How lotus decides where to make its medicinal alkaloids
Nanjing Agricultural University The Academy of Science
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Proposed models for the underlying mechanisms of organ specific accumulation of aporphines and bis-BIAs in the lotus plumules and laminae, respectively.
view moreCredit: Horticulture Research
Medicinal alkaloids in lotus accumulate in highly specific organs, yet the molecular basis of this spatial pattern has remained unclear. A new study reveals the genetic circuitry that explains why aporphine-type benzylisoquinoline alkaloids (BIAs) accumulate in lotus leaves while bis-BIAs concentrate in plumules. Researchers identified two tandemly duplicated but tissue-specialized enzymes, NnCYP80G and NnCYP80A, whose differential expression drives organ-specific alkaloid biosynthesis. They further uncovered a jasmonate-responsive transcriptional cascade involving NnMYC2 and NnMYB14 that activates these enzymes and coordinates BIA production. This work provides the first mechanistic explanation for organ-specific BIA accumulation in lotus and establishes a regulatory framework for improving medicinal alkaloid yield.
Benzylisoquinoline alkaloids (BIAs) are a diverse class of plant-derived compounds with major pharmacological value, including well-known examples such as morphine and berberine. In lotus (Nelumbo nucifera), BIAs serve as key bioactive constituents and contribute to antioxidant, anticancer, and hepatoprotective properties. Remarkably, different lotus organs accumulate distinct BIA types: aporphines are enriched in leaves, whereas bis-BIAs dominate in plumules. Although candidate biosynthetic enzymes had been proposed, the mechanisms controlling their tissue specificity and regulatory hierarchy remained unresolved. Jasmonate signaling is known to stimulate secondary metabolism, yet how it governs spatial alkaloid biosynthesis in lotus was unknown. Based on these challenges, in-depth investigation into the spatial regulation of lotus alkaloid biosynthesis became necessary.
In a study published (DOI: 10.1093/hr/uhaf283) in 2025 in Horticulture Research, scientists from Wuhan Botanical Garden of the Chinese Academy of Sciences report that organ-specific benzylisoquinoline alkaloid biosynthesis in lotus is governed by a transcriptional cascade involving NnMYC2, NnMYB14, and two tissue-specific cytochrome P450 enzymes, NnCYP80G and NnCYP80A. By integrating genome-wide gene mining, enzyme activity assays, transient overexpression experiments, and promoter-binding analyses, the team uncovered how jasmonate signaling connects environmental cues to spatially controlled alkaloid production.
Through genome-wide analysis of lotus P450 genes, researchers identified six CYP80 candidates, among which NnCYP80G and NnCYP80A displayed striking tissue-specific expression patterns. NnCYP80G was predominantly expressed in laminae, while NnCYP80A accumulated specifically in plumules. The two genes are tandemly arranged on chromosome 2 but possess distinct promoter architectures, suggesting functional divergence following gene duplication.
Functional assays in Nicotiana benthamiana confirmed their catalytic specialization. NnCYP80G efficiently converted (R)-reticuline into corytuberine and (R)-N-methylcoclaurine into glaziovine, revealing both proaporphine and aporphine synthase activities. In contrast, NnCYP80A catalyzed the formation of the bis-BIA nelumboferine. Transient overexpression of NnCYP80A in lotus petals significantly enhanced bis-BIA accumulation, validating its in planta function.
Upstream regulation was traced to the jasmonate pathway. The master regulator NnMYC2 activated expression of the R2R3-MYB transcription factor NnMYB14, which directly bound to promoters of both CYP80 genes. While NnMYB14 strongly induced NnCYP80G and aporphine production, its effect on NnCYP80A was comparatively moderate, helping explain the differential alkaloid accumulation between organs.
“Our findings demonstrate how gene duplication followed by promoter divergence can generate organ-specific metabolic specialization,” said the corresponding author. “The NnMYC2–NnMYB14–NnCYP80 module establishes a hierarchical regulatory framework that links jasmonate signaling to spatial control of alkaloid biosynthesis. This not only clarifies long-standing questions about lotus metabolism but also provides valuable targets for metabolic engineering of medicinal compounds.”
By uncovering the regulatory logic that partitions distinct alkaloids into specific lotus organs, this study opens new opportunities for pharmaceutical crop improvement. Manipulating the NnMYC2–NnMYB14 cascade or engineering CYP80 promoter elements could enhance production of desired aporphines or bis-BIAs in targeted tissues. The work also illustrates how tandem gene duplication can drive metabolic innovation through spatial specialization. Beyond lotus, the regulatory model may inform synthetic biology strategies aimed at reconstructing alkaloid pathways in heterologous systems, advancing sustainable and scalable production of high-value medicinal compounds.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhaf283
Funding information
This project was financially supported by the funds received from the National Natural Science Foundation of China (32070336 and 32370428), Hubei Provincial Natural Science Foundation of China (CZRJQ202400159, and the Natural Science Foundation of Shandong Province
(ZR2021MC163).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.
