Td4IN2: A drought-responsive durum wheat (Triticum durum Desf.) gene coding for a resistance like protein with serine/threonine protein kinase, nucleotide binding site and leucine rich domains

A Physiological and Molecular Focus on the Resistance of "Filippo Ceo" Almond Tree to Xylella fastidiosa

The impact of Xylella fastidiosa (Xf) subsp. pauca on the environment and economy of Southern Italy has been devastating. To restore the landscape and support the local economy, introducing new crops is crucial for restoring destroyed olive groves, and the almond tree (Prunus dulcis Mill. D. A. Webb) could be a promising candidate. This work focused on the resistance of the cultivar "Filippo Ceo" to Xf and evaluated its physiological and molecular responses to individual stresses (drought or pathogen stress) and combined stress factors under field conditions over three seasons. Filippo Ceo showed a low pathogen concentration (≈103 CFU mL-1) and a lack of almond leaf scorch symptoms. Physiologically, an excellent plant water status was observed (RWC 82-89%) regardless of the stress conditions, which was associated with an increased proline content compared to that of the control plants, particularly in response to Xf stress (≈8-fold). The plant's response did not lead to a gene modulation that was specific to different stress factors but seemed more indistinct: upregulation of the LEA and DHN gene transcripts by Xf was observed, while the PR transcript was upregulated by drought stress. In addition, the genes encoding the transcription factors (TFs) were differentially induced by stress conditions. Filippo Ceo could be an excellent cultivar for coexistence with Xf subps. pauca, confirming its resistance to both water stress and the pathogen, although this similar health status was achieved differently due to transcriptional reprogramming that results in the modulation of genes directly or indirectly involved in defence strategies.

CePP2C19 confers tolerance to drought by regulating the ABA sensitivity in Cyperus esculentus

BACKGROUND

Tiger nut (Cyperus esculentus) is widely known as an additional source of food, oil and feed worldwide. The agricultural production of tiger nut has been greatly hindered by drought stress, reducing both yield and quality. Protein phosphatase 2 C (PP2Cs) plays an important role in plant responses to drought stress however, the molecular mechanism of PP2Cs in tiger nuts still unclear.

RESULTS

In this study, we identified a putative group A PP2C-encoding gene (CePP2C19) from tiger nut using transcriptome analysis, which is highly induced by drought stress. The transient expression assay suggested that CePP2C19 was localized to nucleus. Furthermore, the interaction between CePP2C19 and CePYR1, a coreceptor for ABA signaling, was first detected using a yeast two-hybrid assay and then verified using a bimolecular fluorescence complementation (BiFC) analysis. In addition, the transgenic Arabidopsis lines overexpressing CePP2C19 exhibited extreme tolerance to ABA and mannitol stresses during seed germination and root growth. At the mature stage, overexpression of CePP2C19 resulted in a higher tolerance to drought stress in transgenic Arabidopsis, as confirmed by a visible phenotype and several physiological parameters. Noticeably, the silencing of CePP2C19 by virus-induced gene silencing (VIGS) showed obvious reduction in drought tolerance in tiger nut plants.

CONCLUSIONS

The CePP2C19 emerges as a pivotal gene involved in the ABA signaling pathway, which likely reduce ABA sensitivity and thus enhances drought tolerance in Cyperus esculentus.

Proteomics approach to investigating osmotic stress effects on pistachio

Osmotic stress can occur due to some stresses such as salinity and drought, threatening plant survival. To investigate the mechanism governing the pistachio response to this stress, the biochemical alterations and protein profile of PEG-treated plants was monitored. Also, we selected two differentially abundant proteins to validate via Real-Time PCR. Biochemical results displayed that in treated plants, proline and phenolic content was elevated, photosynthetic pigments except carotenoid decreased and MDA concentration were not altered. Our findings identified a number of proteins using 2DE-MS, involved in mitigating osmotic stress in pistachio. A total of 180 protein spots were identified, of which 25 spots were altered in response to osmotic stress. Four spots that had photosynthetic activities were down-regulated, and the remaining spots were up-regulated. The biological functional analysis of protein spots exhibited that most of them are associated with the photosynthesis and metabolism (36%) followed by stress response (24%). Results of Real-Time PCR indicated that two of the representative genes illustrated a positive correlation among transcript level and protein expression and had a similar trend in regulation of gene and protein. Osmotic stress set changes in the proteins associated with photosynthesis and stress tolerance, proteins associated with the cell wall, changes in the expression of proteins involved in DNA and RNA processing occur. Findings of this research will introduce possible proteins and pathways that contribute to osmotic stress and can be considered for improving osmotic tolerance in pistachio.

