Molecular Plant Breeding 2025, Vol.16, No.5, 294-302 http://genbreedpublisher.com/index.php/mpb 295 (Feyera et al., 2024). Its synthesis involves two pathways: the phenylpropane pathway provides phenylalanine, the branched-chain fatty acid pathway provides precursors such as valine or leucine, and finally capsaicin is generated in the placenta tissue (Aza-González et al., 2011). There are some key enzymes in the synthesis process, such as AT3 (Pun1) and pAMT. pAMT is responsible for converting vanillin into vanillamine (Figure 1) (Kusaka et al., 2023; Nakaniwa et al., 2023). Capsaicin content is influenced by multiple factors, including genotype, placenta tissue specificity, fruit development stage, temperature, light, hormones and transcription factors (Arce-Rodriguez and Ochoa-Alejo, 2017; Burgos-Valencia et al., 2020; Sun et al., 2022). Some exogenous stimuli, such as chitosan and nano-selenium, can also increase the content of capsaicin by enhancing the expression of related genes (Kabita et al., 2020; Li et al., 2020). Figure 1 Capsaicinoid production and the expression pattern of pAMT and its homologs in chili pepper (Adopted from Kusaka et al., 2023) Image caption: (a) Different tissues of chili pepper. IM: immature fruit stage 15 days after flowering (DAF), MG: mature green fruit stage 30 DAF, M: mature fruit stage 40 DAF. (b) Capsacinnoid accumulation in different tissues and expression levels of GABA-T homologs and Capsaicinoid biosynthesis-realated genes. All data are presented as means of three biological replicates. Error bars show standard errors (n = 3) (Adopted from Kusaka et al., 2023) 2.2 Mechanisms of disease resistance inCapsicumspecies The disease resistance of chili peppers relies on multiple layers of defense, including physical barriers, R gene recognition, signal transduction (hormone pathways such as jasmonic acid, ethylene, abolic acid, etc.) and accumulation of secondary metabolites (Sun et al., 2019; Li et al., 2020). Capsaicin and its derivatives not only bring pungency, but also have antibacterial and antioxidant effects, which can directly inhibit pathogenic bacteria and improve the stress resistance of plants (Yasin et al., 2023). Some transcription factors (MYB, bHLH, AP2/ERF, etc.) regulate defense genes and metabolic pathways and participate in disease resistance responses
RkJQdWJsaXNoZXIy MjQ4ODYzNA==