Tolerant Tomato Research Articles

Elucidating the Role of SlBBX31 in Plant Growth and Heat-Stress Resistance in Tomato.

Heat stress inhibits plant growth and productivity. Among the main regulators, B-box zinc-finger (BBX) proteins are well-known for their contribution to plant photomorphogenesis and responses to abiotic stress. Our research pinpoints that SlBBX31, a BBX protein harboring a conserved B-box domain, serves as a suppressor of plant growth and heat tolerance in tomato (Solanum lycopersicum L.). Overexpressing (OE) SlBBX31 in tomato exhibited yellowing leaves due to notable reduction in chlorophyll content and net photosynthetic rate (Pn). Furthermore, the pollen viability of OE lines obviously decreased and fruit bearing was delayed. This not only affected the fruit setting rate and the number of plump seeds but also influenced the size of the fruit. These results indicate that SlBBX31 may be involved in the growth process of tomato, specifically in terms of photosynthesis, flowering, and the fruiting process. Conversely, under heat-stress treatment, SlBBX31 knockout (KO) plants displayed superior heat tolerance, evidenced by their improved membrane stability, heightened antioxidant enzyme activities, and reduced accumulation of reactive oxygen species (ROS). Further transcriptome analysis between OE lines and KO lines under heat stress revealed the impact of SlBBX31 on the expression of genes linked to photosynthesis, heat-stress signaling, ROS scavenging, and hormone regulation. These findings underscore the essential role of SlBBX31 in regulating tomato growth and heat-stress resistance and will provide valuable insights for improving heat-tolerant tomato varieties.

Editing and genome-wide analysis upstream open reading frames contributes to enhancing salt tolerance in tomato.

The salinization of soil constitutes a substantial hindrance to the advancement of sustainable agriculture. Our research seeks to elucidate the role of a Rab GTPase-activating protein (RabGAP) family member, SlRabGAP22, in salt tolerance and its translational regulation under salt stress in tomatoes, employing gene-editing techniques and ribosome profiling methodologies. Findings demonstrate that SlRabGAP22 acts as a positive regulator of tomato salt tolerance, with four predicted upstream open reading frames (uORFs) classified into three categories. Functional uORFs were found to be negative regulation. Editing these uORFs along with altering their classifications and characteristics mitigated the inhibitory effects on primary ORFs and fine-tuned gene expression. Enhanced tomato salt tolerance was attributed to improved scavenging of reactive oxygen species, reduced toxicity Na+, and diminished osmotic stress effects. Furthermore, we conducted genome-wide analysis of ORFs to lay the foundation for further research on uORFs in tomatoes. In summary, our findings offer novel perspectives and important data for the enhancement of genetic traits via uORF-based strategies and translational regulation against the backdrop of salt stress.

Strigolactones positively regulate HY5-dependent autophagy and the degradation of ubiquitinated proteins in response to cold stress in tomato.

Autophagy, involved in protein degradation and amino acid recycling, plays a key role in plant development and stress responses. However, the relationship between autophagy and phytohormones remains unclear. We used diverse methods, including CRISPR/Cas9, ultra-performance liquid chromatography coupled with tandem mass spectrometry, chromatin immunoprecipitation, electrophoretic mobility shift assays, and dual-luciferase assays to explore the molecular mechanism of strigolactones in regulating autophagy and the degradation of ubiquitinated proteins under cold stress in tomato (Solanum lycopersicum). We show that cold stress induced the accumulation of ubiquitinated proteins. Mutants deficient in strigolactone biosynthesis were more sensitive to cold stress with increased accumulation of ubiquitinated proteins. Conversely, treatment with the synthetic strigolactone analog GR245DS enhanced cold tolerance in tomato, with elevated levels of accumulation of autophagosomes and transcripts of autophagy-related genes (ATGs), and reduced accumulation of ubiquitinated proteins. Meanwhile, cold stress induced the accumulation of ELONGATED HYPOCOTYL 5 (HY5), which was triggered by strigolactones. HY5 further trans-activated ATG18a transcription, resulting in autophagy formation. Mutation of ATG18a compromised strigolactone-induced cold tolerance, leading to decreased formation of autophagosomes and increased accumulation of ubiquitinated proteins. These findings reveal that strigolactones positively regulate autophagy in an HY5-dependent manner and facilitate the degradation of ubiquitinated proteins under cold conditions in tomato.

