Knockout of SlNPR1 enhances tomato plants resistance against Botrytis cinerea by modulating ROS homeostasis and JA/ET signaling pathways.

Tomato is one of the most popular horticultural crops, and many commercial tomato cultivars are particularly susceptible to Botrytis cinerea. Non-expressor of pathogenesis-related gene 1 (NPR1) is a critical component of the plant defense mechanisms. However, our understanding of how SlNPR1 influences disease resistance in tomato is still limited. In this study, two independent slnpr1 mutants were used to study the role of SlNPR1 in tomato resistance against B. cinerea. Compared to (WT), slnpr1 leaves exhibited enhanced resistance against B. cinerea with smaller lesion sizes, higher activities of chitinase (CHI), ß-1, 3-glucanases (GLU) and phenylalanine ammonia-lyase (PAL), and significantly increased expressions of pathogenesis-related genes (PRs). The increased activities of peroxidase (POD), ascorbate peroxidase (APX) and decreased catalase (CAT) activities collectively regulated reactive oxygen species (ROS) homeostasis in slnpr1 mutants. The integrity of the cell wall in slnpr1 mutants was maintained. Moreover, the enhanced resistance was further reflected by induction of defense genes involved in jasmonic acid (JA) and ethylene (ET) signaling pathways. Taken together, these findings revealed that knocking out SlNPR1 resulted in increased activities of defense enzymes, changes in ROS homeostasis and integrity of cell walls, and activation of JA and ET pathways, which confers resistance against B. cinerea in tomato plants.

Knockout of SlMAPK3 enhances tolerance to heat stress involving ROS homeostasis in tomato plants.

BACKGROUND: High temperature is a major environmental stress that limits plant growth and agriculture productivity. Mitogen-activated protein kinases (MAPKs) are highly conserved serine and threonine protein kinases that participate in response to diverse environmental stresses in plants. A total of 16 putative SlMAPK genes are identified in tomato, and SlMAPK3 is one of the most extensively studied SlMAPKs. However, the role of SlMAPK3 in response to heat stress is not clearly understood in tomato plants. In this study, we performed functional analysis of SlMAPK3 for its possible role in response to heat stress. RESULTS: qRT-PCR analyses revealed that SlMAPK3 relative expression was depressed by heat stress. Here, wild-type (WT) tomato plants and CRISPR/Cas9-mediated slmapk3 mutant lines (L8 and L13) were used to investigate the function of SlMAPK3 in response to heat stress. Compared with WT plants, slmapk3 mutants exhibited less severe wilting and less membrane damage, showed lower reactive oxygen species (ROS) contents, and presented higher both activities and transcript levels of antioxidant enzymes, as well as elevated expressions of genes encoding heat stress transcription factors (HSFs) and heat shock proteins (HSPs). CONCLUSIONS: CRISPR/Cas9-mediated slmapk3 mutants exhibited more tolerance to heat stress than WT plants, suggesting that SlMAPK3 was a negative regulator of thermotolerance. Moreover, antioxidant enzymes and HSPs/HSFs genes expression were involved in SlMAPK3-mediated heat stress response in tomato plants.

CRISPR/Cas9-Mediated SlNPR1 mutagenesis reduces tomato plant drought tolerance.