Journal
Horticulture Research
Subject of Research
Not applicable
Article Title
Spatial regulation of benzylisoquinoline alkaloid biosynthesis in lotus (Nelumbo nucifera) is controlled coordinately through the NnMYC2-NnMYB14-NnCYP80 modules
Unlocking the molecular trigger behind melon fruit texture
Nanjing Agricultural University The Academy of Science
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Mechanism of CmbZIP11 regulates CmPMT1 and CmPMT15 expression to regulate methyl-esterification of HG affecting fruit softening in melon. CmbZIP11 through activates the expression of CmPMT1 and CmPMT15 to regulate the degree of methyl-esterification of HG thereby adjust the amount of HG-Ca2+ cross-linked ‘Egg-box’ matrix, leading to different accessibility for PMEs, PGs and PLs for HG degradation and fruit softening. HG: Homogalacturonan; D-GalA: D-Galacturonic acid; GAUTs: Galacturonosyltransferases; GoSAMT: Golgi SAM transporter; PMT: Pectin methyltransferase; PAT: Pectin acetyltransferase; PME: Pectin methylesterase; PG: Polygalacturonase; PL: Pectate lyase.
view moreCredit: Horticulture Research
Fruit softening is a defining trait of ripening, yet the molecular processes that control texture remain incompletely understood. This study reveals a regulatory pathway in melon that links transcriptional control to cell wall chemistry. The researchers show that enhanced activity of pectin methyltransferases alters the methyl-esterification pattern of homogalacturonan, a major cell wall polysaccharide. This biochemical shift reduces calcium-mediated cross-linking within the cell wall, making pectin more accessible to degradation enzymes and accelerating tissue softening. By identifying a transcription factor that activates this pathway, the study provides a mechanistic explanation for how gene regulation directly reshapes cell wall architecture and fruit texture.
Fruit texture is a key determinant of consumer preference, shelf life, and postharvest quality, especially in climacteric fruits such as melon. Softening during ripening is largely driven by remodeling of the cell wall, where pectin plays a central structural role. Homogalacturonan can either form rigid calcium-linked “egg-box” networks or remain loosely associated, depending on its degree of methyl-esterification. While enzymes involved in pectin degradation have been extensively studied, far less is known about how methyl-esterification is regulated at the transcriptional level during fruit development. Based on these challenges, there is a clear need to investigate how gene regulatory networks control pectin modification and fruit softening.
Researchers from Shenyang Agricultural University report a new molecular mechanism controlling fruit softening in melon, published (DOI: 10.1093/hr/uhaf253) in Horticulture Research in 2025. The study identifies the transcription factor CmbZIP11 as a key regulator that activates pectin methyltransferase genes during ripening. By modulating the methyl-esterification of homogalacturonan in the cell wall, this regulatory pathway alters pectin structure, reduces calcium cross-linking, and accelerates tissue softening. The findings provide new insight into how transcriptional control is translated into physical changes in fruit texture.
Using comparative transcriptomics and weighted gene co-expression network analysis, the authors identified CmPMT1 and CmPMT15 as core genes positively associated with homogalacturonan methyl-esterification. Transient overexpression experiments showed that elevated expression of these genes significantly reduced fruit firmness during ripening, whereas overexpression of the Golgi SAM transporter CmGoSAMT1 had little effect on texture.
Biochemical analyses revealed that increased pectin methyltransferase activity decreased calcium-bound pectin fractions while increasing water-soluble pectin, indicating weakened “egg-box” structures in the cell wall. Immunofluorescence and ruthenium red staining confirmed a reduction in tightly cross-linked homogalacturonan, making pectin more susceptible to enzymatic degradation.
Structural modeling further demonstrated that CmPMT1 and CmPMT15 possess conserved catalytic pockets capable of simultaneously binding the methyl donor S-adenosyl-L-methionine and homogalacturonan chains, supporting their role in pectin methyl assembly. Importantly, the transcription factor CmbZIP11 was shown to directly activate CmPMT1 by binding to a C-box motif in its promoter, positioning CmbZIP11 as an upstream regulator that links transcriptional control to cell wall remodeling and fruit softening.
“Fruit softening is often described as a biochemical black box,” said the study’s corresponding author. “Our work shows that it can be traced back to a clear transcriptional switch that controls how pectin is assembled in the cell wall. By regulating pectin methyltransferase genes, CmbZIP11 determines whether homogalacturonan forms rigid calcium networks or remains accessible to degradation. This provides a molecular explanation for texture variation during ripening.”
Understanding how transcription factors control pectin architecture opens new opportunities for precision fruit breeding. Targeting regulators such as CmbZIP11 could allow breeders to fine-tune fruit firmness without broadly disrupting ripening processes. This strategy may help develop melon varieties with improved texture, extended shelf life, and better resistance to postharvest losses. Beyond melon, the conserved nature of pectin methyl-esterification suggests that similar regulatory mechanisms may operate in other fleshy fruits. The findings therefore offer a conceptual framework for manipulating cell wall chemistry to balance fruit quality, transportability, and consumer preference.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhaf253
Funding information
This work was sponsored by China Agriculture Research System of MOF and MARA (CARS-25) and Liao Ning Revitalization Talents Program (XLYC2402014).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.
Journal
Horticulture Research
Subject of Research
Not applicable
Article Title
CmbZIP11 regulates CmPMT1/15 affecting homogalacturonan methyl-esterification and fruit softening in melon
