Heat stress affects carbohydrate metabolism during cold-induced sweetening of potato (Solanum tuberosum L.)

A quick and effective method for thermostability differentiation in cucumber (Cucumis sativus L.)

High temperature affects the growth and production of cucumber. Selecting thermotolerant cucumber cultivars is conducive to coping with high temperatures and improving production. Thus, a quick and effective method for screening thermotolerant cucumber cultivars is needed. In this study, four cucumber cultivars were used to identify heat resistance indexes. The morphological, physiological and biochemical indexes were measured. When exposed to high temperatures, thermotolerant cucumber had a more stable photosystem, membrane, and oxidation-reduction systems. The impact of high temperatures on plants is multifaceted, and the accurate discrimination of heat resistance cannot be achieved solely based on a single or multiple indicators. Therefore, principal component analysis (PCA) was employed to comprehensively evaluate the heat resistance of cucumber plants. The results showed that the heat resistance obtained by PCA was significantly correlated with the heat injury index. In addition, the stepwise regression equation identified two heat-related indices, hydrogen peroxide content (H2 O2 ) and photosynthetic operating efficiency (Fq'/Fm'), and they can quickly distinguish the heat resistance of the other 8 cucumber cultivars. These results will help to accelerate the selection of thermotolerant resources and assist in cucumber breeding.

Heterologous Expression of OtsB Increases Tuber Yield and Phenotypic Stability in Potato under Both Abiotic and Biotic Stresses

Climate-smart and sustainable crops are needed for the future. Engineering crops for tolerance of both abiotic and biotic stress is one approach. The accumulation of trehalose, controlled through trehalose-6-phosphate synthase (TPS) or OtsA and trehalose-6-phosphate phosphatase (TPP) or OtsB genes in microbes, is known to provide protection for many microbial and fungal species against abiotic stress. The effect of trehalose accumulation in plant species is less understood. Here, we studied the heterologous expression of Escherichia coli OtsB in potato (Solanum tuberosum var. 'Desiree') with regards to stress tolerance. The performance of transgenic lines was assessed in both growth chambers and greenhouse mesocosms. Overexpressing potato OtsB lines significantly increased resilience to heat, photoperiod, herbivory, and competition when compared with wildtype plants. Most strikingly, when subjected to high temperatures, transgenic lines exhibited a significantly lower reduction in tuber yield ranging from 40% to 77%, while wildtype plants experienced a 95% decrease in tuber yield. When exposed to competitors in a selected StSP3D::OtsB line, tuber yield was 1.6 times higher than wildtype. Furthermore, transgenic lines performed significantly better under low-nutrient regimes: under competition, yield increased by 1.5-fold. Together, these results demonstrate that increased trehalose has the potential to create more resistant and stable crop plants.

Exploring the Heat Shock Transcription Factor (HSF) Gene Family in Ginger: A Genome-Wide Investigation on Evolution, Expression Profiling, and Response to Developmental and Abiotic Stresses

Ginger is a valuable crop known for its nutritional, seasoning, and health benefits. However, abiotic stresses, such as high temperature and drought, can adversely affect its growth and development. Heat shock transcription factors (HSFs) have been recognized as crucial elements for enhancing heat and drought resistance in plants. Nevertheless, no previous study has investigated the HSF gene family in ginger. In this research, a total of 25 ZoHSF members were identified in the ginger genome, which were unevenly distributed across ten chromosomes. The ZoHSF members were divided into three groups (HSFA, HSFB, and HSFC) based on their gene structure, protein motifs, and phylogenetic relationships with Arabidopsis. Interestingly, we found more collinear gene pairs between ZoHSF and HSF genes from monocots, such as rice, wheat, and banana, than dicots like Arabidopsis thaliana. Additionally, we identified 12 ZoHSF genes that likely arose from duplication events. Promoter analysis revealed that the hormone response elements (MEJA-responsiveness and abscisic acid responsiveness) were dominant among the various cis-elements related to the abiotic stress response in ZoHSF promoters. Expression pattern analysis confirmed differential expression of ZoHSF members across different tissues, with most showing responsiveness to heat and drought stress. This study lays the foundation for further investigations into the functional role of ZoHSFs in regulating abiotic stress responses in ginger.

