Exploring glycine root uptake dynamics in phosphorus and iron deficient tomato plants during the initial stages of plant development.

BACKGROUND: Phosphorus (P) and iron (Fe) deficiencies are relevant plants nutritional disorders, prompting responses such as increased root exudation to aid nutrient uptake, albeit at an energy cost. Reacquiring and reusing exudates could represent an efficient energy and nitrogen saving strategy. Hence, we investigated the impact of plant development, Fe and P deficiencies on this process. Tomato seedlings were grown hydroponically for 3 weeks in Control, -Fe, and -P conditions and sampled twice a week. We used Isotope Ratio Mass-Spectrometry to measure δ13C in roots and shoots after a 2-h exposure to 13C-labeled glycine (0, 50, or 500 µmol L-1). Plant physiology was assessed with an InfraRed Gas Analyzer and ionome with an Inductively Coupled Plasma Mass-Spectrometry. RESULTS: Glycine uptake varied with concentration, suggesting an involvement of root transporters with different substrate affinities. The uptake decreased over time, with -Fe and -P showing significantly higher values as compared to the Control. This highlights its importance during germination and in nutrient-deficient plants. Translocation to shoots declined over time in -P and Control but increased in -Fe plants, suggesting a role of Gly in the Fe xylem transport. CONCLUSIONS: Root exudates, i.e. glycine, acquisition and their subsequent shoot translocation depend on Fe and P deficiency. The present findings highlight the importance of this adaptation to nutrient deficiencies, that can potentially enhance plants fitness. A thorough comprehension of this trait holds potential significance for selecting cultivars that can better withstand abiotic stresses.

Nitrogen-mediated volatilisation of defensive metabolites in tomato confers resistance to herbivores.

Plants synthesise a vast array of volatile organic compounds (VOCs), which serve as chemical defence and communication agents in their interactions with insect herbivores. Although nitrogen (N) is a critical resource in the production of plant metabolites, its regulatory effects on defensive VOCs remain largely unknown. Here, we investigated the effect of N content in tomato (Solanum lycopersicum) on the tobacco cutworm (Spodoptera litura), a notorious agricultural pest, using biochemical and molecular experiments in combination with insect behavioural and performance analyses. We observed that on tomato leaves with different N contents, S. litura showed distinct feeding preference and growth and developmental performance. Particularly, metabolomics profiling revealed that limited N availability conferred resistance upon tomato plants to S. litura is likely associated with the biosynthesis and emission of the volatile metabolite α-humulene as a repellent. Moreover, exogenous application of α-humulene on tomato leaves elicited a significant repellent response against herbivores. Thus, our findings unravel the key factors involved in N-mediated plant defence against insect herbivores and pave the way for innovation of N management to improve the plant defence responses to facilitate pest control strategies within agroecosystems.

The scarecrow-like transcription factor SlSCL3 regulates volatile terpene biosynthesis and glandular trichome size in tomato (Solanum lycopersicum).

Tomato (Solanum lycopersicum L.) type VI glandular trichomes that occur on the surface of leaves, stems, young fruits and flowers produce and store a blend of volatile monoterpenes and sesquiterpenes. These compounds play important roles in the interaction with pathogens and herbivorous insects. Although the function of terpene synthases in the biosynthesis of volatile terpenes in tomato has been comprehensively investigated, the deciphering of their transcriptional regulation is only just emerging. We selected transcription factors that are over-expressed in trichomes based on existing transcriptome data and silenced them individually by virus-induced gene silencing. Of these, SlSCL3, a scarecrow-like (SCL) subfamily transcription factor, led to a significant decrease in volatile terpene content and expression of the corresponding terpene synthase genes when its transcription level was downregulated. Overexpression of SlSCL3 dramatically increased both the volatile terpene content and glandular trichome size, whereas its homozygous mutants showed reduced terpene biosynthesis. However, its heterozygous mutants also showed a significantly elevated volatile terpene content and enlarged glandular trichomes, similar to the overexpression plants. SlSCL3 modulates the expression of terpene biosynthetic pathway genes by transcriptional activation, but neither direct protein-DNA binding nor interaction with known regulators was observed. Moreover, transcript levels of the endogenous copy of SlSCL3 were decreased in the overexpression plants but increased in the heterozygous and homozygous mutants, suggesting feedback repression of its own promoter. Taken together, our results provide new insights into the role of SlSCL3 in the complex regulation of volatile terpene biosynthesis and glandular trichome development in tomato.