BACKGROUND: NPR1, nonexpressor of pathogenesis-related gene 1, is a master regulator involved in plant defense response to pathogens, and its regulatory mechanism in the defense pathway has been relatively clear. However, information about the function of NPR1 in plant response to abiotic stress is still limited. Tomato is the fourth most economically crop worldwide and also one of the best-characterized model plants employed in genetic studies. Because of the lack of a stable tomato NPR1 (SlNPR1) mutant, little is known about the function of SlNPR1 in tomato response to biotic and abiotic stresses. RESULTS: Here we isolated SlNPR1 from tomato 'Ailsa Craig' and generated slnpr1 mutants using the CRISPR/Cas9 system. Analysis of the cis-acting elements indicated that SlNPR1 might be involved in tomato plant response to drought stress. Expression pattern analysis showed that SlNPR1 was expressed in all plant tissues, and it was strongly induced by drought stress. Thus, we investigated the function of SlNPR1 in tomato-plant drought tolerance. Results showed that slnpr1 mutants exhibited reduced drought tolerance with increased stomatal aperture, higher electrolytic leakage, malondialdehyde (MDA) and hydrogen peroxide (H2O2) levels, and lower activity levels of antioxidant enzymes, compared to wild type (WT) plants. The reduced drought tolerance of slnpr1 mutants was further reflected by the down-regulated expression of drought related key genes, including SlGST, SlDHN, and SlDREB. CONCLUSIONS: Collectively, the data suggest that SlNPR1 is involved in regulating tomato plant drought response. These results aid in further understanding the molecular basis underlying SlNPR1 mediation of tomato drought sensitivity.

ABA signaling rather than ABA metabolism is involved in trehalose-induced drought tolerance in tomato plants.

MAIN CONCLUSION: Trehalose increased drought tolerance of tomato plants, accompanied by reduced water loss and closed stomata, which was associated with the upregulated ABA signaling-related genes expression, but not in ABA accumulation. Drought is one of the principal abiotic stresses that negatively influence the growth of plant and yield. Trehalose has great agronomic potential to improve the stress tolerance of plants. However, little information is available on the role of ABA and its signaling components in trehalose-induced drought tolerance. The aim of this study is to elucidate the potential mechanism by which trehalose regulates ABA in response to drought stress. In this study, 6-week-old tomato (Solanum lycopersicum cv. Ailsa Craig) plants were treated with 0 or 15.0 mM trehalose solution. Results showed that trehalose treatment significantly enhanced drought tolerance of tomato plants, accompanied by encouraged stomatal closure and protected chloroplast ultrastructure. Compared with controls, trehalose-treated plants showed lower hydrogen peroxide content and higher antioxidant enzymes activities, which contributed to alleviate oxidative damage caused by drought. Moreover, trehalose treatment decreased ABA content, which was followed by the downregulation of ABA biosynthesis genes expression and the upregulation of ABA catabolism genes expression. In contrast, exogenous trehalose upregulated transcript levels of ABA signaling-related genes, including SlPYL1/3/4/5/6/7/9, SlSnRK2.3/4, SlAREB1/2, and SlDREB1. These results suggested that trehalose treatment enhanced drought tolerance of tomato plants, and it's ABA signaling rather than ABA metabolism that was involved in trehalose-induced drought tolerance in tomato plants. These findings provide evidence for the physiological role of trehalose and bring about a new understanding of the possible relationship between trehalose and ABA.

Ornithine decarboxylase is involved in methyl jasmonate-regulated postharvest quality retention in button mushrooms (Agaricus bisporus).

BACKGROUND: In the present study, we investigated the role of ornithine decarboxylase (ODC) in the methyl jasmonate (MeJA)-regulated postharvest quality maintenance of Agaricus bisporus (J. E. Kange) Imbach button mushrooms by pretreating mushrooms with a specific irreversible inhibitor called α-difluoromethylornithine (DFMO) before exposure to MeJA vapor. RESULTS: Mushrooms were treated with 0 or 100 µmol L-1 MeJA or a combination of 120 µmol L-1 DFMO and 100 µmol L-1 MeJA, respectively, before storage at 4 °C for 21 days. Treatment with MeJA alone induced the increase in ODC activity whereas this effect was greatly suppressed by pretreatment with DFMO. α-Difluoromethylornithine strongly attenuated the effect of MeJA on decreasing cap opening, slowing the decline rate of soluble protein and total sugar, and accumulating total phenolics and flavonoids. α-Difluoromethylornithine pretreatment also counteracted the ability of MeJA to inhibit polyphenol oxidase and lipoxygenase activities, and malondialdehyde production, and to stimulate superoxide dismutase and catalase activities. It also largely downregulated MeJA-induced accumulation of free putrescine (Put). CONCLUSION: These results reveal that ODC is involved in MeJA-regulated postharvest quality retention of button mushrooms, and this involvement is likely to be associated with Put levels. © 2018 Society of Chemical Industry.

