important agronomical traits of the aerial part of transgenic wheat overexpressing TaLBD16-4D. Interestingly, it was revealed that overexpressing TaLBD16-4D could lead to early heading and multiple alterations of plant architecture, including decreased plant height, increased flag leaf size and stem diameter, reduced spike length and tillering number, improved spike density and grain width, and decreased grain length. Moreover, auxin-responsive experiments demonstrated that the expression of TaLBD16-4D in wild-type (WT) wheat plants showed a significant upregulation through 2,4-D treatment. TaLBD16-4D-overexpression lines displayed a hyposensitivity to 2,4-D treatment and reduced shoot gravitropic response. The expressions of a set of auxin-responsive genes were markedly different between WT and transgenic plants. In addition, overexpressing TaLBD16-4D affected the transcript levels of flowering-related genes (TaGI, TaCO1, TaHd1, TaVRN1, TaVRN2, and TaFT1). Notably, the expression of TaGI, TaCO1, TaHd1, TaVRN1, and TaFT1 displayed significant upregulation under IAA treatment. Collectively, our observations indicated that overexpressing TaLBD16-4D could affect aerial architecture and heading time possibly though participating in the auxin pathway.

32Pi Labeled Transgenic Wheat Shows the Accumulation of Phosphatidylinositol 4,5-bisphosphate and Phosphatidic Acid Under Heat and Osmotic Stress.

The ensuing heat stress drastically affects wheat plant growth and development, consequently compromising its grain yield. There are many thermoregulatory processes/mechanisms mediated by ion channels, lipids, and lipid-modifying enzymes that occur in the plasma membrane and the chloroplast. With the onset of abiotic or biotic stresses, phosphoinositide-specific phospholipase C (PI-PLC), as a signaling enzyme, hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2) to generate inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG) which is further phosphorylated into phosphatidic acid (PA) as a secondary messenger and is involved in multiple processes. In the current study, a phospholipase C (PLC) signaling pathway was investigated in spring wheat (Triticum aestivum L.) and evaluated its four AtPLC5 overexpressed (OE)/transgenic lines under heat and osmotic stresses through 32Pi radioactive labeling. Naturally, the wheat harbors only a small amount of PIP2. However, with the sudden increase in temperature (40°C), PIP2 levels start to rise within 7.5 min in a time-dependent manner in wild-type (Wt) wheat. While the Phosphatidic acid (PA) level also elevated up to 1.6-fold upon exposing wild-type wheat to heat stress (40°C). However, at the anthesis stage, a significant increase of ∼4.5-folds in PIP2 level was observed within 30 min at 40°C in AtPLC5 over-expressed wheat lines. Significant differences in PIP2 level were observed in Wt and AtPLC5-OE lines when treated with 1200 mM sorbitol solution. It is assumed that the phenomenon might be a result of the activation of PLC/DGK pathways. Together, these results indicate that heat stress and osmotic stress activate several lipid responses in wild-type and transgenic wheat and can explain heat and osmotic stress tolerance in the wheat plant.

Low-Temperature Effects on the Growth and Phytochemical Properties of Wheat Sprouts

Sprouting is associated with nutritional value, as microgreens stimulate the accumulation of health-promoting phytochemicals. The purpose of this study was to examine the growth rates and cell protection activity against oxidative stress in sprouts of seven wheat varieties, and to investigate the influence of low temperatures on their phytochemical characteristics. Among the seven wheat varieties (five Korean varieties, Australian standard white, and Chinese wild-type wheat germplasm), purple wheat (Ariheuk) had the fastest growth pattern for 8 days and provided the most protection to skin cells and hepatocytes against oxidative stress. Following low-temperature treatment (<4 °C) for 1–4 days, cold exposure had a similar effect on the growth of purple wheat sprouts during an 8-day period. However, growth was negatively affected by exposure to low temperatures for more than 5 days. Purple wheat sprouts treated with low temperatures for 4 days had considerably higher total polyphenol and total flavonoid contents, as well as a higher antioxidant capacity than untreated wheat sprouts. These findings suggest that low-temperature treatment promotes the expression of phytochemicals in purple wheat sprouts. Thus, purple wheat sprouts are considered a high-value crop that could be used as a functional food material.

