Identification and functional characterization of the diterpene synthase family in Pogostemon cablin (Blanco) Benth

Pogostemon cablin (Blanco) Benth (Patchouli) is an aromatic herb extensively used in pharmaceutical and cosmetic industries. Sesquiterpenes are the characteristic constitutes in patchouli which are synthesized in the glandular trichomes on leaves and stems. Gibberellic acid (GA), a tetracyclic diterpenoid, plays a crucial role in the formation of glandular trichome. However, the diterpene biosynthesis remains largely unknown in patchouli. Here we identified a small diterpene synthases (diTPSs) family comprising three class II diTPSs (PatCPS1-3) and three class I diTPSs (PatKSL1 and PatGLS1-2). These diTPSs are functionally characterized using a yeast heterologous expression system. PatCPS1 was identified as an ent-copalyl diphosphate synthase (ent-CPS), in combination with PatKSL1, yield ent-kaurene, the precursor of GA, indicating their involvement in primary metabolism. PatCPS2 converted GGPP into (+)-8, 13-copalyl diphosphate (CPP). No activity was detected for PatCPS3, PatGLS1 and PatGLS2. Three ohnologs of PatCPS1 were further characterized to explore the possible functional differentiation of ent-CPS during the evolution of tetraploid hybrid patchouli genome. GC-MS analysis showed all ohnologs are functional ent-CPSs, demonstrating the functional conservation of PatCPS1 during evolution. Expression profiling by qRT-PCR showed PatCPS1 and PatKSL1 are ubiquitously expressed in all tissues, consistent with their involvement in primary metabolism. Conversely, PatCPS2 and PatCPS3 were predominantly expressed in the above ground parts, indicating a role in specialized metabolism. In summary, these findings clarify the early stages of GA biosynthesis in patchouli and provide gene elements for further metabolic engineering of sesquiterpenes via diterpenoids.

Unraveling the impact of nanopollution on plant metabolism and ecosystem dynamics

Nanopollution (NPOs), a burgeoning consequence of the widespread use of nanoparticles (NPs) across diverse industrial and consumer domains, has emerged as a critical environmental issue. While extensive research has scrutinized the repercussions of NPs pollution on ecosystems and human health, scant attention has been directed towards unraveling its implications for plant life. This comprehensive review aims to bridge this gap by delving into the nuanced interplay between NPOs and plant metabolism, encompassing both primary and secondary processes. Our exploration encompasses an in-depth analysis of the intricate mechanisms governing the interaction between plants and NPs. This involves a thorough examination of how physicochemical properties such as size, shape, and surface characteristics influence the uptake and translocation of NPs within plant tissues. The impact of NPOs on primary metabolic processes, including photosynthesis, respiration, nutrient uptake, and water transport. Additionally, this study explored the multifaceted alterations in secondary metabolism, shedding light on the synthesis and modulation of secondary metabolites in response to NPs exposure. In assessing the consequences of NPOs for plant life, we scrutinize the potential implications for plant growth, development, and environmental interactions. The intricate relationships revealed in this review underscore the need for a holistic understanding of the plant-NPs dynamics. As NPs become increasingly prevalent in ecosystems, this investigation establishes a fundamental guide that underscores the importance of additional research to shape sustainable environmental management strategies and address the extensive effects of NPs on the development of plant life and environmental interactions.

Adjusting function of camphor on primary metabolism in Cinnamomum camphora stressed by high temperature