Impact of Fusarium Infection on Potato Quality, Starch Digestibility, In Vitro Glycemic Response, and Resistant Starch Content

Potato dry rot disease caused by multiple Fusarium species is a major global concern in potato production. In this investigation, the tubers of cultivars Kufri Jyoti and Kufri Frysona were artificially inoculated with an individual or combined inoculum of Fusarium sambucinum and Fusarium solani. Fusarium sambucinum caused a significantly higher lesion development (p < 0.01) than Fusarium solani, irrespective of cultivars. The combined inoculum of both the Fusarium species caused significantly higher rot development (p < 0.005) in inoculated tubers. Analyses of starch and amylose content revealed that individual or mixed infection of fungi caused a significant reduction (p < 0.005) in these parameters compared to healthy tubers. The increased starch digestibility due to fungal infection caused a higher glycemic index and glycemic load. The resistant starch also deteriorated in the infected potato tubers as compared to the control. Kufri Jyoti showed a higher starch and amylose content reduction in response to the treatments compared to Kufri Frysona. The correlation analysis demonstrated a negative correlation in lesion diameter and rot volume with starch and amylose content (p < -0.80). However, the glycemic index and resistant starch were positively correlated with lesion development. Altogether, these findings highlight the progressive deterioration of quality parameters, which will be a critical concern for processing industry stakeholders and consumers.

Differential Physiological, Transcriptomic, and Metabolomic Responses of Paspalum wettsteinii Under High-Temperature Stress

Global warming has far-reaching effects on plant growth and development. As a warm-season forage grass, Paspalum wettsteinii is highly adaptable to high temperatures. However, the response mechanism of P. wettsteinii under high-temperature stress is still unclear. Therefore, we investigated the physiological indicators, transcriptome and metabolome of P. wettsteinii under different heat stress treatments. Plant height, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and the contents of soluble sugar, proline, chlorophyll a, and chlorophyll b increased and then decreased, while the malondialdehyde (MDA) content decreased and then increased with increasing heat stress. Transcriptomic analysis revealed that genes related to energy and carbohydrate metabolism, heat shock proteins (HSPs), and transcription factors (TFs), secondary metabolite biosynthesis and the antioxidant system significantly changed to varying degrees. Metabolomic analysis showed that only free fatty acids were downregulated, while amino acids and their derivatives, organic acids, flavonoids, and sugars were both up- and downregulated under heat stress. These combined analyses revealed that growth was promoted at 25-40°C, while at 45°C, excess reactive oxygen species (ROS) damage reduced antioxidant and osmoregulatory effects and inactivated genes associated with the light and electron transport chains (ETCs), as well as damaged the PS II system and inhibited photosynthesis. A small number of genes and metabolites were upregulated to maintain the basic growth of P. wettsteinii. The physiological and biochemical changes in response to high-temperature stress were revealed, and the important metabolites and key genes involved in the response to high temperature were identified, providing an important reference for the physiological and molecular regulation of high-temperature stress in plants.

Genome-Wide Analysis of the HSP20 Gene Family and Expression Patterns of HSP20 Genes in Response to Abiotic Stresses in Cynodon transvaalensis

