Transcriptomic and Metabolomic Analyses Reveals That Exogenous Methyl Jasmonate Regulates Galanthamine Biosynthesis in Lycoris longituba Seedlings

The Amaryllidaceae alkaloid galanthamine (Gal) in Lycoris longituba is a secondary metabolite that has been used to treat Alzheimer’s disease. Plant secondary metabolism is affected by methyl jasmonate (MeJA) exposure, although the regulatory mechanisms of MeJA on L. longituba seedlings remains largely unknown. In the present study, 75, 150, and 300 μM MeJA were used as treatments on L. longituba seedlings for 7, 14, 21, and 28 days, while 0 μM MeJA was used as the control (MJ-0). The effect of exogenous MeJA on Gal synthesis in L. longituba was then investigated using transcriptomic sequencing and metabolite profiling via GC-MS and LC-MS analysis. Galanthamine (Gal), lycorine (Lyc), and lycoramine (Lycm) abundances were 2. 71-, 2. 01-, and 2.85-fold higher in 75 μM MeJA (MJ-75) treatment plants compared to MJ-0 treatment plants after 7 days of cultivation. Transcriptomic analysis further showed that MJ-75 treatment significantly induced the expression of norbelladine synthase (NBS) and norbelladine 4′-O-methyltransferase (OMT), which are involved in the Gal biosynthesis pathway. In addition, increased expression was observed in MJ-75 treatment plants for genes in the JA synthesis and JA signaling pathways including those of allene oxide cyclase (AOC), 12-oxo-phytodienoic acid reductase (OPR), jasmonic acid amino acid synthase (JAR), and transcription factor MYC. The L. longituba tyrosine decarboxylase (LlTYDC) enzyme was identified and proposed to be involved in the Gal biosynthetic pathway. Metabolomics results demonstrated that the accumulation of Amaryllidaceae alkaloids, and especially alkaloids in the Gal biosynthesis pathway, could be induced by MJ-75 treatment. Interestingly, metabolites in the JA synthesis pathway were also affected by MeJA treatment. Overall, this multi-omics study suggests that both the JA synthesis/JA signaling and Gal biosynthesis pathways were affected by exogenous MeJA treatment. This comprehensive study of gene expression and metabolite contents can help us better understand the molecular mechanisms underlying MeJA-mediated Gal biosynthesis in L. longituba.

Comparative Proteomic Analysis of Dipsacus asperoides Roots from Different Habitats in China

Dipsacus asperoides is a kind of Chinese herbal medicine with beneficial health properties. To date, the quality of D. asperoides from different habitats has shown significant differences. However, the molecular differences in D. asperoides from different habitats are still unknown. The aim of this study was to investigate the differences in protein levels of D. asperoides from different habitats. Isobaric tags for relative and absolute quantification (iTRAQ) and 2DLC/MS/MS were used to detect statistically significant changes in D. asperoides from different habitats. Through proteomic analysis, a total of 2149 proteins were identified, of which 42 important differentially expressed proteins were screened. Through in-depth analysis of differential proteins, the protein metabolism energy and carbohydrate metabolism of D. asperoides from Hubei Province were strong, but their antioxidant capacity was weak. We found that three proteins, UTP-glucose-1-phosphate uridylyltransferase, allene oxide cyclase, and isopentyl diphosphate isomerase 2, may be the key proteins involved in dipsacus saponin VI synthesis. Eight proteins were found in D. asperoides in response to environmental stress from different habitats. Quantitative real-time PCR analysis confirmed the accuracy and authenticity of the proteomic analysis. The results of this study may provide the basic information for exploring the cause of differences in secondary metabolites in different habitats of D. asperoides and the protein mechanism governing differences in quality.

Identification and Expression Analysis of Two allene oxide cyclase (AOC) Genes in Watermelon

Allene oxide cyclase (AOC, EC 5.3.99.6) catalyzes the most important step in the jasmonic acid (JA) biosynthetic pathway and mediates plant defense response to a wide range of biotic and abiotic stresses. In this study, two AOC genes were identified from watermelon. Sequence analysis revealed that each of ClAOC1 and ClAOC2 contained an allene oxide cyclase domain and comprised eight highly conserved β-strands, which are the typical characteristics of AOC proteins. Phylogenetic analysis showed that ClAOC1 and ClAOC2 were clustered together with AOCs from dicotyledon, with the closest relationships with JcAOC from Jatropha curcas and Ljaoc1 from Lotus japonicus. Different intron numbers were observed in ClAOC1 and ClAOC2, which may result in their functional divergence. qRT-PCR analysis revealed that ClAOC1 and ClAOC2 have specific and complex expression patterns in multiple organs and under hormone treatments. Both ClAOC1 and ClAOC2 displayed the highest transcriptional levels in stem apex and fruit and exhibited relatively lower expression in stem. JA, salicylic acid (SA), and ethylene (ET) could enhance the expression of ClAOC1 and ClAOC2, particularly that of ClAOC2. Red light could induce the expression of ClAOC2 in root-knot nematode infected leaf and root of watermelon, indicating that ClAOC2 might play a primary role in red light-induced resistance against root-knot nematodes through JA signal pathway. These findings provide important information for further research on AOC genes in watermelon.

Identification of Jasmonic Acid Biosynthetic Genes in Sweet Cherry and Expression Analysis in Four Ancient Varieties from Tuscany

Sweet cherries are non-climacteric fruits whose early development is characterized by high levels of the phytohormone jasmonic acid (JA). Important parameters, such as firmness and susceptibility to cracking, can be affected by pre- and postharvest treatments of sweet cherries with JA. Despite the impact of JA on sweet cherry development and fruit characteristics, there are no studies (to the best of our knowledge) identifying the genes involved in the JA biosynthetic pathway in this species. We herein identify the sweet cherry members of the lipoxygenase family (13-LOX); allene oxide synthase, allene oxide cyclase and 12-oxo-phytodienoic acid reductase 3, as well as genes encoding the transcriptional master regulator MYC2. We analyze their expression pattern in four non-commercial Tuscan varieties (‘Carlotta’, ‘Maggiola’, ‘Morellona’, ‘Crognola’) having different levels of bioactives (namely phenolics). The highest differences are found in two genes encoding 13-LOX in the variety ‘Maggiola’ and one MYC2 isoform in ‘Morellona’. No statistically-significant variations are instead present in the allene oxide synthase, allene oxide cyclase and 12-oxo-phytodienoic acid reductase 3. Our data pave the way to follow-up studies on the JA signaling pathway in these ancient varieties, for example in relation to development and post-harvest storage.