SlGRAS4 mediates a novel regulatory pathway promoting chilling tolerance in tomato.

Tomato (Solanum lycopersicum L.) plants are cold-sensitive, and the fruit are susceptible to postharvest chilling injury when stored at low temperature. However, the mechanisms underlying cold stress responses in tomato are poorly understood. We demonstrate that SlGRAS4, encoding a transcription factor induced by low temperature, promotes chilling tolerance in tomato leaves and fruit. Combined genome-wide ChIP-seq and RNA-seq approaches identified among cold stress-associated genes those being direct targets of SlGRAS4 and protein studies revealed that SlGRAS4 forms a homodimer to self-activate its own promoter. SlGRAS4 can also directly bind tomato SlCBF promoters to activate their transcription without inducing any growth retardation. The study identifies the SlGRAS4-regulon as a new cold response pathway conferring cold stress tolerance in tomato independently of the ICE1-CBF pathway. This provides new track for breeding strategies aiming to improve chilling tolerance of cultivated tomatoes and to preserve sensory qualities of tomato fruit often deteriorated by storage at low temperatures.

Tomato roots have a functional silicon influx transporter but not a functional silicon efflux transporter.

Silicon (Si) accumulation in shoots differs greatly with plant species, but the molecular mechanisms for this interspecific difference are unknown. Here, we isolated homologous genes of rice Si influx (SlLsi1) and efflux (SlLsi2) transporter genes in tomato (Solanum lycopersicum L.) and functionally characterized these genes. SlLsi1 showed transport activity for Si when expressed in both rice lsi1 mutant and Xenopus laevis oocytes. SlLsi1 was constitutively expressed in the roots. Immunostaining showed that SlLsi1 was localized at the plasma membrane of both root tip and basal region without polarity. Furthermore, overexpression of SlLsi1 in tomato increased Si concentration in the roots and root cell sap but did not alter the Si concentration in the shoots. By contrast, two Lsi2-like proteins did not show efflux transport activity for Si in Xenopus oocytes. However, when functional CsLsi2 from cucumber was expressed in tomato, the Si uptake was significantly increased, resulting in higher Si accumulation in the leaves and enhanced tolerance of the leaves to water deficit and high temperature. Our results suggest that the low Si accumulation in tomato is attributed to the lack of functional Si efflux transporter Lsi2 required for active Si uptake although SlLsi1 is functional.

A subtracted cDNA library identifies genes up-regulated during PHOT1-mediated early step of de-etiolation in tomato (Solanum lycopersicum L.).

BACKGROUND: De-etiolation is the switch from skoto- to photomorphogenesis, enabling the heterotrophic etiolated seedling to develop into an autotrophic plant. Upon exposure to blue light (BL), reduction of hypocotyl growth rate occurs in two phases: a rapid inhibition mediated by phototropin 1 (PHOT1) within the first 30-40 min of illumination, followed by the cryptochrome 1 (CRY1)-controlled establishment of the steady-state growth rate. Although some information is available for CRY1-mediated de-etiolation, less attention has been given to the PHOT1 phase of de-etiolation. RESULTS: We generated a subtracted cDNA library using the suppression subtractive hybridization method to investigate the molecular mechanisms of BL-induced de-etiolation in tomato (Solanum lycopersicum L.), an economically important crop. We focused our interest on the first 30 min following the exposure to BL when PHOT1 is required to induce the process. Our library generated 152 expressed sequence tags that were found to be rapidly accumulated upon exposure to BL and consequently potentially regulated by PHOT1. Annotation revealed that biological functions such as modification of chromatin structure, cell wall modification, and transcription/translation comprise an important part of events contributing to the establishment of photomorphogenesis in young tomato seedlings. Our conclusions based on bioinformatics data were supported by qRT-PCR analyses the specific investigation of V-H(+)-ATPase during de-etiolation in tomato. CONCLUSIONS: Our study provides the first report dealing with understanding the PHOT1-mediated phase of de-etiolation. Using subtractive cDNA library, we were able to identify important regulatory mechanisms. The profound induction of transcription/translation, as well as modification of chromatin structure, is relevant in regard to the fact that the entry into photomorphogenesis is based on a deep reprograming of the cell. Also, we postulated that BL restrains the cell expansion by the rapid modification of the cell wall.