Starch structure and exchangeable protons contribute to reduced aging of high-amylose wheat bread

Breads were prepared from wild-type wheat flour (WTWF) and high-amylose wheat flour (HAWF) with amylose content (AM) 71% and 84%. Melting enthalpy of recrystallized amylopectin (ΔHAP) increased significantly on storage for wild-type (WT), slightly for 71% AM but not at all for bread with 84% AM. Firmness of bread was positively related to AM content and ΔHAP. Exchangeable proton populations and mobility in high-amylose wheat bread (HAWB) crumb were higher than WT bread measured by 1H T2 NMR, consistent with the higher water content needed to make doughs from HAWF leading to the crumb network being more plasticized and hindering crumb aging. Although starch recrystallization and bread firming increased, no increase in enzyme-resistant starch (RS) content was observed during bread aging, with RS content only dependent on AM content. Although HAWB has a harder crumb than wild-type, it has greater shelf-life stability and higher nutritional value.

A separation-of-function ZIP4 wheat mutant allows crossover between related chromosomes and is meiotically stable

Many species, including most flowering plants, are polyploid, possessing multiple genomes. During polyploidisation, fertility is preserved via the evolution of mechanisms to control the behaviour of these multiple genomes during meiosis. On the polyploidisation of wheat, the major meiotic gene ZIP4 duplicated and diverged, with the resulting new gene TaZIP4-B2 being inserted into chromosome 5B. Previous studies showed that this TaZIP4-B2 promotes pairing and synapsis between wheat homologous chromosomes, whilst suppressing crossover between related (homoeologous) chromosomes. Moreover, in wheat, the presence of TaZIP4-B2 preserves up to 50% of grain number. The present study exploits a ‘separation-of-function’ wheat Tazip4-B2 mutant named zip4-ph1d, in which the Tazip4-B2 copy still promotes correct pairing and synapsis between homologues (resulting in the same pollen profile and fertility normally found in wild type wheat), but which also allows crossover between the related chromosomes in wheat haploids of this mutant. This suggests an improved utility for the new zip4-ph1d mutant line during wheat breeding, compared to the previously described CRISPR Tazip4-B2 and ph1 mutant lines. The results also reveal that loss of suppression of homoeologous crossover between wheat chromosomes does not in itself reduce wheat fertility when promotion of homologous pairing and synapsis by TaZIP4-B2 is preserved.

High-amylose wheat bread with reduced in vitro digestion rate and enhanced resistant starch content

High amylose wheat flour (HAWF) is a relatively new food ingredient, with potential for enhanced nutritional functionality of slower digestion and greater resistant starch levels compared to wild-type wheat flour (WTWF) products. This study focusses on the role of amylose content in the baking process and eating qualities of bread, made using an industry-standard rapid dough method. DSC, XRD and polarized light microscopy were used to monitor changes of ordered structure in starch after baking, and showed more retained crystalline structure in the high-amylose wheat bread (HAWB) than wild-type wheat bread (WTWB). Moreover, HAWB had lower loaf volume, more dense crumb structure, as well as higher hardness than WTWB. These starch structural and local density features subsequently lead to bread made with 100% or 50% HAWF being more resistant to enzyme hydrolysis compared to WTWB. Resistant starch levels were significantly increased by ∼11 and 12 times in bread made using 100% HAWF with amylose content 71% and 84% respectively, and ∼6 times in bread prepared with 50% incorporation HAWF (84% AM) than WTWB. The nutritional and physical properties of bread are highly correlated to starch amylose content (AM), starch thermal properties and crumb hardness, with AM playing the leading role. This study identifies the structural basis for flour amylose content effects in baking and nutritional functionality and can help guide development of nutritionally-enhanced foods with HAWF.