Genotypic Selection Using Quantitative Trait Loci for Better Productivity under High Temperature Stress in Tomato (Solanum lycopersicum L.)

High temperature stress affects tomato production both in tropical and sub-tropical environments worldwide. To explore genetic variation for heat tolerance in tomato, 329 transcontinental tomato genotypes were evaluated at the Ministry of Municipality and Environment (MME) greenhouses near Doha, Qatar, where the average daytime temperature was 38 °C with a big fluctuation during the tomato growth season. A preliminary phenotypic analysis identified a panel of 71 hybrid and pure-line tomato genotypes for more detailed studies. The selected subset was examined in the greenhouse using a randomized complete block design under heat stress. The materials were phenotyped for fruit size, fruit weight, fruit hardness, fruit locules, fruit set, total soluble solids (TSS), and fruit yield. Significant phenotypic differences among genotypes were observed for all the traits assessed. To explore the genetic basis of the variation among the examined genotypes, the subset was genotyped using 104 SNP markers identified in previous heat-tolerance genome-wide association studies (GWAS). Nineteen QTL-associated SNP markers could reliably select heat-tolerant genotypes in terms of better fruit yield, fruit set, and TSS. These markers are located on chromosome 1, 5, 6, 8, 9, and 12. Interestingly, two clusters of markers on chromosome 6 were linked to significant effects on yield, fruit set, and TSS under high temperature. Eighteen out of nineteen SNP markers were mapped within a gene body. Based on the phenotypic and the genotypic analysis, an elite set of five genotypes was selected for approval for heat stress environments in Qatar. The aim of the present work is to provide significant results that are exploitable not only in the Qatar region but also worldwide. Specifically, the 19 molecular markers identified in this study can serve as useful tools for breeders in selecting heat-tolerant material.

SlWRKY51 regulates proline content to enhance chilling tolerance in tomato.

Chilling stress is a major environmental factor that significantly reduces crop production. To adapt to chilling stress, plants activate a series of cellular responses and accumulate an array of metabolites, particularly proline. Here, we report that the transcription factor SlWRKY51 increases proline contents in tomato (Solanum lycopersicum) under chilling stress. SlWRKY51 expression is induced under chilling stress. Knockdown or knockout of SlWRKY51 led to chilling-sensitive phenotypes, with lower photosynthetic capacity and more reactive oxygen species (ROS) accumulation than the wild type (WT). The proline contents were significantly reduced in SlWRKY51 knockdown and knockout lines under chilling stress, perhaps explaining the phenotypes of these lines. D-1-pyrroline-5-carboxylate synthetase (P5CS), which catalyses the rate-limiting step of proline biosynthesis, is encoded by two closely related P5CS genes (P5CS1 and P5CS2). We demonstrate that SlWRKY51 directly activates the expression of P5CS1 under chilling stress. In addition, the VQ (a class of plant-specific proteins containing the conserved motif FxxhVQxhTG) family member SlVQ10 physically interacts with SlWRKY51 to enhance its activation of P5CS1. Our study reveals that the chilling-induced transcription factor SlWRKY51 enhances chilling tolerance in tomato by promoting proline accumulation.

The Use of Compost and Arbuscular Mycorrhizal Fungi and Their Combination to Improve Tomato Tolerance to Salt Stress.