Metabolic Fingerprinting to Assess the Impact of Salinity on Carotenoid Content in Developing Tomato Fruits.

As the presence of health-promoting substances has become a significant aspect of tomato fruit appreciation, this study investigated nutrient solution salinity as a tool to enhance carotenoid accumulation in cherry tomato fruit (Solanum lycopersicum L. cv. Juanita). Hereby, a key objective was to uncover the underlying mechanisms of carotenoid metabolism, moving away from typical black box research strategies. To this end, a greenhouse experiment with five salinity treatments (ranging from 2.0 to 5.0 decisiemens (dS) m(-1)) was carried out and a metabolomic fingerprinting approach was applied to obtain valuable insights on the complicated interactions between salinity treatments, environmental conditions, and the plant's genetic background. Hereby, several hundreds of metabolites were attributed a role in the plant's salinity response (at the fruit level), whereby the overall impact turned out to be highly depending on the developmental stage. In addition, 46 of these metabolites embraced a dual significance as they were ascribed a prominent role in carotenoid metabolism as well. Based on the specific mediating actions of the retained metabolites, it could be determined that altered salinity had only marginal potential to enhance carotenoid accumulation in the concerned tomato fruit cultivar. This study invigorates the usefulness of metabolomics in modern agriculture, for instance in modeling tomato fruit quality. Moreover, the metabolome changes that were caused by the different salinity levels may enclose valuable information towards other salinity-related plant processes as well.

Solanum lycopersicum AUXIN RESPONSE FACTOR 9 regulates cell division activity during early tomato fruit development.

The transformation of the ovary into a fruit after successful completion of pollination and fertilization has been associated with many changes at transcriptomic level. These changes are part of a dynamic and complex regulatory network that is controlled by phytohormones, with a major role for auxin. One of the auxin-related genes differentially expressed upon fruit set and early fruit development in tomato is Solanum lycopersicum AUXIN RESPONSE FACTOR 9 (SlARF9). Here, the functional analysis of this ARF is described. SlARF9 expression was found to be auxin-responsive and SlARF9 mRNA levels were high in the ovules, placenta, and pericarp of pollinated ovaries, but also in other plant tissues with high cell division activity, such as the axillary meristems and root meristems. Transgenic plants with increased SlARF9 mRNA levels formed fruits that were smaller than wild-type fruits because of reduced cell division activity, whereas transgenic lines in which SlARF9 mRNA levels were reduced showed the opposite phenotype. The expression analysis, together with the phenotype of the transgenic lines, suggests that, in tomato, ARF9 negatively controls cell division during early fruit development.

Assessment of genetic variation in Bulgarian tomato (Solanum lycopersicum L.) genotypes, using fluorescent SSR genotyping platform.

Genetic variability in modern crops is limited due to domestication and selection processes. Genetic variation in eight Bulgarian tomato varieties and breeding lines (variety Plovdivska karotina, variety IZK Alya, L21ß, L53ß, L1140, L1116, L975, L984) differing in their morphological and biochemical composition was assessed using a highly efficient and low-cost fluorescent simple sequence repeat (SSR) genotyping platform. Genotyping was conducted with 165 publicly available microsatellite markers developed from different research groups under a number of projects in tomato (SOL Genomics SSRs, Kazusa TGS and TES, SLM, TMS and LEMDDNa) among which only five (3.03%) failed to amplify the expected PCR fragments. Of the remaining markers, 81 (50.62%) were polymorphic in the whole collection of eight genotypes. Among the marker groups used, SLM markers were most polymorphic, followed by TMS and SOL Genomics SSR markers. The total number of amplified alleles was 299, with a mean of 1.869; and the average polymorphic information content (PIC) was 0.196. The genetic diversity within the collection was relatively low (0.2222). Nei's genetic distance varied from 0.0953 to 0.3992. Cluster analysis using the un-weighted pair group method with arithmetic mean (UPGMA) method indicated that the studied tomato genotypes are grouped in four main clusters, which is to some extent consistent with the morpho- and hemo-types of the studied tomatoes. Variety IZK Alya (cherry type) and two of the breeding lines (L1140, L1116) formed three separate and more distant clusters. The fourth cluster includes the other five genotypes. The observed grouping of these genotypes in two sub-clusters reflects their similar morphological and biochemical composition. The genetic distance information from this study might be useful for further implementation of breeding strategies and crosses among these inbred lines.

