Metabolic and Molecular Changes of the Phenylpropanoid Pathway in Tomato (Solanum lycopersicum) Lines Carrying Different Solanum pennellii Wild Chromosomal Regions

Abstract

Solanum lycopersicum represents an important dietary source of bioactive compounds including the antioxidants flavonoids and phenolic acids. We previously identified two genotypes (IL7-3 and IL12-4) carrying loci from the wild species Solanum pennellii, which increased antioxidants in the fruit. Successively, these lines were crossed and two genotypes carrying both introgressions at the homozygous condition (DHO88 and DHO88-SL) were selected. The amount of total antioxidant compounds was increased in DHOs compared to both ILs and the control genotype M82. In order to understand the genetic mechanisms underlying the positive interaction between the two wild regions pyramided in DHO genotypes, detailed analyses of the metabolites accumulated in the fruit were carried out by colorimetric methods and LC/MS/MS. These analyses evidenced a lower content of flavonoids in DHOs and in ILs, compared to M82. By contrast, in the DHOs the relative content of phenolic acids increased, particularly the fraction of hexoses, thus evidencing a redirection of the phenylpropanoid flux toward the biosynthesis of phenolic acid glycosides in these genotypes. In addition, the line DHO88 exhibited a lower content of free phenolic acids compared to M82. Interestingly, the two DHOs analyzed differ in the size of the wild region on chromosome 12. Genes mapping in the introgression regions were further investigated. Several genes of the phenylpropanoid biosynthetic pathway were identified, such as one 4-coumarate:CoA ligase and two UDP-glycosyltransferases in the region 12-4 and one chalcone isomerase and one UDP-glycosyltransferase in the region 7-3. Transcriptomic analyses demonstrated a different expression of the detected genes in the ILs and in the DHOs compared to M82. These analyses, combined with biochemical analyses, suggested a central role of the 4-coumarate:CoA ligase in redirecting the phenylpropanoid pathways toward the biosynthesis of phenolic acids in the pyramided lines. Moreover, analyses here carried out suggest the presence in the introgression regions of novel regulatory proteins, such as one Myb4 detected on chromosome 7 and one bHLH detected in chromosome 12. Overall our data indicate that structural and regulatory genes identified in this study might have a key role for the manipulation of the phenylpropanoid metabolic pathway in tomato fruit.

A basic Helix-Loop-Helix (SlARANCIO), identified from a Solanum pennellii introgression line, affects carotenoid accumulation in tomato fruits

“…Similarly, the genes coding for the transcription factors WD40 and bHLH showed a reduction of the mRNA levels in IL12-4SL vs M82 (3-fold and 2-fold, respectively). These results were in line with those previously obtained in the parental line IL12-4 19 . The expression of the genes coding for the two MYBs showed an opposite trend compared to the structural gene Z-ISO (Fig.…”

“…pennellii subline IL12-4SL. IL12-4SL was previously obtained in our laboratory using the introgression line IL12-4, carrying a QTL (lyc12.1) controlling lycopene accumulation 14,19 . We found that, compared to the parental cultivated line M82, IL12-4SL shows the phenotype already observed in IL12-4 by Rigano et al .…”

De novo assembly of Persea americana cv. ‘Hass’ transcriptome during fruit development

“…The pathways of fatty acid biosynthesis and starch and sucrose metabolism were also observed, where sugars are important to promote cell growth and to control fruit metabolism during development [34]. Additionally, the phenylpropanoid biosynthesis pathway was also represented, where the secondary metabolites act as antioxidants and in tomato fruit are involved in pigmentation and aroma [35].…”

Chlorogenic acids and the acyl-quinic acids: discovery, biosynthesis, bioavailability and bioactivity

“…139 Four isoforms of 4CL have been iden-tied in Morus notabilis (mulberry) 140 and Arabidopsis. 141 The subcellular localization of specic isoforms of 4CL plays a central role in redirecting the biosynthetic pathway either towards the p-coumaroyl-CoA or towards other branch points in the phenylpropanoid pathway. 141 The conversion of p-coumaroyl-CoA to 5-CQA involves the enzymes hydroxycinnamoyl CoA:quinate hydroxycinnamoyl transferase (HQT) and a cytochrome P450 oxidase p-coumaroyl-3 0 -hydroxylase (C3H) (Fig.…”