Salinity poses a significant challenge to tomato plant development and metabolism. This study explores the use of biostimulants as eco-friendly strategies to enhance tomato plant tolerance to salinity. Conducted in a greenhouse, the research focuses on the Solanum lycopersicum L. behavior under saline conditions. Tomato seeds were treated with arbuscular mycorrhizal fungi (AMF), compost, and their combination under both non-saline and saline conditions (0 and 150 mM NaCl). Plant height, number of flowers and fruits, shoot fresh weight, and root dry weight were negatively impacted by salt stress. The supplementation with compost affected the colonization of AMF, but the application of stress had no effect on this trait. However, the use of compost and AMF separately or in combination showed positive effects on the measured parameters. At the physiological level, compost played a beneficial role in increasing photosynthetic efficiency, whether or not plants were subjected to salinity. In addition, the application of these biostimulants led to an increase in nitrogen content in the plants, irrespective of the stress conditions. AMF and compost, applied alone or in combination, showed positive effects on photosynthetic pigment concentrations and protein content. Under salt stress, characterized by an increase in lipid peroxidation and H2O2 content, the application of these biostimulants succeeded in reducing both these parameters in affected plants through exhibiting an increase in antioxidant enzyme activity. In conclusion, incorporating compost, AMF, or their combined application emerges as a promising approach to alleviate the detrimental impacts of salt stress on both plant performances. These findings indicate optimistic possibilities for advancing sustainable and resilient agricultural practices.

ABIOTIC STRESS GENE 1 mediates aroma volatiles accumulation by activating MdLOX1a in apple.

Fruit aroma is an important organoleptic quality, which influences consumer preference and market competitiveness. Aroma compound synthesis pathways in plants have been widely identified, among the lipoxygenase pathway is crucial for fatty acid catabolism to form esters in apple. However, the regulatory mechanism of this pathway remains elusive. In this study, linear regression analysis and transgene verification revealed that the lipoxygenase MdLOX1a is involved in ester biosynthesis. Yeast one-hybrid library screening indicated that a protein, MdASG1 (ABIOTIC STRESS GENE 1), was a positive regulator of MdLOX1a and ester production based on yeast one-hybrid and dual-luciferase assays, as well as correlation analysis among eight different apple cultivars. Overexpression of MdASG1 in apple and tomato stimulated the lipoxygenase pathway and increased the fatty acid-derived volatile content, whereas the latter was decreased by MdASG1 silencing and CRISPR/Cas9 knockout. Furthermore, MdASG1 overexpression enhanced the salt-stress tolerance of tomato and apple 'Orin' calli accompanied by a higher content of fatty acid-derived volatiles compared to that of non-stressed transgenic tomato fruit, while MdASG1-Cas9 knockdown calli do not respond to salt stress and promote the biosynthesis of fatty acid-derived volatiles. Collectively, these findings indicate that MdASG1 activates MdLOX1a expression and participates in the lipoxygenase pathway, subsequently increasing the accumulation of aroma compounds, especially under moderate salt stress treatment. The results also provide insight into the theory for improving fruit aroma quality in adversity.

Salt stress mitigation and improvement in fruit nutritional characteristics of tomato plants: New opportunities from the exploitation of a halotorelant Agrobacterium strain

Soil salinity is considered one of the most limiting factors in large agricultural areas, and tomato (Solanum lycopersicum L.) is highly sensitive to this abiotic stress, which exacerbates under drought. The use of halotolerant PGPR is a promising strategy to enhance tomato tolerance and productivity in saline soils. The present study tested the capability of the recently discovered bacterial strain PVr_9 to increase tolerance to salinity in tomato plants in vitro, greenhouse and open field conditions. When inoculated with PVr_9, in vitro seedlings showed a significant increase in primary root length, number of secondary roots and fresh weight both in absence of stress and when exposed to 150 mM NaCl. In plants exposed to salt treatment, PVr_9 upregulated the salt tolerance genes SOS1 and NHX1, and the enzyme prolyl aminopeptidase involved in proline metabolism. Proteins associated with resistance against pathogens were also upregulated by PVr_9 in absence of salt stress. In greenhouse, PVr_9-inoculated tomato plants treated for 1-week with 150 mM NaCl showed a significant increase in shoot fresh biomass, chlorophyll, proline content, and APX activity. Tomato fruits from PVr_9 inoculated plants, exposed in the field to salt stress during the flowering stage, showed higher levels of carotenoids, lycopene, and l-ascorbic acid, as well as an increased antioxidant capacity compared to fruits of uninoculated plants. These results indicate PVr_9 as a potential biostimulant in tomato for better tackling soil salinization in a context of climate change and expansion of coastal salinity, while there is large scope for the improvement of the nutritional characteristics of tomato fruits.