Cinnamomum camphora has great economic value for its wide utilization in traditional medicine and furniture material, and releases lots of monoterpenes to tolerate high temperature. To uncover the adjusting function of monoterpenes on primary metabolism and promoting their utilization as anti-high temperature agents, the photosynthetic capacities, primary metabolite levels, cell ultrastructure and associated gene expression were surveyed in C. camphora when it was blocked monoterpene biosynthesis with fosmidomycin (Fos) and fumigated with camphor (a typical monoterpene in the plant) under high temperature (Fos+38 °C+camphor). Compared with the control (28 °C), high temperature at 38 °C decreased the starch content and starch grain size, and increased the fructose, glucose, sucrose and soluble sugar content. Meanwhile, high temperature also raised the lipid content, with the increase of lipid droplet size and numbers. These variations were further intensified in Fos+ 38 °C treatment. Compared with Fos+ 38 °C treatment, Fos+ 38 °C+camphor treatment improved the starch accumulation by promoting 4 gene expression in starch biosynthesis, and lowered the sugar content by suppressing 3 gene expression in pentose phosphate pathway and promoting 15 gene expression in glycolysis and tricarboxylic acid cycle. Meanwhile, Fos+ 38 °C+camphor treatment also lowered the lipid content, which may be caused by the down-regulation of 2 genes in fatty acid formation and up-regulation of 4 genes in fatty acid decomposition. Although Fos+ 38 °C+camphor treatment improved the photosynthetic capacities in contrast to Fos+ 38 °C treatment, it cannot explain the variations of these primary metabolite levels. Therefore, camphor should adjust related gene expression to maintain the primary metabolism in C. camphora tolerating high temperature.

Quinoa panicles contribute to carbon assimilation and are more tolerant to salt stress than leaves

Contribution of inflorescences to seed filling have attracted great attention given the resilience of this photosynthetic organ to stressful conditions. However, studies have been almost exclusively focused to small grain cereals. In this study, we aimed to explore these responses in quinoa, as a climate resilient seed crop of elevated economic and nutritious potential. We compared the physiological and metabolic performance of panicles and leaves of two quinoa cultivars growing under contrasting salinity levels. Plant growth, photosynthetic and transpiratory gas exchange and chlorophyll fluorescence were monitored in inflorescences and leaves throughout the experiment. At flowering stage, young and mature leaves and panicles were sampled for key metabolic markers related to carbon, nitrogen and secondary metabolisms. When subjected to salt stress, panicles showed attenuated declines on photosynthesis, water use, pigments, amino acids, and protein levels as compared to leaves. In fact, the assimilation rates, together with a high hexose content evidenced an active photosynthetic role of the panicle under optimal and salt stress conditions. Moreover, we also found significant genotypic variability for physiological and metabolic traits of panicles and leaves, which emphasizes the study of genotype-dependent stress responses at the whole plant level. We conclude that quinoa panicles are less affected by salt stress than leaves, which encourages further research and exploitation of this organ for crop improvement and stress resilience considering the high natural diversity.

A comprehensive view of metabolic responses to CYP98 perturbation in ancestral plants

Cytochrome P450 monooxygenase 98 (CYP98) is a critical rate-limiting enzyme of the phenylpropanoid pathway. One of the end-product of the phenylpropanoid pathway is a lignin monomer, although the occurrence of lignin in bryophytes is controversial. Here we investigated the functions of PpCYP98 in Physcomitrium patens by transcriptome and metabolome analyses. We identified 5266 differentially expressed genes (DEGs) and 68 differentially abundant secondary metabolites between wild-type and ΔPpCYP98 gametophores. Of the identified metabolites, 23 phenolic acids were identified, with only one showing upregulation. Among the phenolic acids, 4-coumaroyl tartaric acid and chlorogenic acid showed significant decreases. Declines were also observed in coniferylaldehyde and coniferin, precursor substances and downstream products of the lignin monomer coniferyl alcohol, respectively. Thus, the pre-lignin synthesis pathway already exists in bryophytes, and PpCYP98 plays vital roles in this pathway. Besides, most flavonoids show significant reductions, including eriodyctiol, dihydroquecetin, and dihydromyricetin, whereas naringenin chalone and dihydrokaempferol were increased after PpCYP98 knockout. Therefore, the synthesis of flavonoids shares the core pathway with phenylpropanoids and mainly starts from caffeoyl-CoA, that is the compound of divergence between the two pathways in moss. PpCYP98 showed systemic effects on metabolisms, including carbohydrate, fatty acid, and hormonal signaling transductions, suggesting that PpCYP98 might indirectly regulate carbon influx allocation. Our results demonstrated roles of PpCYP98 were essential for the development of the early landing plant.