Identification and Expression of the CorA/MRS2/ALR Type Magnesium Transporters in Tomato.

Magnesium (Mg2+) is the most abundant divalent ion in plants, participating in numerous metabolic processes in growth and development. CorA/MRS2/ALR type Mg2+ transporters are essential for maintaining Mg2+ homeostasis in plants. However, the candidate protein and its potential functions in the tomato plant have not been fully understood. In this study, we identified seven MGT genes (SlMRS2) in tomato based on sequence similarity, domain analysis, conserved motif identification, and structure prediction. Two SlMRS2 genes were analyzed in the bacterial strain MM281, and a functional complementary assay demonstrated their high-affinity transport of Mg2+. Quantitative real-time PCR analysis revealed that the expressions of these Mg2+ transporters were down-regulated in leaves under Mg2+ limitation, with a greater impact on lower and middle leaves compared to young leaves. Conversely, under Mg2+ toxicity, several genes were up-regulated in leaves with a circadian rhythm. Our findings indicate that members of the SlMRS2 family function as Mg2+ transporters and lay the groundwork for further analysis of their distinct functions in tomato.

Elevated CO2 altered the nano-ZnO-induced influence on bacterial and fungal composition in tomato (Solanum lycopersicum L.) rhizosphere soils.

To investigate whether elevated CO2 (eCO2) changes the influence of nanoparticles (NPs) on soil microbial communities and the mechanisms, various nano-ZnO (0, 100, 300, and 500 mg·kg-1) and CO2 concentrations (400 and 800 µmol·mol-1) were applied to tomato plants (Solanum lycopersicum L.) in growth chambers. Plant growth, soil biochemical properties, and rhizosphere soil microbial community composition were analyzed. In 500 mg·kg-1 nano-ZnO-treated soils, root Zn content was 58% higher, while total dry weight (TDW) was 39.8% lower under eCO2 than under atmospheric CO2 (aCO2). Compared with the control, the interaction of eCO2 and 300 mg·kg-1 nano-ZnO decreased and increased bacterial and fungal alpha diversities, respectively, which was caused by the direct effect of nano-ZnO (r = - 1.47, p < 0.01). Specifically, the bacterial OTUs decreased from 2691 to 2494, while fungal OTUs increased from 266 to 307, when 800-300 was compared with 400-0 treatment. eCO2 enhanced the influence of nano-ZnO on bacterial community structure, while only eCO2 significantly shaped fungal composition. In detail, nano-ZnO explained 32.4% of the bacterial variations, while the interaction of CO2 and nano-ZnO explained 47.9%. Betaproteobacteria, which are involved in C, N, and S cycling, and r-strategists, such as Alpha- and Gammaproteobacteria and Bacteroidetes, significantly decreased under 300 mg·kg-1 nano-ZnO, confirming reduced root secretions. In contrast, Alpha- and Gammaproteobacteria, Bacteroidetes, Chloroflexi, and Acidobacteria were enriched in 300 mg·kg-1 nano-ZnO under eCO2, suggesting greater adaptation to both nano-ZnO and eCO2. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States 2 (PICRUSt2) analysis demonstrated that bacterial functionality was unchanged under short-term nano-ZnO and eCO2 exposure. In conclusion, nano-ZnO significantly affected microbial diversities and the bacterial composition, and eCO2 intensified the damage of nano-ZnO, while the bacterial functionality was not changed in this study.

Paraburkholderia tagetis sp. nov., a novel species isolated from roots of Tagetes patula enhances the growth and yield of Solanum lycopersicum L. (tomato).