CaMYB80 enhances the cold tolerance of pepper by directly targeting CaPOA1.

Cold temperatures negatively impact crop yield and quality, posing significant limitations to the advancement of the vegetable industry. MYB transcription factors are pivotal in enhancing plant resilience against various abiotic stresses, including low-temperature stress. Pepper (Capsicum annuum L.) is a nutrient-rich vegetable crop sensitive to low temperatures. This study aimed to determine the function of CaMYB80 in the cold stress response of pepper through virus-induced silencing. The study also conducted heterologous expression of CaMYB80 in Arabidopsis and tomato plants. The results showed that CaMYB80 could respond to low-temperature stress in pepper. CaMYB80 was localized in the nucleus and cytoplasm and exhibited transcriptional activation ability. Moreover, CaMYB80 silencing decreased cold tolerance in pepper, while its heterologous overexpression increased cold tolerance in Arabidopsis and tomato. Further analysis showed that CaMYB80 interacted with CaPOA1 (peroxidase N1-like). Similarly, the expression of CaPOA1 also responded to low-temperature stress. Overexpression of CaPOA1 enhanced freezing tolerance in Arabidopsis, while its silencing reduced cold stress tolerance in pepper. Furthermore, overexpression of CaMYB80 in Arabidopsis and tomato could increase the activity of peroxidases and the expression levels of genes in the ICE-CBF-COR (inducer of CBF expression, C-repeat binding factor, cold-responsive) regulatory network. In conclusion, our research results indicate that CaMYB80 enhances pepper cold tolerance by interacting with CaPOA1 to increase peroxidase activity and influence the expression of ICE-CBF-COR related genes.

Loss of cold tolerance is conferred by absence of the WRKY34 promoter fragment during tomato evolution

Natural evolution has resulted in reduced cold tolerance in cultivated tomato (Solanum lycopersicum). Herein, we perform a combined analysis of ATAC-Seq and RNA-Seq in cold-sensitive cultivated tomato and cold-tolerant wild tomato (S. habrochaites). We identify that WRKY34 has the most significant association with differential chromatin accessibility and expression patterns under cold stress. We find that a 60 bp InDel in the WRKY34 promoter causes differences in its transcription and cold tolerance among 376 tomato accessions. This 60 bp fragment contains a GATA cis-regulatory element that binds to SWIBs and GATA29, which synergistically suppress WRKY34 expression under cold stress. Moreover, WRKY34 interferes with the CBF cold response pathway through regulating transcription and protein levels. Our findings emphasize the importance of polymorphisms in cis-regulatory regions and their effects on chromatin structure and gene expression during crop evolution.

Genetic variability for salinity tolerance of tomato (Solanum lycopersicon MILL.) genotypes determined by stress tolerance indices

BackgroundTomato is an important vegetable crop; however, salinity hampers its growth and yield-related traits. Different tomato genotypes significantly differ in their salinity tolerance; thus, selecting the tolerant genotypes could improve yield and productivity under saline environments. MethodsThis study investigated salinity tolerance of five tomato genotypes, i.e., ‘Pakit’, ‘Riogrande’, ‘Roma’, ‘Continental’, and ‘Nagina’ under 0-, 100-, 150- and 200-mM salinity levels. Data relating yield-related traits (plant height, shoot fresh and dry weights, number of fruits per plant, single fruit weight and fruit yield per plant) and nine different stress tolerance indices were employed to infer salinity-tolerance of the genotypes. ResultsIncreasing salinity levels negatively affected the yield-related traits of genotypes; however, genotypes exhibited varied tolerance to salinity. The better and the poor yield-related traits were noted under 0- and 200-mM salinity levels, respectively. Similarly, genotypes ‘Pakit’ and ‘Nagina’ recorded the highest and the lowest values of yield-related traits. The genotype ‘Pakit’ proved the most tolerant to tested salinity levels compared to the rest of the genotypes. The ‘Pakit’ genotypes had the highest stress tolerance index (0.19, 1.06 and 1.79) and the lowest relative change in yield (6.00, 32.59, and 55.75%) under all salinity levels. Principal component analysis biplot revealed that ‘Pakit’ genotypes had superior yield traits and tolerance indices. ConclusionThe genotype ‘Pakit’ exhibited a higher level of salinity tolerance (6 % yield reduction under 100 mM salinity compared to 27.67 % reduction in ‘Nagina’ genotype. Therefore, genotype ‘Pakit’ can be recommended for cultivation on low to moderate saline soils without significant yield losses. On the other hand, ‘Nagina’ genotype proved the most sensitive to salinity (27.67 %, 56.79 %, and 68.90 % yield reduction under 100-, 150-, and 200-mM salinity, respectively). Therefore, this genotype should not be cultivated on saline soils.