Identification and active site analysis of the 1-aminocyclopropane-1-carboxylic acid oxidase catalysing the synthesis of ethylene in Agaricus bisporus.

BACKGROUND: 1-Aminocyclopropane-1-carboxylate oxidase (ACO) is a key enzyme that catalyses the final step in the biosynthesis of the plant hormone ethylene. Recently, the first ACO homologue gene was isolated in Agaricus bisporus, whereas information concerning the nature of the ethylene-forming activity of this mushroom ACO is currently lacking. METHODS: Recombinant ACO from A. bisporus (Ab-ACO) was purified and characterised for the first time. Molecular modelling combined with site-directed mutagenesis and kinetic and spectral analysis were used to investigate the property of Ab-ACO. RESULTS: Ab-ACO has eight amino acid residues that are conserved in the Fe (II) ascorbate family of dioxygenases, including four catalytic residues in the active site, but Ab-ACO lacks a key residue, S289. In comparison to plant ACOs, Ab-ACO requires ACC and Fe (II) but does not require ascorbate. In addition, Ab-ACO had relatively low activity and was completely dependent on bicarbonate, which could be ascribed to the replacement of S289 by G289. Moreover, the ferrous ion could induce a change in the tertiary, but not the secondary, structure of Ab-ACO. CONCLUSIONS: These results provide crucial experimental support for the ability of Ab-ACO to catalyse ethylene formation in a similar manner to that of plant ACOs, but there are differences between the biochemical and catalytic characteristics of Ab-ACO and plant ACOs. GENERAL SIGNIFICANCE: This work enhances the understanding of the ethylene biosynthesis pathways in fungi and could promote profound physiological research of the role of ethylene in the regulation of mushroom growth and development.

Characterization of WRKY transcription factors in Solanum lycopersicum reveals collinearity and their expression patterns under cold treatment.

WRKY transcription factors play an important role in cold defense of plants. However, little information is available about the cold-responsive WRKYs in tomato (Solanum lycopersicum). In the present study, a complete characterization of this gene family was described. Eighty WRKY genes in the tomato genome were identified. Almost all WRKY genes contain putative stress-responsive cis-elements in their promoter regions. Segmental duplications contributed significantly to the expansion of the SlWRKY gene family. Transcriptional analysis revealed notable differential expression in tomato tissues and expression patterns under cold stress, which indicated wide functional divergence in this family. Ten WRKYs in tomato were strongly induced more than 2-fold during cold stress. These genes represented candidate genes for future functional analysis of WRKYs involved in the cold-related signal pathways. Our data provide valuable information about tomato WRKY proteins and form a foundation for future studies of these proteins, especially for those that play an important role in response to cold stress.

Bacterial community compositions of tomato (Lycopersicum esculentum Mill.) seeds and plant growth promoting activity of ACC deaminase producing Bacillus subtilis (HYT-12-1) on tomato seedlings.

Study of endophytic bacteria within plant seeds is very essential and meaningful on account of their heritability and versatility. This study investigated Bacillus bacterial communities within the seeds of four commercial tomato varieties, by 16S rRNA gene PCR-RFLP (restriction fragment length polymorphism). Phylogenetic analysis of 16S rRNA gene sequences indicated that the 22 representative isolates belonged to five species of genus Bacillus and the bacterial compositions showed remarkable differences among tomato varieties. Isolates exhibited multiple plant growth promoting (PGP) traits: 37 % of indole-3-acetic acid production; 37 % of phosphate solubilization; 24 % of siderophores production; 85 % of potential nitrogen fixation and 6 % of 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity. Isolate HYT-12-1 was shown to have highest ACC deaminase activity (112.02 nmol α-ketobutyrate mg⁻¹ protein h⁻¹) among the five ACC deamiase producing strains. 16S rRNA gene sequencing indicated that the isolate HYT-12-1 shared the highest sequence similarity (100 %) with B. subtilis. PGP experiments under gnotobiotic and greenhouse conditions revealed the ability of strain HYT-12-1 to enhance the growth of tomato seedlings. This is the first study to describe endophytic Bacillus communities within tomato seeds, and the results suggest that B. subtilis strain HYT-12-1 would have a great potential for industrial application as biofertilizer in the future.