African bermudagrass (Cynodon transvaalensis Burtt-Davy) is an important warm-season turfgrass and forage grass species. Heat shock protein 20 (HSP20) is a diverse, ancient, and important protein family. To date, HSP20 genes have not been characterized genome-widely in African bermudagrass. Here, we confirmed 41 HSP20 genes in African bermudagrass genome. On the basis of the phylogenetic tree and cellular locations, the HSP20 proteins were classified into 12 subfamilies. Motif composition was consistent with the phylogeny. Moreover, we identified 15 pairs of paralogs containing nine pairs of tandem duplicates and six pairs of WGD/segmental duplicates of HSP20 genes. Unsurprisingly, the syntenic genes revealed that African bermudagrass had a closer evolutionary relationship with monocots (maize and rice) than dicots (Arabidopsis and soybean). The expression patterns of HSP20 genes were identified with the transcriptome data under abiotic stresses. According to the expression profiles, HSP20 genes could be clustered into three groups (Groups I, II, and III). Group I was the largest, and these genes were up-regulated in response to heat stress as expected. In Group II, one monocot-specific HSP20, CtHSP20-14 maintained higher expression levels under optimum temperature and low temperature, but not high temperature. Moreover, a pair of WGD/segmental duplicates CtHSP20-9 and CtHSP20-10 were among the most conserved HSP20s across different plant species, and they seemed to be positively selected in response to extreme temperatures during evolution. A total of 938 cis-elements were captured in the putative promoters of HSP20 genes. Almost half of the cis-elements were stress responsive, indicating that the expression pattern of HSP20 genes under abiotic stresses might be largely regulated by the cis-elements. Additionally, three-dimensional structure simulations and protein-protein interaction networks were incorporated to resolve the function mechanism of HSP20 proteins. In summary, the findings fulfilled the HSP20 family analysis and could provide useful information for further functional investigations of the specific HSP20s (e.g., CtHSP20-9, CtHSP20-10, and CtHSP20-14) in African bermudagrass.

Transcriptome analysis of heat stress response genes in potato leaves

Heat stress has a severe impact on potato growth and tuberization process, always resulting in the decrease of tuber yield and quality. Therefore, it is of great significance for potato breeding to illuminate the mechanism of heat stress on potato and explore heat resistant genes. In this study, two cDNA libraries from normal potato leaves (20 °C day/18 °C night) and potato leaves with 3 days of heat treatment (35 °C day/28 °C night) were constructed respectively. Totally, 1420 differentially expressed genes (DEGs) were identified. The expression patterns of 12 randomly selected genes detected using droplet digital PCR agreed with the sequencing data. Gene ontology analysis showed that these DEGs were clustered into 49 different GO types, reflecting the functional diversity of the heat stress response genes. The results of KEGG pathway enrichment showed the potential biological pathways in which the DEGs were involved, indicating that these pathways may be involved in heat tolerance regulation. Most potato heat transcription factors (StHsfs) and heat shock proteins (StHsps) were not expressed efficiently based on expression profile of these DEGs. StHsp26-CP and StHsp70 were markedly increased after 3 days of heat treatment. These data will be useful for further understanding the molecular mechanisms of potato plant tolerance to heat stress and provide a basis for breeding heat-tolerance varieties.

Cultivar-specific nutritional status of potato (Solanum tuberosum L.) crops

Gradients in the elemental composition of a potato leaf tissue (i.e. its ionome) can be linked to crop potential. Because the ionome is a function of genetics and environmental conditions, practitioners aim at fine-tuning fertilization to obtain an optimal ionome based on the needs of potato cultivars. Our objective was to assess the validity of cultivar grouping and predict potato tuber yields using foliar ionomes. The dataset comprised 3382 observations in Québec (Canada) from 1970 to 2017. The first mature leaves from top were sampled at the beginning of flowering for total N, P, K, Ca, and Mg analysis. We preprocessed nutrient concentrations (ionomes) by centering each nutrient to the geometric mean of all nutrients and to a filling value, a transformation known as row-centered log ratios (clr). A density-based clustering algorithm (dbscan) on these preprocessed ionomes failed to delineate groups of high-yield cultivars. We also used the preprocessed ionomes to assess their effects on tuber yield classes (high- and low-yields) on a cultivar basis using k-nearest neighbors, random forest and support vector machines classification algorithms. Our machine learning models returned an average accuracy of 70%, a fair diagnostic potential to detect in-season nutrient imbalance of potato cultivars using clr variables considering potential confounding factors. Optimal ionomic regions of new cultivars could be assigned to the one of the closest documented cultivar.

