Sugar metabolic changes in protein expression associated with different light quality combinations in tomato fruit

Abstract

Light quality is an important environmental factor that drives photosynthesis and regulates plant growth and development. The purpose of this study was to investigate effects of light quality on sugar metabolism of tomato fruit. Tomato variety ‘Micro-Tom’ was used as the test material. After a 30-day cultivation period, seedlings were moved to an artificial climate chamber and grown under different light conditions: ratio of red and blue light, 1:1 (RB11), ratio of red and blue light, 3:1 (RB31), ratio of red and blue light, 5:1 (RB51), ratio of red and blue light, 7:1 (RB71), and white light as the control (CK). Fruit were harvested at the mature green, breaker, and ripe stages. The soluble sugar, total soluble solids, glucose, fructose, and sucrose contents in developing tomato fruit were highest under the RB31 condition. To further investigate effects of light quality on tomato fruit sugar metabolism, proteomic analysis using total proteins extracted from the CK and RB31-treated tomato fruit revealed that nine, three, and two proteins related to sugar metabolism were differentially accumulated between the CK and RB31-treated fruit at mature green, breaker, and ripe stages, respectively. Seven of them were up-regulated and the rest were down-regulated. The transcript abundances of these corresponding genes were analyzed by qRT-PCR. The expression levels of 12 genes were consistent with the protein abundances, but expression levels of xylose isomerase and l-iditol 2-dehydrogenase did not correlate with their protein abundances.