Recent Advances in Dissecting the Function of Ethylene in Interaction between Host and Pathogen.

Pathogens influence the growth and development of plants, resulting in detrimental damage to their yields and quality. Ethylene, a gaseous phytohormone, serves a pivotal function in modulating diverse physiological processes in plants, including defense mechanisms against pathogen invasion. Ethylene biosynthesis is involved in both plants and pathogens. Recent empirical research elucidates the intricate interactions and regulatory mechanisms between ethylene and pathogens across various plant species. In this review, we provide a comprehensive overview of the latest findings concerning ethylene's role and its regulatory networks in host-pathogen interactions. Additionally, we explore the crosstalk between ethylene and other phytohormones. Points regarding ethylene emission and its modulation by pathogens are also emphasized. Moreover, we also discuss potential unresolved issues in the field that warrant further investigation.

Tomato SlMAPK3 Modulates Cold Resistance by Regulating the Synthesis of Raffinose and the Expression of SlWRKY46.

Mitogen-activated protein kinase (MAPK) cascades and raffinose have been observed to increase in plants exposed to cold. However, it remains elusive whether and how MAPK regulates raffinose synthesis under cold stress. Here, overexpression of SlMAPK3 promoted the accumulation of galactinol and raffinose under cold stress, while CRISPR/Cas9-mediated mutants showed the opposite results. Moreover, SlMAPK3 promoted the expression of SlWRKY46 at low temperatures and interacted with SlWRKY46 protein. Overexpression of SlWRKY46 enhanced cold resistance. Furthermore, SlWRKY46 directly bound to the promoter of SlGols1 to enhance its expression and promoted the accumulation of raffinose. Virus-induced gene-silencing (VIGS)-mediated knockdown of SlGols1 remarkably elevated cold sensitivity and reduced raffinose content. Meanwhile, exogenous supplementation of raffinose could improve the cold tolerance of tomato plants. Thus, our data indicates that SlMAPK3 modulates cold resistance by regulating raffinose content and SlWRKY46 expression. SlWRKY46 also promotes the accumulation of raffinose by inducing the expression of SlGols1.

How Sugar Labeling Affects Consumer Sugar Reduction: A Case of Sucrose Grade Labels in China.

The effectiveness of sugar labeling depends not only on direct sugar reduction but also on the extent to which compensatory eating occurs. This study focuses on the use of sucrose grade labels in the Chinese market to investigate not only consumers' willingness to pay (WTP) for different sucrose labels but also the consistency of their sugar control behavior when confronted with unlabeled processed foods. The findings reveal that consumers are willing to pay approximately 4%, 7%, and 7% more for yogurt labeled as "low sucrose", "no sucrose", and "no sucrose with sugar substitutes", respectively, compared to yogurt labeled as "regular sucrose." Furthermore, when subsequently presented with unlabeled toast, a significant proportion of consumers who initially chose "no sucrose" yogurt continued to select wholewheat toast, which contains less sugar than white and coconut toast. This indicates their commitment to maintaining their sugar control behavior. The study provides valuable experimental evidence for researchers, food manufacturers, and policymakers regarding the efficacy of sucrose grade labels. In particular, it offers policymakers insights into guiding consumers to promote sustainable healthy diets.

Knowledge Maps and Emerging Trends in Cell-Cultured Meat since the 21st Century Research: Based on Different National Perspectives of Spatial-Temporal Analysis.

