Tomato Cotyledons Research Articles

Transcriptome analysis of tomato plants following salicylic acid-induced immunity against Clavibacter michiganensis ssp. michiganensis.

Salicylic acid (SA) is known to be involved in the immunity against Clavibacter michiganensis ssp. michiganensis (Cmm) that causes bacterial canker in tomato. To identify the candidate genes associated with SA-inducible Cmm resistance, transcriptome analysis was conducted via RNA sequencing in tomato plants treated with SA. SA treatment upregulated various defense-associated genes, such as PR and GST genes, in tomato cotyledons. A comparison of SA- and Cmm-responsive genes revealed that both SA treatment and Cmm infection commonly upregulated a large number of genes. Gene Ontology (GO) analysis indicated that the GO terms associated with plant immunity were over-represented in both SA- and Cmm-induced genes. The genes commonly downregulated by both SA treatment and Cmm infection were associated with the cell cycle and may be involved in growth and immunity trade-off through cell division. After SA treatment, several proteins that were predicted to play a role in immune signaling, such as resistance gene analogs, Ca2+ sensors, and WRKY transcription factors, were transcriptionally upregulated. The W-box element, which was targeted by WRKYs, was over-represented in the promoter regions of genes upregulated by both SA treatment and Cmm infection, supporting the speculation that WRKYs are important for the SA-mediated immunity against Cmm. Prediction of protein-protein interactions suggested that genes encoding receptor-like kinases and EF-hand proteins play an important role in immune signaling. Thus, various candidate genes involved in SA-inducible Cmm resistance were identified.

Ticarcillin degradation product thiophene acetic acid is a novel auxin analog that promotes organogenesis in tomato.

Efficient regeneration of transgenic plants from explants after transformation is one of the crucial steps in developing genetically modified plants with desirable traits. Identification of novel plant growth regulators and developmental regulators will assist to enhance organogenesis in culture. In this study, we observed enhanced shoot regeneration from tomato cotyledon explants in culture media containing timentin, an antibiotic frequently used to prevent Agrobacterium overgrowth after transformation. Comparative transcriptome analysis of explants grown in the presence and absence of timentin revealed several genes previously reported to play important roles in plant growth and development, including Auxin Response Factors (ARFs), GRF Interacting Factors (GIFs), Flowering Locus T (SP5G), Small auxin up-regulated RNAs (SAUR) etc. Some of the differentially expressed genes were validated by quantitative real-time PCR. We showed that ticarcillin, the main component of timentin, degrades into thiophene acetic acid (TAA) over time. TAA was detected in plant tissue grown in media containing timentin. Our results showed that TAA is indeed a plant growth regulator that promotes root organogenesis from tomato cotyledons in a manner similar to the well-known auxins, indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA). In combination with the cytokinin 6-benzylaminopurine (BAP), TAA was shown to promote shoot organogenesis from tomato cotyledon in a concentration-dependent manner. To the best of our knowledge, the present study reports for the first time demonstrating the function of TAA as a growth regulator in a plant species. Our work will pave the way for future studies involving different combinations of TAA with other plant hormones which may play an important role in in vitro organogenesis of recalcitrant species. Moreover, the differentially expressed genes and long noncoding RNAs identified in our transcriptome studies may serve as contender genes for studying molecular mechanisms of shoot organogenesis.

Optimization of Callus Induction and Shoot Regeneration from Tomato Cotyledon Explants.

Cultivated tomato (Solanum lycopersicum L.) is one of the most important horticultural crops in the world. The optimization of culture media for callus formation and tissue regeneration of different tomato genotypes presents numerous biotechnological applications. In this work, we have analyzed the effect of different concentrations of zeatin and indole-3-acetic acid on the regeneration of cotyledon explants in tomato cultivars M82 and Micro-Tom. We evaluated regeneration parameters such as the percentage of callus formation and the area of callus formed, as well as the initiation percentage and the number of adventitious shoots. The best hormone combination produced shoot-like structures after 2-3 weeks. We observed the formation of leaf primordia from these structures after about 3-4 weeks. Upon transferring the regenerating micro-stems to a defined growth medium, it was possible to obtain whole plantlets between 4 and 6 weeks. This hormone combination was applied to other genotypes of S. lycopersicum, including commercial varieties and ancestral tomato varieties. Our method is suitable for obtaining many plantlets of different tomato genotypes from cotyledon explants in a very short time, with direct applications for plant transformation, use of gene editing techniques, and vegetative propagation of elite cultivars.