A multifunctional, Gram-stain-negative, aerobic, motile by flagella, short-rod shaped bacteria, designated strain RG36T was isolated from roots of marigold plant (Tagetes patula) sampled at Dongguk University, Republic of Korea. A 16S rRNA sequences indicated that the closest phylogenetic neighbors were Paraburkholderia acidiphila 7Q-K02T (99.0%) and Paraburkholderia sacchari IPT101T (98.9%) of the family Burkholderiaceae. The draft genome size was 8.52 Mb (63.7% GC). The genome contained 7,381 coding sequences. Digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values of strain RG36T with its most closely related species were only 83.1-88.7 and 27.6-36.7%, respectively. Strain RG36T contained Q-8 as the major respiratory quinone and its main fatty acids (>10%) were C16:0, C17:0 cyclo, C19:0 cyclo ω8c, and summed feature 8 (comprising C18:1 ω7c and/or C18:1 ω6c). Strain RG36T accumulates polyhydroxybutyrates (PHB) and exhibits multiple plant growth-promoting properties including production of indole-3-acetic acid (IAA), siderophores, protease, phosphate solubilization, and harboring gene clusters for its multifunctional properties. A pot experiment was conducted to evaluate the effect of PGPR on the growth of Solanum lycopersicum L. (Tomato). Result also confirmed the ability of strain RG36T to promote tomato plant growth, especially it increases the yield of tomatoes. Structural assessment of the bioplastic by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and GC-MS spectroscopy, which confirmed the structure of the polymer as PHB. Our study revealed the potential of strain RG36T to promote the growth of tomato plant and fruit yield by stimulating the various phytohormones, which could be use as bio-fertilizers to reduce the use of chemical fertilizers and promotes sustainable agricultural production. The phenotypic, chemotaxonomic and phylogenetic data, and genome analysis showed that strain RG36T represents a novel species of the genus Paraburkholderia, for which the name Paraburkholderia tagetis sp. nov. is proposed. The type strain is RG36T (=KACC 22685T = TBRC 15696T).

Differential physiological response to heat and cold stress of tomato plants and its implication on fruit quality.

The upcoming climate change presents a great challenge for plant growth and development being extremes temperatures among the major environmental limitations to crop productivity. Understanding the repercussions of these extreme temperatures is of high importance to elaborate future strategies to confront crop damages. Tomato plants (Solanum lycopersicum L.) are one of the most cultivated crops and their fruits are consumed worldwide standing out for their organoleptic characteristics and nutritional value. Tomato plants are sensitive to temperatures below 12 °C and above 32 °C. In this study, Micro-Tom cultivar was used to evaluate the effects of extreme temperatures on the plant of tomato and the fruit productivity and quality from the stressed plants, either exposed to cold (4 °C for three nights per week) or heat (32 °C during the day, seven days per week) treatments. Total productivity and the percentage of ripe fruits per plant were evaluated together with foliar stress markers and the contents of photosynthetic pigments and tocochromanols. Fruit quality was also assessed determining lycopene contents, total soluble solids, total acidity and ascorbate contents. High temperatures altered multiple physiological parameters indicating a moderate stress, particularly decreasing fruit yield. As a response to this stress, plants enhanced their antioxidant contents both at leaf and fruit level. Low temperatures did not negatively affect the physiology of plants with similar yields as compared to controls, suggesting chilling acclimation. Both high and low temperatures, but most particularly the former, increased total soluble solids contents indicating that temperature control may be used as a strategy to modulate fruit quality.

The combined application of γ-PGA-producing bacteria and biochar reduced the content of heavy metals and improved the quality of tomato (Solanum lycopersicum L.).

Plant growth-promoting bacteria and biochar have been widely used as immobilizers to remediate heavy metal contaminated soil. However, few studies have unraveled the effect and synergistic mechanism of combined application of plant growth-promoting bacteria and biochar on in situ heavy metal contaminated soil remediation and plant yield and quality improvement under heavy metal pollution stress. In this study, the effects of biochar, γ-PGA-producing bacteria (Bacillus amyloliquefaciens strain W25) and their combined application on Cd and Pb immobilization, γ-PGA production in soil filtrate, the bacterial community in rhizosphere soil, physicochemical properties of soil, heavy metal uptake, and quality and yield of tomato in heavy metal-contaminated soil were investigated. The application of W25, biochar, and their combinations significantly reduced Cd content in mature tomato fruits by 22-60%, increased the single fruit weight and lycopene content by 7-21% and 23-48%, respectively, and the combination of biochar and W25 had the best effect. All the treatments significantly reduced DTPA-Cd and DTPA-Pb contents in rhizosphere soil (42-53% and 6.5-35%), increased the pH value and the activities of urease-alkaline phosphatase of soil, but did not affect the expression of heavy metal transporter gene LeNRAMP1 in tomato roots. Biochar + W25 increased the relative abundance of plant growth-promoting bacteria such as Bacillus and Streptomyces. Biochar-enhanced plant growth-promoting bacteria to settle and colonize in soil significantly improved the ability of strain W25 to produce γ-PGA, and immobilized Cd in soil filtrate. The combination of biochar and plant growth-promoting bacteria ensures safe crop production in heavy metal-contaminated soil.