Non-canonical and developmental roles of the TCA cycle in plants

Over recent years, our understanding of the tricarboxylic acid cycle (TCAC) in living organisms has expanded beyond its canonical role in cellular energy production. In plants, TCAC metabolites and related enzymes have important roles in physiology, including vacuolar function, chelation of metals and nutrients, photorespiration, and redox regulation. Research in other organisms, including animals, has demonstrated unexpected functions of the TCAC metabolites in a number of biological processes, including signaling, epigenetic regulation, and cell differentiation. Here, we review the recent progress in discovery of non-canonical roles of the TCAC. We then discuss research on these metabolites in the context of plant development, with a focus on research related to tissue-specific functions of the TCAC. Additionally, we review research describing connections between TCAC metabolites and phytohormone signaling pathways. Overall, we discuss the opportunities and challenges in discovering new functions of TCAC metabolites in plants.

Inhibition of nitrogen assimilation promotes carbon-based secondary metabolism in callus of Cyclocarya paliurus

The biosynthesis and accumulation of secondary metabolites are critical important to quality formation of medicinal plants, which are usually give way to primary processes and growth. Here, methionine sulfoximine (MSO) was used to inhibit the nitrogen assimilation in callus of Cyclocarya paliurus. The newly assimilated nitrogen characterized by ¹⁵N atom percentage excess, and the levels of amino acid and protein were reduced. The other primary processes such as carbohydrate metabolism and lipid metabolism were also repressed. In addition, the expression of the growth-related target of rapamycin (TOR) signaling was repressed, indicating nitrogen assimilation inhibition led to a systematic down-regulated primary metabolisms and resulted in a disruption of growth. In contrast, the biosynthesis of flavonoids and triterpenoids, antioxidase system, and the SnRK2-mediated abscisic acid (ABA) and jasmonic acid (JA) signaling were induced, which can improve plant stress resistance and defense. Nitrogen assimilation inhibition led to the carbon metabolic flux redirection from primary processes to secondary pathways, and facilitated the biosynthesis of flavonoids and triterpenoids in calluses of C. paliurus. Our results provide a comprehensive understanding of metabolic flux redirection between primary and secondary metabolic pathways and a potential means to improve the quality of medicinal plants.

Subcellular compartmentalization of aluminum reduced its hazardous impact on rye photosynthesis

Aluminum (Al) toxicity limits crops growth and production in acidic soils. Compared to roots, less is known about the toxic effects of Al in leaves. Al subcellular compartmentalization is also largely unknown. Using rye (Secale cereale L.) Beira (more tolerant) and RioDeva (more sensitive to Al) genotypes, we evaluated the patterns of Al accumulation in leaf cell organelles and the photosynthetic and metabolic changes to cope with Al toxicity. The tolerant genotype accumulated less Al in all organelles, except the vacuoles. This suggests that Al compartmentalization plays a role in Al tolerance of Beira genotype. PSII efficiency, stomatal conductance, pigment biosynthesis, and photosynthesis metabolism were less affected in the tolerant genotype. In the Calvin cycle, carboxylation was compromised by Al exposure in the tolerant genotype. Other Calvin cycle-related enzymes, phoshoglycerate kinase (PGK), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), triose-phosphate isomerase (TPI), and fructose 1,6-bisphosphatase (FBPase) activities decreased in the sensitive line after 48 h of Al exposure. Consequentially, carbohydrate and organic acid metabolism were affected in a genotype-specific manner, where sugar levels increased only in the tolerant genotype. In conclusion, Al transport to the leaf and compartmentalization in the vacuoles tolerant genotype's leaf cells provide complementary mechanisms of Al tolerance, protecting the photosynthetic apparatus and thereby sustaining growth.