Highly efficient heritable genome editing in wheat using an RNA virus and bypassing tissue culture

Genome editing provides novel strategies for improving plant traits but mostly relies on conventional plant genetic transformation and regeneration procedures, which can be inefficient. In this study, we have engineered a Barley stripe mosaic virus–based sgRNA delivery vector (BSMV-sg) that is effective in performing heritable genome editing in Cas9-transgenic wheat plants. Mutated progenies were present in the next generation at frequencies ranging from 12.9% to 100% in three different wheat varieties, and 53.8%–100% of mutants were virus free. We also achieved multiplex mutagenesis in progeny using a pool of BSMV-sg vectors harboring different sgRNAs. Furthermore, we devised a virus-induced transgene-free editing procedure to generate Cas9-free wheat mutants by crossing BSMV-infected Cas9-transgenic wheat pollen with wild-type wheat. Our study provides a robust, convenient, and tissue culture–free approach for genome editing in wheat through virus infection.

Molecular cloning and functional characterization of TaIRI9 gene in wheat (Triticum aestivum L.).

The vernalization of wheat is one of the important factors that determine the planting region, introduction and cultivation techniques of wheat. However, the known vernalization genes (molecular marker) cannot precisely distinguish the vernalization requirement of winter wheat cultivars. Therefore, it is important to explore new vernalization genes and elucidate the mechanism of vernalization regulation. To explore the gene network in the vernalization pathway, we screened TaIRI9 (ice recrystallization inhibitor protein) gene associated with the expression profile of vernalization treatment of winter wheat Jing 841. Overexpression of TaIRI9 in wild type wheat resulted in reduced plant height, increased tiller number and delayed heading days. After 4°C vernalization treatment for 30, 35, 45 or 50days, TaIRI9 overexpression lines showed increased vernalization requirement and delayed heading time than wild type, indicating that TaIRI9 may affect vernalization process of wheat. In addition, the expression of the TaIRI9 genes were analyzed in winter Jing 841, strong winter wheat cultivar Xindong 18 and ten recombinant inbred lines (RILs, Hussar×Yanzhan1). The data showed that the expression of TaIRI9 was positively associated with the requirement of vernalization. These results indicated that TaIRI9 regulates heading and flowering time in wheat by promoting VRN2 and inhibiting flowering promoter VRN1 and VRN3 and may be involved in wheat vernalization regulation pathway.

Discrimination of Waxy Wheats Using Near-Infrared Hyperspectral Spectroscopy

Wheat (Triticum aestivum L.) carries three waxy loci (Wx-A1, Wx-B1, and Wx-D1) encoding granule-bound starch synthase (GBSS) which are related to amylose synthesis. The present study was to investigate the possibility of using near-infrared (NIR) hyperspectral spectroscopy to differentiate waxy wheat and three partial waxy wheats from wild-type wheat. Nearly 267 seeds from the same harvest year were used to obtain hyperspectral imaging maps in the near-infrared range (930–2548 nm), and then the data were analyzed based on chemometric methods. The first derivative, standard normal variable (SNV) transformation, and multivariate scattering correction (MSC) were used for spectral pretreatment. Support vector machine (SVM) and partial least square discriminant analysis (PLS-DA) and backpropagation neural network (BPNN) were applied to build discrimination models for wheat line classification. The results demonstrate that the highest classification accuracy of 98.51% for the prediction set was achieved by SVM model based on raw spectral data in full NIR region, and the classification accuracy of wild-type and partial waxy wheats all reached 100%. SVM models’ prediction accuracy (98.51%) is higher than PLS-DA and BPNN models’ (75.76% and 82.10%). The above results show that NIR hyperspectral spectroscopy combined SVM model was useful in identification of waxy and partial waxy wheats from wild-type wheat.