The Ups and Downs of Plant NLR Expression During Pathogen Infection

Plant Nucleotide binding-Leucine rich repeat (NLR) proteins play a significant role in pathogen detection and the activation of effector-triggered immunity. NLR regulation has mainly been studied at a protein level, with large knowledge gaps remaining regarding the transcriptional control of NLR genes. The mis-regulation of NLR gene expression may lead to the inability of plants to recognize pathogen infection, lower levels of immune response activation, and ultimately plant susceptibility. This highlights the importance of understanding all aspects of NLR regulation. Three main mechanisms have been shown to control NLR expression: epigenetic modifications, cis elements which bind transcription factors, and post-transcriptional modifications. In this review, we aim to provide an overview of these mechanisms known to control NLR expression, and those which contribute toward successful immune responses. Furthermore, we discuss how pathogens can interfere with NLR expression to increase pathogen virulence. Understanding how these molecular mechanisms control NLR expression would contribute significantly toward building a complete picture of how plant immune responses are activated during pathogen infection-knowledge which can be applied during crop breeding programs aimed to increase resistance toward numerous plant pathogens.

Association Mapping of Drought Tolerance Indices in Ethiopian Durum Wheat (Triticum turgidum ssp. durum)

Ethiopia is a major producer of durum wheat in sub-Saharan Africa. However, its production is prone to drought stress as it is fully dependent on rain, which is erratic and unpredictable. This study aimed to detect marker-trait associations (MTAs) and quantitative trait loci (QTLs) related to indices. Six drought tolerance indices, i.e., drought susceptibility index (DSI), geometric mean productivity (GMP), relative drought index (RDI), stress tolerance index (STI), tolerance index (TOL), and yield stability index (YSI) were calculated from least-square means (lsmeans) of grain yield (GY) and traits significantly (p < 0.001) correlated with grain yield (GY) under field drought stress (FDS) and field non-stress (FNS) conditions. GY, days to grain filling (DGF), soil plant analysis development (SPAD) chlorophyll meter, seeds per spike (SPS), harvest index (HI), and thousand kernel weight (TKW) were used to calculate DSI, GMP, RDI, STI, TOL, and YSI drought indices. Accessions, DW084, DW082, DZ004, C037, and DW092 were selected as the top five drought-tolerant based on DSI, RDI, TOL, and YSI combined ranking. Similarly, C010, DW033, DW080, DW124-2, and C011 were selected as stable accessions based on GMP and STI combined ranking. A total of 184 MTAs were detected linked with drought indices at -log₁₀p ≥ 4.0,79 of which were significant at a false discovery rate (FDR) of 5%. Based on the linkage disequilibrium (LD, r ² ≥ 0.2), six of the MTAs with a positive effect on GY-GMP were detected on chromosomes 2B, 3B, 4A, 5B, and 6B, explaining 14.72, 10.07, 26.61, 21.16, 21.91, and 22.21% of the phenotypic variance, respectively. The 184 MTAs were clustered into 102 QTLs. Chromosomes 1A, 2B, and 7A are QTL hotspots with 11 QTLs each. These chromosomes play a key role in drought tolerance and respective QTL may be exploited by marker-assisted selection for improving drought stress tolerance in wheat.

A stress-related transcription factor belonging to the YL-1 family is differently regulated in durum wheat cultivars differing in drought sensitivity

The Mediterranean area is characterised by unfavorable environmental conditions such as heat stress and drought responsible for yield loss of crops like durum wheat, widely cultivated in this area. The response of plants to stressing environments is mediated by activation of a complex gene network, strictly related to the genetic background. Among the genes induced by drought, those coding for proteins acting as key regulators of signal transduction are of great interest. Characterization of these genes is a crucial point to understand their potential roles in plant stress response, also in view of their possible use in molecular breeding. In this work we have characterised a Triticum durum gene, named TdDRG1, in two commercial cultivars, Primadur and Svevo, differing for drought stress resistance. TdDRG1 codes for a putative transcription factor belonging to the VPS72/YL-1 family, highly conserved in plants and animals. The expression analysis indicates that this gene is expressed at higher level in roots of the resistant cultivar Svevo, than in the susceptible Primadur. The gene structure was determined in both cultivars and the regulatory activity of 5' upstream regions was analyzed by transient expression analysis using tobacco protoplasts. Dissimilar expression level of TdDRG1 in the two cultivars can be explained by the differences observed in gene structure. In particular, differences in 5' upstream regions could account for contrasting ability to cope with drought of the two cultivars. The data obtained in this study provide indications for further insight into the molecular basis of differences in drought stress response.