Origin of the 3-methylglutaryl moiety in caprazamycin biosynthesis

BACKGROUND

Caprazamycins are liponucleoside antibiotics showing bioactivity against Gram-positive bacteria including clinically relevant Mycobacterium tuberculosis by targeting the bacterial MraY-translocase. Their chemical structure contains a unique 3-methylglutaryl moiety which they only share with the closely related liposidomycins. Although the biosynthesis of caprazamycin is understood to some extent, the origin of 3-methylglutaryl-CoA for caprazamycin biosynthesis remains elusive.

RESULTS

In this work, we demonstrate two pathways of the heterologous producer Streptomyces coelicolor M1154 capable of supplying 3-methylglutaryl-CoA: One is encoded by the caprazamycin gene cluster itself including the 3-hydroxy-3-methylglutaryl-CoA synthase Cpz5. The second pathway is part of primary metabolism of the host cell and encodes for the leucine/isovalerate utilization pathway (Liu-pathway). We could identify the liu cluster in S. coelicolor M1154 and gene deletions showed that the intermediate 3-methylglutaconyl-CoA is used for 3-methylglutaryl-CoA biosynthesis. This is the first report of this intermediate being hijacked for secondary metabolite biosynthesis. Furthermore, Cpz20 and Cpz25 from the caprazamycin gene cluster were found to be part of a common route after both individual pathways are merged together.

CONCLUSIONS

The unique 3-methylglutaryl moiety in caprazamycin originates both from the caprazamycin gene cluster and the leucine/isovalerate utilization pathway of the heterologous host. Our study enhanced the knowledge on the caprazamycin biosynthesis and points out the importance of primary metabolism of the host cell for biosynthesis of natural products.

Jasmonate: A hormone of primary importance for plant metabolism

Over the years, jasmonates (JAs) have become recognized as one of the main plant hormones that regulate stress responses by activating defense programs and the production of specialized metabolites. High JA levels have been associated with reduced plant growth, supposedly as a result of the reallocation of carbon sources from primary growth to the biosynthesis of defense compounds. Recent advances suggest however that tight regulatory networks integrate several sensing pathways to steer plant metabolism, and thereby drive the trade-off between growth and defense. In this review, we discuss how JA influences primary metabolism and how it is connected to light-regulated processes, nutrient sensing and energy metabolism. Finally, we speculate that JA, in a conceptual parallelism with adrenaline for humans, overall boosts cellular processes to keep up with an increased metabolic demand during harsh times.

3-Deoxy-D-arabino-heptulosonate 7-phosphate synthase as the gatekeeper of plant aromatic natural product biosynthesis

The shikimate pathway connects the central carbon metabolism with the biosynthesis of aromatic amino acids-l-tyrosine, l-phenylalanine, and l-tryptophan-which play indispensable roles as precursors of numerous aromatic phytochemicals. Despite the importance of the shikimate pathway-derived products for both plant physiology and human society, the regulatory mechanism of the shikimate pathway remains elusive. This review summarizes the recent progress and current understanding on the plant 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase (DAHP synthase or DHS) enzymes that catalyze the committed reaction of the shikimate pathway. We particularly focus on how the DHS activity is regulated in plants in comparison to those of microbes and discuss potential roles of DHS as the critical gatekeeper for the production of plant aromatic compounds.

Deep roots and many branches: Origins of plant-specialized metabolic enzymes in general metabolism

Collectively, plants produce hundreds of thousands of specialized metabolites from simple building blocks such as amino acids, fatty acids, and isoprenoids. As additional specialized metabolic enzymes are described, there is increasing recognition of the importance of cooption of general metabolic enzymes to specialized metabolism by gene duplication, narrowing of expression, and alteration of enzymatic activities. Here, we examine how several classes of enzymes were each coopted multiple times. We demonstrate the simplicity of achieving the synthesis of analogous chemicals by coopting existing enzymes and summarize emerging insights that could inform rational metabolic engineering of both general and specialized metabolic enzymes.

