Role of sucrose in modulating the low‐nitrogen‐induced accumulation of phenolic compounds in lettuce (Lactuca sativa L.)

Abstract

BACKGROUND: Phenolic compounds are phytochemicals present in vegetables which contribute to human health. Although nitrogen deficiency and sucrose (Suc) are linked to phenolic production in vegetables, the relationship between them in the regulation of phenolic biosynthesis remains unknown. This study investigated the potential role of Suc in regulating phenolic biosynthesis of lettuce under low-nitrogen (LN) conditions. RESULTS: Our results showed that LN treatment significantly increased Suc content in lettuce by inducing rapid increases in activities of sucrose synthesis-related enzymes. Exogenous Suc further stimulated LN-induced phenolic accumulation in lettuce by upregulating the expression of genes (PAL, CHS, F3H, DFR, F35H and UFGT) involved in phenolic biosynthesis. The opposite effects were true for exogenous 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) application. No changes were observed in chlorophyll content in LN-treated lettuce, in either the presence or absence of Suc application. Notably, exogenous DCMU resulted in decreases of maximum quantum efficiency of photosystem II (PSII) photochemistry, actual efficiency of PSII and electron transport rate in PSII and increase of quantum yield of non-regulated energy dissipation in PSII in lettuce under LN conditions, whereas these effects were reversed on Suc application. Exogenous Suc also increased glutamine synthetase and glutamate synthase activities in LN-treated lettuce. CONCLUSIONS: These results suggest that Suc is involved in LN-induced phenolic production in lettuce by enhancing photosynthetic and nitrogen assimilation efficiency to increase the supply of carbon resources and precursors for phenolic biosynthesis.

Carbon and nitrogen metabolism under nitrogen variation affects flavonoid accumulation in the leaves of Coreopsis tinctoria

“…First, SPS and SS are the basic enzymes that enter the C metabolism pathway. The activities of the two enzymes are consistent with the changes in the content of sucrose, which clearly shows that the activities of SPS and SS are directly related to the synthesis of sucrose (Zhou et al, 2020). The accumulation pattern of starch in the leaves further validates the accumulation pattern of carbohydrates (Figs.…”

“…Previous studies have revealed that mineral nutrients further regulate the activities of key enzymes such as PAL, C4H and 4CL (Li et al, 2021). The reduction in N levels can directly promote carbohydrate content and quickly activate the activity of flavonoid-metabolizing enzymes (Zhou et al, 2020). Throughout the process, these ammonium ions released from the PAL pathway are generated by the GS/GOGAT assimilation system to produce glutamate, which provides an amino donor for phenylalanine regeneration and N cycle completion (Singh, Lewis & Towers, 1998), thereby affecting the biosynthesis of flavonoids.…”

Coevolution and photoprotection as complementary hypotheses for autumn leaf reddening: a nutrient‐centered perspective

“…The synergistic effects of high soluble sugars (especially sucrose) and low N on anthocyanin production in the presence of light have been demonstrated in numerous plant systems (e.g. Lea et al ., 2007; Boussadia et al ., 2010; Su et al ., 2016; Zhou et al ., 2020), and appear to result from upregulation of multiple independent transcription factors related to anthocyanin synthesis (e.g. PAP1 and PAP2), which together result in greater anthocyanin synthesis than individual stimuli alone (Lea et al ., 2007).…”

Yield and nutritional quality of soil‐cultivated crisphead lettuce (Lactuca sativa L. var. capitata) and corn salad (Valerianella spp.) harvested at different growing periods

“…Due to their antioxidant, anti‐inflammatory, and antitumoral effects, various human health benefits have been reported (Kang et al, 2018 ). Phenolic compounds such as phenolic acids and flavonoids are phytochemicals widely distributed in leafy vegetables and are also considered compounds with antioxidant properties (Negrao et al, 2021 ; Zhou et al, 2020 ).…”