Selection of the high efficient sgRNA for CRISPR-Cas9 to edit herbicide related genes, PDS, ALS, and EPSPS in tomato

Herbicide resistance is one of the main crop traits that improve farming methods and crop productivity. CRISPR-Cas9 can be applied to the development of herbicide-resistant crops based on a target site resistance mechanism, by editing genes encoding herbicide binding proteins. The sgRNAs capable of editing the target genes of herbicides, pds (phytoene desaturase), ALS (acetolactate synthase), and EPSPS (5-Enolpyruvylshikimate-3-phosphate synthase), were designed to use with the CRISPR-Cas9 system in tomato (Solanum lycopersicum cv. Micro-Tom). The efficiency of the sgRNAs was tested using Agrobacterium mediated transient expression in the tomato cotyledons. One sgRNA designed for editing the target site of PDS had no significant editing efficiency. However, three different sgRNAs designed for editing the target site of ALS had significant efficiency, and one of them, ALS2-P sgRNA, showed over 0.8% average efficiency in the cotyledon genome. The maximum efficiency of ALS2-P sgRNA was around 1.3%. An sgRNA for editing the target site of EPSPS had around 0.4% editing efficiency on average. The sgRNA efficiency testing provided confidence that editing of the target sites could be achieved in the transformation process. We confirmed that 19 independent transgenic tomatoes were successfully edited by ALS2_P or ALS1_W sgRNAs and two of them had three base deletion mutations, which are expected to have altered herbicide resistance. In this study, we demonstrated the usefulness of performing an sgRNA efficiency test before crop transformation, and confirmed that the CRISPR-Cas9 system is a valuable tool for breeding herbicide-resistant crops.

Transcriptome analysis of Clavibacter michiganensis subsp. michiganensis-infected tomatoes: a role of salicylic acid in the host response

Bacterial canker of tomato (Solanum lycopersicon) caused by the Gram-positive bacterium Clavibacter michiganensis subsp. michiganensis (Cmm) is an economically important disease. To understand the host defense response to Cmm infection, transcriptome sequences in tomato cotyledons were analyzed by RNA-seq. Overall, 1788 and 540 genes were upregulated and downregulated upon infection, respectively. Gene Ontology enrichment analysis revealed that genes involved in the defense response, phosphorylation, and hormone signaling were over-represented by the infection. Induced expression of defense-associated genes suggested that the tomato response to Cmm showed similarities to common plant disease responses. After infection, many resistance gene analogs (RGAs) were transcriptionally upregulated, including the expressions of some receptor-like kinases (RLKs) involved in pattern-triggered immunity. The expressions of WRKYs, NACs, HSFs, and CBP60s encoding transcription factors (TFs) reported to regulate defense-associated genes were induced after infection with Cmm. Tomato genes orthologous to Arabidopsis EDS1, EDS5/SID1, and PAD4/EDS9, which are causal genes of salicylic acid (SA)-deficient mutants, were upregulated after infection with Cmm. Furthermore, Cmm infection drastically stimulated SA accumulation in tomato cotyledons. Genes involved in the phenylalanine ammonia lyase pathway were upregulated, whereas metabolic enzyme gene expression in the isochorismate synthase pathway remained unchanged. Exogenously applied SA suppressed bacterial growth and induced the expression of WRKYs, suggesting that some Cmm-responsive genes are regulated by SA signaling, and SA signaling activation should improve tomato immunity against Cmm.

AGROBACTERIUM-MEDIATED TRANSFORMATION OF TWO TOMATO CULTIVARS (LYCOPERSICON ESCULENTUM MILL.) CV. SANDRA AND ROCKY

An efficient protocol for Agrobacterium-mediated transformation of tomato cultivars Sandra and Rocky was conducted to examine the possibility of producing transgenic tomato plants cultivars harbouring the nptII gene, conferring kanamycin resistance. To achieve this aim, tomato cotyledon explants were transformed using EHA105 Agrobacterium tumefaciens strain harboring the binary vectors pBI121 which contains Gus gene, and neomycin phosphotransferase II (nptII) as selectable marker gene under the control of a CaMV35S promoter and nopaline synthase (nos) Terminator. Transformant detection was carried out in three distinct ways. First antibiotic selection, Kanamycin at a concentration of100 mgl-1 found to be efficient for this purpose. Second histochemical GUS assay revealed the presence of blue colored zones in a number of shoots and leaves for both in vitro and the greenhouse-grown transgenic plants. Third PCR analysis indicated positive result by showing the fragment for nptII gene in tested transformants, while was absent in non-transgenic control (wild type). On the other hand, the results showed that Sandra cultivar was more efficient for regeneration and subsequently transformation frequency than Rocky cultivar, which record 26.66% of transformation frequency compared with 11.57% in Rocky cultivar.