Integrated physiological and genetic data reveal key-traits for heat tolerance in tomato

As global temperatures continue to rise, high summer temperatures severely affect crop growth, reducing yield and quality. The projections of annual declines in crop yield require more in-depth multidisciplinary studies on plant tolerance to abiotic stresses. As tomato is a major crop in the Mediterranean region, its response to heat stress has become important to be addressed in order to identify those traits affecting stress tolerance. In this study, physiological and genomic analyses were performed on two heat-tolerant genotypes (LA3120 and E42) grown at high temperatures during the entire life cycle. The results showed that heat stress diversely affected gas exchange and fluorescence parameters in the two genotypes. In particular, E42 regulated the photosynthetic machinery under heat stress by modulating the electron transport chain, whereas LA3120 was less affected by the applied stress. Genotyping data obtained from a GBS (genotyping by sequencing) analysis were used to explore the genetic variability of both genotypes with the aim of identifying candidate genes that might regulate their stress response. These results further deepen our understanding of the physiological mechanisms activated in response to heat stress and allowed to select key traits that could be used in breeding program to select thermotolerant tomato genotypes.

Enhancement of Drought Tolerance and Plant Growth in Tomato by Trichoderma harzianum Seed Treatment

The proficiencies of soil microorganisms to drought tolerance have been known for many years, but their use as crop inoculants was not explored in agriculture commercially. One possibility to increase the drought tolerance is to use beneficial microorganisms as seed treatment. This study was conducted to investigate the effect of Trichoderma harzianum on the growth and development of Tomato (Solanum lycopersicum L.) plant under water stress condition. Trichoderma harzianum is applied to the seeds by treating seeds with Trichoderma harzianum before sowing. Parameters including germination percentage, chlorophyll content, leaf area, number of leaves, plant height, root length, plant fresh and dry weight and yield were recorded in all the treatments along with the untreated control. Tomato seeds treated with Trichoderma harzianum had higher seed germination percentage and chlorophyll content 95.50%, (2.41%), 42.59 SAPAD units (13.83%) respectively than untreated seed. Maximum leaf area and number of leaves 11.71 cm² (19.40%), 190.75 (15.43%) respectively recorded in the plants of Trichoderma harzianum treated seeds in water stress condition as compared to untreated seeds. Under extreme water stress condition plant height and root length of tomato plant increased significantly 98.25 cm, (19.45%), 41.25 cm (42.24%) respectively in Trichoderma harzianum treated seeds as compare to untreated seed. Also, Trichoderma harzianum seed treatment in tomato showed a significantly higher plant fresh and dry weight 189.43 g (8.65%) and 31.98 g (47.57%) respectively in drought condition as compared to untreated seeds. Trichoderma harzianum seed treatment played critical role in drought condition by increasing yield 731.25 g/plant (27.62%) increase over untreated seeds. Taken together, the study recommends that in drought condition for enhanced tomato growth Trichoderma harzianum should be used as eco-friendly solutions by seed treatment.

ELONGATED HYPOCOTYL 5 regulates steroidal glycoalkaloid biosynthesis and fungal tolerance in tomato.

