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A naturally unique variation in Al-activated malate transporter 9 determines fruit malate in cultivated tomato

ABSTRACT: Purpose: Understanding the mechanism of malate accumulation in plants is beneficial for both plant nutrient and human health. However, little is known regarding regulation of malate accumulation in horticulture plants such as tomato. The goals of this study are to investigate potential regulation network of Al-Activated Malate Transporter 9 (ALMT9) which is the major locus responsible for the variation in fruit malate concentration observed in cultivared tomato. Methods: The transcriptomes of fruit at ripening stage from CK and SlALMT9 overexpressing line1 were evaluated using single-ended sequencing of Illumina HiSeq 2500. Raw sequences were filtered and the resulting sets of clean reads were used for the following analysis by tophat and edgeR software. Results: Among 1,887 differentially expressed genes, some structural genes involved in sugar and organic acid metabolism were differently expressed in SlALMT9 overexpressing line, which partially coincide with changes of sugar and organic acid concentration. PR genes was also altered in the OX lines, in agreement with previous study that tomato fruit malate is involved in pathogen infection. Three members of malate transporters, MATE (multidrug and toxin efflux), were up-regulated (SlMATE5 and 6) or down-regulated (SlMATE9) . Besides, three sugar transport proteins and four vacuole membrane or plasma membrane proteins were up-regulated in OX line Conclusions: Using RNA-seq analysis, 1,887 differentially expressed genes was revealed. Among them, several genes related to sugar and organic acid metabolism and transport, pathogen resistances were identified. This transcriptome study provides insight into the regulatory mechanism of fruit malate accumulation and the effect of the SlALMT9 to primary metabolism.

ORGANISM(S): Solanum lycopersicum

PROVIDER: GSE89772 | GEO | 2018/02/16

REPOSITORIES: GEO

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Project description:Tomatoes are one of the valuable sources of antioxidants such as carotenes, ascorbic acid (AsA), and phenolic compounds (flavonoids and hydroxycinnamic acid derivatives). These secondary metabolites have been proved to be beneficial for humans and animals because their involvement in the prevention of many proliferative and degenerative diseases. The aim of this work is to gain greater insights in the genetic control of phenylpropanoid accumulation in tomato fruit by using genomics-based strategies. In order to identify QTLs controlling antioxidant accumulation in tomato fruit we carried out a comparative analysis of Solanum pennellii x S. lycopersicum cv. M82 introgression lines (ILs) over three year trials in greenhouse environment. Among all, IL7-3 showed higher fruit content of total phenolics and the HPLC-UV profile revealed that chlorogenic acid mainly accounted for the higher performance of this line. To investigate in details genetic mechanisms and candidate genes controlling phenols synthesis and accumulation in IL7-3 fruit we performed a comparative transcriptomic analysis in tomato pericarp. In particular, RNA was extracted from percarp of IL7-3 and M82 parental line and hybridized on a 90k Combimatrix TomatArray 1.0. The experiment was repeated over two consecutive years. The transcriptomic approach allowed to identify 291 differentially expressed transcripts, 149 showing up-rgulation and 142 down-regulation. The ethylene signaling pathway has been involved in the modulation of the level of total phenolics in ripe fruit. In particular, an Ethilene Responsive Factor 1 (ERF1) was functionally characterized by TILLING (Targeting Local Lesion IN Genomes) approach. The mutant line expressed lower accumulation of phenolics in the fruit and additional insights on the regulation of phenolics in tomato ripe fruit were provided. Comparative microarray analysis between a tomato introgression line (IL7-3) expressing higher level of fruit total phenolics and its parental cultivar M82 (reference) was performed. In particular, samples were generated by pooling red-ripe fruit from the same plant and discarding the seeds, jelly parenchyma, columella and placenta tissues. Three plant replica were used for each line (IL7-3 and M82) and the experiment was replicated over two consecutive years.

Project description:Malic enzymes decarboxylate the tricarboxylic acid (TCA) cycle intermediate malate to the glycolytic end-product pyruvate and are well positioned to regulate metabolic flux in central carbon metabolism. The bacterium Sinorhizobium meliloti has a NAD(P)-malic enzyme (DME) and a NADP-malic enzyme (TME) and DME is required for symbiotic N2-fixation. To help understand the role of these enzymes, we examined growth, metabolic and transcriptional consequences resulting from the deletion of these enzymes. Few effects were observed upon growth with glucose, whereas growth with the gluconeogenic substrate, succinate, resulted in transcriptional and metabolic effects particularly in the dme mutant strains. When grown with succinate, DME mutant cells accumulated hexose sugar phosphates and trehalose, while TME mutants accumulated putrescine. Succinate-grown DME mutant cells also showed increased transcription of genes for gluconeogenesis and for pathways such as amino acid and fatty acid synthesis that divert metabolites away from the TCA cycle. These data suggested that, DME is required to regulate the levels of TCA cycle intermediates and that the activity of TME is insufficient to prevent the accumulation of TCA cycle intermediates in cells utilizing succinate as carbon source. Consistent with this, in short-1-3 hour incubations with succinate, dme mutant cells excreted large amounts of malate whereas little malate was excreted from tme or wild-type cells. These results support the suggestion that DME is required for N2-fixation in alfalfa because it is required for synthesis of pyruvate and acetyl-CoA and the rapid metabolism of C4-dicarboxylates supplied by the plant. RNA expression was measured for S. meliloti in exponential phase grown in MOPS (morpholinpropanesulfonic acid) buffered minimal media under 2 growth conditions: 1) 15 mM succinate, 2) 15 mM glucose; using wild type cells as well as dme and tme mutant strains (6 experiments, 2 replicates: total 12 samples)

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A naturally unique variation in Al-activated malate transporter 9 determines fruit malate in cultivated tomato

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