Resistant Starch Type 2 from Wheat Reduces Postprandial Glycemic Response with Concurrent Alterations in Gut Microbiota Composition

The majority of research on the physiological effects of dietary resistant starch type 2 (RS2) has focused on sources derived from high-amylose maize. In this study, we conduct a double-blind, randomized, placebo-controlled, crossover trial investigating the effects of RS2 from wheat on glycemic response, an important indicator of metabolic health, and the gut microbiota. Overall, consumption of RS2-enriched wheat rolls for one week resulted in reduced postprandial glucose and insulin responses relative to conventional wheat when participants were provided with a standard breakfast meal containing the respective treatment rolls (RS2-enriched or conventional wheat). This was accompanied by an increase in the proportions of bacterial taxa Ruminococcus and Gemmiger in the fecal contents, reflecting the composition in the distal intestine. Additionally, fasting breath hydrogen and methane were increased during RS2-enriched wheat consumption. However, although changes in fecal short-chain fatty acid (SCFA) concentrations were not significant between control and RS-enriched wheat roll consumption, butyrate and total SCFAs were positively correlated with relative abundance of Faecalibacterium, Ruminoccocus, Roseburia, and Barnesiellaceae. These effects show that RS2-enriched wheat consumption results in a reduction in postprandial glycemia, altered gut microbial composition, and increased fermentation activity relative to wild-type wheat.

Overexpression of Soybean-Derived Lunasin in Wheat and Assessment of Its Anti-Proliferative Activity in Colorectal Cancer HT-29 Cells.

Lunasin is a soybean-derived peptide that exhibits anticancer bioactivity in different cancer cells and has been identified in different plants. However, recent studies revealed through molecular and chemical analyses that lunasin was absent in wheat and other cereals. In this study, the soybean-derived lunasin was cloned into pCAMBIA3300 and we transferred the expression vector into wheat via an Agrobacterium-mediated transformation. The identification of transgenic wheat was detected by polymerase chain reaction, Western blot analysis, and ultra-performance liquid chromatography with tandem mass spectrometry. An enzyme-linked immunosorbent assay showed that lunasin content in transgenic wheat L32-3, L32-6, and L33-1 was 308.63, 436.78, and 349.07 µg/g, respectively, while lunasin was not detected in wild-type wheat. Lunasin enrichment from transgenic wheat displayed an increased anti-proliferative activity compared with peptide enrichment from wild-type wheat in HT-29 cells. Moreover, the results of a real-time quantitative polymerase chain reaction showed a significant elevation in p21, Bax, and caspase-3 expression, while Bcl-2 was significantly downregulated. In conclusion, soybean-derived lunasin was successfully expressed in wheat via Agrobacterium-mediated transformation and may exert anti-proliferative activity by regulating the apoptosis pathway in HT-29 cells, which provides an effective approach to compensate for the absence of lunasin in wheat.

Wheat Line "RYNO3936" Is Associated With Delayed Water Stress-Induced Leaf Senescence and Rapid Water-Deficit Stress Recovery.

Random mutagenesis was applied to produce a new wheat mutant (RYNO3926) with superior characteristics regarding tolerance to water deficit stress induced at late booting stage. The mutant also displays rapid recovery from water stress conditions. Under water stress conditions mutant plants reached maturity faster and produced more seeds than its wild type wheat progenitor. Wild-type Tugela DN plants died within 7 days after induction of water stress induced at late booting stage, while mutant plants survived by maintaining a higher relative moisture content (RMC), increased total chlorophyll, and a higher photosynthesis rate and stomatal conductance. Analysis of the proteome of mutant plants revealed that they better regulate post-translational modification (SUMOylation) and have increased expression of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) proteins. Mutant plants also expressed unique proteins associated with dehydration tolerance including abscisic stress-ripening protein, cold induced protein, cold-responsive protein, dehydrin, Group 3 late embryogenesis, and a lipoprotein (LAlv9) belonging to the family of lipocalins. Overall, our results suggest that our new mutant RYNO3936 has a potential for inclusion in future breeding programs to improve drought tolerance under dryland conditions.

Misexpression of a transcriptional repressor candidate provides a molecular mechanism for the suppression of awns by Tipped 1 in wheat.