Tomato (Solanum lycopersicum L.) is rich in nutrients and has been an important target for enhancing the accumulation of various metabolites. Tomato also contains cholesterol-derived molecules, steroidal glycoalkaloids (SGAs), which contribute to pathogen defense but are toxic to humans and considered antinutritional compounds. Previous studies suggest the role of various transcription factors in SGA biosynthesis; however, the role of light and associated regulatory factors has not been studied in tomatoes. Here, we demonstrated that SGA biosynthesis is regulated by light through the ELONGATED HYPOCOTYL 5 homolog, SlHY5, by binding to light-responsive G-boxes present in the promoters of structural and regulatory genes. SlHY5 complemented Arabidopsis (Arabidopsis thaliana) and tobacco (Nicotiana tabacum) hy5 mutants at molecular, morphological, and biochemical levels. CRISPR/Cas9-based knockout tomato plants, SlHY5CR, showed downregulation of SGA and phenylpropanoid pathway genes, leading to a significant reduction in SGA (α-tomatine and dehydrotomatine) and flavonol contents, whereas plants overexpressing SlHY5 (SlHY5OX) showed the opposite effect. Enhanced SGA and flavonol levels in SlHY5OX lines provided tolerance against Alternaria solani fungus, while SlHY5CR lines were susceptible to the pathogen. This study advances our understanding of the HY5-dependent light-regulated biosynthesis of SGAs and flavonoids and their role in biotic stress in tomatoes.

Stress response in tomato as influenced by repeated waterlogging.

Plants respond to water stress with a variety of physiological and biochemical changes, but their response varies among species, varieties and cultivars. Waterlogging in tomato reduces plant growth, degrade chlorophyll and increase concentration of oxidative parameters. Priming can alleviate stress in plants caused by waterlogging enabling plants to be more tolerant to an additional stress in the current or even subsequent generation. The aim of this study was to evaluate tomato genotypes for their sensitivity to waterlogging stress applied during early vegetative growth and at full flowering stage. The study included two local genotypes, Trebinjski sitni (GB1126) and Žuti (GB1129), and the reference variety Novosadski jabučar (NJ), which is the variety most commonly used in Serbia and Bosnia and Herzegovina. The activity of class III peroxidase (POX), hydrogen peroxide (H2O2) content and malondialdehyde (MDA) content were measured spectrophotometrically, and for quantification of individual phenolic compounds, targeted approach was adopted, using UHPLC/DAD/(-)HESI-MS2 instrument (Dionex UltiMate 3000 UHPLC system with a DAD detector, configured with a triple quadrupole mass spectrometer TSQ Quantum Access Max (Thermo Fisher Scientific, Germany)). Oxidative parameters (H2O2 and MDA) exhibited an increase in content in leaves of tomato plants that underwent waterlogging stress compared to control plants. Moreover, oxidative parameters showed positive correlation with proteins and phenolics content. The obtained correlations can indicate that one of the response strategies of tomato plants to waterlogging is the increased synthesis of proteins and phenolic compounds. The POX activity was not correlated with other parameters except with the polyphenols. A positive correlation was shown between POX activity and the content of phenolic compounds, indicating their independent roles in the removal of ROS. Changes in the phenolic profiles after the exposure of plants to waterlogging stress are recorded, and these changes were more severe in leaves and fruits of GB1129 and NJ genotypes than in GB1126. Thus, genotype GB1126 is the most efficient in maintaining the phenolic profiles of leaves and fruits, and therefore of the nutritive and organoleptic qualities of fruits following the exposure to waterlogging. Also, genotype GB1126 exhibited the ability to maintain the content of oxidative parameters during waterlogging at certain growth stages, implying certain waterlogging tolerance. Waterlogging triggered stress memory but not at all growth stages. The most pronounced stress memory was obtained in fruit samples in the phase of full fruit maturity on the 1st truss. This study shed light on the defense mechanisms of tomato plants to repeated waterlogging stress from the perspectives of the changes in the composition of major phenolics, and pointed to the 5-O-caffeoylquinic acid and rutin as the chemical markers of the waterlogging stress tolerance in tomato. However, it remains to be determined whether this modulation has a positive or negative effect on the overall plant metabolism. Further investigations are needed to fully elucidate the benefits of waterlogging pretreatment in this context.

