Synergetic effects of nitrogen depletion, temperature, and light on the content of phenolic compounds and gene expression in leaves of tomato.
Tomato plants (Solanum lycopersicum, cv. Suzanne) were subjected to complete nutrient solution or a solution without nitrogen (N), and placed at different temperatures and light conditions to test the effects of environment on flavonoids and caffeoyl derivatives and related gene expression. N depletion during 4-8days resulted in enhanced levels of flavonoids and caffeoyl derivatives. Anthocyanins showed pronounced increased levels when lowering the growth temperature from 24 degrees C to 18 degrees C or 12 degrees C. Flavonol levels increased when the light intensity was increased from 100 micromol m(-2) s(-1) PAR to 200 micromol m(-2) s(-1) PAR. Synergistic effects of the various environmental factors were observed. The increase in content of quercetin derivatives in response to low temperatures was only found under conditions of N depletion, and especially at the higher light intensity. Expression of structural genes in the phenylpropanoid and flavonoid pathways, PAL (phenylalanine ammonia lyase), CHS (chalcone synthase), F3H (flavanone 3-hydroxylase), and FLS (flavonol synthase) increased in response to N depletion, in agreement with a corresponding increase in flavonoid and caffeoyl content. Expression of these structural genes generally also increased in response to lower temperatures. As indicated through expression studies and correlation analysis, effects of N depletion were apparently mediated through the overall regulators of the pathway the MYB transcription factor ANT1 (ANTHOCYANIN 1) and SlJAF13 (a bHLH transcription factor orthologue of petunia JAF13 and maize RED genes). A PAL gene (PAL6) was identified, and correlation analysis was compatible with PAL6 being an actively expressed gene with function in flavonoid synthesis.
Løvdal
Trond
T
Faculty of Science and Technology, Centre for Organelle Research, University of Stavanger, Stavanger, Norway.
Olsen
Kristine M
KM
Slimestad
Rune
R
Verheul
Michel
M
Lillo
Cathrine
C
D000217:Acyltransferases / Q000378:metabolism; D003080:Cold Temperature; D004777:Environment; D005419:Flavonoids / Q000378:metabolism*; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008027:Light; D018551:Solanum lycopersicum / Q000235:genetics / Q000378:metabolism*; D053858:Metabolic Networks and Pathways / Q000235:genetics; D006899:Mixed Function Oxygenases / Q000378:metabolism; D009584:Nitrogen / Q000172:deficiency*; D010088:Oxidoreductases / Q000378:metabolism; D010636:Phenols / Q000378:metabolism*; D010650:Phenylalanine Ammonia-Lyase / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D020005:Propanols; D013696:Temperature
D005419:Flavonoids; D010636:Phenols; D010940:Plant Proteins; D020005:Propanols; C439395:1-phenylpropanol; D006899:Mixed Function Oxygenases; D010088:Oxidoreductases; C048797:flavanone 3-dioxygenase; C085313:flavonol synthase; D000217:Acyltransferases; C020141:flavanone synthetase; D010650:Phenylalanine Ammonia-Lyase; D009584:Nitrogen