Expression responses of XTH genes in tomato and potato to environmental mechanical forces: focus on behavior in response to rainfall, wind and touch.

Rainfall, wind and touch, as mechanical forces, were mimicked on 6-week-old soil-grown tomato and potato under controlled conditions. Expression level changes of xyloglucan endotransglucosylase/hydrolase genes (XTHs) of tomato (Solanum lycopersicum L. cv. Micro Tom; SlXTHs) and potato (Solanum tuberosum L. cv. Desirée; StXTHs) were analyzed in response to these mechanical forces. Transcription intensity of every SlXTHs of tomato was altered in response to rainfall, while the expression intensity of 72% and 64% of SlXTHs was modified by wind and touch, respectively. Ninety-one percent of StXTHs (32 out of 35) in potato responded to the rainfall, while 49% and 66% of the StXTHs were responsive to the wind and touch treatments, respectively. As previously demonstrated, all StXTHs were responsive to ultrasound treatment, and all were sensitive to one or more of the environmental mechanical factors examined in the current study. To our best knowledge, this is the first study to demonstrate that these ubiquitous mechanical environmental cues, such as rainfall, wind and touch, influence the transcription of most XTHs examined in both species.

Exploring the crop epigenome: a comparison of DNA methylation profiling techniques.

Epigenetic modifications play a vital role in the preservation of genome integrity and in the regulation of gene expression. DNA methylation, one of the key mechanisms of epigenetic control, impacts growth, development, stress response and adaptability of all organisms, including plants. The detection of DNA methylation marks is crucial for understanding the mechanisms underlying these processes and for developing strategies to improve productivity and stress resistance of crop plants. There are different methods for detecting plant DNA methylation, such as bisulfite sequencing, methylation-sensitive amplified polymorphism, genome-wide DNA methylation analysis, methylated DNA immunoprecipitation sequencing, reduced representation bisulfite sequencing, MS and immuno-based techniques. These profiling approaches vary in many aspects, including DNA input, resolution, genomic region coverage, and bioinformatics analysis. Selecting an appropriate methylation screening approach requires an understanding of all these techniques. This review provides an overview of DNA methylation profiling methods in crop plants, along with comparisons of the efficacy of these techniques between model and crop plants. The strengths and limitations of each methodological approach are outlined, and the importance of considering both technical and biological factors are highlighted. Additionally, methods for modulating DNA methylation in model and crop species are presented. Overall, this review will assist scientists in making informed decisions when selecting an appropriate DNA methylation profiling method.

Ultrasound, as a hypomethylating agent, remodels DNA methylation and alters mRNA transcription in winter wheat (Triticum aestivum L.) seedlings.

Any treatment that affects seed germination and seedling development is of paramount importance from an agricultural point of view since they are critical prerequisites for successful crop production. In present study, we have examined the after-effect of ultrasonication (at 30 kHz, 70 W for 5 min) of winter wheat (Triticum aestivum L. cv. SE15) seeds on the early seedling growth and development, and accompanying changes in the DNA methylation and transcriptomic pattern in 7-day-old seedlings. We used mRNA-sequencing and whole genome bisulfite sequencing (WGBS) to identify significantly differentially expressed genes (DEGs), significantly differently methylated regions (DMRs) and genes (DMGs). Ultrasonication of seeds did not alter the germination rate but increased both the length and weight of roots and shoots of 7-day-old seedlings significantly by 23%-68% and 16%-28%, respectively. Analyzing the expression intensity of 107,891 genes, significantly differentially expressed sequences related mainly to starch biosynthesis, IAA biosynthesis, photosynthesis and TCA cycle pathways. The same pathways were also affected by DNA-methylation changes. DNA hypomethylation occurred in the global methylation profile after ultrasound treatment altering the accessibility of some genes for transcription. Transcriptomic changes suggested alterations in the crosstalk between IAA and sucrose signaling, enhancement of growth processes, and increased activity of nuclear transcription factor stimulating the transcription of genes having CCAAT motif in the promoter. In the present first whole genome level study, we have identified seed ultrasonication as a priming technique that can act as a hypomethylating agent and thereby is able to modify the mRNA transcription allowing enhanced seedling growth.

Promoter analysis of the SPATULA (FvSPT) and SPIRAL (FvSPR) genes in the woodland diploid strawberry (Fragaria vesca L.).

The aim of this study was to identify transcription factor (TF) binding sites and cis-regulatory elements (CREs) on the promoters of FvSPR1-like2 (SPIRAL) and FvSPT (SPATULA) genes in the woodland diploid strawberry (Fragaria vesca L.). We identified: (1) MYB59, WRKY25 and WRKY8 TFs which play a role in ethylene signaling; (2) ARF family of TFs which play a role in ARF-mediated auxin signaling on the promoter of FvSPR1-like2 gene; (3) ARR family of TFs which play a role in cytokinin signaling; (4) ERF family of TFs which play a role in ethylene signaling on the promoter of FvSPT. This bioinformatic analysis of TFs and CREs may provide a better understanding of the function of genes involved in, and the mechanism underlying, non-climateric ripening during strawberry fruit maturation.