Genome-wide investigation of the heat shock transcription factor (Hsf) gene family in Tartary buckwheat (Fagopyrum tataricum)

Background

Heat shock transcription factor (Hsfs) is widely found in eukaryotes and prokaryotes. Hsfs can not only help organisms resist high temperature, but also participate in the regulation of plant growth and development (such as involved in the regulation of seed maturity and affects the root length of plants). The Hsf gene was first isolated from yeast and then gradually found in plants and sequenced, such as Arabidopsis thaliana, rice, maize. Tartary buckwheat is a rutin-rich crop, and its nutritional value and medicinal value are receiving more and more attention. However, there are few studies on the Hsf genes in Tartary buckwheat. With the whole genome sequence of Tartary buckwheat, we can effectively study the Hsf gene family in Tartary buckwheat.

Results

According to the study, 29 Hsf genes of Tartary buckwheat (FtHsf) were identified and renamed according to location of FtHsf genes on chromosome after removing a redundant gene. Therefore, only 29 FtHsf genes truly had the functional characteristics of the FtHsf family. The 29 FtHsf genes were located on 8 chromosomes of Tartary buckwheat, and we found gene duplication events in the FtHsf gene family, which may promote the expansion of the FtHsf gene family. Then, the motif compositions and the evolutionary relationship of FtHsf proteins and the gene structures, cis-acting elements in the promoter, synteny analysis of FtHsf genes were discussed in detail. What’s more, we found that the transcription levels of FtHsf in different tissues and fruit development stages were significantly different by quantitative real-time PCR (qRT-PCR), implied that FtHsf may differ in function.

Conclusions

In this study, only 29 Hsf genes were identified in Tartary buckwheat. Meanwhile, we also classified the FtHsf genes, and studied their structure, evolutionary relationship and the expression pattern. This series of studies has certain reference value for the study of the specific functional characteristics of Tartary buckwheat Hsf genes and to improve the yield and quality of Tartary buckwheat in the future.

Effects of (S)-Carvone and Gibberellin on Sugar Accumulation in Potatoes during Low Temperature Storage

Potato tubers (Solanum tuberosum L.) are usually stored at low temperature, which can suppress sprouting and control the occurrence of diseases. However, low temperatures lead potatoes to easily suffer from cold-induced sweetening (CIS), which has a negative effect on food processing. The aim of this research was to investigate potential treatments on controlling CIS in potatoes during postharvest storage. “Atlantic” potatoes were treated with gibberellin and (S)-carvone, respectively, and stored at 4 °C for 90 days. The results showed that gibberellin can significantly accelerate sprouting and sugar accumulation by regulating expressions of ADP-glucose pyrophosphorylase (AGPase), granule-bound starch synthase (GBSS), β-amylase (BAM1/2), UDP-glucose pyrophosphorylase (UGPase) and invertase inhibitor (INH1/2) genes. The opposite effects were found in the (S)-carvone treatment group, where CIS was inhibited by modulation of the expressions of GBSS and INH1/2 genes. In summary, gibberellin treatment can promote sugar accumulation while (S)-carvone treatment has some effects on alleviating sugar accumulation. Thus, (S)-carvone can be considered as a potential inhibitor of some of the sugars which are vital in controlling CIS in potatoes. However, the chemical concentration, treatment time, and also the treatment method needs to be optimized before industrial application.

'Agricultural Waste to Treasure' - Biochar and eggshell to impede soil antibiotics/antibiotic resistant bacteria (genes) from accumulating in Solanum tuberosum L

Soil contamination with antibiotics and antibiotic resistant bacteria/genes (ARB/ARGs) has becoming an emerging environmental problem. Moreover, the mixed pollutants' transfer and accumulation from soil to tuberous vegetables has posed a great threat against food security and human health. In this work, the application of two absorbing materials (maize biochar and sulfate modified eggshell) was able to reduce the poisonous effect of soil antibiotics on potato root system by stimulate the dissipation of water-soluble antibiotics in soil; and also improve food quality by increasing potato starch, protein, fat, and vitamins. Meanwhile, both amendments could effectively decrease the classes and the accumulative abundance of ARB and ARGs (sulI, sulII, catI, catII, ermA, ermB) in the edible parts of potato. The lowest abundance of ARGs was detected in the biochar application treatment, with the accumulative ARG level of 8.9 × 10² and 7.2 × 10² copies mL^-1 in potato peel (sull + catI + ermA) and tuberous root (sulI), respectively. It is the first study to demonstrate the feasibility of biochar and eggshell derived from agricultural wastes as green absorbing materials to reduce soil antibiotic, ARB, and ARGs accumulation risk in tuberous vegetable.

