Chlorogenic Acid Content and Metabolism-related Gene Regulation of Potato Tuber Flesh Induced by Sucrose and Phytohormones

Chlorogenic acid (5-O-caffeoylquinic acid, CGA) is the most abundant phenolic compound in potatoes, serving as one of the material bases for potato resistance to insects and diseases. Nevertheless, excessive CGA can impact the taste of potatoes. The application of exogenous phytohormones is an effective technical approach to regulate CGA metabolism through gene expression of transcriptional regulatory pathways. Herein, we determined the content of CGA under the application of sucrose and multiple phytohormones and explored the expression changes of related genes. As a proof-of-concept, the effects of exogenous sucrose and multiple phytohormones on CGA metabolism in potato tuber flesh were investigated. The CGA content was significantly decreased in sucrose-treated potato tuber tissues, as well as in those treated with abscisic acid (ABA), salicylic acid (SA), and methyl jasmonate (MeJA). Among these treatments, the effect of SA was the most obvious. Meanwhile, the expression changes of six major enzyme genes involved in potato CGA metabolism, including phenylalanine ammonia-lyase (PAL), 4-coumarate coenzyme A ligase (4CL), hydroxycinnamoyl CoA quinate hydroxycinnamoyl transferase (HQT), hydroxycinnamoyl CoA shikimate/quinate hydroxycinnamoyl transferase (HCT), ρ-coumarate 3’-hydroxilase (C3H), and caffeoyl shikimate esterase (CSE), were analyzed. Under sucrose treatment, HQT was down-regulated, whereas three genes (PAL, 4CL, and CSE) were notably up-regulated, and expressions of HCT and C3H did not show significant changes. ABA induced the expression of HCT, but inhibited the expression of PAL, 4CL, HQT, C3H, and CSE. The expression of all six enzyme genes was down-regulated under SA treatment. MeJA induced the expression of HQT, but inhibited the expression of PAL, 4CL, HCT, C3H, and CSE. Collectively, sucrose and phytohormones can regulate CGA accumulation in potato tuber flesh by regulating the expression levels of genes involved in the CGA pathway. These results provided a theoretical basis for further elucidating the transcriptional regulation mechanism of CGA metabolism.