Transcriptomic Analyses Reveal the Role of Cytokinin and the Nodal Stem in Microtuber Sprouting in Potato (Solanum tuberosum L.).

In potatoes, tuber secondary growth, especially sprouting, deforms the tubers and severely lowers their commercial value. Tuber sprouting is induced by signal substances, such as gibberellin (GA), which are transported to the tuber from the plant body. The molecular mechanism underlying GA-induced sprouting remains ambiguous. Here, we tried to recreate tuber secondary growth using in vitro stemmed microtubers (MTs) (with the nodal stem attached) and MT halves (with the nodal stem entirely removed). Our experiments showed that GA alone could initiate the sprouting of stemmed microtubers; however, GA failed to initiate MT halves unless 6-benzyladenine, a synthetic cytokinin CK, was co-applied. Here, we analyzed the transcriptional profiles of sprouting buds using these in vitro MTs. RNA-seq analysis revealed a downregulation of cytokinin-activated signaling but an upregulation of the "Zeatin biosynthesis" pathway, as shown by increased expression of CYP735A, CISZOG, and UGT85A1 in sprouting buds; additionally, the upregulation of genes, such as IAA15, IAA22, and SAUR50, associated with auxin-activated signaling and one abscisic acid (ABA) negative regulator, PLY4, plays a vital role during sprouting growth. Our findings indicate that the role of the nodal stem is synonymous with CK in sprouting growth, suggesting that CK signaling and homeostasis are critical to supporting GA-induced sprouting. To effectively control tuber sprouting, more effort is required to be devoted to these critical genes.

Exogenous Gibberellin Treatment Enhances Melatonin Synthesis for Melatonin-Enriched Rice Production.

Melatonin production is induced by many abiotic and biotic stressors; it modulates the levels of many plant hormones and their signaling pathways. This study investigated the effects of plant hormones on melatonin synthesis. Melatonin synthesis in rice seedlings was significantly induced upon exogenous gibberellin 3 (GA3) treatment, while it was severely decreased by GA synthesis inhibitor paclobutrazol. In contrast, abscisic acid (ABA) strongly inhibited melatonin synthesis, whereas its inhibitor norflurazon (NF) induced melatonin synthesis. The observed GA-mediated increase in melatonin was closely associated with elevated expression levels of melatonin biosynthetic genes such as TDC3, T5H, and ASMT1; it was also associated with reduced expression levels of catabolic genes ASDAC and M2H. In a paddy field, the treatment of immature rice seeds with exogenous GA led to enhanced melatonin production in rice seeds; various transgenic rice plants downregulating a GA biosynthesis gene (GA3ox2) and a signaling gene (Gα) showed severely decreased melatonin levels, providing in vivo genetic evidence that GA has a positive effect on melatonin synthesis. This is the first study to report that GA is positively involved in melatonin synthesis in plants; GA treatment can be used to produce melatonin-rich seeds, vegetables, and fruits, which are beneficial for human health.

RNA-Binding Protein MAC5A Is Required for Gibberellin-Regulated Stamen Development.

The development of floral organs is coordinated by an elaborate network of homeotic genes, and gibberellin (GA) signaling is involved in floral organ development; however, the underlying molecular mechanisms remain elusive. In the present study, we found that MOS4-ASSOCIATED COMPLEX 5A (MAC5A), which is a protein containing an RNA-binding motif, was involved in the development of sepals, petals, and stamens; either the loss or gain of MAC5A function resulted in stamen malformation and a reduced seed set. The exogenous application of GA considerably exacerbated the defects in mac5a null mutants, including fewer stamens and male sterility. MAC5A was predominantly expressed in pollen grains and stamens, and overexpression of MAC5A affected the expression of homeotic genes such as APETALA1 (AP1), AP2, and AGAMOUS (AG). MAC5A may interact with RABBIT EARS (RBE), a repressor of AG expression in Arabidopsis flowers. The petal defect in rbe null mutants was at least partly rescued in mac5a rbe double mutants. These findings suggest that MAC5A is a novel factor that is required for the normal development of stamens and depends on the GA signaling pathway.

Shorter and more efficient pretreatment for germination of perilla mericarps.

