Identification, Classification, and Expression Analysis of the <i>Triacylglycerol Lipase</i> (<i>TGL</i>) Gene Family Related to Abiotic Stresses in Tomato

Triacylglycerol Lipases (TGLs) are the major enzymes involved in triacylglycerol catabolism. TGLs hydrolyze long-chain fatty acid triglycerides, which are involved in plant development and abiotic stress responses. Whereas most studies of TGLs have focused on seed oil metabolism and biofuel in plants, limited information is available regarding the genome-wide identification and characterization of the TGL gene family in tomato (Solanum lycopersicum L.). Based on the latest published tomato genome annotation ITAG4.0, 129 SlTGL genes were identified and classified into 5 categories according to their structural characteristics. Most SlTGL genes were distributed on 3 of 12 chromosomes. Segment duplication appeared to be the driving force underlying expansion of the TGL gene family in tomato. The promoter analysis revealed that the promoters of SlTGLs contained many stress responsiveness cis-elements, such as ARE, LTR, MBS, WRE3, and WUN-motifs. Expression of the majority of SlTGL genes was suppressed following exposure to chilling and heat, while it was induced under drought stress, such as SlTGLa9, SlTGLa6, SlTGLa25, SlTGLa26, and SlTGLa13. These results provide valuable insights into the roles of the SlTGL genes family and lay a foundation for further functional studies on the linkage between triacylglycerol catabolism and abiotic stress responses in tomato

Identification, Classification, and Expression Analysis of the Triacylglycerol Lipase (TGL) Gene Family Related to Abiotic Stresses in Tomato

Triacylglycerol Lipases (TGLs) are the major enzymes involved in triacylglycerol catabolism. TGLs hydrolyze long-chain fatty acid triglycerides, which are involved in plant development and abiotic stress responses. Whereas most studies of TGLs have focused on seed oil metabolism and biofuel in plants, limited information is available regarding the genome-wide identification and characterization of the TGL gene family in tomato (Solanum lycopersicum L.). Based on the latest published tomato genome annotation ITAG4.0, 129 SlTGL genes were identified and classified into 5 categories according to their structural characteristics. Most SlTGL genes were distributed on 3 of 12 chromosomes. Segment duplication appeared to be the driving force underlying expansion of the TGL gene family in tomato. The promoter analysis revealed that the promoters of SlTGLs contained many stress responsiveness cis-elements, such as ARE, LTR, MBS, WRE3, and WUN-motifs. Expression of the majority of SlTGL genes was suppressed following exposure to chilling and heat, while it was induced under drought stress, such as SlTGLa9, SlTGLa6, SlTGLa25, SlTGLa26, and SlTGLa13. These results provide valuable insights into the roles of the SlTGL genes family and lay a foundation for further functional studies on the linkage between triacylglycerol catabolism and abiotic stress responses in tomato

The tomato 2-oxoglutarate-dependent dioxygenase gene SlF3HL is critical for chilling stress tolerance

Chill stress: Gene regulator identified in tomato plants A gene involved in regulating responses to chill stress in tomato plants may prove valuable in reducing crop damage caused by low temperatures. A significant limiting factor in growing certain crops is cold stress – for example, tomato and cucumber plants suffer chill damage and reduced productivity at low temperatures (0 to 12 °C). Xianggiang Zhan at the Northwest A&F University in Shaanxi, China, and co-workers demonstrated that the gene SIF3HL is a key regulator of chilling stress tolerance in tomato plants. The team generated plants with no SIF3HL expressed and found that they responded poorly at low temperatures, with higher levels of reactive oxygen species and decreased levels of metabolic enzymes. Expression levels of four cold-responsive genes were also reduced. Plants overexpressing SIF3HL, on the other hand, coped well at low temperatures

Modification of Serine 1040 of SIBRI1 Increases Fruit Yield by Enhancing Tolerance to Heat Stress in Tomato

High temperature is a major environmental factor that adversely affects plant growth and production. SlBRI1 is a critical receptor in brassinosteroid signalling, and its phosphorylation sites have differential functions in plant growth and development. However, the roles of the phosphorylation sites of SIBRI1 in stress tolerance are unknown. In this study, we investigated the biological functions of the phosphorylation site serine 1040 (Ser-1040) of SlBRI1 in tomato. Phenotype analysis indicated that transgenic tomato harbouring SlBRI1 dephosphorylated at Ser-1040 showed increased tolerance to heat stress, exhibiting better plant growth and plant yield under high temperature than transgenic lines expressing SlBRI1 or SlBRI1 phosphorylated at Ser-1040. Biochemical and physiological analyses further showed that antioxidant activity, cell membrane integrity, osmo-protectant accumulation, photosynthesis and transcript levels of heat stress defence genes were all elevated in tomato plants harbouring SlBRI1 dephosphorylated at Ser-1040, and the autophosphorylation level of SlBRI1 was inhibited when SlBRI1 dephosphorylated at Ser-1040. Taken together, our results demonstrate that the phosphorylation site Ser-1040 of SlBRI1 affects heat tolerance, leading to improved plant growth and yield under high-temperature conditions. Our results also indicate the promise of phosphorylation site modification as an approach for protecting crop yields from high-temperature stress

Genome-Wide Analysis of <i>MBF1</i> Family Genes in Five Solanaceous Plants and Functional Analysis of <i>SlER24</i> in Salt Stress