A plant balancing act: Meshing new and existing metabolic pathways towards an optimized system

Specialized metabolic pathways evolve from existing pathways, creating new functionality potentially boosting fitness. However, how these pathways are integrated into a pre-existing working and well-balanced metabolic system is unclear. They could be integrated to the system as a functional appendage, or they could be fully embedded into primary metabolism by establishing new biochemical and regulatory connections. A full integration into the primary metabolic system requires substantial system re-wiring and because of this complexity, the latter is often not experimentally pursued. New studies provide evidence that some specialized metabolic pathways are fully embedded in primary metabolism with extensive new regulatory and biochemical connections. This suggests, that we should consider whether other specialized metabolic pathways could be fully integrated rather than being simple appendages. In this mini review, we survey compelling evidence supporting that some specialized metabolic pathways are fully integrated and ask if these metabolites now act as de-facto primary metabolites?

Coenzymes and the primary and specialized metabolism interface

In plants, primary and specialized metabolism have classically been distinguished as either essential for growth or required for survival in a particular environment. Coenzymes (organic cofactors) are essential for growth but their importance to specialized metabolism is often not considered. In line with the recent proposal of viewing primary and specialized metabolism as an integrated whole rather than segregated lots with a defined interface, we highlight here the importance of collating information on the regulation of coenzyme supply with metabolic demands using examples of vitamin B derived coenzymes. We emphasize that coenzymes can have enormous influence on the outcome of metabolic as well as engineered pathways and should be taken into account in the era of synthetic biology.

Compartmentalization at the interface of primary and alkaloid metabolism

Plants produce many compounds used by humans as medicines, including alkaloids of the benzylisoquinoline (BIA), monoterpene indole (MIA) and tropane classes. The biosynthetic pathways of these pharmaceutical alkaloids are complex and spatially segregated across several tissues, cell-types and organelles. This review discusses the origin of primary metabolic inputs required by these specialized biosynthetic pathways and considers aspects relevant to their spatial organization. These factors are important for alkaloid production both in the native plants and for synthetic biology pathway reconstruction in microorganisms.

Early stem growth mutation alters metabolic flux changes enhance sesquiterpenoids biosynthesis in Atractylodes lancea (Thunb.) DC

Atractylodes lancea (Thunb.) DC. is a well-known medicinal herb in China, containing abundant active components, including a variety of sesquiterpenoids. Owing to a shortage of wild resources, artificial cultivation has become the main breeding mode, leading to the germplasm degradation. In preliminary research, our research group found that a mutant tissue culture seedling of A. lancea is an excellent germplasm resource, characterized by early stem growth and higher sesquiterpenoid content than that of the wild type. In this study, the physiological and biochemical mechanisms underlying efficient sesquiterpenoids synthesis by this mutant A. lancea were systematically evaluated. The results showed that the photosynthetic efficiency, central carbon metabolism efficiency, and energy metabolism efficiency were significantly improved in mutant A. lancea compared with the wild type, and the content of endogenous hormones, such as gibberellin and jasmonic acid, changed significantly. In addition, levels of key metabolites and the expression level of key genes in the mevalonate and 2-C-methyl-d-erythritol-4-phosphate pathways were significantly higher in mutant type than in wild type, resulting in elevated sesquiterpenoid synthesis in the mutant. These physiological and biochemical properties explain the rapid growth and high sesquiterpenoid content of mutant A. lancea.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11240-022-02240-5.