Perilla (Perilla frutescens (L.) Britton) mericarps are known to undergo dormancy; however, this can be broken by sulfuric acid treatment and cold stratification. Cold stratification is thought to be the most effective treatment and is customarily performed for 2 weeks to induce germination of perilla mericarps. However, this procedure requires an additional 2 weeks before sowing and cultivation, thereby decreasing cultivation efficiency. To address this problem, germination experiments were conducted in this study in order to identify a shorter and more efficient pretreatment strategy for germination of perilla mericarps. Pretreatment with sulfuric acid (10 min versus 1 min) and gibberellin (8 h and 1 h versus 5 min, at a rate of 100 versus 10 ppm) were performed using mericarps from pure strains of perilla. As a result, sulfuric acid treatment tended to reduce the germination rate, while gibberellin treatment resulted in an equivalent or similar germination rate as cold stratification. Gibberellin treatment was also found to be effective in mericarps with a relatively old harvest date and low germination energy. Considering the convenience and safety of the treatment process as well as the results of the germination experiments, these findings suggest that a short period of gibberellin treatment could help shorten the process of perilla cultivation.

Genome-Wide Identification and Characterization of KNOTTED-Like Homeobox (KNOX) Homologs in Garlic (Allium sativum L.) and Their Expression Profilings Responding to Exogenous Cytokinin and Gibberellin.

Garlic (Allium sativum L.) is an important vegetable and is cultivated and consumed worldwide for its economic and medicinal values. Garlic cloves, the major reproductive and edible organs, are derived from the axillary meristems. KNOTTED-like homeobox (KNOX) proteins, such as SHOOT MERISTEM-LESS (STM), play important roles in axillary meristem formation and development. However, the KNOX proteins in garlic are still poorly known. Here, 10 AsKNOX genes, scattered on 5 of the 8 chromosomes, were genome-wide identified and characterized based on the newly released garlic genome. The typical conserved domains of KNOX proteins were owned by all these 10 AsKNOX homologs, which were divided into two Classes (Class I and Class II) based on the phylogenetic analysis. Prediction and verification of the subcellular localizations revealed the diverse subcellular localization of these 10 AsKNOX proteins. Cis-element prediction, tissue expression analysis, and expression profilings in responding to exogenous GA3 and 6-BA showed the potential involvement of AsKNOX genes in the gibberellin and cytokinin signaling pathways. Overall, the results of this work provided a better understanding of AsKNOX genes in garlic and laid an important foundation for their further functional studies.

Gibberellin Signaling Promotes the Secondary Growth of Storage Roots in Panax ginseng.

Gibberellins (GAs) are an important group of phytohormones associated with diverse growth and developmental processes, including cell elongation, seed germination, and secondary growth. Recent genomic and genetic analyses have advanced our knowledge of GA signaling pathways and related genes in model plant species. However, functional genomics analyses of GA signaling pathways in Panax ginseng, a perennial herb, have rarely been carried out, despite its well-known economical and medicinal importance. Here, we conducted functional characterization of GA receptors and investigated their physiological roles in the secondary growth of P. ginseng storage roots. We found that the physiological and genetic functions of P. ginseng gibberellin-insensitive dwarf1s (PgGID1s) have been evolutionarily conserved. Additionally, the essential domains and residues in the primary protein structure for interaction with active GAs and DELLA proteins are well-conserved. Overexpression of PgGID1s in Arabidopsis completely restored the GA deficient phenotype of the Arabidopsis gid1a gid1c (atgid1a/c) double mutant. Exogenous GA treatment greatly enhanced the secondary growth of tap roots; however, paclobutrazol (PCZ), a GA biosynthetic inhibitor, reduced root growth in P. ginseng. Transcriptome profiling of P. ginseng roots revealed that GA-induced root secondary growth is closely associated with cell wall biogenesis, the cell cycle, the jasmonic acid (JA) response, and nitrate assimilation, suggesting that a transcriptional network regulate root secondary growth in P. ginseng. These results provide novel insights into the mechanism controlling secondary root growth in P. ginseng.

Gibberellin Increases the Bud Yield and Theanine Accumulation in Camellia sinensis (L.) Kuntze.