Genome-wide analysis of the potato Hsp20 gene family: identification, genomic organization and expression profiles in response to heat stress

Background

Heat shock proteins (Hsps) are essential components in plant tolerance mechanism under various abiotic stresses. Hsp20 is the major family of heat shock proteins, but little of Hsp20 family is known in potato (Solanum tuberosum), which is an important vegetable crop that is thermosensitive.

Results

To reveal the mechanisms of potato Hsp20s coping with abiotic stresses, analyses of the potato Hsp20 gene family were conducted using bioinformatics-based methods. In total, 48 putative potato Hsp20 genes (StHsp20s) were identified and named according to their chromosomal locations. A sequence analysis revealed that most StHsp20 genes (89.6%) possessed no, or only one, intron. A phylogenetic analysis indicated that all of the StHsp20 genes, except 10, were grouped into 12 subfamilies. The 48 StHsp20 genes were randomly distributed on 12 chromosomes. Nineteen tandem duplicated StHsp20s and one pair of segmental duplicated genes (StHsp20-15 and StHsp20-48) were identified. A cis-element analysis inferred that StHsp20s, except for StHsp20-41, possessed at least one stress response cis-element. A heatmap of the StHsp20 gene family showed that the genes, except for StHsp20-2 and StHsp20-45, were expressed in various tissues and organs. Real-time quantitative PCR was used to detect the expression level of StHsp20 genes and demonstrated that the genes responded to multiple abiotic stresses, such as heat, salt or drought stress. The relative expression levels of 14 StHsp20 genes (StHsp20-4, 6, 7, 9, 20, 21, 33, 34, 35, 37, 41, 43, 44 and 46) were significantly up-regulated (more than 100-fold) under heat stress.

Conclusions

These results provide valuable information for clarifying the evolutionary relationship of the StHsp20 family and in aiding functional characterization of StHsp20 genes in further research.

Electronic supplementary material

The online version of this article (dio: 10.1186/s12864-018-4443-1) contains supplementary material, which is available to authorized users.

Genome-wide analysis of the potato Hsp20 gene family: identification, genomic organization and expression profiles in response to heat stress

BACKGROUND

Heat shock proteins (Hsps) are essential components in plant tolerance mechanism under various abiotic stresses. Hsp20 is the major family of heat shock proteins, but little of Hsp20 family is known in potato (Solanum tuberosum), which is an important vegetable crop that is thermosensitive.

RESULTS

To reveal the mechanisms of potato Hsp20s coping with abiotic stresses, analyses of the potato Hsp20 gene family were conducted using bioinformatics-based methods. In total, 48 putative potato Hsp20 genes (StHsp20s) were identified and named according to their chromosomal locations. A sequence analysis revealed that most StHsp20 genes (89.6%) possessed no, or only one, intron. A phylogenetic analysis indicated that all of the StHsp20 genes, except 10, were grouped into 12 subfamilies. The 48 StHsp20 genes were randomly distributed on 12 chromosomes. Nineteen tandem duplicated StHsp20s and one pair of segmental duplicated genes (StHsp20-15 and StHsp20-48) were identified. A cis-element analysis inferred that StHsp20s, except for StHsp20-41, possessed at least one stress response cis-element. A heatmap of the StHsp20 gene family showed that the genes, except for StHsp20-2 and StHsp20-45, were expressed in various tissues and organs. Real-time quantitative PCR was used to detect the expression level of StHsp20 genes and demonstrated that the genes responded to multiple abiotic stresses, such as heat, salt or drought stress. The relative expression levels of 14 StHsp20 genes (StHsp20-4, 6, 7, 9, 20, 21, 33, 34, 35, 37, 41, 43, 44 and 46) were significantly up-regulated (more than 100-fold) under heat stress.

CONCLUSIONS

These results provide valuable information for clarifying the evolutionary relationship of the StHsp20 family and in aiding functional characterization of StHsp20 genes in further research.