Abiotic stress elements in in vitro potato (Solanum tuberosum L.) exposed to air-based and liquid-based ultrasound: A comparative transcriptomic assessment.

Ultrasound (US) can modify the plant growth and development. Previous assessments of the transcriptome of in vitro potato (Solanum tuberosum L.) exposed to US transmitted through air (AB-US) or liquid (PE-US) revealed the up- or down-regulation of several stress-related differentially expressed genes (DEGs) related to abiotic stress. In a bid to better characterize stress-related elements over a four-week period, the transcriptome of AB-US was compared to that of PE-US. When comparing the controls of both treatments, DEGs related to hypoxia were not detected. Nevertheless, hypoxia-related DEGs were detected in the combination of liquid medium and ultrasonication. DEGs coding for chitinase, peroxidase, glutathione-S-transferase, transcription factors of ERF (ethylene responsive factor), DREB (dehydration-responsive element-binding), WRKY and MYB were also significantly highly expressed in PE-US, relative to AB-US. Up- and down-regulation of DEGs related to metabolic processes, and enzymes of the antioxidant system also confirm that PE-US is a more acute abiotic stress than AB-US. KEY MESSAGE: A transcriptomic analysis revealed that liquid-based ultrasonication was a stronger abiotic stressor than air-based ultrasonication. Of particular interest were the heat shock proteins and transcription factors in this comparison. Despite the ultrasound stress, explants survived and plantlets developed.

Shoot tip necrosis of in vitro plant cultures: a reappraisal of possible causes and solutions.

MAIN CONCLUSION: Shoot tip necrosis is a physiological condition that negatively impacts the growth and development of in vitro plant shoot cultures across a wide range of species. Shoot tip necrosis is a physiological condition and disorder that can arise in plantlets or shoots in vitro that results in death of the shoot tip. This condition, which can spread basipetally and affect the emergence of axillary shoots from buds lower down the stem, is due to the cessation of apical dominance. STN can occur at both shoot multiplication and rooting stages. One of the most common factors that cause STN is nutrient deficiency or imbalance. Moreover, the presence or absence of plant growth regulators (auxins or cytokinins) at specific developmental stages may impact STN. The cytokinin to auxin ratio within an in vitro plant can be modified by varying the concentration of cytokinins used in the culture medium. The supply of nutrients to in vitro shoots or plantlets might also affect their hormonal balance, thus modifying the occurrence of STN. High relative humidity within culture vessels and hyperhydricity are associated with STN. An adequate supply of calcium as the divalent cation (Ca2+) can hinder STN by inhibiting the accumulation of phenolic compounds and thus programmed cell death. Moreover, the level of Ca2+ affects auxin transport and ethylene production, and higher ethylene production, which can occur as a result of high relative humidity in or poor ventilation of the in vitro culture vessel, induces STN. High relative humidity can decrease the mobility of Ca2+ within a plant, resulting in Ca2+ deficiency and STN. STN of in vitro shoots or plantlets can be halted or reversed by altering the basal medium, mainly the concentration of Ca2+, adjusting the levels of auxins or cytokinins, or modifying culture conditions. This review examines the literature related to STN, seeks to discover the associated factors and relations between them, proposes practical solutions, and attempts to better understand the mechanism(s) underlying this condition in vitro.

Mining sequences with similarity to XTH genes in the Solanum tuberosum L. transcriptome: introductory step for identifying homologous XTH genes.

The xyloglucan endotransglucosylase/hydrolase (XTH) genes in Arabidopsis thaliana (L.) Heynh. form part of a group of mechano-stimulated genes and play an important role in abiotic stress tolerance. Mining the RNAseq transcriptomic database of 40,430 potato (Solanum tuberosum L.) genes based on functional annotation and homology search, our objective was to discover potentially homologous XTH genes. A Gene Ontology-based XTH homology search and functional annotation discovered, from among the 33 A. thaliana (AtXTH) and 25 tomato (Solanum lycopersicum L.) (SlXTH) XTH genes, 35 gene sequences corresponding to 20 AtXTH genes and 40 gene sequences corresponding to 21 SlXTH genes, respectively. Thirteen sequences corresponding to 11 putative XTH genes in potato, named as StXTH after SlXTH genes, were significantly up- or down-regulated in response to ultrasound. These putative StXTH genes in potato can serve for future functional genetic analyses.

Changes in DNA methylation pattern of apple long-term in vitro shoot culture and acclimatized plants.

