The Influence of Different Factors on the Metabolism of Capsaicinoids in Pepper (Capsicum annuum L.)

Abstract

Pepper is a globally cultivated vegetable known for its distinct pungent flavor, which is derived from the presence of capsaicinoids, a class of unique secondary metabolites that accumulate specifically in pepper fruits. Since the accumulation of capsaicinoids is influenced by various factors, it is imperative to comprehend the metabolic regulatory mechanisms governing capsaicinoids production. This review offers a thorough examination of the factors that govern the metabolism of capsaicinoids in pepper fruit, with a specific focus on three primary facets: (1) the impact of genotype and developmental stage on capsaicinoids metabolism, (2) the influence of environmental factors on capsaicinoids metabolism, and (3) exogenous substances like methyl jasmonate, chlorophenoxyacetic acid, gibberellic acid, and salicylic acid regulate capsaicinoid metabolism. The findings of this study are expected to enhance comprehension of capsaicinoids metabolism and aid in the improvement of breeding and cultivation practices for high-quality pepper in the future.

Keywords: capsaicinoids; different factors; metabolism pattern; pepper.

Figure 1

Capsaicinoid biosynthetic pathway. (A): Cross-section of chili fruit; (B): schematic diagram of capsaicin biosynthesis pathway and regulatory genes. Abbreviations: PAL, phenylalanine ammonia lyase; C4H, coumarate 4-hydroxylase; 4CL, 4-coumaroyl-CoA ligase; HCT, hydroxycinnamoyl transferase; C3H, coumarate 3-hydroxylase; COMT, caffeoyl-CoA 3-O-methyltransferase; HCHL, hydroxycinnamoyl-coenzyme A hydratase lyase; pAMT, Putative aminotransferase; BCAT, branched-chain amino acid aminotransferase; KAS, ketoacyl-ACP synthetase; ACL, acyl carrier protein; FatA, acyl-ACP-thiesterase; ACS, acyl-CoA synthetase; CS, capsaicinoid synthase; WRKY (WRKY9, 25), bHLH (bHLH7, 9, 26, 63 and 86), MYB (MYB4, 24, 31, 37 and 48) are the genes that have been shown in current studies to be involved in the capsaicin regulatory pathway, adapted from Naves et al. [20] and QIN et al. [68]. Note: Refer to Aza-Gonzalez et al. [12] for the chemical structure of capsaicin synthesis pathway-related substances. Refer to Zhang et al. [69]and Naves et al. [20] for the pictures of germplasm resources of different varieties.

Figure 2

Effect of different environmental factors on capsaicinoids. Note: CPA: chlorophenoxyacetic acid; GA3: Gibberellic acid; SA: salicylic acid. Red arrows indicate different conditions promoting the synthesis of capsaicinoids, where the arrow in the pathogen module indicates that capsaicin improves disease resistance in chili.