Awns are bristle-like structures formed at the tip of the lemma on the florets of some cereal grasses. Wild-type wheat is awned, but awnletted and awnless variants have been selected and nowadays all forms are cultivated. In this study, we dissected the genetic control underlying variation of this characteristic feature by association mapping in a large panel of 1110 winter wheat cultivars of worldwide origin. We identified the B1 (Tipped 1) locus on chromosome 5A as the major determinant of awnlessness globally. Using a combination of fine-mapping and expression analysis, we identified a putative C2H2 zinc finger protein with an EAR domain, characteristic of transcriptional repressors, as a likely candidate for Tipped 1. This gene was found to be up-regulated in awnless B1 compared with awned b1 plants, indicating that misexpression of this transcriptional regulator may contribute to the reduction of awn length in B1 plants. Taken together, our study provides an entry point towards a better molecular understanding of the evolution of morphological features in cereals through selection and breeding.

ITRAQ-based quantitative proteome analysis reveals metabolic changes between a cleistogamous wheat mutant and its wild-type wheat counterpart.

BackgroundWheat is one of the most important staple crops worldwide. Fusarium head blight (FHB) severely affects wheat yield and quality. A novel bread wheat mutant, ZK001, characterized as cleistogamic was isolated from a non-cleistogamous variety Yumai 18 (YM18) through static magnetic field mutagenesis. Cleistogamy is a promising strategy for controlling FHB. However, little is known about the mechanism of cleistogamy in wheat.MethodsWe performed a FHB resistance test to identify the FHB infection rate of ZK001. We also measured the agronomic traits of ZK001 and the starch and total soluble sugar contents of lodicules in YM18 and ZK001. Finally, we performed comparative studies at the proteome level between YM18 and ZK001 based on the proteomic technique of isobaric tags for relative and absolute quantification.ResultsThe infection rate of ZK001 was lower than that of its wild-type and Aikang 58. The abnormal lodicules of ZK001 lost the ability to push the lemma and palea apart during the flowering stage. Proteome analysis showed that the main differentially abundant proteins (DAPs) were related to carbohydrate metabolism, protein transport, and calcium ion binding. These DAPs may work together to regulate cellular homeostasis, osmotic pressure and the development of lodicules. This hypothesis is supported by the analysis of starch, soluble sugar content in the lodicules as well as the results of Quantitative reverse transcription polymerase chain reaction.ConclusionsProteomic analysis has provided comprehensive information that should be useful for further research on the lodicule development mechanism in wheat. The ZK001 mutant is optimal for studying flower development in wheat and could be very important for FHB resistant projects via conventional crossing.

Improved salt tolerance in a wheat stay-green mutant tasg1

Salt stress inhibited the growth of both tasg1 and wild-type (WT) wheat seedlings, but the inhibition in tasg1 plants was relatively weaker than that of WT. Compared to the WT, the chlorophyll content, thylakoid membrane polypeptides, Hill reaction activity, actual photochemical efficiency of PSII (ΦPSII), and Mg2+- and Ca2+-ATPase activities were higher in tasg1 under salt stress. At the same time, the photosynthetic activity of the tasg1 was significantly higher than that of WT. In addition, tasg1 plants displayed relatively less accumulation of reactive oxygen species and oxidative damage accompanied by higher activity of some antioxidant enzymes, and the up-regulation of antioxidant genes further demonstrated the improvement of antioxidant activity in tasg1 under salt stress. Furthermore, tasg1 plants also showed relatively weaker Na+ fluorescence and lower Na+ content, but relatively higher content of K+ in their roots and shoots, and then, the roots of tasg1 plants enhanced net outward Na+ flux and a correspondingly increased net inward K+ flux during salt stress. This might be associated with the relatively higher activity of H+-ATPase in tasg1 plants. These results suggest that the improved antioxidant competence and Na+/K+ ion homeostasis play an important role in the enhanced salinity tolerance of tasg1 plants.

Melatonin alleviates low PS I-limited carbon assimilation under elevated CO2 and enhances the cold tolerance of offspring in chlorophyll b-deficient mutant wheat.

