Wheat and Barley: Acclimatization to Abiotic and Biotic Stress

Salinity inhibits seed germination and embryo growth by reducing starch mobilization efficiency in barley

Barley is one of the world's earliest domesticated crops, which is widely used for beer production, animal feeding, and health care. Barley seed germination, particularly in increasingly saline soils, is key to ensure the safety of crop production. However, the mechanism of salt-affected seed germination in barley remains elusive. Here, two different colored barley varieties were used to independently study the regulation mechanism of salt tolerance during barley seed germination. High salinity delays barley seed germination by slowing down starch mobilization efficiency in seeds. The starch plate test revealed that salinity had a significant inhibitory effect on α-amylase activity in barley seeds. Further, NaCl treatment down-regulated the expression of Amy1, Amy2 and Amy3 genes in germinated seeds, thereby inhibiting α-amylase activity. In addition, the result of embryogenic culture system in vitro showed that the shoot elongation of barley was significantly inhibited by salt stress. These findings indicate that it is a feasible idea to study the regulation mechanism of salinity on barley seed germination and embryo growth from the aspect of starch-related source-sink communication.

Basic helix-loop-helix (bHLH) gene family in rye (Secale cereale L.): genome-wide identification, phylogeny, evolutionary expansion and expression analyses

BACKGROUND

Rye (Secale cereale), one of the drought and cold-tolerant crops, is an important component of the Triticae Dumortier family of Gramineae plants. Basic helix-loop-helix (bHLH), an important family of transcription factors, has played pivotal roles in regulating numerous intriguing biological processes in plant development and abiotic stress responses. However, no systemic analysis of the bHLH transcription factor family has yet been reported in rye.

RESULTS

In this study, 220 bHLH genes in S. cereale (ScbHLHs) were identified and named based on the chromosomal location. The evolutionary relationships, classifications, gene structures, motif compositions, chromosome localization, and gene replication events in these ScbHLH genes are systematically analyzed. These 220 ScbHLH members are divided into 21 subfamilies and one unclassified gene. Throughout evolution, the subfamilies 5, 9, and 18 may have experienced stronger expansion. The segmental duplications may have contributed significantly to the expansion of the bHLH family. To systematically analyze the evolutionary relationships of the bHLH family in different plants, we constructed six comparative genomic maps of homologous genes between rye and different representative monocotyledonous and dicotyledonous plants. Finally, the gene expression response characteristics of 22 ScbHLH genes in various biological processes and stress responses were analyzed. Some candidate genes, such as ScbHLH11, ScbHLH48, and ScbHLH172, related to tissue developments and environmental stresses were screened.

CONCLUSIONS

The results indicate that these ScbHLH genes exhibit characteristic expression in different tissues, grain development stages, and stress treatments. These findings provided a basis for a comprehensive understanding of the bHLH family in rye.

Analysis of Raffinose Synthase Gene Family in Bread Wheat and Identification of Drought Resistance and Salt Tolerance Function of TaRS15-3B

Raffinose synthase (RS) plays a crucial role in plant growth and development, as well as in responses to biotic stresses and abiotic stresses, yet few studies have been conducted on its role in bread wheat. Therefore, in this study we screened and identified a family of bread wheat raffinose synthase genes based on bread wheat genome information and analyzed their physicochemical properties, phylogenetic evolutionary relationships, conserved structural domains, promoter cis-acting elements, and expression patterns. The BSMV-induced silencing of TaRS15-3B resulted in the bread wheat seedlings being susceptible to drought and salt stress and reduced the expression levels of stress-related and ROS-scavenging genes in bread wheat plants. This further affected the ability of bread wheat to cope with drought and salt stress. In conclusion, this study revealed that the RS gene family in bread wheat plays an important role in plant response to abiotic stresses and that the TaRS15-3B gene can improve the tolerance of transgenic bread wheat to drought and salt stresses, provide directions for the study of other RS gene families in bread wheat, and supply candidate genes for use in molecular breeding of bread wheat for stress resistance.

Abscisic acid mimic-fluorine derivative 4 alleviates water deficit stress by regulating ABA-responsive genes, proline accumulation, CO2 assimilation, water use efficiency and better nutrient uptake in tomato plants

Water deficit represents a serious limitation for agriculture and both genetic and chemical approaches are being used to cope with this stress and maintain plant yield. Next-generation agrochemicals that control stomatal aperture are promising for controlling water use efficiency. For example, chemical control of abscisic acid (ABA) signaling through ABA-receptor agonists is a powerful method to activate plant adaptation to water deficit. Such agonists are molecules able to bind and activate ABA receptors and, although their development has experienced significant advances in the last decade, few translational studies have been performed in crops. Here, we describe protection by the ABA mimic-fluorine derivative 4 (AMF4) agonist of the vegetative growth in tomato plants subjected to water restriction. Photosynthesis in mock-treated plants is markedly impaired under water deficit conditions, whereas AMF4 treatment notably improves CO₂ assimilation, the relative plant water content and growth. As expected for an antitranspirant molecule, AMF4 treatment diminishes stomatal conductance and transpiration in the first phase of the experiment; however, when photosynthesis declines in mock-treated plants as stress persists, higher photosynthetic and transpiration parameters are recorded in agonist-treated plants. Additionally, AMF4 increases proline levels over those achieved in mock-treated plants in response to water deficit. Thus water deficit and AMF4 cooperate to upregulate P5CS1 through both ABA-independent and ABA-dependent pathways, and therefore, higher proline levels are produced Finally, analysis of macronutrients reveals higher levels of Ca, K and Mg in AMF4- compared to mock-treated plants subjected to water deficit. Overall, these physiological analyses reveal a protective effect of AMF4 over photosynthesis under water deficit and enhanced water use efficiency after agonist treatment. In summary, AMF4 treatment is a promising approach for farmers to protect the vegetative growth of tomatoes under water deficit stress.