Tea (Camellia sinensis) is one of the most important cash crops in the world. Theanine, as an important amino acid component in tea, is a key quality index for excellent tea quality and high economic value. People increase theanine accumulation in tea mainly through the application of nitrogen fertilizer, shading and pruning. However, these methods are not effective. In this study, we treated tea buds with a 100 µM solution of GA3 containing 1‰ tween-20, investigated the effects of GA3 on theanine accumulation, bud yield, chlorophyll fluorescence parameters and expression level of theanine biosynthesis pathway genes in tea plant by qPCR, LC-MS/MS etc. Results showed that change trends of theanine and GA3 was extremely positively correlated with each other. Exogenous GA3 upregulated the expression level of theanine biosynthesis pathway genes, caused an increase of theanine content (mg·g-1) by 27% in tea leaves compared with Mock, and accelerated the germination of buds and elongation of shoots, which lead to a significant increase of tea yield by 56% (w/w). Moreover, the decrease of chlorophyll contents, photochemical quenching coefficient (qP) and relative electron transport rate (rETR) under GA3 treatment suggested that GA3 reduced photosynthesis in the tender tea leaves, indicating that the decline of carbon assimilation in tea plants was conducive to the nitrogen metabolism, and it was beneficial to the accumulation of theanine. This study provided a new technical and theoretical support for the precise control of tea quality components and phenophase.

Rice Non-Specific Phospholipase C6 Is Involved in Mesocotyl Elongation.

Mesocotyl elongation of rice is crucial for seedlings pushing out of deep soil. The underlying mechanisms of phospholipid signaling in mesocotyl growth of rice are elusive. Here we report that the rice non-specific phospholipase C6 (OsNPC6) is involved in mesocotyl elongation. Our results indicated that all five OsNPCs (OsNPC1, OsNPC2, OsNPC3, OsNPC4 and OsNPC6) hydrolyzed the substrate phosphatidylcholine to phosphocholine (PCho), and all of them showed plasma membrane localization. Overexpression (OE) of OsNPC6 produced plants with shorter mesocotyls compared to those of Nipponbare and npc6 mutants. Although the mesocotyl growth of npc6 mutants was not much affected without gibberellic acid (GA)3, it was obviously elongated by treatment with GA. Upon GA3 treatment, SLENDER RICE1 (SLR1), the DELLA protein of GA signaling, was drastically increased in OE plants; by contrast, the level of SLR1 was found decreased in npc6 mutants. The GA-enhanced mesocotyl elongation and the GA-impaired SLR1 level in npc6 mutants were attenuated by the supplementation of PCho. Further analysis indicated that the GA-induced expression of phospho-base N-methyltransferase 1 in npc6 mutants was significantly weakened by the addition of PCho. In summary, our results suggest that OsNPC6 is involved in mesocotyl development via modulation of PCho in rice.

Transcriptome dynamic landscape underlying the improvement of maize lodging resistance under coronatine treatment.

BACKGROUND: Lodging is one of the important factors causing maize yield. Plant height is an important factor in determining plant architecture in maize (Zea mays L.), which is closely related to lodging resistance under high planting density. Coronatine (COR), which is a phytotoxin and produced by the pathogen Pseudomonas syringae, is a functional and structural analogue of jasmonic acid (JA). RESULTS: In this study, we found COR, as a new plant growth regulator, could effectively reduce plant height and ear height of both hybrids (ZD958 and XY335) and inbred (B73) maize by inhibiting internode growth during elongation, thus improve maize lodging resistance. To study gene expression changes in internode after COR treatment, we collected spatio-temporal transcriptome of inbred B73 internode under normal condition and COR treatment, including the three different regions of internode (fixed, meristem and elongation regions) at three different developmental stages. The gene expression levels of the three regions at normal condition were described and then compared with that upon COR treatment. In total, 8605 COR-responsive genes (COR-RGs) were found, consist of 802 genes specifically expressed in internode. For these COR-RGs, 614, 870, 2123 of which showed expression changes in only fixed, meristem and elongation region, respectively. Both the number and function were significantly changed for COR-RGs identified in different regions, indicating genes with different functions were regulated at the three regions. Besides, we found more than 80% genes of gibberellin and jasmonic acid were changed under COR treatment. CONCLUSIONS: These data provide a gene expression profiling in different regions of internode development and molecular mechanism of COR affecting internode elongation. A putative schematic of the internode response to COR treatment is proposed which shows the basic process of COR affecting internode elongation. This research provides a useful resource for studying maize internode development and improves our understanding of the COR regulation mechanism based on plant height.