Utilising cold plasma seed treatment technologies to delay cotyledon senescence in tomato seedlings

Cotyledon senescence is an important problem in industrialized seedling production. The effects of cold plasma (CP) treatments with different power levels from 0 to 100 W on the cotyledon chlorosis ratio and abscission ratio of tomato (Solanum lycopersicum L.) seedlings were investigated under normal conditions. CP treatment with 25 W resulted in the lowest ratios of chlorosis and abscission, which significantly inhibited cotyledon senescence. Further study of dark-induced cotyledon senescence indicated that 25 W CP treatment inhibited chlorophyll breakdown, the loss of photosystem II function, and the transcription of senescence-related genes SAG12 and ORE1 during darkness. Transcripts of RBOH1, MAPK1/2 and hydrogen peroxide (H2O2) concentrations were induced by CP treatment under normal conditions and early periods of darkness. However, both antioxidant enzymes and ascorbate-glutathione cycle were activated by CP treatment in late periods of darkness. In addition, the levels of three kinds of cytokinins (CKs) were enhanced, and ethylene concentrations were inhibited by CP treatment during darkness. Taken together, these physiological changes, which were caused by CP treatment, led to a senescence-delayed phenotype of tomato cotyledons. The present study provides a novel CP treatment approach for delaying cotyledon senescence in tomato seedlings, which is an easy, effective, and industrial technology that can significantly improve tomato seedling quality.

CRISPR/Cas9-mediated SlAN2 mutants reveal various regulatory models of anthocyanin biosynthesis in tomato plant.

Combining phenotype and gene expression analysis of the CRISPR/Cas9-induced SlAN2 mutants, we revealed that SlAN2 specifically regulated anthocyanin accumulation in vegetative tissues in purple tomato cultivar 'Indigo Rose.' Anthocyanins play an important role in plant development and also exhibit human health benefits. The tomato genome contains four highly homologous anthocyanin-related R2R3-MYB transcription factors: SlAN2, SlANT1, SlANT1-like, and SlAN2-like/Aft. SlAN2-like/Aft regulates anthocyanin accumulation in the fruit; however, the genetic function of the other three factors remains unclear. To better understand the function of R2R3-MYB transcription factors, we conducted targeted mutagenesis of SlAN2 in the purple tomato cultivar 'Indigo Rose' using clustered regularly interspersed short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9). The SlAN2 mutants had a fruit color and anthocyanin content similar to cv. 'Indigo Rose,' while the anthocyanin content and the relative expression levels of several anthocyanin-related genes in vegetative tissues were significantly lower in the SlAN2 mutant relative to cv. Indigo Rose. Furthermore, we found that anthocyanin biosynthesis is controlled by different regulators between tomato hypocotyls and cotyledons. In addition, SlAN2 mutants were shorter, with smaller and lighter fruits than cv. 'Indigo Rose.' Our findings further our understanding of anthocyanin production in tomato and other plant species.

Influence of Selected Antibiotics on the Tomato Regeneration in In Vitro Cultures

Generally, antimicrobial agents are frequently used in micropropagation techniques to obtain free elite clones or after genetic transformation to select putative transformants. Their successful application minimizes bacterial contamination however; they may be phytotoxic and may diversely affect the regeneration ability in plant tissue cultures. The objective of the current study was to estimate the effects of four antibiotics i.e. ampicillin, carbenicillin, cefotaxime and kanamycin on morphogenesis of three Polish tomato cultivars, cultured on MS medium with phytohormones. In this experiment the ability of tomato cotyledon explants to regenerate entire plants via indirect organogenesis was tested. Among four antibiotics tested, kanamycin was most harmful for the explants. This antibiotic, even at low doses (10-20 mg/L), inhibited tomato morphogenesis. On the other hand, the current study revealed significant influence of different concentrations of ampicillin, carbenicillin, cefotaxime on the frequency of bud formation. While the addition of cefotaxime at low concentration (100-200 mg/L) stimulated the bud formation, its increasing concentration adversely affected the organogenesis of tomato. The results clearly pointed out that carbenicillin and ampicillin at low concentrations (100-400 mg/L) were not only non-toxic, but they promoted bud regeneration. The obtained results show the crucial role not only of use of efficient antibiotics, but also of their proper doses in obtaining successful transformation and regeneration of tomato.
 