Deciphering salt stress responses in Solanum pimpinellifolium through high-throughput phenotyping.

Soil salinity is a major environmental stressor affecting agricultural productivity worldwide. Understanding plant responses to salt stress is crucial for developing resilient crop varieties. Wild relatives of cultivated crops, such as wild tomato, Solanum pimpinellifolium, can serve as a useful resource to further expand the resilience potential of the cultivated germplasm, S. lycopersicum. In this study, we employed high-throughput phenotyping in the greenhouse and field conditions to explore salt stress responses of a S.pimpinellifolium diversity panel. Our study revealed extensive phenotypic variations in response to salt stress, with traits such as transpiration rate, shoot mass, and ion accumulation showing significant correlations with plant performance. We found that while transpiration was a key determinant of plant performance in the greenhouse, shoot mass strongly correlated with yield under field conditions. Conversely, ion accumulation was the least influential factor under greenhouse conditions. Through a Genome Wide Association Study, we identified candidate genes not previously associated with salt stress, highlighting the power of high-throughput phenotyping in uncovering novel aspects of plant stress responses. This study contributes to our understanding of salt stress tolerance in S. pimpinellifolium and lays the groundwork for further investigations into the genetic basis of these traits, ultimately informing breeding efforts for salinity tolerance in tomato and other crops.

Halotolerant Bacillus sp. strain RA coordinates myo-inositol metabolism to confer salt tolerance to tomato.

Soil salinity is a worldwide problem threatening crop yields. Some plant growth-promoting rhizobacteria (PGPR) could survive in high salt environment and assist plant adaptation to stress. Nevertheless, the genomic and metabolic features, as well as the regulatory mechanisms promoting salt tolerance in plants by these bacteria remain largely unknown. In the current work, a novel halotolerant PGPR strain, namely, Bacillus sp. strain RA can enhance tomato tolerance to salt stress. Comparative genomic analysis of strain RA with its closely related species indicated a high level of evolutionary plasticity exhibited by strain-specific genes and evolutionary constraints driven by purifying selection, which facilitated its genomic adaptation to salt-affected soils. The transcriptome further showed that strain RA could tolerate salt stress by balancing energy metabolism via the reprogramming of biosynthetic pathways. Plants exude a plethora of metabolites that can strongly influence plant fitness. The accumulation of myo-inositol in leaves under salt stress was observed, leading to the promotion of plant growth triggered by Bacillus sp. strain RA. Importantly, myo-inositol serves as a selective force in the assembly of the phyllosphere microbiome and the recruitment of plant-beneficial species. It promotes destabilizing properties in phyllosphere bacterial co-occurrence networks, but not in fungal networks. Furthermore, interdomain interactions between bacteria and fungi were strengthened by myo-inositol in response to salt stress. This work highlights the genetic adaptation of RA to salt-affected soils and its ability to impact phyllosphere microorganisms through the adjustment of myo-inositol metabolites, thereby imparting enduring resistance against salt stress in tomato.

New population of Solanum pimpinellifolium backcross inbred lines as a resource for heat stress tolerance in tomato.

The occurring temperature increase in crop production areas worldwide is generating conditions of heat stress that negatively affect crop productivity. Tomato (Solanum lycopersicum), a major vegetable crop, is highly susceptible to elevated temperatures. Under such conditions, fruit set is dramatically reduced, leading to significant yield losses. Solanum pimpinellifolium, a wild species closely related to the cultivated tomato, was shown to have beneficial attributes under various abiotic stress growth conditions. We have utilized a new population of backcross inbred lines originated from a cross between S. pimpinellifolium and S. lycopersicum, in order to evaluate its potential as a new genetic resource for improvement of reproductive performance of cultivated tomato under heat stress conditions. This population was screened for various heat stress-related traits, under controlled heat stress and non-stress conditions. Our results show that significant variation exists for all the heat stress related traits that were examined and point at individual lines with better reproductive performance under heat stress conditions that share a common introgression from the wild S. pimpinellifolium parent, suggesting several candidate genes as potential drivers of thermotolerance. Thus, our results place this population as a valuable new resource for the discovery of heat stress related genetic loci for the future development of heat stress tolerant tomato cultivars.