Genetic Structure of Cucumber Mosaic Virus From Natural Hosts in Nigeria Reveals High Diversity and Occurrence of Putative Novel Recombinant Strains.

Cucumber mosaic virus (CMV, Bromoviridae: Cucummovirus), one of the most widespread plant viruses with several hosts, causes huge losses in yield quality and quantity. The occurrence of various CMV strains and high genetic diversity within the virus complicate its management. We describe the population structure of CMV in Nigeria using partial RNA1 and RNA3 gene sequences from three natural hosts: pepper (Capsicum annuum), tomato (Solanum lycopersicum), and watermelon (Citrullus lanatus). One hundred and six leaf samples were obtained from 16 locations across Nigeria, and specific primers were used to amplify the two gene fragments using PCR. Twenty-four samples tested positive for CMV using RNA1 primers, and amplicons were sequenced from 12 isolates, revealing 82.94-99.80% nucleotide and 85.42-100% amino acid sequence similarities within the population. The partial RNA3 fragment, corresponding to the complete coat protein (CP) gene, was sequenced from seven isolates, with 95.79-97.90% and 98.62-100% nucleotide and amino acid intrapopulation similarities, respectively. The isolates belonged to subgroup IB and formed distinct phylogenetic clusters in both gene sets, indicating putative novel strains. Recombination signals, supported by phylogenetic inferences, were detected within the RNA1 dataset (P ≤ 0.05) and identified a recombinant isolate within the Nigerian sequences. No recombination was detected within the CP genes. Population genetics parameters established high diversity within the Nigerian population compared to other isolates worldwide, while selection pressure estimates revealed the existence of negative selection in both gene sets. Although CMV subgroup IB strains were postulated to originate from Asia, this study reveals their prevalence across several hosts from different locations in Nigeria. To our knowledge, this is the first comprehensive description of a recombinant CMV subgroup IB isolate from West Africa, which has implications for its robust detection and overall management.

Erratum: Protective Effect of γ-Aminobutyric Acid Against Chilling Stress During Reproductive Stage in Tomato Plants Through Modulation of Sugar Metabolism, Chloroplast Integrity, and Antioxidative Defense Systems.

[This corrects the article DOI: 10.3389/fpls.2021.663750.].

Protective Effect of γ-Aminobutyric Acid Against Chilling Stress During Reproductive Stage in Tomato Plants Through Modulation of Sugar Metabolism, Chloroplast Integrity, and Antioxidative Defense Systems.

Despite the role of γ-aminobutyric acid (GABA) in plant tolerance to chilling stress having been widely discussed in the seedling stage, very little information is clear regarding its implication in chilling tolerance during the reproductive stage of the plant. Here, we investigated the influence of GABA (1 and 2mM) as a foliar application on tomato plants (Solanum lycopersicum L. cv. Super Marmande) subjected to chilling stress (5°C for 6h/day) for 5 successive days during the flowering stage. The results indicated that applied GABA differentially influenced leaf pigment composition by decreasing the chlorophyll a/b ratio and increasing the anthocyanin relative to total chlorophyll. However, carotenoids were not affected in both GABA-treated and non-treated stressed plants. Root tissues significantly exhibited an increase in thermo-tolerance in GABA-treated plants. Furthermore, applied GABA substantially alleviated the chilling-induced oxidative damage by protecting cell membrane integrity and reducing malondialdehyde (MDA) and H2O2. This positive effect of GABA was associated with enhancing the activity of phenylalanine ammonia-lyase (PAL), catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX). Conversely, a downregulation of peroxidase (POX) and polyphenol oxidase (PPO) was observed under chilling stress which indicates its relevance in phenol metabolism. Interesting correlations were obtained between GABA-induced upregulation of sugar metabolism coinciding with altering secondary metabolism, activities of antioxidant enzymes, and maintaining the integrity of plastids' ultrastructure Eventually, applied GABA especially at 2mM improved the fruit yield and could be recommended to mitigate the damage of chilling stress in tomato plants.

Characterization of RIN Isoforms and Their Expression in Tomato Fruit Ripening.