Primary metabolic processes as drivers of leaf ageing

Ageing in plants is a highly coordinated and complex process that starts with the birth of the plant or plant organ and ends with its death. A vivid manifestation of the final stage of leaf ageing is exemplified by the autumn colours of deciduous trees. Over the past decades, technological advances have allowed plant ageing to be studied on a systems biology level, by means of multi-omics approaches. Here, we review some of these studies and argue that these provide strong support for basic metabolic processes as drivers for ageing. In particular, core cellular processes that control the metabolism of chlorophyll, amino acids, sugars, DNA and reactive oxygen species correlate with leaf ageing. However, while multi-omics studies excel at identifying correlative processes and pathways, molecular genetic approaches can provide proof that such processes and pathways control ageing, by means of knock-out and ectopic expression of predicted regulatory genes. Therefore, we also review historic and current molecular evidence to directly test the hypotheses unveiled by the systems biology approaches. We found that the molecular genetic approaches, by and large, confirm the multi-omics-derived hypotheses with notable exceptions, where there is scant evidence that chlorophyll and DNA metabolism are important drivers of leaf ageing. We present a model that summarises the core cellular processes that drive leaf ageing and propose that developmental processes are tightly linked to primary metabolism to inevitably lead to ageing and death.

Downregulation of the E2 Subunit of 2-Oxoglutarate Dehydrogenase Modulates Plant Growth by Impacting Carbon-Nitrogen Metabolism in Arabidopsis thaliana

In Arabidopsis thaliana, two genes encode the E2 subunit of the 2-oxoglutarate dehydrogenase (2-OGDH), a multimeric complex composed of three subunits. To functionally characterize the isoforms of E2 subunit, we isolated Arabidopsis mutant lines for each gene encoding the E2 subunit and performed a detailed molecular and physiological characterization of the plants under controlled growth conditions. The functional lack of expression of E2 subunit isoforms of 2-OGDH increased plant growth, reduced dark respiration and altered carbohydrate metabolism without changes in the photosynthetic rate. Interestingly, plants from e2-ogdh lines also exhibited reduced seed weight without alterations in total seed number. We additionally observed that downregulation of 2-OGDH activity led to minor changes in the levels of tricarboxylic acid cycle intermediates without clear correlation with the reduced expression of specific E2-OGDH isoforms. Furthermore, the e2-ogdh mutant lines exhibited a reduction by up to 25% in the leaf total amino acids without consistent changes in the amino acid profile. Taken together, our results indicate that the two isoforms of E2 subunit play a similar role in carbon-nitrogen metabolism, in plant growth and in seed weight.

Silicon influenced ripening metabolism and improved fruit quality traits in apples

The benefits of silicon against abiotic stress in different annual plant species have been described in many studies, however the regulation of ripening of fruit tree crops by silicon remains largely uncharacterized. Therefore, the present study aimed to explore the impact of foliar silicon application in the apple (cv. 'Fuji') fruit ripening traits along with the effect of silicon in the nutrient and metabolic changes in the fully expanded leaves, annual shoots, fruit outer pericarp (peel) and fruit mesocarp (skin) tissues. Data indicated that fruit firmness and apple peel color attributes, such as redness (a*) and percentage of red-blushed surface were induced by silicon application. Moreover, several fruit ripening traits, such as titratable acidity, soluble solid content and respiration rate were unaffected by silicon. Endogenous silicon level in leaves shoots and peel tissues were increased by exogenously applied silicon while several elements (i.e., P, Mg, Mn, Fe and Cu) were altered in the tested tissues that exposed to silicon. In addition, silicon increased the accumulation of total phenolic and total anthocyanin compounds in the various apple tissues. The level of various primary metabolites including sorbitol, fructose, maltose cellobiose, malic acid, phosphoric acid and gluconic acid was also notably affected by silicon in a tissue-specific manner. Overall, this study provides a valuable resource for future research, aiming in the elucidation of the role of silicon in fruit tree physiology.

Potassium dependency of enzymes in plant primary metabolism

Potassium is a macroelement essential to many aspects of plant life, such as photosynthesis, phloem transport or cellular electrochemistry. Many enzymes in animals or microbes are known to be stimulated or activated by potassium (K⁺ ions). Several plant enzymes are also strictly K⁺-dependent, and this can be critical when plants are under K deficiency and thus intracellular K⁺ concentration is low. Although metabolic effects of low K conditions have been documented, there is presently no review focusing on roles of K⁺ for enzyme catalysis or activation in plants. In this mini-review, we compile the current knowledge on K⁺-requirement of plant enzymes and take advantage of structural data to present biochemical roles of K⁺. This information is instrumental to explain direct effects of low K⁺ content on metabolism and this is illustrated with recent metabolomics data.

