Metabolomic profiling in tomato reveals diel compositional changes in fruit affected by source-sink relationships

Area of Science:

• Plant Physiology
• Metabolomics
• Agricultural Science

Background:

• Understanding diurnal changes in plant metabolism is crucial for optimizing crop yield.
• Tomato (Solanum lycopersicum) is a globally significant crop, yet its dynamic metabolic responses require further investigation.
• Environmental factors like light availability significantly influence plant physiology and carbon partitioning.

Purpose of the Study:

• To investigate diurnal compositional changes in tomato leaves and fruits under varying light conditions.
• To analyze the impact of shading on carbon metabolism and metabolite fluctuations.
• To explore the relationship between leaf and fruit metabolite profiles and their dependence on environmental cues.

Main Methods:

• High-throughput robotized biochemical phenotyping and untargeted metabolomic profiling (proton nuclear magnetic resonance, mass spectrometry).
• Analysis of approximately 70 metabolites in leaves and 60 in fruits.
• Ecophysiological measurements, multivariate and univariate statistical analyses, and correlation network construction.

Main Results:

• Shaded, carbon-limited tomato plants exhibited reduced leaf area and sink demand with subtle compositional shifts.
• Leaf metabolites related to photosynthesis and photorespiration showed diurnal variation, peaking at midday, but with limited transitory carbon storage.
• Fruit metabolites displayed fewer and lower-amplitude diel fluctuations, with organic acids being prominent; patterns differed between cloudy and sunny days and growth conditions.

Conclusions:

• Diurnal metabolite dynamics in tomato leaves and fruits are influenced by light availability and growth conditions.
• Limited transitory carbon storage in leaves suggests rapid carbon allocation.
• Fruit metabolic processes are closely linked to the immediate sucrose supply from source leaves, highlighting source-sink relationships.