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 In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 3, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue.
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Red fruit, orange fruit, orange fruit, red fruit: genome editing in tomato.

Red fruit, orange fruit, orange fruit, red fruit: genome editing in tomato.

Metabolomic homeostasis shifts after callus formation and shoot regeneration in tomato.

Plants can regenerate from a variety of tissues on culturing in appropriate media. However, the metabolic shifts involved in callus formation and shoot regeneration are largely unknown. The metabolic profiles of callus generated from tomato (Solanum lycopersicum) cotyledons and that of shoot regenerated from callus were compared with the pct1-2 mutant that exhibits enhanced polar auxin transport and the shr mutant that exhibits elevated nitric oxide levels. The transformation from cotyledon to callus involved a major shift in metabolite profiles with denser metabolic networks in the callus. In contrast, the transformation from callus to shoot involved minor changes in the networks. The metabolic networks in pct1-2 and shr mutants were distinct from wild type and were rewired with shifts in endogenous hormones and metabolite interactions. The callus formation was accompanied by a reduction in the levels of metabolites involved in cell wall lignification and cellular immunity. On the contrary, the levels of monoamines were upregulated in the callus and regenerated shoot. The callus formation and shoot regeneration were accompanied by an increase in salicylic acid in wild type and mutants. The transformation to the callus and also to the shoot downregulated LST8 and upregulated TOR transcript levels indicating a putative linkage between metabolic shift and TOR signalling pathway. The network analysis indicates that shift in metabolite profiles during callus formation and shoot regeneration is governed by a complex interaction between metabolites and endogenous hormones.

Regulations on growth and development in tomato cotyledon, flower and fruit via destruction of miR396 with short tandem target mimic

Despite many studies about functions of miR396 were concentrated on cotyledon and leaf growth and development, only few researches were focused on flower and fruit, especially for fleshy fruit, for example, tomato fruit. Here, the roles of miR396 throughout the growth and development of tomato plant were explored with combining bioinformatics and transgene-mediated methods. In tomato, miR396 had two mature types (miR396a and miR396b), and miR396a expressed significantly higher than miR396b in cotyledon, flower, sepal and fruit. Generally, plant growth and development were regulated by miR396 via growth-regulating factors (GRFs). In tomato, all 13 SlGRFs were analyzed comprehensively, including phylogeny, domain and expression patterns. To investigate the roles of miR396 further, STTM396a/396a-88 was over-expressed in tomato, which induced miR396a and miR396b both dramatical down-regulation, and the target GRFs general up-regulation. As a result, the flowers, sepals and fruits all obviously became bigger. Most significantly, the sepal length of transgenic lines #3 and #4 at 39 days post-anthesis was separately increased 75% and 81%, and the fruit weight was added 45% and 39%, respectively. Overall, these results revealed novel roles of miR396 in regulating flower and fruit development, and provided a new potential way for improving tomato fruit yield.

Nitric Oxide, Ethylene, and Auxin Cross Talk Mediates Greening and Plastid Development in Deetiolating Tomato Seedlings.

The transition from etiolated to green seedlings involves the conversion of etioplasts into mature chloroplasts via a multifaceted, light-driven process comprising multiple, tightly coordinated signaling networks. Here, we demonstrate that light-induced greening and chloroplast differentiation in tomato (Solanum lycopersicum) seedlings are mediated by an intricate cross talk among phytochromes, nitric oxide (NO), ethylene, and auxins. Genetic and pharmacological evidence indicated that either endogenously produced or exogenously applied NO promotes seedling greening by repressing ethylene biosynthesis and inducing auxin accumulation in tomato cotyledons. Analysis performed in hormonal tomato mutants also demonstrated that NO production itself is negatively and positively regulated by ethylene and auxins, respectively. Representing a major biosynthetic source of NO in tomato cotyledons, nitrate reductase was shown to be under strict control of both phytochrome and hormonal signals. A close NO-phytochrome interaction was revealed by the almost complete recovery of the etiolated phenotype of red light-grown seedlings of the tomato phytochrome-deficient aurea mutant upon NO fumigation. In this mutant, NO supplementation induced cotyledon greening, chloroplast differentiation, and hormonal and gene expression alterations similar to those detected in light-exposed wild-type seedlings. NO negatively impacted the transcript accumulation of genes encoding phytochromes, photomorphogenesis-repressor factors, and plastid division proteins, revealing that this free radical can mimic transcriptional changes typically triggered by phytochrome-dependent light perception. Therefore, our data indicate that negative and positive regulatory feedback loops orchestrate ethylene-NO and auxin-NO interactions, respectively, during the conversion of colorless etiolated seedlings into green, photosynthetically competent young plants.