Cell-cultured meat holds significant environmental value as an alternative protein source. Throughout the 21st century, cell-cultured meat has progressively penetrated commercial markets. However, a systematic review encompassing the entire field needs improvement. Employing Citespace, Vosviewer, and R-Bibliometrix software, a bibliometric analysis was used to present the research progress and general development trends of 484 articles on cell-cultured meat from 2000 to 2022 based on countries, authors, institutions, and keywords. This analysis provides ideas for the future development of cell-cultured meat in different countries or regions worldwide. Research on cell-cultured meat from 2000 to 2022 has undergone two phases: fluctuating growth (2000-2013) and rapid growth (2013-2022). Noteworthy contributions to cell-cultured meat studies emerge from author groups in the United States of America, the United Kingdom, and China, with influential institutions like the University of Bath significantly impacting pertinent research. Furthermore, over the past two decades, research has leaned towards exploring topics such as "biomaterials", "cultured", "land use", "public opinion", "animal welfare", and "food safety". Furthermore, this study reveals differences in nomenclature between regions and institutions. "Cultured meat" is more popular in some countries than in other forms. Institutions in Asia use "cultured meat" more frequently; however, institutions in the Americas adopt "cultivated meat" and rarely adopt "in vitro meat", and institutions in the European region have no particularly prominent tendency towards a specific nomenclature. Future research should emphasize aligning the labeling of cell-cultured meat with effective management strategies and referencing regulatory policies across various countries. For the first time, we use three different bibliometric methods to analyze temporal and spatial variation in research on cellular meat. The results of this study have a multiplier effect. We provide a theoretical basis and a practical reference for the identification of alternatives in the dual context of "food crisis and food security" and "climate crisis". At the same time, we also provide a reference for the sustainable development of the food system.

Hot air treatment-induced arginine catabolism is associated with elevated polyamines and proline levels and alleviates chilling injury in postharvest tomato fruit.

BACKGROUND: To understand whether arginine catabolism might be involved in hot air (HA)-induced chilling tolerance mechanism in tomato fruit, we investigated the effect of HA treatment on endogenous arginine catabolism in relation to chilling injury. RESULTS: Tomato fruit were harvested at mature green stage and treated with HA at 38°C for 12 h and then stored at 2°C for 21 days. The effects of HA treatment on fruit chilling injury and gene expression levels or enzyme activity, and metabolites related to arginine catabolism were evaluated. HA treatment reduced the chilling injury symptoms of tomato fruit and enhanced the accumulation of endogenous polyamines, especially putrescine and proline. This accumulation is associated with the increased transcript levels of genes encoding arginase (LeARG1 and LeARG2), arginine decarboxylase (LeADC), ornithine decarboxylase (LeODC) and ornithine aminotransferase (LeOAT) at most sampling times. However, HA treatment had little effect on nitric oxide synthase activity and nitric oxide concentration. CONCLUSION: These results revealed that the reduction in chilling injury by HA treatment may be due to the accumulation of putrescine and proline induced primarily by activating the catabolism of endogenous arginine.

LeMAPK4 participated in cold-induced ethylene production in tomato fruit.

BACKGROUND: Mitogen-activated protein kinase (MAPK, EC 2.7.11.24) cascade from several plant species has been shown to be activated during response to abiotic stress. Ethylene plays an important role in fruit tolerance to environmental stress. However, the mechanisms by which MAPK regulates defence systems in fruit and the relationship between MAPK and ethylene remain to be determined. RESULTS: MAPK inhibitor significantly decreased the chilling tolerance of tomato (Lycopersicon esculentum cv. Lichun) fruit during cold storage. Moreover, decreases in ethylene content, LeACS2 expression and activities of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS, EC 4.4.1.14) and ACC oxidase (ACO, EC 1.14.17.4) due to MAPK inhibitor occurred within 24 h after cold treatment. Upon treatment with cold and ethephon, the ethylene content, activities of ACS and ACO and expression of LeACS2, LeACO1 and LeMAPK4 increased. CONCLUSION: The results showed the regulation of MAPK in ethylene biosynthesis to protect tomato fruit from cold stress. In addition, the participation of LeMAPK4 in cold-induced ethylene biosynthesis in tomato fruit was indicated.

