Persicaria minor is one of the native aromatic plants in Malaysia and widely used in traditional foods and medicines. Previous studies have shown that treatment of P. minor with jasmonic acid upregulated genes involved in the secondary metabolites production and also gene encoding an F-box protein named PmFbox-1. It is known that F-box proteins play important roles in gene expression regulatory. However, the function of PmF-box1 protein is still unknown. In this study, the full length cDNA sequence of PmF-box1, with NCBI accession number JQ429325, consisting of 2768 bp was isolated followed by characterization of the deduced protein sequence of 487 amino acids. The putative F-box protein belongs to Kelch repeat-containing F-box protein family (KFB) and has a moderate level of homology with other F-box proteins from different organisms, showing a maximum identity score of 60 % with an F-box motif and two conserved kelch repeat motifs. Time course semi-quantitative reverse-transcriptase PCR gel image analyses showed that PmF-box1 was induced after JA treatment, indicating that PmF-box1 is a JA inducible gene. PmF-box1 also differentially expressed in different tissues after treatment with JA, indicating a spatial regulation of its activity. Interestingly, there was high correlation in the expression pattern between PmF-box1 and PmADH1 (P. minor Alcohol dehydrogenase 1) (R= 0.90 ± 0.05) after treatment with 150 µM JA, indicating that PmF-box1 possibly involves in regulating the activity of PmADH1. The content of hexanal was significantly increased in JA-treated plants and even higher in JA plus SA-treated plants. The level of six carbon alcohols was increased at 48 hours after JA treatment, consistent with the upregulation of PmADH1 in JA treated plants. These results suggest that PmF-box1 encodes a KFB-type F-box protein that may be involved in plant stress signaling by influencing the expression of PmADH1; thus, modulating the production of green leaf volatiles.

AtSKIP11, a kelch-repeat containing F-box protein from Arabidopsis thaliana, negatively regulates the HPL pathway and can serve as a potential molecular switch for the biosynthesis of green leaf volatiles.

This study aimed to determine the effects of different concentrations and combinations of the phytohormones 2,4-dichlorophenoxy acetic acid (2,4-D), kinetin, 6-benzylaminopurine (BAP), and 1-naphthaleneacetic acid (NAA) on callus induction and to demonstrate the role of elicitors and exogenous precursors on the production of mitragynine in a Mitragyna speciosa suspension culture. The best callus induction was achieved from petiole explants cultured on WPM that was supplemented with 4 mg L−1 2, 4-D (70.83%). Calli were transferred to liquid media and agitated on rotary shakers to establish Mitragyna speciosa cell suspension cultures. The optimum settled cell volume was achieved in the presence of WPM that contained 3 mg L−1 2,4-D and 3% sucrose (9.47 ± 0.4667 mL). The treatment of cultures with different concentrations of yeast extract and salicylic acid for different inoculation periods revealed that the highest mitragynine content as determined by HPLC was achieved from the culture treated with 250 mg L−1 yeast extract (9.275 ± 0.082 mg L−1) that was harvested on day 6 of culturing; salicylic acid showed low mitragynine content in all concentrations used. Tryptophan and loganin were used as exogenous precursors; the highest level of mitragynine production was achieved in cultures treated with 3 μM tryptophan and harvested at 6 days (13.226 ± 1.98 mg L−1).

Terpenoids represent an important class of plant secondary metabolites, serving as component of plant defense against various biotic and abiotic stresses. A large number of structurally diverse terpenoid compounds have been identified from Persicaria minor (P. minor), an aromatic plant native to Malaysia. However, number of studies focusing on the P. minor terpenoid metabolism, especially at the genetic level is still very scarce. In the present study, a cDNA sequence (KT192706) from the leaves of P. minor, encoding a sesquiterpene synthase (PmSS) gene was successfully cloned. The complete sequence of PmSS comprised of 1724 bp with a 1680 bp open reading frame, corresponding to a deduced protein of 559 amino acids. Under the normal conditions, PmSS gene was found to be differentially expressed in the organs of P. minor. Significantly higher expression level of PmSS was recorded in leaves and stems which are, respectively, about 98 folds and 49 folds higher than that in the roots. In addition, the present study has also shown that the expression of PmSS gene was responsive towards the exogenous application of jasmonic acid in all organs of the P. minor.