Multiprotein bridging factor 1 (MBF1) is an ancient family of transcription coactivators that play a crucial role in the response of plants to abiotic stress. In this study, we analyzed the genomic data of five Solanaceae plants and identified a total of 21 MBF1 genes. The expansion of MBF1a and MBF1b subfamilies was attributed to whole-genome duplication (WGD), and the expansion of the MBF1c subfamily occurred through transposed duplication (TRD). Collinearity analysis within Solanaceae species revealed collinearity between members of the MBF1a and MBF1b subfamilies, whereas the MBF1c subfamily showed relative independence. The gene expression of SlER24 was induced by sodium chloride (NaCl), polyethylene glycol (PEG), ABA (abscisic acid), and ethrel treatments, with the highest expression observed under NaCl treatment. The overexpression of SlER24 significantly enhanced the salt tolerance of tomato, and the functional deficiency of SlER24 decreased the tolerance of tomato to salt stress. SlER24 enhanced antioxidant enzyme activity to reduce the accumulation of reactive oxygen species (ROS) and alleviated plasma membrane damage under salt stress. SlER24 upregulated the expression levels of salt stress-related genes to enhance salt tolerance in tomato. In conclusion, this study provides basic information for the study of the MBF1 family of Solanaceae under abiotic stress, as well as a reference for the study of other plants

Transcriptome Profiling of Tomato Fruit Development Reveals Transcription Factors Associated with Ascorbic Acid, Carotenoid and Flavonoid Biosynthesis

<div><p>Tomato (<i>Solanum lycopersicum</i>) serves as a research model for fruit development; however, while it is an important dietary source of antioxidant nutrients, the transcriptional regulation of genes that determine nutrient levels remains poorly understood. Here, the transcriptomes of fruit at seven developmental stages (7, 14, 21, 28, 35, 42 and 49 days after flowering) from two tomato cultivars (Ailsa Craig and HG6-61) were evaluated using the Illumina sequencing platform. A total of 26,397 genes, which were expressed in at least one developmental stage, were detected in the two cultivars, and the expression patterns of those genes could be divided into 20 groups using a K-mean cluster analysis. Gene Ontology term enrichment analysis indicated that genes involved in RNA regulation, secondary metabolism, hormone metabolism and cell wall metabolism were the most highly differentially expressed genes during fruit development and ripening. A co-expression analysis revealed several transcription factors whose expression patterns correlated with those of genes associated with ascorbic acid, carotenoid and flavonoid biosynthesis. This transcriptional correlation was confirmed by agroinfiltration mediated transient expression, which showed that most of the enzymatic genes in the ascorbic acid biosynthesis were regulated by the overexpression of each of the three transcription factors that were tested. The metabolic dynamics of ascorbic acid, carotenoid and flavonoid were investigated during fruit development and ripening, and some selected transcription factors showed transcriptional correlation with the accumulation of ascorbic acid, carotenoid and flavonoid. This transcriptome study provides insight into the regulatory mechanism of fruit development and presents candidate transcription factors involved in secondary metabolism.</p></div

Differential expression of structural genes involved in the ascorbic acid metabolic pathway regulated by transiently expressed transcription factors.

<p>The Figure shows transcript levels of different structural genes involved in the ascorbic acid biosynthetic pathway. MYB (<i>Solyc09g010840</i>.<i>1</i>), NAC (<i>Solyc12g013620</i>.<i>1</i>) and ZIF (<i>Solyc06g065440</i>.<i>1</i>) were used for agroinfiltration and AC means agroinfiltrated with empty vector. For each transcription factor, two independent lines were selected Results shown represent mean values (±SE) from three independent experiments. Asterisks indicate significant differences as determined by Student’s t-test (*<i>P<0</i>.<i>05</i>; ** <i>P<0</i>.<i>01</i>).</p

Main pathways expressed during fruit development in the two genotypes (AC and HG6-61).

<p>Gene expression data are presented as log₂ fold change values compared to the first sampling point (7 DAF) within each genotype. The data were subjected to a Wilcoxon test in PageMan [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130885#pone.0130885.ref046" target="_blank">46</a>], and the results are displayed as a false-color code. Bins colored in red correspond to genes that were significantly up-regulated and bins colored in blue correspond to genes that were significantly down-regulated.</p

Dynamics of ascorbic acid, carotenoids and flavonoids accumulation during fruit development and ripening.

<p>The concentrations of ascorbic acid (A) and carotenoids (B) were determined by HPLC. The flavonoids contents (C) were determined by LC-MS. DHA (gray squares in AC and light blue squares in HG6-61) and AsA (black squares in AC and white squares in HG6-61) means oxidized ascorbate and reduced ascorbate, respectively in (A). Fruits of AC (black squares) and HG6-61(gray squares) at each of seven selected developmental stages were used in the analysis in (B) and (C). Bars represent the standard error (n = 3). DAF, days after flowering.</p

Functional categorization of differentially expressed genes during tomato fruit development in Ailsa Craig.

<p>The differences between 14 and 7 DAF are indicated by light green squares (</p><p></p><p></p><p><mn>∎</mn></p><p></p><p></p>). The differences between 21 and 7 DAF are indicated by green squares (<p></p><p></p><p><mn>∎</mn></p><p></p><p></p>). The differences between 28 and 7 DAF are indicated by dark green squares (<p></p><p></p><p><mn>∎</mn></p><p></p><p></p>), The differences between 35 and 7 DAF are indicated by yellow squares (<p></p><p></p><p><mn>∎</mn></p><p></p><p></p>), The differences between 42 and 7 DAF are indicated by orange squares (<p></p><p></p><p><mn>∎</mn></p><p></p><p></p>), The differences between 49 and 7 DAF are indicated by red squares (<p></p><p></p><p><mn>∎</mn></p><p></p><p></p>). Percentages are calculated based on the proportion of the number of genes in each set.<p></p