Coregulation of Biosynthetic Genes and Transcription Factors for Aporphine-Type Alkaloid Production in Wounded Lotus Provides Insight into the Biosynthetic Pathway of Nuciferine

Abstract

Lotus ( Nelumbo nucifera Gaertn.) contains various bioactive compounds, with benzylisoquinoline alkaloids (BIAs) as one of the major groups. The biosynthetic pathways of two major bioactive BIAs in this plant, nuciferine and N -nornuciferine, are still not clear. Therefore, several genes related to BIA biosynthesis were searched from the lotus database to study the role of key genes in regulating these pathways. In this study, the expression profiles of NCS , CNMT , 6 OMT , CYP 80 G 2, and WRKY TFs were investigated in mechanically wounded lotus leaves. It was found that the accumulation of nuciferine and N -nornuciferine significantly increased in the mechanically wounded lotus leaves in accordance with the relative expression of putative CYP 80 G 2 and one WRKY transcription factor ( NNU_ 24385), with the coregulation of CNMT . Furthermore, the role of methyltransferase-related genes in this study suggested that methylation of the isoquinoline nucleus to yield a methylated-BIA structure may occur at the N position before the O position. Altogether, this study provides improved understanding of the genes regulating BIA biosynthesis under stressed conditions, which could lead to improvements in BIA production from the commercial lotus.

Secoiridoids Metabolism Response to Wounding in Common Centaury (Centaurium erythraea Rafn) Leaves

“…In LL and SL, noteworthy changes in total iridoids (predominantly SGs) content were observed from 24 HAW until 96 HAW. Generally, these results are in accordance with some previous studies that demonstrated that wounding-induced accumulation of specialized metabolites occur in both LL and SL leaves, which further supported the hypothesis that wounding stress signals are transmitted throughout the whole plant [16,25,44,48]. As previously mentioned, SGs biosynthesis in C. erythraea goes through secologanin (3), which is a known precursor for numerous monoterpenoid indole alkaloids (MIAs) [7].…”

“…Furthermore, the content of total SGs in C. erythraea leaves is reported not to be significantly influenced by the developmental stage [4]. Nevertheless, the production of constitutive specialized metabolites can be influenced by various endogenous and environmental factors [4,26,42], with wounding being one of the latter [22,25,43,44].…”

“…Thus, the largest increase of strictosidine was recorded 48 h and 72 h after leaves damage by Manduca sexta, while, after 72 h, in both local and distal leaves of C. roseus, a significant increase of ajmalicene, serpentine, and vindorosine was observed [25]. The accumulation of benzyl isoquinoline alkaloids (BIAs-nuciferine and N-nornuciferine), was significantly increased in the mechanically wounded lotus leaves, whereby fluctuating the accumulation of total alkaloids content in a temporal manner, which varied between wounded and non-wounded leaves, was observed [44]. Increased levels of certain BIAs were also recorded 3 h and 5 h after wounding in the leaves of Papaver somniferum L. [50].…”

Benzylisoquinoline Alkaloids Biosynthesis in Sacred Lotus

“…At least five functional isoforms of norcoclaurine synthase (NnNCS) have been purported in sacred lotus, based on the occurrence of homologs in the genome [ 34 ], and in various transcriptomes [ 34 , 49 , 61 , 62 ]. These NCS candidates must be functionally characterized to determine which, if any, are responsible for the formation of norcoclaurine and variations in the stereochemistry of BIAs in sacred lotus.…”

“…However, functional characterization of these enzymes has not been investigated. Most work has focused on the aporphine metabolism, primarily through correlational analysis of gene expression profiles and alkaloid content in different organs and developmental stages of sacred lotus [ 34 , 49 , 61 , 62 , 69 ].…”