Exogenous phytohormone application and transcriptome analysis of Mikania micrantha provides insights for a potential control strategy.

Effective and complete control of the invasive weed Mikania micrantha is required to avoid increasing damages. We exogenously applied indole 3-acetic acid (IAA), gibberellin (GA), and N-(2-Chloro-4-pyridyl)-N'-phenylurea (CPPU), and their combinations i.e. IAA + CPPU (IC), GA + CPPU (GC), and GA + IAA + CPPU (GIC), at 5, 10, 25, 50, and 75 ppm against distilled water as a control (CK), to examine their effects on the weed. The increasing concentrations of these hormones when applied alone or in combination were fatal to M. micrantha and led towards the death of inflorescences and/or florets. CPPU and GIC were found as the most effective phytohormones. Transcriptome analysis revealed differential regulation of genes in auxin, cytokinin, gibberellin and abscisic acid signaling pathways, suggesting their role in the prohibition of axillary bud differentiation. Collectively, CPPU and GIC at a high concentration (75 ppm) could be used as a control measure to protect forests and other lands from the invasion of M. micrantha.

smi-miR396b targeted SmGRFs, SmHDT1, and SmMYB37/4 synergistically regulates cell growth and active ingredient accumulation in Salvia miltiorrhiza hairy roots.

KEY MESSAGE: MIR396b had been cloned and overexpressed in Salvia miltiorrhiza hairy roots. MiR396b targets SmGRFs, SmHDT1, and SmMYB37/4 to regulate cell growth and secondary metabolism in S. miltiorrhiza hairy roots. Danshen (Salvia miltiorrhiza Bunge) is a valuable medicinal herb with two kinds of clinically used natural products, salvianolic acids and tanshinones. miR396 is a conserved microRNA and plays extensive roles in plants. However, it is still unclear how miR396 works in S. miltiorrhiza. In this study, an smi-MIR396b has been cloned from S. miltiorrhiza. Overexpression of miR396b in danshen hairy roots inhibited hairy root growth, reduced salvianolic acid concentration, but enhanced tanshinone accumulation, resulting in the biomass and total salvianolic acids respectively reduced to 55.5 and 72.1% of the control and total tanshinones increased up to 1.91-fold of the control. Applied degradome sequencing, 5'RLM-RACE, and qRT-PCR, 13 targets for miR396b were identified including seven conserved SmGRF1-7 and six novel ones. Comparative transcriptomics and microRNomics analysis together with qRT-PCR results confirmed that miR396b targets SmGRFs, SmHDT1, and SmMYB37/4 to mediate the phytohormone, especially gibberellin signaling pathways and consequentially resulted in the phenotype variation of miR396b-OE hairy roots. Furthermore, miR396b could be activated by methyl jasmonate, abscisic acid, gibberellin, salt, and drought stresses. The findings in this study indicated that smi-miR396b acts as an upstream and central regulator in cell growth and the biosynthesis of tanshinones and salvianolic acids, shedding light on the coordinated regulation of plant growth and biosynthesis of active ingredients in S. miltiorrhiza.

Gibberellic acid-induced generation of hydrogen sulfide alleviates boron toxicity in tomato (Solanum lycopersicum L.) plants.