Impacts of recent climate change on crop yield can depend on local conditions in climatically diverse regions of Norway

Globally, climate change greatly impacts the production of major crops, and there have been many attempts to model future yields under warming scenarios in recent years. However, projections of future yields may not be generalisable to all crop growing regions, particularly those with diverse topography and bioclimates. In this study, we demonstrate this by evaluating the links between changes in temperature and precipitation and changes in wheat, barley, and potato yields at the county-level during 1980-2019 in Norway, a Nordic country with a range of climates across a relatively small spatial scale. The results show that the impacts of climate variables on yield vary widely by county, and that for some crops, the strength and direction of the link depends on underlying local bioclimate. In addition, our analysis demonstrates the need for some counties to focus on weather changes during specific crucial months corresponding with certain crop growth stages. Furthermore, due to the local climatic conditions and varying projected climate changes, different production opportunities are likely to occur in each county.

Drought-Stress Induced Physiological and Molecular Changes in Plants 2.0

Plant adaptation to soil drought is a topic that is currently under investigation [...].

Exploring and exploiting cuticle biosynthesis for abiotic and biotic stress tolerance in wheat and barley

Wheat and barley are widely distributed cereal crops whose yields are adversely affected by environmental stresses such as drought, salinity, extreme temperatures, and attacks of pathogens and pests. As the interphase between aerial plant organs and their environments, hydrophobic cuticle largely consists of a cutin matrix impregnated and sealed with cuticular waxes. Increasing evidence supports that the cuticle plays a key role in plant adaptation to abiotic and biotic stresses, which could be harnessed for wheat and barley improvement. In this review, we highlighted recent advances in cuticle biosynthesis and its multifaceted roles in abiotic and biotic stress tolerance of wheat and barley. Current strategies, challenges, and future perspectives on manipulating cuticle biosynthesis for abiotic and biotic stress tolerance in wheat and barley are discussed.

Transcriptome and Proteome Co-Profiling Offers an Understanding of Pre-Harvest Sprouting (PHS) Molecular Mechanisms in Wheat (Triticum aestivum)

While wheat (Triticum aestivum L.) is a widely grown and enjoyed crop, the diverse and complex global situation and climate are exacerbating the instability of its supply. In particular, pre-harvest sprouting (PHS) is one of the major abiotic stresses that frequently occurs due to irregular climate conditions, causing serious damage to wheat and its quality. In this study, transcriptomic analysis with RNA-seq and proteomic analysis with LC-MS/MS were performed in PHS-treated spikes from two wheat cultivars presenting PHS sensitivity and tolerance, respectively. A total of 13,154 differentially expressed genes (DEGs) and 706 differentially expressed proteins (DEPs) were identified in four comparison groups between the susceptible/tolerant cultivars. Gene function and correlation analysis were performed to determine the co-profiled genes and proteins affected by PHS treatment. In the functional annotation of each comparative group, similar functions were confirmed in each cultivar under PHS treatment; however, in Keumgang PHS+7 (K7) vs. Woori PHS+7 (W7), functional annotations presented clear differences in the "spliceosome" and "proteasome" pathways. In addition, our results indicate that alternative splicing and ubiquitin-proteasome support the regulation of germination and seed dormancy. This study provides an advanced understanding of the functions involved in transcription and translation related to PHS mechanisms, thus enabling specific proposals for the further analysis of germination and seed dormancy mechanisms and pathways in wheat.

Natural 2-Amino-3-Methylhexanoic Acid as Plant Elicitor Inducing Resistance against Temperature Stress and Pathogen Attack

2-Amino-3-methylhexanoic acid (AMHA) was synthetized as a non-natural amino acid more than 70 years ago; however, its possible function as an inducer of plant resistance has not been reported. Plant resistance inducers, also known as plant elicitors, are becoming a novel and important development direction in crop protection and pest management. We found that free AMHA accumulated in the mycelia but not in fermentation broths of four fungal species, Magnaporthe oryzae and three Alternaria spp. We unequivocally confirmed that AMHA is a naturally occurring endogenous (2S, 3S)-α-amino acid, based on isolation, purification and structural analyses. Further experiments demonstrated that AMHA has potent activity-enhancing resistance against extreme temperature stresses in several plant species. It is also highly active against fungal, bacterial and viral diseases by inducing plant resistance. AMHA pretreatment strongly protected wheat against powdery mildew, Arabidopsis against Pseudomonas syringae DC3000 and tobacco against Tomato spotted wilt virus. AMHA exhibits a great potential to become a unique natural elicitor protecting plants against biotic and abiotic stresses.