Genome-Wide Association of Stem Carbohydrate Accumulation and Remobilization during Grain Growth in Bread Wheat (Triticum aestivum L.) in Mediterranean Environments

Water deficit represents an important challenge for wheat production in many regions of the world. Accumulation and remobilization of water-soluble carbohydrates (WSCs) in stems are part of the physiological responses regulated by plants to cope with water stress and, in turn, determine grain yield (GY). The genetic mechanisms underlying the variation in WSC are only partially understood. In this study, we aimed to identify Single Nucleotide Polymorphism (SNP) markers that account for variation in a suite of WSC and GY, evaluated in 225 cultivars and advanced lines of spring wheat. These genotypes were established in two sites in the Mediterranean region of Central Chile, under water-limited and full irrigation conditions, and assessed in two growing seasons, namely anthesis and maturity growth periods. A genome-wide association study (GWAS) was performed by using 3243 SNP markers. Genetic variance accounted for 5 to 52% of phenotypic variation of the assessed traits. A rapid linkage disequilibrium decay was observed across chromosomes (r² ≤ 0.2 at 2.52 kbp). Marker-trait association tests identified 96 SNPs related to stem weight (SW), WSCs, and GY, among other traits, at the different sites, growing seasons, and growth periods. The percentage of SNPs that were part of the gene-coding regions was 34%. Most of these genes are involved in the defensive response to drought and biotic stress. A complimentary analysis detected significant effects of different haplotypes on WSC and SW, in anthesis and maturity. Our results evidence both genetic and environmental influence on WSC dynamics in spring wheat. At the same time, they provide a series of markers suitable for supporting assisted selection approaches and functional characterization of genes.

Identifying resurrection genes through the differentially expressed genes between Selaginella tamariscina (Beauv.) spring and Selaginella moellendorffii Hieron under drought stress

Selaginella tamariscina (Beauv.) spring, a primitive vascular resurrection plant, can survive extreme drought and recover when water becomes available. To identify drought-inducible genes and to clarify the molecular mechanism of drought tolerance, a comparative transcriptional pattern analysis was conducted between S. tamariscina and Selaginella moellendorffii Hieron (drought sensitive). 133 drought related genes were identified, including 72 functional genes and 61 regulatory genes. And several drought responsive reactions, such as antioxidant activity, osmotic balance, cuticle defense and signal transduction were highlighted in S. tamariscina under drought. Notably, besides peroxidase, catalase and L-ascorbate oxidase genes, DEGs associated with phenylalanine metabolism and polyamine catabolism could be alternative ways to enhance antioxidant ability in S. tamariscina. DEGs related to soluble carbohydrate metabolism, late embryogenesis abundant protein (LEA) and aquaporin protein (AQP) confirmed that osmotic adjustment could resist drought during desiccation. DEGs involved in xyloglucan metabolic process, pectin metabolic process and cutin biosynthesis may also contribute to drought tolerance of S. tamariscina by cuticle defense. Drought-responsive genes encoding protein kinases, calcium sensors, transcription factors (TFs) and plant hormones also help to drought resistance of S. tamariscina. The preliminary validation experiments were performed and the results were consistent with our hypothetical integrated regulatory network. The results of this study provide candidate resurrection genes and an integrated regulatory network for further studies on the molecular mechanisms of stress tolerance in S. tamariscina.

Knock-down the expression of TaH2B-7D using virus-induced gene silencing reduces wheat drought tolerance

Background

Drought is a major abiotic stress affecting global wheat (Triticum aestivum L.) production. Exploration of drought-tolerant genes is essential for the genetic improvement of drought tolerance in wheat. Previous studies have shown that some histone encoding genes are involved in plant drought tolerance. However, whether the H2B family genes are involved in drought stress response remains unclear.

Methods

Here, we identified a wheat histone H2B family gene, TaH2B-7D, which was significantly up-regulated under drought stress conditions. Virus-induced gene silencing (VIGS) technology was used to further verify the function of TaH2B-7D in wheat drought tolerance. The phenotypic and physiological changes were examined in the TaH2B-7D knock-down plants.

Results

In the TaH2B-7D knock-down plants, relative electrolyte leakage rate and malonaldehyde (MDA) content significantly increased, while relative water content (RWC) and proline content significantly decreased compared with those in the non-knocked-down plants under drought stress conditions. TaH2B-7D knock-down plants exhibited severe sagging, wilting and dwarf phenotypes under drought stress conditions, but not in the non-knocked-down plants, suggesting that the former were more sensitive to drought stress.

Conclusion

These results indicate that TaH2B-7D potentially plays a vital role in conferring drought tolerance in wheat.