Nicolas Dimopoulos

Southern Cross University

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Trends

Author Order

Document Type

Co-Authors

Tobias Kretzschmar

Southern Cross University

Qi Guo

Southern Cross University

Bronwyn J. Barkla

Southern Cross University

Lennard Garcia-de Heer

Southern Cross University

Lei Liu

Southern Cross University

Jos C. Mieog

Southern Cross University

Simone D. Castellarin

University of British Columbia

Matthew Nolan

University of Oxford

Gregory A. Gambetta

Université de Bordeaux

Darren C. J. Wong

Australian National University

Cooperative Institutions

Southern Cross University

University of British Columbia

Okanagan University College

Heidelberg University

Wine Council of Ontario

University of Giessen

Universidad Nacional Autónoma de México

Canada's Michael Smith Genome Sciences Centre

Michigan State University

University of Oxford

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

Combined physiological, transcriptome, and cis-regulatory element analyses indicate that key aspects of ripening, metabolism, and transcriptional program in grapes (Vitis vinifera L.) are differentially modulated accordingly to fruit size

BMC Genomics (2016)

Darren C. J. Wong Rodrigo Lopez Gutierrez Nicolas Dimopoulos Gregory A. Gambetta Simone D. Castellarin

In wine grape production, management practices have been adopted to optimize grape and wine quality attributes by producing, or screening for, berries of smaller size. Fruit size and composition are influenced by numerous factors that include both internal (e.g. berry hormone metabolism) and external (e.g. environment and cultural practices) factors. Combined physiological, biochemical, and transcriptome analyses were performed to improve our current understanding of metabolic and transcriptional pathways related to berry ripening and composition in berries of different sizes. The comparison of berry physiology between small and large berries throughout development (from 31 to 121 days after anthesis, DAA) revealed significant differences in firmness, the rate of softening, and sugar accumulation at specific developmental stages. Small berries had significantly higher skin to berry weight ratio, lower number of seeds per berry, and higher anthocyanin concentration compared to large berries. RNA-sequencing analyses of berry skins at 47, 74, 103, and 121 DAA revealed a total of 3482 differentially expressed genes between small and large berries. Abscisic acid, auxin, and ethylene hormone pathway genes were differentially modulated between berry sizes. Fatty acid degradation and stilbenoid pathway genes were upregulated at 47 DAA while cell wall degrading and modification genes were downregulated at 74 DAA in small compared to large berries. In the late ripening stage, concerted upregulation of the general phenylpropanoid and stilbenoid pathway genes and downregulation of flavonoid pathway genes were observed in skins of small compared to large berries. Cis-regulatory element analysis of differentially expressed hormone, fruit texture, flavor, and aroma genes revealed an enrichment of specific regulatory motifs related to bZIP, bHLH, AP2/ERF, NAC, MYB, and MADS-box transcription factors. The study demonstrates that physiological and compositional differences between berries of different sizes parallel transcriptome changes that involve fruit texture, flavor, and aroma pathways. These results suggest that, in addition to direct effects brought about by differences in size, key aspects involved in the regulation of ripening likely contribute to different quality profiles between small and large berries.

Phenylpropanoid

Metabolic pathway

Flavonoid Biosynthesis

Aroma of wine

Plant hormone

10.1186/s12864-016-2660-z

Cite

Citations (69)

Drought stress modulates cuticular wax composition of the grape berry

Journal of Experimental Botany (2020)

Nicolas Dimopoulos Ricco Tindjau Darren C. J. Wong Till Matzat Tegan M. Haslam

Drought events are a major challenge for many horticultural crops, including grapes, which are often cultivated in dry and warm climates. It is not understood how the cuticle contributes to the grape berry response to water deficit (WD); furthermore, the cuticular waxes and the related biosynthetic pathways are poorly characterized in this fruit. In this study, we identified candidate wax-related genes from the grapevine genome by phylogenetic and transcriptomic analyses. Developmental and stress response expression patterns of these candidates were characterized across pre-existing RNA sequencing data sets and confirmed a high responsiveness of the pathway to environmental stresses. We then characterized the developmental and WD-induced changes in berry cuticular wax composition, and quantified differences in berry transpiration. Cuticular aliphatic wax content was modulated during development and an increase was observed under WD, with wax esters being strongly up-regulated. These compositional changes were related to up-regulated candidate genes of the aliphatic wax biosynthetic pathway, including CER10, CER2, CER3, CER1, CER4, and WSD1. The effect of WD on berry transpiration was not significant. This study indicates that changes in cuticular wax amount and composition are part of the metabolic response of the grape berry to WD, but these changes do not reduce berry transpiration.