It was aimed to examine the role of gibberellic acid (GA) induced production of hydrogen sulfide (H2S) in alleviating boron toxicity (BT) in tomato plants. Two weeks after germination, a solution consisting of GA (100 mg L-1) was sprayed once a week for 14 days to the leaves of cv. "SC 2121" of tomato under BT stress (BT; 2.0 mM). Before starting BT treatment, half of the seedlings were retained in a solution containing a scavenger of H2S, 0.1 mM hypotaurine (HT), for 12 h. Boron toxicity led to a substantial decrease in dry biomass, leaf water potential, leaf relative water content, chlorophyll a, chlorophyll b, photosynthetic quantum yield (Fv/Fm), ascorbate (AsA) and glutathione (GSH) in the tomato plants. However, it increased the accumulation of hydrogen peroxide (H2O2), malondialdehyde (MDA), endogenous hydrogen sulfide (H2S), and free proline as well as the activities of catalase, superoxide dismutase and peroxidase. The supplementation of GA mitigated BT by increasing the endogenous H2S, and leaf Ca2+ and K+, and reducing the contents of leaf H2O2, MDA, and B as well as membrane leakage. GA-induced BT tolerance was further enhanced by the supplementation of sodium hydrosulfide (0.2 mM NaHS), an H2S donor. A scavenger of H2S, hypotaurine (0.1 mM HT) was supplied along with the GA and NaHS treatments to assess if H2S was involved in GA-induced BT tolerance of tomato plants. Addition of HT reversed the beneficial effect of GA on oxidative stress and antioxidant defence system by reducing the endogenous H2S without changing L-DES activity, suggesting that H2S participates in GA-induced tolerance to BT of tomato plants.

Different Classes of Phytohormones Act Synergistically to Enhance the Growth, Lipid and DHA Biosynthetic Capacity of Aurantiochytrium sp. SW1.

In the present study, the impact of eight phytohormones from six different classes on the growth, lipid and docosahexaenoic acid (DHA) biosynthetic capacity of Aurantiochytrium sp. SW1 (SW1) was evaluated. Kinetin (KIN), jasmonic acid (JA) and gibberellic acid (GA) significantly enhanced the growth and DHA production of SW1 by 16%-28% and 66%-84% in comparison to the control, respectively. The synergistic effect of these three phytohormones, evaluated by the response surface methodology (RSM), showed that a combination of 3.6 mg/L GA, 2.0 mg/L KIN and 20.0 mg/L JA further increased the growth and DHA production of SW1 by 16% to 28% and 22% to 36%, respectively, in comparison to the individual supplementation. The synergistic effect of these phytohormones was also shown to be time-dependent, where feeding at 24 h of cultivation led to 15%, 26% and 35% further increments in the biomass, lipid and DHA production in comparison to that of 0 h, respectively. The determination of stress markers, antioxidant enzymes and key enzymes involved in fatty acid biosynthesis aided to elucidate the potential mechanism underlying the improvement of growth and DHA production by SW1 at various times of feeding. Supplementation with the phytohormones at 24 h exhibited the maximum impact on reducing the level of reactive oxygen species (ROS) and malondialdehyde (MDA), as well as augmented the antioxidants (superoxide dismutase and catalase) and key metabolic enzymes involved in lipogenesis (malic, glucose-6-phosphate dehydrogenase and ATP-citrate lyase) in comparison to the control and other time points. This study signifies the potential application of phytohormones for improving the growth, lipid and DHA production in Aurantiochytrium spp.

The effectiveness of light emitting diodes on shoot regeneration in vitro from shoot tip tissues of Limnophila aromatica (Lamk.) Merr. and Rotala rotundifolia (Buch-Ham. ex Roxb) Koehne.

Light emitting diodes (LEDs) have become a promising technology for agriculture and horticulture. I investigated the effects of white (W), red (R) and blue (B) LED lights on the propagation of Limnophila aromatica (Lamk.) Merr. and Rotala rotundifolia (Buch-Ham. ex Roxb) Koehne using tissue culture. The shoot tip explants of L. aromatica and R. rotundifolia under different light environments were cultured in Murashige and Skoog (MS) basic nutrient medium with 6-benzylaminopurine (BAP) (0.05, 0.10 and 0.20 mg/l) and gibberellic acid (GA3) 0.25 mg/l) + kinetin (KIN) 0.25, 0.50 and 0.75 mg/l. The explants grown under combinations of white, red and blue LEDs were more effective for propagation of the plants in vitro. In L. aromatica, the maximum number of shoots/explant and the longest shoot lengths were obtained using the combination of white, red and blue LED lights in a 1:2:1 ratio in MS medium supplemented with 0.10 and 0.20 mg/l BAP. In R. rotundifolia, the maximum shoots/explant and shoot lengths were obtained in the explants using the combination of white, red and blue LED lights in a 1:2:1 ratio in the MS culture media fortified with 0.25 mg/l GA3 + 0.25 and 0.75 mg/l KIN. After the regenerated shoots were rooted, they were adapted successfully to external conditions. LEDs have significant advantages over fluorescent lights.