Simultaneous silencing of five lipoxygenase genes increases the contents of α-linolenic and linoleic acids in tomato (Solanum lycopersicum L.) fruits.

α-Linolenic and linoleic acids are essential fatty acids (EFAs) for humans and required for maintenance of optimal health, but they cannot be synthesized by the human body and must be obtained from dietary sources. Using TomloxC fragment, TomloxD fragment, and partial TomloxA sequence that is highly identical with TomloxB and TomloxE, a RNAi expression vector was constructed. The construct was used to transform tomato cotyledon explants with the Agrobacterium-mediated co-cultivation method. The real-time reverse transcription polymerase chain reaction analysis showed that the expression of TomloxA, TomloxB, TomloxC, TomloxD, and TomloxE in transgenic tomato plants was drastically repressed, which led to a marked decrease in the levels of lipoxygenase activity. Finally, higher accumulations of the endogenous α-linolenic and linoleic acids were detected in the transgenic tomato fruits, which were 1.65-3.99 and 2.91-4.98 times that of the non-transformed tomato fruits, respectively.

Utilization of the plant methionine sulfoxide reductase B genes as selectable markers in Arabidopsis and tomato transformation

Plant transformation is an important tool for basic research and agricultural biotechnology. In most cases, selection of putative transformants is based on antibiotic or herbicide resistance. Overexpression of plant genes that provide protection from abiotic or biotic stresses can result in a conferred phenotype that can be used as a means for selection. We have demonstrated herein that specific methionine sulfoxide reductase B (MsrB) genes that are overexpressed in transgenic plants may constitute a new selectable marker with concomitantly increased tolerance to methyl viologen (MV) treatment. Arabidopsis transformants overexpressing cytosolic MsrB7, MsrB8 or MsrB9 are viable and survive after MV selection. To establish whether these native plant origin genes serve as new non-antibiotic markers that can be applied to crop transformation, tomato cotyledons were used as transformation materials. MsrB7 transgenic tomato plants were successfully obtained by Agrobacterium-mediated transformation and selection on medium supplemented with MV. We suggest that specific MsrB genes that are overexpressed in transgenic plants may constitute a new selectable marker with increased tolerance to oxidative stress concomitant with MV treatment.

Cloning, Transformation and Expression of Human Gamma Interferon Gene in Tomato (Lycopersicon Esculentum Mill.)

ABSTRACTThe demand for recombinant proteins for therapeutic or diagnostic use is expanding rapidly in recent years. Human gamma interferon (Hu-IFN-γ) is one of these proteins against viruses that it has a high value in therapy Therefore interferon is used against viral infection, cancer and autoimmune diseases. In this study appropriate primers were designed and used for PCR amplification of the Hu-IFN-γ gene which was cloned in the plant expression vector pCAMBIA1304. The created construct was transferred in Agrobacterium tumefaciens strain LBA4404 and used for transformation of tomato cotyledon explants. The presence of the Hu-IFN-γ transgene in the genomic DNA of transgenic plants was proven by PCR. Finally, total protein of tomato was extracted and the presence of Hu-IFN-γ proteins was detected using dotblot assay.

Factors Affecting Regeneration of Tomato Cotyledons

In this research, we employed the tomato cultivar named Zhongshu Si Hao as research material to study the influences on the regeneration of adventitious buds under the different conditions with hormone combinations, various explants, different parts of cotyledons and cotyledon inoculatingmethods; we also screened the best method for seed surface disinfection and the most appropriate medium for the rooting of adventitious buds. The results showed that the best procedures for surface disinfection of tomato seeds would be as follows: firstly, immersing the seeds in 70% ethanol for 30 second, then rinsing them in 20% NaClO with tween-20 for 20 min. The most ideal explant for inducing buds is the middle part of the cotyledon, followed by the stem and the leaf. the best medium formula for cotyledon regeneration is MS+ZT 2 mg/L+IAA 0.1 mg/L, and placing the cotyledon upside down is better to induce the adventitious buds than that placing upside. The best medium for rooting of adventitious buds is 1/2MS+IAA 0.3 mg/L. This research would lay a foundation establish transformation system of tomato in our future research.