Drought stress

Cold stress

10.1093/jxb/eraa046

Cite

Citations (66)

An In Vitro Phytohormone Survey Reveals Concerted Regulation of the Cannabis Glandular Trichome Disc Cell Proteome

Plants (2025)

Nicolas Dimopoulos Qi Guo Lei Liu Matthew Nolan Rekhamani Das

Cannabis (Cannabis sativa L.) flower glandular trichomes (GTs) are the main site of cannabinoid synthesis. Phytohormones, such as jasmonic acid (JA) and salicylic acid (SA), have been shown to increase cannabinoid content in cannabis flowers, but how this is regulated remains unknown. This study aimed to understand which biological processes in GT disc cells phytohormones control by using an in vitro assay. Live GT disc cells were isolated from a high-tetrahydrocannabinol cannabis cultivar and incubated on basal media plates supplemented with either kinetin (KIN), JA, SA, abscisic acid, ethephon, gibberellic acid, brassinolide, or sodium diethyldithiocarbamate. Quantitative proteomic analysis revealed that KIN, JA, and SA caused the greatest number of changes in the GT disc cell proteome. Surprisingly, none of the treatments concertedly increased cannabinoid content or the abundance of related biosynthetic proteins in the GT, suggesting that cannabinoid increases in previous in planta phytohormone studies are likely due to other processes, such as increased GT density. As well, KIN-, JA-, and SA-treated GTs had numerous differentially abundant proteins in common. Several were key proteins for leucoplast differentiation, cuticular wax and fatty acid metabolism, and primary metabolism regulation, denoting that cytokinin, JA, and SA signalling are likely important for coordinating cannabis GT differentiation and development.

Trichome

Proteome

10.3390/plants14050694

Cite

Citations (0)

Additional file 1: Table S1. of Combined physiological, transcriptome, and cis-regulatory element analyses indicate that key aspects of ripening, metabolism, and transcriptional program in grapes (Vitis vinifera L.) are differentially modulated accordingly to fruit size

Figshare (2016)

Darren C. J. Wong Rodrigo Lopez Gutierrez Nicolas Dimopoulos Gregory A. Gambetta Simone D. Castellarin

Summary of RNA sequencing analysis metrics. RNA sequencing were carried in skins of small and large berries at four berry developmental stages namely 47 (before ripening, 4.9 °Brix), 74 (early ripening, 17.5 °Brix), 103 (ripening, 22.4 °Brix), and 121 (late ripening, 25.3 °Brix) days after anthesis (DAA). Table S2. Transcript abundance of the DE genes, reported as log2 (FPKM + 1) values, for each individual biological replicate (R1, R2, R3) in each treatment (small and large berry) at 47, 74, 103, and 121 days after anthesis. Table S3. Summary of differentially expressed genes between small and large berries at four berry developmental stages. All differentially expressed genes (Adj. P-value <0.05) and detailed description of the 12×V1 gene ID, log2 fold change values (small vs large), differential expression calls across four developmental stages, average log2 (FPKM + 1) values (3 replicates) of small and large berries together and individually, k-means assigned cluster (based on response and developmental stage), functional annotations based on Grimplet et al. [37] (including transcription factors), and MapMan pipeline. Table S4. Summary of PLACE- and PBM-curated cis-regulatory elements (CRE) analysis of k-means assigned clusters and selected group of genes. All information on the number of promoters with the specified CRE (match_in_sample), the number of genes within each group, number of promoters in the genome containing the specified CRE (match_in_genome), P-value and FDR of enriched CRE (FDR

RNA-Seq

Table (database)

10.6084/m9.figshare.c.3640925_d1

Cite

Citations (0)

Characterisation of Cannabis glandular trichome development reveals distinct features of cannabinoid biosynthesis

Plant Cell Reports (2025)

Matthew Nolan Qi Guo Lei Liu Nicolas Dimopoulos Lennard Garcia-de Heer

Trichome

Secondary metabolite

Secretory protein

Secondary metabolism

10.1007/s00299-024-03410-9

Cite

Citations (0)

Regulation of Cannabis Sativa Glandular Trichome Metabolism by Abscisic Acid and Water Deficit Stress During Late Flowering Development

Nicolas Dimopoulos Qi Guo Lei Liu Razlin Azman Halimi Lennard Garcia-de Heer

Cannabis sativa

Trichome

Water Stress

10.2139/ssrn.5098792

Cite

Citations (0)

An In Vitro Phytohormone Survey Reveals Concerted Regulation of the Cannabis Glandular Trichome Disc Cell Proteome