An Efficient Strategy for Enhancement of Bioactive Compounds in the Fruit Body of Caterpillar Medicinal Mushroom, Cordyceps militaris (Ascomycetes), by Spraying Biotic Elicitors.

Cordyceps militaris is a mushroom species with high nutritive and medicinal values based on diverse bioactive metabolites. The contents of bioactive ingredients are indicative of the quality of commercially available fruit body of this fungus. Although the application of biotic elicitors has been an efficient strategy to induce the accumulation of valuable bioactive compounds in vivo, related research in C. militaris is rarely reported. In this study, five biotic elicitors in different concentrations (0.05, 0.5, 1, and 2 mg/mL), including chitosan (CHT), 2,4-dichlorophenoxyacetic acid (2,4-D), methyl jasmonate (MeJA), gibberellic acid (GA), and triacontanol (TRIA), were first introduced to enhance the production of 10 kinds of major bioactive components in the fruit body of C. militaris. Results showed that the effect of biotic elicitors on bioactive compounds in the fruit body of C. militaris was elicitor-specific and concentration-dependent. Overall, 1 mg/L CHT was considered the most favorable for the production of 10 bioactive ingredients in C. militaris fruit body, which could increase the content of protein, polysaccharides, polyphenol, triterpenoids, flavonoids, cordyceps acid, cordycepin, and anthocyanins by 20.38-, 1.41-, 0.7-, 0.47-, 11.90-, 1.09-, 0.34-, and 2.64-fold, respectively, compared with the control. The results of this study would provide an efficient strategy for the production of a superior quality fruit body of and contribute to further elucidation of the effects of biotic elicitors on metabolite accumulation in C. militaris.

Dual Activities of Plant cGMP-Dependent Protein Kinase and Its Roles in Gibberellin Signaling and Salt Stress.

Cyclic GMP (cGMP) is an important regulator in eukaryotes, and cGMP-dependent protein kinase (PKG) plays a key role in perceiving cellular cGMP in diverse physiological processes in animals. However, the molecular identity, property, and function of PKG in plants remain elusive. In this study, we have identified PKG from plants and characterized its role in mediating the gibberellin (GA) response in rice (Oryza sativa). PKGs from plants are structurally unique with an additional type 2C protein phosphatase domain. Rice PKG possesses both protein kinase and phosphatase activities, and cGMP stimulates its kinase activity but inhibits its phosphatase activity. One of PKG's targets is GAMYB, a transcription factor in GA signaling, and the dual activities of PKG catalyze the reversible phosphorylation of GAMYB at Ser6 and modulate the nucleocytoplasmic distribution of GAMYB in response to GA. Loss of PKG impeded the nuclear localization of GAMYB and abolished GAMYB function in the GA response, leading to defects in GA-induced seed germination, internode elongation, and pollen viability. In addition to GAMYB, PKG has multiple potential targets and thus has broad effects, particularly in the salt stress response.

Integrated metabolomics signature for assessing the longevity of Panax ginseng seeds.

BACKGROUND: Panax ginseng seeds have strong dormancy and a prolonged germination period in comparison to other seeds; thus, it is a great challenge to propagate ginseng. Seed longevity is closely associated with germination rate and viability, so we assumed that if a seed loses its viability, specific metabolic alterations regarding plant growth factors might occur. In this study, we divided ginseng seeds into normal and accelerated-aging groups. Both groups were treated with gibberellic acid, which is one of the most important plant-growth regulators. Afterward, gas chromatography-mass spectrometry (GC-MS) was used to analyze the samples, to identify the metabolic alterations between the two groups. RESULTS: Forty-four endogenous metabolites in normal and accelerated aging groups were putatively identified. To determine the differential significance of these metabolites, t-tests and fold-change analysis were conducted followed by principal component analysis and partial least-squares discriminant analysis to determine the metabolites that showed distinct responses between the groups. Among the differentially expressed metabolites (P value < 0.05 and FDR < 0.1), nine metabolites were selected as potential biomarker candidates for the prediction of seed longevity. CONCLUSION: Nine metabolites related to ginseng seed longevity were identified by comparing metabolomes. Our findings suggest that ginseng propagation can be facilitated by the regulation of these distinctive metabolic features of the seeds. © 2019 Society of Chemical Industry.