Revealing floral metabolite network in tuberose that underpins scent volatiles synthesis, storage and emission

The role of central carbon metabolism in the synthesis and emission of scent volatiles in tuberose flowers was revealed through measurement of changes in transcripts and metabolites levels. Tuberose or Agave amica (Medikus) Thiede & Govaerts is a widely cultivated ornamental plant in several subtropical countries. Little is known about metabolite networking involved in biosynthesis of specialized metabolites utilizing primary metabolites. In this study, metabolite profiling and gene expression analyses were carried out from six stages of maturation throughout floral lifespan. Multivariate analysis indicated distinction between early and late maturation stages. Further, the roles of sugars viz. sucrose, glucose and fructose in synthesis, glycosylation and emission of floral scent volatiles were studied. Transcript levels of an ABC G family transporter (picked up from the floral transcriptome) was in synchronization with terpene volatiles emission during the anthesis stage. A diversion from phenylpropanoid/benzenoid to flavonoid metabolism was observed as flowers mature. Further, it was suggested that this metabolic shift could be mediated by isoforms of 4-Coumarate-CoA ligase along with Myb308 transcription factor. Maximum glycosylation of floral scent volatiles was shown to occur at the late mature stage when emission declined, facilitating both storage and export from the floral tissues. Thus, this study provides an insight into floral scent volatiles synthesis, storage and emission by measuring changes at transcripts and metabolites levels in tuberose throughout floral lifespan.

Proteomic analysis validates previous findings on wounding-responsive plant hormone signaling and primary metabolism contributing to the biosynthesis of secondary metabolites based on metabolomic analysis in harvested broccoli (Brassica oleracea L. var. italica)

The plant wound-response is a complex process that generates physiological modifications for protecting the wounded tissue. In this study, tandem mass tag (TMT)-based quantitative proteomic analysis was performed to clarify the comprehensive molecular mechanism for the wound-response of broccoli subjected to two wounding intensities (0.04 and 1.85 m² kg^-1 for florets and shreds, respectively). Furthermore, integrated proteomic and metabolomic analysis was performed to reveal the interaction among the critical metabolic pathway responses to wounding. The results show that a total of 399 proteins and 266 proteins were identified as differentially expressed proteins (DEPs) in florets and shreds broccoli compared to control, respectively. Furthermore, 167 DEPs were detected in shreds broccoli compared to the florets broccoli. Salicylic acid (SA) and ethylene (ET) biosynthesis were more susceptible to being induced by wounding with lower intensities, whereas, phenylpropanoid biosynthesis, aliphatic glucosinolate synthesis and jasmonic acid (JA) biosynthesis were more susceptible to being activated by wounding with higher intensities. The activation of starch and sucrose metabolism, TCA cycle, glycolysis, pentose phosphate could provide carbon sources and ATP for the production of amino acids including phenylalanine, valine, threonine, isoleucine, L-methionine, methionine and histidine. The motivation of carbohydrate metabolic pathways and amino acid biosynthesis-related pathways promotes the precursor levels for phenolic substances and glucosinolate synthesis. Furthermore, the accumulation of SA, ET and JA may activated secondary metabolite biosynthesis through the regulation of critical proteins involved in the corresponding metabolic pathways.