In-Vivo Biophoton Emission, Physiological and Oxidative Responses of Biostimulant-Treated Winter Wheat (Triticum eastivum L.) as Seed Priming Possibility, for Heat Stress Alleviation

High temperature induces oxidative processes in wheat, the alleviation of which is promising using biostimulants. Priming has been used for enhancing stress tolerance of seedlings. However, the usage of biostimulants for priming is an unexplored area under either normal or stress conditions. Therefore, the aim of our study was to evaluate the heat stress alleviation capability of differentially applied biostimulant treatments on wheat seedlings. The investigation included stress parameters (fresh/dry weight ratio, chlorophyll content estimation, antioxidant capacity and lipid oxidation) combined with biophoton emission measurement, since with this latter non-invasive technique, it is possible to measure and elucidate in vivo stress conditions in real-time using lipid oxidation-related photon emissions. We confirmed that a single biostimulant pretreatment increased antioxidant capacity and decreased biophoton release and lipid oxidation, indicating the reduction of the harmful effects of heat stress. Therefore, biophoton emission proved to be suitable for detecting and imaging the effects of heat stress on wheat seedlings for the first time. Two-way analysis of variance (ANOVA) revealed that biostimulant (p = 4.01 × 10⁻⁷) treatments, temperature (p = 9.07 × 10⁻⁸), and the interaction of the two factors (p = 2.07 × 10⁻⁵) had a significant effect on the overall count per second values of biophoton emission, predicting more efficient biostimulant utilization practices, even for seed priming purposes.

Wheat inositol pyrophosphate kinase TaVIH2-3B modulates cell-wall composition and drought tolerance in Arabidopsis

Background

Inositol pyrophosphates (PP-InsPs) are high-energy derivatives of inositol, involved in different signalling and regulatory responses of eukaryotic cells. Distinct PP-InsPs species are characterized by the presence of phosphate at a variable number of the 6-carbon inositol ring backbone, and two distinct classes of inositol phosphate kinases responsible for their synthesis have been identified in Arabidopsis, namely ITPKinase (inositol 1,3,4 trisphosphate 5/6 kinase) and PP-IP5Kinase (diphosphoinositol pentakisphosphate kinases). Plant PP-IP5Ks are capable of synthesizing InsP₈ and were previously shown to control defense against pathogens and phosphate response signals. However, other potential roles of plant PP-IP5Ks, especially towards abiotic stress, remain poorly understood.

Results

Here, we characterized the physiological functions of two Triticum aestivum L. (hexaploid wheat) PPIP5K homologs, TaVIH1 and TaVIH2. We demonstrate that wheat VIH proteins can utilize InsP₇ as the substrate to produce InsP₈, a process that requires the functional VIH-kinase domains. At the transcriptional level, both TaVIH1 and TaVIH2 are expressed in different wheat tissues, including developing grains, but show selective response to abiotic stresses during drought-mimic experiments. Ectopic overexpression of TaVIH2-3B in Arabidopsis confers tolerance to drought stress and rescues the sensitivity of Atvih2 mutants. RNAseq analysis of TaVIH2-3B-expressing transgenic lines of Arabidopsis shows genome-wide reprogramming with remarkable effects on genes involved in cell-wall biosynthesis, which is supported by the observation of enhanced accumulation of polysaccharides (arabinogalactan, cellulose, and arabinoxylan) in the transgenic plants.

Conclusions

Overall, this work identifies a novel function of VIH proteins, implicating them in modulation of the expression of cell-wall homeostasis genes, and tolerance to water-deficit stress. This work suggests that plant VIH enzymes may be linked to drought tolerance and opens up the possibility of future research into using plant VIH-derived products to generate drought-resistant plants.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01198-8.

An Overview of Abiotic Stress in Cereal Crops: Negative Impacts, Regulation, Biotechnology and Integrated Omics

Abiotic stresses (AbS), such as drought, salinity, and thermal stresses, could highly affect the growth and development of plants. For decades, researchers have attempted to unravel the mechanisms of AbS for enhancing the corresponding tolerance of plants, especially for crop production in agriculture. In the present communication, we summarized the significant factors (atmosphere, soil and water) of AbS, their regulations, and integrated omics in the most important cereal crops in the world, especially rice, wheat, sorghum, and maize. It has been suggested that using systems biology and advanced sequencing approaches in genomics could help solve the AbS response in cereals. An emphasis was given to holistic approaches such as, bioinformatics and functional omics, gene mining and agronomic traits, genome-wide association studies (GWAS), and transcription factors (TFs) family with respect to AbS. In addition, the development of omics studies has improved to address the identification of AbS responsive genes and it enables the interaction between signaling pathways, molecular insights, novel traits and their significance in cereal crops. This review compares AbS mechanisms to omics and bioinformatics resources to provide a comprehensive view of the mechanisms. Moreover, further studies are needed to obtain the information from the integrated omics databases to understand the AbS mechanisms for the development of large spectrum AbS-tolerant crop production.