Transformation of HBsAg (hepatitis B surface antigen) gene into tomato mediated by Agrobacterium tumefaciens

The plant expression vector pBRSAg was constructed as suitable for transformation via Agrobacterium-mediated approach. It contains all elements for plant expression, such as CaMV 35S promoter, both left and right border sequence for transferred DNA (T-DNA) in Agrobacterium, plant reporter gene gus, and plant selection marker gene hpt. The recombinant binary vector pBRSAg was transformed into Agrobacterium tumefaciens strains by using the freeze-thaw method. Tomato cotyledon explants were transformed by A. tumefaciens and plants were regenerated on selection medium. GUS staining, PCR and PCR-Southern analysis of the plants were positive. It was for the first time shown that the HBsAg (hepatitis B surface antigen) gene was introduced into tomato plants. The expression of transgene is under investigation.

Expression of Malaria Antigens in Transgenic Tomatoes

Humanities’ inability to fully eradicate several deadly diseases in the 21 st century, in spite of all the new discoveries and advances in technologies, still plagues billions of people from developing countries across the world. One of these diseases, malaria, caused by Plasmodium sp. and transmitted through the Anofel vector, is found mainly in tropical countries, especially in the sub-Saharan and East Asian subregions, and predominantly affects children. Due to a series of reasons, a significant number of people in these areas are poor and cannot afford expensive medication to cure diseases. The present study conducted since 2008 was aimed to develop vaccines against malaria by expressing its antigens in tomato plants. The main goal was to obtain a low-cost affordable edible vaccine that would be easily and efficiently made available to the affected populations from underdeveloped countries and, more importantly, a vaccine that would treat malaria through a more accessible, selfsustaining, and healthier manner. Therefore, in order to obtain transgenic tomatoes using Agrobacterium tumefaciens, seven day-old tomato cotyledons were transformed with the malaria antigens PfCP-2.9 (a combination of parts of MSP 1 and AMA 1) and PfCSP-RC (largely consisting of CSP aminoacids). A total number of thirteen transformed plants resulted after transformation with malaria antigens. Transgene expression in the T1 (first generation transformed plants) was verified at the DNA, RNA, and protein levels. DNA, RNA and protein were extracted from the leaves and fruits of all transformed plants. The presence of the gene of interest in transgenic plants DNA extracts was demonstrated through PCR analysis. Reverse Transcpriptase PCR was performed for the RNA analysis, while Western Blot analysis and ELISA method were used to identify the presence of the protein of interest in the T1 transgenic plants. Transgene expression at the DNA and RNA levels was then confirmed in ten plants. However, the protein expression was observed in only two of the four transgenic plants transformed with PfCP -2.9 gene and in four out of seven plants transformed with PfCSP-RC. Finally, the gene of interest was also identified when DNA and RNA from the second generation (T2) of transformed plants were tested. This is the first known successful study in identifying the expression of malaria antigens in both first and secondgeneration transformed tomato plants.

Ultraviolet A-specific induction of anthocyanin biosynthesis and PAL expression in tomato (Solanum lycopersicum L.)

Ultraviolet A (UV-A) is an environmental stimulus, and UV-A-induced anthocyanin biosynthesis has been previously investigated in the tomato plant (Solanum lycopersicum L.). UV-A induced anthocyanin biosynthesis in tomato seedlings and co-irradiation with visible light and UV-A did not influence the content of UV-A-induced anthocyanin accumulation. UV-A irradiation induced significant accumulations of anthocyanin in both the cotyledons and hypocotyls of tomato seedlings. Anthocyanin production increased gradually in the tomato hypocotyls after exposure to UV-A and reached maximum levels at 12 h. In the cotyledons, anthocyanin accumulation was significantly increased at 1 h after UV-A exposure and was reduced afterward; however, it increased again beginning at 3 h. The expression of the phenylalanine ammonia-lyase (SlPAL5) gene was shown to be increased after UV-A exposure in a time-dependent manner. UV-A irradiation was also shown to induce anthocyanin accumulation in the epidermis of the tomato fruit; however, SlPAL5 transcripts were detected only at 3 and 24 h after UV-A treatment. After a 1 h pulse of UV-A, SlPAL5 transcripts were increased significantly in tomato cotyledons and hypocotyls after transfer to dark conditions for a short time.