Exogenous methyl jasmonate prevents necrosis caused by mechanical wounding and increases terpenoid biosynthesis in Panax ginseng

Upon mechanical wounding, plants locally induce necrosis, accumulate methyl jasmonate (MeJA) and acquire systemic resistance in nearby tissues. One-month-old in vitro grown Panax ginseng seedlings were treated with either 50 µM MeJA or mechanical wounding alone or a combination of both, to evaluate jasmonic acid (JA) signaling and terpene biosynthetic pathway genes along with terpenoid accumulation. After MeJA treatment, JA pathway genes, such as lipoxygenase (PgLOX), hydrogen peroxidase lyase (PgHPL), allene oxide synthase (PgAOS), and allene oxide cyclase (PgAOC1), and terpene pathway genes, such as isopentenyl diphosphate isomerase (PgIPP) and farnesyl diphosphate synthase (PgFPS), were highly expressed and resulted in the accumulation of mono- and sesquiterpenes. During mechanical wounding, PgLOX expression was induced relatively late after 72 h of treatment, however PgAOC1 was not induced. This resulted in decreased production of MeJA that in turn may have lowered terpenoid production. In contrast, wounding + MeJA treatment increased PgAOC1 and PgLOX gene expression earlier after 6 h and slowly promoted the production of mono- and sesquiterpenes. Furthermore, we monitored the effect of MeJA upon wounding in in vitro grown 1-month-old seedlings treated with MeJA + wounding. These result demonstrated that exogenous MeJA is able to promote recovery from the wounding effect by functioning as a long distance signal. Additionally, these results suggest that exogenous MeJA supplied at the time of mechanical wounding prevents necrosis in the ginseng leaves by increasing the production of terpenoids

Isolation and characterization of Panax ginseng geranylgeranyl-diphosphate synthase genes responding to drought stress

Geranylgeranyl-diphosphate synthases (GGDPS) catalyze branch point enzymatic reactions producing isoprenoid-derived products which are necessary for plant growth and responses to a wide range of biotic and abiotic stresses. In our study, full length geranylgeranyl-diphosphate synthase 1 (PgGGDPS1) and 2 (PgGGDPS2) cDNA were isolated and characterized from the flower of Panax ginseng and 4-year old P. ginseng cv. Gumpoong. The cDNA had open reading frame of 1032 and 1116 bp with a deduced amino acid sequence of 343 and 371 residues for GGDPS1 and GGDPS2, respectively. The calculated molecular mass of GGDPS1 and GGDPS2 were approximately 37.66 and 40.21 kDa with a predicated isoelectric point of 5.32 and 6.23 and predicted localization of plastid. A GenBank Blast X search revealed that the deduced amino acid of PgGGDPS1 shared a high degree of homology with GGDPS from Panax notoginseng. The transcription pattern of GGDPS genes was different at various developmental stages. Both GGDPS genes were highly expressed in aerial parts of the plant, especially in rapidly growing tissues such as 4-year old flower and stem tissues. Transcript level of PgGGDPS1 was differentially induced in ginseng not only during Pseudomonas syringae pv tomato infection but also after exposure to abiotic stresses. Our results suggested that the induction of GGDPS genes specifically PgGGDPS1 by drought stress may affect chlorophyll levels, intracellular GA content and accumulation of carotenoids as the precursor for higher production of ABA and possibly stomatal closure as the barrier for water loss

Molecular characterization of lipoxygenase genes and their expression analysis against biotic and abiotic stresses in Panax ginseng

Lipoxygenase (LOX) belongs to a family of non-heme-iron-containing fatty acid dioxygenases that are widely distributed in plants and animals. LOX involved in the synthesis of jasmonic acid and six-carbon (C6) volatiles which is necessary for plant growth and responses to a wide range of biotic and abiotic stresses. We have isolated and characterized LOX cDNA clones from Panax ginseng Meyer. From their deduced amino acid sequences, two diverse classes of 9-LOX (LOX1, LOX2, and LOX3) and 13-LOX (LOX4, LOX5) are defined in P. ginseng. A GenBank Blast X search revealed that the deduced amino acid of PgLOXs share a high degree of homology with LOX from other plants and mammals especially in three distinct motifs; motif1 harboring iron binding regions, motif2 and motif3. Chloroplast localization was predicted for PgLOX5. PgLOXs displayed organ-specific expression, highly expressed in aerial parts of the plant such as 3-year old flower, stem and leaf tissues. PgLOXs mRNAs were elevated strongly by bacterial infection. Expression of PgLOXs was differentially induced in ginseng not only by mechanical damage and methyl jasmonate but also after exposure to withholding water. Ginseng 13-LOXs positively respond to wounding that may involve in production of C6 volatiles and jasmonic acid at the wounded sites. However, the higher expression of PgLOX3 by water deficit and 82 % of the nucleotide sequence identity with the EST from severe drought-stressed leaves of Populus (CU229089.1) at +6371 bp downstream of PgLOX3 genomic DNA structure can suggest drought tolerance role for PgLOX3. Ginseng LOX genes have different expression pattern which may suggest different specific function against various environmental stresses

Exogenous methyl jasmonate prevents necrosis caused by mechanical wounding and increases terpenoid biosynthesis in Panax ginseng

Upon mechanical wounding, plants locally induce necrosis, accumulate methyl jasmonate (MeJA) and acquire systemic resistance in nearby tissues. One-month-old in vitro grown Panax ginseng seedlings were treated with either 50 µM MeJA or mechanical wounding alone or a combination of both, to evaluate jasmonic acid (JA) signaling and terpene biosynthetic pathway genes along with terpenoid accumulation. After MeJA treatment, JA pathway genes, such as lipoxygenase (PgLOX), hydrogen peroxidase lyase (PgHPL), allene oxide synthase (PgAOS), and allene oxide cyclase (PgAOC1), and terpene pathway genes, such as isopentenyl diphosphate isomerase (PgIPP) and farnesyl diphosphate synthase (PgFPS), were highly expressed and resulted in the accumulation of mono- and sesquiterpenes. During mechanical wounding, PgLOX expression was induced relatively late after 72 h of treatment, however PgAOC1 was not induced. This resulted in decreased production of MeJA that in turn may have lowered terpenoid production. In contrast, wounding + MeJA treatment increased PgAOC1 and PgLOX gene expression earlier after 6 h and slowly promoted the production of mono- and sesquiterpenes. Furthermore, we monitored the effect of MeJA upon wounding in in vitro grown 1-month-old seedlings treated with MeJA + wounding. These result demonstrated that exogenous MeJA is able to promote recovery from the wounding effect by functioning as a long distance signal. Additionally, these results suggest that exogenous MeJA supplied at the time of mechanical wounding prevents necrosis in the ginseng leaves by increasing the production of terpenoids