Nicolas Dimopoulos Qi Guo Lei Liu Matthew Nolan Rekhamani Das

Cannabis sativa flower glandular trichomes (GTs) are the main site of cannabinoid synthesis. Phytohormones, such as jasmonic acid (JAS) and salicylic acid (SAL) have been shown to increase cannabinoid content in Cannabis flowers, but how this is regulated remains unknown. This study aimed to understand the mechanisms of action of phytohormones on mature GT disc cells using an in vitro assay. Live GT disc cells were isolated from a high-tetrahydrocannabinol Cannabis cultivar and incubated on basal media plates supplemented with either kinetin (KIN), JAS, SAL, abscisic acid, ethephon, gibberellic acid, brassinolide, or sodium diethyldithiocarbamate. Quantitative proteomic analysis revealed that KIN, JAS and SAL caused the greatest number of changes in the GT disc cell proteome. Surprisingly, none of the treatments concertedly increased cannabinoid content or the abundance of related biosynthetic proteins in the GT, suggesting that cannabinoid increases in previous in planta phytohormone studies are likely due to other processes, such as increased GT density. As well, KIN, JAS and SAL treated GTs had numerous differentially abundant proteins in common. Several were key proteins for leucoplast differentiation, cuticular wax and fatty acid metabolism and primary metabolism regulation. Denoting that cytokinin, JAS and SAL signalling are likely important for coordinating Cannabis GT differentiation and development.

Trichome

Proteome

10.20944/preprints202411.1045.v1

Cite

Citations (0)

A Putative Glutathione Peroxidase of Drosophila Encodes a Thioredoxin Peroxidase That Provides Resistance against Oxidative Stress But Fails to Complement a Lack of Catalase Activity

Biological Chemistry (2003)

Fanis Missirlis Stefan Rahlfs Nicolas Dimopoulos Holger Bauer Katja Becker

Cellular defense systems against reactive oxygen species (ROS) include thioredoxin reductase (TrxR) and glutathione reductase (GR). They generate sulfhydryl-reducing systems which are coupled to antioxidant enzymes, the thioredoxin and glutathione peroxidases (TPx and GPx). The fruit fly Drosophila lacks a functional GR, suggesting that the thioredoxin system is the major source for recycling glutathione. Whole genome in silico analysis identified two non-selenium containing putative GPx genes. We examined the biochemical characteristics of one of these gene products and found that it lacks GPx activity and functions as a TPx. Transgene-dependent overexpression of the newly identified Glutathione peroxidase homolog with thioredoxin peroxidase activity (Gtpx-1) gene increases resistance to experimentally induced oxidative stress, but does not compensate for the loss of catalase, an enzyme which, like GTPx-1, functions to eliminate hydrogen peroxide. The results suggest that GTPx-1 is part of the Drosophila Trx antioxidant defense system but acts in a genetically distinct pathway or in a different cellular compartment than catalase.

Glutathione reductase

GPX1

GPX3

GPX4

10.1515/bc.2003.052

Cite

Citations (81)

From dawn ‘til dusk: daytime progression regulates primary and secondary metabolism in Cannabis glandular trichomes

Journal of Experimental Botany (2024)

Nicolas Dimopoulos Qi Guo Sarah Purdy Matthew Nolan Razlin Azman Halimi

Abstract Cannabis sativa L. glandular trichomes synthesize large amounts of secondary metabolites, predominantly cannabinoids and terpenoids. The associated demand for carbon and energy makes glandular trichomes strong sink tissues with indications that their secondary metabolism is coupled to the availability of photoassimilates. Many metabolites show diurnal patterns of flux, but it is unknown whether cannabinoids and terpenoids are regulated by time of day. We quantified cannabinoids, terpenoids, and the glandular trichome proteome over a 12 h light period in flowers of ‘Hindu Kush’, a high-tetrahydrocannabinol cultivar. Major cannabinoids changed significantly over the course of the day, resulting in an increase in total measured cannabinoids. Major terpenoids also changed, with sesquiterpenes generally decreasing with day progression. While monoterpenes generally did not decrease, the second most abundant, α-pinene, increased. The glandular trichome proteome changed the most within the first 6 h of the day, and analysis of differentially abundant proteins indicated up-regulation of primary metabolism. Surprisingly, key cannabinoid biosynthetic enzymes decreased with daytime progression despite increases in cannabinoid content, which indicates that daytime increases of photoassimilates are the main driver of cannabinoid regulation. This first reporting of variability of cannabinoid and terpenoid biosynthesis over the course of the day has implications for Cannabis research and production.

Trichome

Proteome

Secondary metabolism

10.1093/jxb/erae148

Cite

Citations (6)

Compositional changes of the grape berry (Vitis vinifera L.) cuticle during fruit development in response to water deficit stress

Nicolas Dimopoulos

Water Stress

Cuticle (hair)

10.14288/1.0362313

Cite

Citations (0)