DNA methylation is a process of epigenetic modification that can alter the functionality of a genome. Using whole-genome bisulfite sequencing, this study quantify the level of DNA methylation in the epigenomes of two diploid apple (Malus x domestica) scion cultivars ('McIntosh' and 'Húsvéti rozmaring') derived from three environmental conditions: in vivo mother plants in an orchard, in vitro culture, and acclimatized in vitro plants. The global DNA methylation levels were not dependent on the source of plant material, and the average level of DNA methylation was 49.77%, 34.65% and 8.77% in CpG, CHG and CHH contexts, respectively. Significant differences in DNA methylation were identified in 586 (specifically 334, 201 and 131 in CpG, CHG and CHH contexts, respectively) out of 45,116 genes, including promoter and coding sequences. These were classified as differentially methylated genes (DMGs). This is a 1.3% difference in the level of DNA methylation of genes in response to a change in the environment. Differential methylation was visualised by MA plots and functional genomic maps were established for biological processes, molecular functions and cellular components. When the DMGs were considered, in vitro tissue culture resulted in the highest level of methylation, but it was lower in acclimatized in vitro plants which was similar to that in the mother tree. Methylation patterns of the two scions differed, indicating cultivar-specific epigenetic regulation of gene expression during adaptation to various environments. After selecting genes that displayed differences larger than ±10% in CpG and CHG contexts, or larger than ±1.35% in the CHH context from among the DMGs, they were annotated in Blast2 GO v5.1.12 for Gene Ontology. DMGs identified as MD07G1113000 (protein transport), MD08G1041600 (extracellular space), MD09G1054800 (phosphatidic acid binding), and MD10G1265800 (not annotated) were methylated in all three contexts in in vitro shoots. These DNA methylation results suggest that epigenetic changes may contribute to the adaptation of apple to environmental changes by modifying the epigenome and thereby gene expression.

mRNA transcription profile of potato (Solanum tuberosum L.) exposed to ultrasound during different stages of in vitro plantlet development.

KEY MESSAGE: In response to an ultrasound pulse, several hundred DEGs, including in response to stress, were up- or down-regulated in in vitro potato plantlets. Despite this abiotic stress, plantlets survived. Ultrasound (US) can influence plant growth and development. To better understand the genetic mechanism underlying the physiological response of potato to US, single-node segments of four-week-old in vitro plantlets were subjected to US at 35 kHz for 20 min. Following mRNA purification, 10 cDNA libraries were assessed by RNA-seq. Significantly differentially expressed genes (DEGs) were categorized by gene ontology or Kyoto Encyclopedia of Genes and Genomes identifiers. The expression intensity of 40,430 genes was studied. Several hundred DEGs associated with biosynthesis, carbohydrate metabolism and catabolism, cellular protein modification, and response to stress, and which were expressed mainly in the extracellular region, nucleus, and plasma membrane, were either up- or down-regulated in response to US. RT-qPCR was used to validate RNA-seq data of 10 highly up- or down-regulated DEGs, and both Spearman and Pearson correlations between SeqMonk LFC and RT-qPCR LFC were highly positive (0.97). This study examines how some processes evolved over time (0 h, 24 h, 48 h, 1 week and 4 weeks) after an abiotic stress (US) was imposed on in vitro potato explants, and provides clues to the temporal dynamics in DEG-based enzyme functions in response to this stress. Despite this abiotic stress, plantlets survived.

The changing epitome of species identification - DNA barcoding.

The discipline taxonomy (the science of naming and classifying organisms, the original bioinformatics and a basis for all biology) is fundamentally important in ensuring the quality of life of future human generation on the earth; yet over the past few decades, the teaching and research funding in taxonomy have declined because of its classical way of practice which lead the discipline many a times to a subject of opinion, and this ultimately gave birth to several problems and challenges, and therefore the taxonomist became an endangered race in the era of genomics. Now taxonomy suddenly became fashionable again due to revolutionary approaches in taxonomy called DNA barcoding (a novel technology to provide rapid, accurate, and automated species identifications using short orthologous DNA sequences). In DNA barcoding, complete data set can be obtained from a single specimen irrespective to morphological or life stage characters. The core idea of DNA barcoding is based on the fact that the highly conserved stretches of DNA, either coding or non coding regions, vary at very minor degree during the evolution within the species. Sequences suggested to be useful in DNA barcoding include cytoplasmic mitochondrial DNA (e.g. cox1) and chloroplast DNA (e.g. rbcL, trnL-F, matK, ndhF, and atpB rbcL), and nuclear DNA (ITS, and house keeping genes e.g. gapdh). The plant DNA barcoding is now transitioning the epitome of species identification; and thus, ultimately helping in the molecularization of taxonomy, a need of the hour. The 'DNA barcodes' show promise in providing a practical, standardized, species-level identification tool that can be used for biodiversity assessment, life history and ecological studies, forensic analysis, and many more.