Developmental and Feedforward Control of the Expression of Folate Biosynthesis Genes in Tomato Fruit

Abstract

Little is known about how plants regulate their folate content, including whether the expression of folate biosynthesis genes is orchestrated during development or modulated by folate levels. Nor is much known about how folate levels impact the expression of other genes. These points were addressed using wild-type tomato fruit and fruit engineered for high folate content. In wild-type fruit, the expression of genes specifying early steps in folate biosynthesis declined during development but that of other genes did not. In engineered fruit overexpressing foreign GTP cyclohydrolase I and aminodeoxychorismate synthase genes, the expression of the respective endogenous genes did not change, but that of three downstream pathway genes-aminodeoxychorismate lyase, dihydroneopterin aldolase, and mitochondrial folylpolyglutamate synthase-respectively increased by up to 7.8-, 2.8-, and 1.7-fold, apparently in response to the build-up of specific folate pathway metabolites. These results indicate that, in fruit, certain folate pathway genes are developmentally regulated and that certain others are subject to feedforward control by pathway intermediates. Microarray analysis showed that only 14 other transcripts (of 11 000 surveyed) increased in abundance by two-fold or more in high-folate fruit, demonstrating that the induction of folate pathway genes is relatively specific.

Manipulation of Metabolic Pathways to Develop Vitamin-Enriched Crops for Human Health

“…These observations are markedly different from those reported in tomato and rice (Storozhenko et al, 2007; Waller et al, 2010). Therefore, probably there is a bottleneck in the folate biosynthesis pathway in potato tubers, and a further research is needed to investigate the mechanisms of regulating folate status in these plants that are different, lacking, or of minor importance in rice seeds and tomato fruit.…”

The arbuscular mycorrhizal status has an impact on the transcriptome profile and amino acid composition of tomato fruit

“…A limited number of regulated transcripts (fourteen) was also reported by Waller et al . [38] in a work on the expression of folate biosynthesis genes during tomato fruit development, demonstrating how tomato fruit pathways are finely regulated.…”

“…We in fact followed the plant development till the fruit formation, and focused our attention on the fruit transcriptome by performing a microarray experiment to determine the gene expression profiles in the fruits from mycorrhizal plants. Our transcriptomic analysis was based on the TOM2 oligo-array, which contains about 12000 unigenes, and which is estimated to include about half the genes expressed in fruit [38]. We demonstrate that only a limited number of genes were differentially regulated in the fruit from mycorrhizal plants, most of which were involved in ripening and N metabolism.…”

Tomato (Solanum lycopersicum L.) in the service of biotechnology

“…3 years later, the same research team reported a 25-fold increase in folate accumulation in transgenic tomato fruits (de la Garza et al 2007). On the other hand, Waller et al (2010) showed that in engineered fruit overexpressing foreign GTP cyclohydrolase I and aminodeoxychorismate synthase genes, the expression of endogenous genes was not changed, but those of three downstream pathway genes, aminodeoxychorismate lyase, dihydroneopterin aldolase and mitochondrial folylpolyglutamate synthase, increased by up to 7.8-, 2.8-, and 1.7-fold respectively, apparently in response to the build-up of specific folate pathway metabolites.…”