Proteo-metabolomic journey across olive drupe development and maturation

Maturity is one of the most important factors associated with the quality of olive products, however the molecular events underlying olive drupe development remain poorly characterized. Using proteomic and metabolomic approaches, this study investigated the changes in the olive drupes (cv. Chondrolia Chalkidikis) across six developmental stages (S1-S6) that characterize the dynamics of fruit growth and color. Primary metabolites, including carbohydrates and organic acids (i.e., xylose, malic acid), showed significant accumulation in the black maturation stage. Temporal changes in various secondary metabolites (e.g., oleuropein, oleacin and tyrosol) were also observed. Proteins involved in oxidation-reduction (i.e., LOX1/5), carbohydrate metabolism (i.e., GLUA, PG) and photosynthesis (i.e., chlorophyll a-b binding proteins) significantly altered in the turning black compared to the green mature stage. By providing the first proteometabolomic study of olive drupe development, this investigation offers a novel framework for further studies on this economically relevant crop.

Overexpression and Inhibition of 3-Hydroxy-3-Methylglutaryl-CoA Synthase Affect Central Metabolic Pathways in Tobacco

Little has been established on the relationship between the mevalonate (MVA) pathway and other metabolic pathways except for the sterol and glucosinolate biosynthesis pathways. In the MVA pathway, 3-hydroxy-3-methylglutaryl-CoA synthase (HMGS) catalyzes the condensation of acetoacetyl-CoA and acetyl-CoA to form 3-hydroxy-3-methylglutaryl-coenzyme A. Our previous studies had shown that, while the recombinant Brassica juncea HMGS1 (BjHMGS1) mutant S359A displayed 10-fold higher enzyme activity than wild-type (wt) BjHMGS1, transgenic tobacco overexpressing S359A (OE-S359A) exhibited higher sterol content, growth rate and seed yield than OE-wtBjHMGS1. Herein, untargeted proteomics and targeted metabolomics were employed to understand the phenotypic effects of HMGS overexpression in tobacco by examining which other metabolic pathways were affected. Sequential window acquisition of all theoretical mass spectra quantitative proteomics analysis on OE-wtBjHMGS1 and OE-S359A identified the misregulation of proteins in primary metabolism and cell wall modification, while some proteins related to photosynthesis and the tricarboxylic acid cycle were upregulated in OE-S359A. Metabolomic analysis indicated corresponding changes in carbohydrate, amino acid and fatty acid contents in HMGS-OEs, and F-244, a specific inhibitor of HMGS, was applied successfully on tobacco to confirm these observations. Finally, the crystal structure of acetyl-CoA-liganded S359A revealed that improved activity of S359A likely resulted from a loss in hydrogen bonding between Ser359 and acyl-CoA, which is evident in wtBjHMGS1. This work suggests that regulation of plant growth by HMGS can influence the central metabolic pathways. Furthermore, this study demonstrates that the application of the HMGS-specific inhibitor (F-244) in tobacco represents an effective approach for studying the HMGS/MVA pathway.

Primary and secondary metabolites produced in Salvia miltiorrhiza hairy roots by an endophytic fungal elicitor from Mucor fragilis

Salvia miltiorrhiza is one of the most commonly used medicinal materials in China. In recent years, the quality of S. miltiorrhiza has attracted much attention. Biotic and abiotic elicitors are widely used in cultivation to improve the quality of medicinal plants. We isolated an endophytic fungus, Mucor fragilis, from S. miltiorrhiza. We compared the effects of endophytic fungal elicitors with those of yeast extract together with silver ion, widely used together as effective elicitors, on S. miltiorrhiza hairy roots. Seventeen primary metabolites (amino acids and fatty acids) and five secondary metabolites (diterpenoids and phenolic acids) were analyzed after elicitor treatment. The mycelium extract promoted the accumulation of salvianolic acid B, rosmarinic acid, stearic acid, and oleic acid in S. miltiorrhiza hairy roots. Additionally, qPCR revealed that elicitors affect the accumulation of primary and secondary metabolites by regulating the expression of key genes (SmAACT, SmGGPPS, and SmPAL). This is the first detection of both the primary and secondary metabolites of S. miltiorrhiza hairy roots, and the results of this work should help guide the quality control of S. miltiorrhiza. In addition, the findings confirm that Mucor fragilis functions as an effective endophytic fungal elicitor with excellent application prospect for cultivation of medicinal plants.