Transcriptomic and Metabolic Insights into the Distinctive Effects of Exogenous Melatonin and Gibberellin on Terpenoid Synthesis and Plant Hormone Signal Transduction Pathway in Camellia sinensis.

Melatonin and gibberellin are bioactive molecules in plants. In the present study, the role of exogenous melatonin (MT) and gibberellin (GA) in the tea plant was explored by transcriptome and metabolic analysis. Results showed that the growth of tea plant was enhanced by MT treatment. The pathways of terpenoid synthesis and plant-pathogen interaction were significantly strengthened, combined with the upregulation of LRR-RLK and transcription factors which contributed to the growth of tea plant. The internode elongation and leaf enlargement were hastened by GA treatment. Significantly modulated expression occurred in the plant hormonal signal transduction, complemented by the upregulation of phenylpropanoid biosynthesis and expansins to achieve growth acceleration, whereas the flavonoid synthesis was repressed in GA treatment. Therefore, the distinctive effect of MT and GA treatment on tea plant was different. The MT exhibited significant promotion in terpenoid synthesis, especially, TPS14 and TPS1. GA was prominent in coordinated regulation of plant hormonal signal transduction.

Effects of (S)-Carvone and Gibberellin on Sugar Accumulation in Potatoes during Low Temperature Storage.

Potato tubers (Solanum tuberosum L.) are usually stored at low temperature, which can suppress sprouting and control the occurrence of diseases. However, low temperatures lead potatoes to easily suffer from cold-induced sweetening (CIS), which has a negative effect on food processing. The aim of this research was to investigate potential treatments on controlling CIS in potatoes during postharvest storage. "Atlantic" potatoes were treated with gibberellin and (S)-carvone, respectively, and stored at 4 °C for 90 days. The results showed that gibberellin can significantly accelerate sprouting and sugar accumulation by regulating expressions of ADP-glucose pyrophosphorylase (AGPase), granule-bound starch synthase (GBSS), ß-amylase (BAM1/2), UDP-glucose pyrophosphorylase (UGPase) and invertase inhibitor (INH1/2) genes. The opposite effects were found in the (S)-carvone treatment group, where CIS was inhibited by modulation of the expressions of GBSS and INH1/2 genes. In summary, gibberellin treatment can promote sugar accumulation while (S)-carvone treatment has some effects on alleviating sugar accumulation. Thus, (S)-carvone can be considered as a potential inhibitor of some of the sugars which are vital in controlling CIS in potatoes. However, the chemical concentration, treatment time, and also the treatment method needs to be optimized before industrial application.

The expression of monoterpene synthase genes and their respective end products are affected by gibberellic acid in Thymus vulgaris.

Thymus vulgaris L. (Lamiaceae), a well-known aromatic medicinal herb, has many important essential constituents in its oil, including γ-terpinene, carvacrol, thymol, and p-cymene. Gibberellins comprise hundreds of components, which regulate several various growths and underlying developmental processes, such as cell division and elongation, shoot elongation, seed germination, and gene expression. In this study, we investigated the influence of sprayed gibberellic acid (GA3) treatments on the internode length, leaf morphology, length of new shoot, expression of monoterpene synthase genes and monoterpenes content during two plant growth stages. Our results showed that increasing of internode length was a clear effect of GA3 that was varied with internode position. The results also showed that all internodes displayed a dramatic increase in the highest concentration of GA3. Also, the foliar application of GA3 resulted in not only an increased expression level of monoterpene synthase genes, but also the improved production of a monoterpene, especially in the moderate concentration of GA3 that they were up-regulated. In the lowest GA3 concentrations, relative expression levels were similar or lower than the control plants and a notable downregulation in those genes was observed in the application of the highest concentration of GA3 rather than the moderate concentrations. Overall, the expression of two out of five monoterpene synthase genes, TPS and CYP71D181, showed a correlation with the level of γ-terpinene and carvacrol, respectively, indicating that they are regulated at the transcriptional levels.