The role of environmental-related message on consumer acceptance of novel food production technology: an experimental investigation on artificial meat products.

This study investigates the effects of environmental-related message on consumers' acceptance of artificial meat products in China. By focusing on the introduction of plant-based and cultured meat, a novel dataset involving 3441 research participants was collected in China through the online platform with randomized controlled experiments. The results show that for promotion-focused participants, gain-oriented message is effective while avoidance-oriented message is not in improving their acceptance of artificial meat. For prevention-focused participants, both gain- and avoidance-oriented messages are found to increase their acceptance of artificial meat effectively. To quantify the average impacts of environmental-related message and consumers' regulatory focus fit on the acceptance of plant-based meat and cultured meat, a seemingly unrelated regression model is applied. The results reveal that for a randomly selected individual, exposing with both gain- and avoidance-oriented messages would increase his or her acceptance of artificial meat comparing to exposing with neutral message. In addition, we find participants who use promotion focus more tend to have higher acceptance scores for both kinds of artificial meat on average.

SlMAPK3 Positively Regulates the Ethylene Production of Postharvest Tomato Fruits and Is Involved in Ethylene-Mediated Cold Tolerance.

Mitogen-activated protein kinase (MAPK) cascades and ethylene are crucial for plant growth, development, and stress responses, but their potential mechanisms in cold resistance remain unclear. We revealed that SlMAPK3 transcript levels were dramatically induced by cold treatment in an ethylene-dependent manner. Under cold stress, the proline content of SlMAPK3-overexpression fruit was 96.5 and 115.9% higher than that of wild-type fruit (WT), respectively, while the ion leakage was 37.3 and 32.5% lower than that of WT. RNA sequencing revealed that overexpression of SlMAPK3 caused upregulation of genes that are enriched in the ethylene-activated signaling pathway (GO:0009873), cold signaling pathway (GO:0009409), and heat signaling pathway (GO:0009408). RT-qPCR demonstrated that the expression levels of SlACS2, SlACS4, SlSAHH, SlCBF1, SlDREB, SlGolS1, and SlHSP17.7 in the OE.MAPK3 fruits were consistent with the RNA sequencing results. Meanwhile, the knockout of SlMAPK3 reduced the ethylene content, ACC content, and ACS activity. Moreover, the knockout of SlMAPK3 reduced the positive effect of ethylene in cold stress, while suppressing the expression of SlICE1 and SlCBF1. In conclusion, our study demonstrated a novel mechanism by which SlMAPK3 positively regulates the ethylene production of postharvest tomato fruits and is involved in ethylene-mediated cold tolerance.

Postharvest fruit quality of tomatoes influenced by an ethylene signaling component during long-term cold storage.

Ethylene production is essential for improving cold resistance of postharvest tomatoes. However, the role of ethylene signaling pathway in maintaining fruit quality during long-term cold storage remains poorly understood. Here, we demonstrated that a partial loss of function in ethylene signaling by mutation of Ethylene Response Factor 2 (SlERF2), worsened fruit quality during cold storage, as determined by visual characterization, and physiological analyses of membrane damage and reactive oxygen species metabolism. In addition, the transcriptions of genes related to abscisic acid (ABA) biosynthesis and signaling were also altered by SlERF2 gene in response to cold storage. Furthermore, mutation of SlERF2 gene compromised cold-induced expression of genes in the C-repeat/dehydration-responsive binding factor (CBF) signaling pathway. Therefore, it's concluded that an ethylene signaling component, SlERF2 contributed to the regulations of ABA biosynthesis and signaling, as well as CBF cold signaling pathway, ultimately affecting the fruit quality during long-term cold storage of tomatoes.

Consumers' Preferences and Attitudes towards Plant-Based Milk.