SERK3A and SERK3B could be S-nitrosylated and enhance the salt resistance in tomato seedlings

Salinity hinders plant growth and development, resulting in reduced crop yields and diminished crop quality. Nitric oxide (NO) and brassinolides (BR) are plant growth regulators that coordinate a plethora of plant physiological responses. Nonetheless, the way in which these factors interact to affect salt tolerance is not well understood. BR is perceived by the BR receptor BRASSINOSTEROID INSENSITIVE 1 (BRI1) and its co-receptor BRI1-associated kinase 1 (BAK1) to form the receptor complex, eventually inducing BR-regulated responses. To response stress, a wide range of NO-mediated protein modifications is undergone in eukaryotic cells. Here, we showed that BR participated in NO-enhanced salt tolerance of tomato seedlings (Solanum lycopersicum cv. Micro-Tom) and NO may activate BR signaling under salt stress, which was related to NO-mediated S-nitrosylation. Further, in vitro and in vivo results suggested that BAK1 (SERK3A and SERK3B) was S-nitrosylated, which was inhibited under salt condition and enhanced by NO. Accordingly, knockdown of SERK3A and SERK3B reduced the S-nitrosylation of BAK1 and resulted in a compromised BR response, thereby abolishing NO-induced salt tolerance. Besides, we provided evidence for the interaction between BRI1 and SERK3A/SERK3B. Meanwhile, NO enhanced BRI1-SERK3A/SERK3B interaction. These results imply that NO-mediated S-nitrosylation of BAK1 enhances the interaction BRI1-BAK1, facilitating BR response and subsequently improving salt tolerance in tomato. Our findings illustrate a mechanism by which redox signaling and BR signaling coordinate plant growth in response to abiotic stress.

Xanthohumol and echinocystic acid induces PSTVd tolerance in tomato.

Tomato is a popular vegetable worldwide; its production is highly threatened by infection with the potato spindle tuber viroid (PSTVd). We obtained the full-length genome sequence of previously conserved PSTVd and inoculated it on four genotypes of semi-cultivated tomatoes selected from a local tomato germplasm resource. SC-5, which is a PSTVd-resistant genotype, and SC-96, which is a PSTVd-sensitive genotype, were identified by detecting the fruit yield, plant growth, biomass accumulation, physiological indices, and PSTVd genome titer after PSTVd inoculation. A non-target metabolomics study was conducted on PSTVd-infected and control SC-5 to identify potential anti-PSTVd metabolites. The platform of liquid chromatography-mass spectrometry detected 158 or 123 differential regulated metabolites in modes of positive ion or negative ion. Principal component analysis revealed a clear separation of the global metabolite profile between PSTVd-infected leaves and control regardless of the detection mode. The potential anti-PSTVd compounds, xanthohumol, oxalicine B, indole-3-carbinol, and rosmarinic acid were significantly upregulated in positive ion mode, whereas echinocystic acid, chlorogenic acid, and 5-acetylsalicylic acid were upregulated in negative ion mode. Xanthohumol and echinocystic acid were detected as the most upregulated metabolites and were exogenously applied on PSTVd-diseased SC-96 seedlings. Both xanthohumol and echinocystic acid had instant and long-term inhibition effect on PSTVd titer. The highest reduction of disease symptom was induced by 2.6mg/L of xanthohumol and 2.0mg/L of echinocystic acid after 10days of leaf spraying, respectively. A superior effect was seen on echinocystic acid than on xanthohumol. Our study provides a statistical basis for breeding anti-viroid tomato genotypes and creating plant-originating chemical preparations to prevent viroid disease.