Ripening of tomato fleshy fruit is coordinated by transcription factor RIN, which triggers ethylene and carotenoid biosynthesis, sugar accumulation, and cell wall modifications. In this study, we identified and characterized complete sequences of the RIN chromosomal locus in two tomato Solanum lycopersicum cultivars, its rin/RIN genotype, and three wild green-fruited species differing in fruit color and composition. The results reveal that S. lycopersicum cultivars and some wild species (S. pennellii, S. habrochaites, and S. huaylasense) had a 3'-splicing site enabling the transcription of RIN1i and RIN2i isoforms. The other wild species (S. arcanum, S. chmielewskii, S. neorickii, and S. peruvianum) had a 3'-splicing site only for RIN2i, which was consistent with RIN1i and RIN2i expression patterns. The genotype rin/RIN, which had an extended 3'-terminal deletion in the rin allele, mainly expressed the chimeric RIN-MC transcript, which was also found in cultivars (RIN/RIN). The RIN1, but not RIN2, protein is able to induce the transcription of the reporter gene in the Y2H system, which positively correlated with the transcription profile of RIN1i and RIN target genes. We suggest that during fruit ripening, RIN1 activates ripening-related genes, whereas RIN2 and RIN-MC act as modulators by competing for RIN-binding sites in gene promoters, which should be confirmed by further studies on the association between RIN-splicing mechanisms and tomato fruit ripening.

In vitro gastrointestinal digestion and colonic fermentation of tomato (Solanum lycopersicum L.) and husk tomato (Physalis ixocarpa Brot.): Phenolic compounds released and bioconverted by gut microbiota.

Two of the most important Mexican plant-foods are tomato (Solanum lycopersicum L.) and husk tomato (Physalis ixocarpa Brot.). In this study three objectives were followed: i) to evaluate the bioaccessible phenolic compounds (PC) in T and HT during upper gastrointestinal digestion, ii) to in vitro ferment the indigestible fractions of the samples to evaluate the short-chain fatty acids (SCFA) production, iii) the microbial metabolites, bioconverted PC and volatile organic compounds (VOCs) generated during the fermentation. Vanillic acid was the most bioaccessible PC and after 48 h, 3-hydroxyphenylacetic acid was the most abundant microbial metabolite identified in both samples. The identification of VOCs belonging to terpenes (and derivatives) group in T and HT can be product of the microbial metabolism of carotenoids. The study shows new knowledge of the in vitro intestinal digestion and fermentation of T and HT final compounds with biological potential which should be evaluated in further studies.

Reduced phytotoxicity of nonylphenol on tomato (Solanum lycopersicum L.) plants by earthworm casts.

Concentrations as high as thousands of milligrams per kilogram (dry weight) of nonylphenol (NP), an endocrine-disrupting chemical of great concern, have been reported in soil. Soil is considered one of the primary pathways for exposure of crop plants to NP. However, there have been few studies on the toxicity of soil NP to crop plants, especially with comprehensive consideration of the application of organic fertiliser which is a common agricultural practice. In this study, tomato plants were grown in soils treated with NP in the presence and/or absence of earthworm casts (EWCs). After four weeks, we tested the physiological and biochemical responses (accumulative levels of hydrogen peroxide (H2O2) and superoxide anion radicals (O2-·), total chlorophyll content, degree of membrane lipid peroxidation, activities of defence-related enzymes, and level of DNA damage) and the changes in plant growth (elongation and biomass). The growth inhibition, reactive oxygen species (H2O2 and O2-·) accumulation, decrease in chlorophyll content, increase in activity of defence-related enzymes (including superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, glutathione S-transferase and glutathione reductase), enhancement of membrane lipid peroxidation, and DNA damage in NP-treated seedlings were clearly reversed by the intervention of EWCs. In particular, the suppressed elongation, biomass, and chlorophyll content in tomato plants exposed to NP alone were significantly restored by EWCs to even greater levels than those of the undisturbed control. In other words, EWCs could efficiently invigorate the photosynthesis of crops via up-regulating the chlorophyll content, thereby overwhelming the NP stress on plant growth. Accordingly, except for reducing the bioavailability of soil NP as reported in our previous study, EWCs could also help crop plants to cope with NP stress by strengthening their stress resistance ability. Our findings are of practical significance for the formulation of strategies to relieve the negative effects of soil NP on crop growth.