Plant-based milk (PBM) has become increasingly popular due to its environmental sustainability, health benefits, ingredient abundance, and unique taste. This study aims to identify the main factors that affect consumer preferences and attitudes towards PBM, and to examine the effect of consumer attitudes including environmental awareness, health consciousness, and food neophobia on WTP. We use the double-bounded dichotomy choice (DBDC) method to calculate consumers' willingness to pay (WTP) for PBM. We find that the appearance, taste, nutritional value, and environmental benefits of PBM significantly increase consumers' WTP for it. Consumers with high environmental awareness are more likely to perceive PBM as environmentally friendly and are willing to pay a higher price for it. Consumers with high health consciousness tend to value the environmental benefits of PBM and prioritize purchase convenience, as it aligns with their health-conscious lifestyle, leading to a higher WTP for PBM. The results of our study can help design effective strategies to market plant-based milk and develop sustainable and healthy food systems.

CRISPR/Cas9-Mediated SlATG5 Mutagenesis Reduces the Resistance of Tomato Fruit to Botrytis cinerea.

Tomato fruit is highly susceptible to infection by Botrytis cinerea (B. cinerea), a dominant pathogen, during storage. Recent studies have shown that autophagy is essential for plant defense against biotic and abiotic stresses. Autophagy-related gene 5 (ATG5) plays a key role in autophagosome completion and maturation, and is rapidly induced by B. cinerea, but the potential mechanisms of ATG5 in Solanum lycopersicum (SlATG5) in postharvest tomato fruit resistance to B. cinerea remain unclear. To elucidate the role of SlATG5 in tomato fruit resistant to B. cinerea, CRISPR/Cas9-mediated knockout of SlATG5 was used in this study. The results showed that slatg5 mutants were more vulnerable to B. cinerea and exhibited more severe disease symptoms and lower activities of disease-resistant enzymes, such as chitinase (CHI), ß-1,3-glucanase (GLU), phenylalanine ammonia-lyase (PAL), and polyphenol oxidase (PPO), than the wild type (WT). Furthermore, the study observed that after inoculation with B. cinerea, the relative expression levels of genes related to salicylic acid (SA) signaling, such as SlPR1, SlEDS1, SlPAD4, and SlNPR1, were higher in slatg5 mutants than in WT. Conversely, the relative expression levels of jasmonic acid (JA) signaling-related genes SlLoxD and SlMYC2 were lower in slatg5 mutants than in WT. These findings suggested that SlATG5 positively regulated the resistance response of tomato fruit to B. cinerea by inhibiting the SA signaling pathway and activating the JA signaling pathway.

Identification of bHLH family genes in Agaricus bisporus and transcriptional regulation of arginine catabolism-related genes by AbbHLH1 after harvest.

Basic helix-loop-helix (bHLH) transcription factors (TFs) are widely distributed in eukaryotes and play an important role in biological growth and development. The identification and functional analyses of bHLH genes/proteins in edible mushrooms (Agaricus bisporus) have yet to be reported. In the present study, we identified 10 putative bHLH members carrying the conserved bHLH domains. Phylogenetic analyses revealed that the 10 AbbHLHs were the closest to sequences of species belonging to 7 different fungal subgroups, which was supported by loop length, intron patterns, and key amino acid residues. The substantial increase after harvest and continuously elevated expression of AbbHLH1 during the development until the disruption of mushroom velum, and the preferential expression in cap and gill tissues suggest the important function of AbbHLH1 in postharvest development of A. bisporus. The relationship of arginine catabolism-related genes with the early stage of postharvest continuing development also was revealed by expression determination. Subcellular localization showed that AbbHLH1 could be localized in nucleus. Importantly, the electrophoretic mobility shift and dual-luciferase reporter assays showed that AbbHLH1 activated the promoters of AbOAT, AbSPDS, and AbSAMDC and suppressed the expression of AbARG, AbUREA, and AbODC, probably for the modulation of arginine catabolism and thus control of postharvest mushroom development. Taken together, the available data provide valuable functional insight into the role of AbbHLH proteins in postharvest mushrooms.