Melatonin is involved in the regulation of carbohydrate metabolism and induction of cold tolerance in plants. The objective of this study was to investigate the roles of melatonin in modulation of carbon assimilation of wild-type wheat and the Chl b-deficient mutant ANK32B in response to elevated CO2 concentration ([CO2 ]) and the transgenerational effects of application of exogenous melatonin (hereafter identified as melatonin priming) on the cold tolerance in offspring. The results showed that the melatonin priming enhanced the carbon assimilation in ANK32B under elevated [CO2 ], via boosting the activities of ATPase and sucrose synthesis and maintaining a relatively higher level of total chlorophyll concentration in leaves. In addition, melatonin priming in maternal plants at grain filling promoted the seed germination in offspring by accelerating the starch degradation and improved the cold tolerance of seedlings through activating the antioxidant enzymes and enhancing the photosynthetic electron transport efficiency. These findings suggest the important roles of melatonin in plant response to future climate change, indicating that the melatonin priming at grain filling in maternal plants could be an effective approach to improve cold tolerance of wheat offspring at seedling stage.

Photosynthetic Responses of a Wheat Mutant (Rht-B1c) with Altered DELLA Proteins to Salt Stress

Salinity increases in the world’s land area and significantly affects the rate of photosynthesis and corresponding plant growth. In this study, the impact of salt stress (200 mM NaCl equivalent to an electrical conductivity of 18.6 mS cm−1) on the photosynthetic apparatus and some growth parameters were investigated in wheat DELLA mutant (Rht-B1c) and wild-type (Rht-B1a) seedlings grown on a half-strength Hoagland solution. Results revealed that salt toxicity was alleviated in the Rht-B1c mutant compared to the Rht-B1a wild type, as manifested by less-reduced leaf pigment content, relative water content, and photochemical activity of photosystem II (PSII) and photosystem I (PSI) after a 9-day salt exposure of plants. Compared to the wild-type wheat, a higher capacity for PSI-dependent cyclic electron flow, preventing the photosynthetic apparatus from oxidative damage, was observed in the mutant plants before and after salt treatment. In addition, an increase of PsaB proteins was detected in the mutant plants after long-term salt stress unlike the wild type. The observed higher oxidation level of P700 (P700+) in the mutant was consistent with higher abundance of PSI-related protein complexes. The data demonstrated that alterations in thylakoid membrane proteins and/or their structural reorganization in wheat DELLA mutant (Rht-B1c) significantly contribute to the alleviation of salt-induced damage of the photosynthetic apparatus. Molecular mechanisms involved in the photosynthetic responses of wheat DELLA mutants to salt stress are discussed.

Effects of the maize C4 phosphoenolpyruvate carboxylase (ZmPEPC) gene on nitrogen assimilation in transgenic wheat

Nitrogen (N) is the primary limiting factor for crop growth, development, and productivity. Transgenic technology is a straightforward strategy for improving N assimilation in crops. The present study assessed the effects of maize C4 phosphoenolpyruvate carboxylase (ZmPEPC) gene overexpression on N assimilation in three independent transgenic lines and wild-type (WT) wheat (Triticum aestivum L.). The transgenic wheat lines depicted ZmPEPC overexpression and higher PEPC enzyme activity relative to that in the WT. The leaves of the transgenic wheat lines subjected to low N treatment showed an increase in ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) expression, content, and carboxylase activity. The transgenic wheat lines also depicted an upregulation of genes associated with the anaplerotic pathway for the TCA cycle, suggesting that more carbon (C) skeleton material is being allocated for N assimilation under low N conditions. Furthermore, ZmPEPC expression in transgenic wheat lines induced the upregulated of genes associated primary N metabolism, including TaNR, TaGS2, TaGOGAT, TaAspAT, and TaASN1. The average total free amino acid content in the transgenic wheat lines was 48.18% higher than that in the WT, and asparagine (Asn), glutamine (Gln), aspartic acid (Asp), and serine (Ser) were also markedly enhanced. In addition, elementary analysis showed that N and C content, and the biomass of the transgenic wheat lines increased with low N treatment. Yield trait analysis indicated that ZmPEPC overexpression improved grain yield by increasing 1000-grain weight. In conclusion, ZmPEPC overexpression in wheat could modulate C metabolism, significantly improve N assimilation, enhances growth, and improves yield under low N conditions.