Transcriptional responses of Hypericum perforatum cells to Agrobacterium tumefaciens and differential gene expression in dark glands.

Hypericum perforatum L. (St. John's wort) is a well-known medicinal plant that possesses secondary metabolites with beneficial pharmacological properties. However, improvement in the production of secondary metabolites via genetic manipulation is a challenging task as H. perforatum remains recalcitrant to Agrobacterium tumefaciens-mediated transformation. Here, the transcripts of key genes involved in several plant defence responses (secondary metabolites, RNA silencing, reactive oxygen species (ROS) and specific defence genes) were investigated in H. perforatum suspension cells inoculated with A. tumefaciens by quantitative real-time PCR. Results indicated that key genes from the xanthone, hypericin and melatonin biosynthesis pathways, the ROS-detoxification enzyme HpAOX, as well as the defence genes Hyp-1 and HpPGIP, were all upregulated to rapidly respond to A. tumefaciens elicitation in H. perforatum. By contrast, expression levels of genes involved in hyperforin and flavonoid biosynthesis pathways were markedly downregulated upon A. tumefaciens elicitation. In addition, we compared the expression patterns of key genes in H. perforatum leaf tissues with and without dark glands, a major site of secondary metabolite production. Overall, we provide evidence for the upregulation of several phenylpropanoid pathway genes in response to elicitation by Agrobacterium, suggesting that production of secondary metabolites could modulate H. perforatum recalcitrance to A. tumefaciens-mediated transformation.

Chitosan Upregulates the Genes of the ROS Pathway and Enhances the Antioxidant Potential of Grape (Vitis vinifera L. 'Touriga Franca' and 'Tinto Cão') Tissues.

Chitosan is an environmentally-friendly active molecule that has been explored for numerous agricultural uses. Its use in crop protection is well-known, however, other properties, such as bioactivity, deserve attention. Moreover, the modes of actions of chitosan remain to be elucidated. The present study assessed the levels of total phenolic compounds, the antioxidant potential, and the expression of reactive oxygen species (ROS) scavenging genes in the berries (skins and seeds), leaves, cluster stems, and shoots upon chitosan application on two red grapevine varieties (Touriga Franca and Tinto Cão). The application of chitosan on the whole vine before and after veraison led to the increased levels of polyphenols, anthocyanins, and tannins in Tinto Cão berries, and polyphenols and tannins in Touriga Franca berries, respectively. CUPric Reducing Antioxidant Capacity (CUPRAC) and Ferric Reducing Antioxidant Power (FRAP) assays indicated an increase in the antioxidant potential of berries. With the exception of ascorbate peroxidase (APX), all the ROS pathway genes tested, i.e., iron-superoxide dismutase (Fe-SOD), copper-zinc-superoxide dismutase (Cu/Zn-SOD), catalase (CAT), glutathione reductase (GR), glutaredoxin (Grx), respiratory burst oxidase (Rboh), amine oxidase (AO), peroxidase (POD) and polyphenol oxidase (PPO), were found up-regulated in chitosan-treated berries. Results from the analyses of leaves, stems, and shoots revealed that chitosan not only induced the synthesis of phenolic compounds but also acted as a facilitator for the transfer of polyphenols from the leaves to the berries.

Metallothionein-like gene from Cicer microphyllum is regulated by multiple abiotic stresses.

Cicer microphyllum, a wild relative of cultivated chickpea, is a high altitude cold desert-adapted species distributed in western and trans-Himalayas. A complementary DNA (cDNA) encoding metallothionein-like protein has been identified from a cold-induced subtraction cDNA library from C. microphyllum. The sequence of the cloned metallothionein gene from C. microphyllum (GQ900702) contains 240-bp-long open reading frame and encodes predicted 79-amino acid protein of 7.9 kDa. Sequence analysis identified the motifs characteristic of type II metallothionein and designated as CmMet-2. Southern hybridization confirms a single copy of the CmMet-2 gene in C. microphyllum genome. In situ hybridization indicated spatial transcript regulation of CmMet-2 in root and aerial parts and also confirmed through real-time PCR-based quantitative transcript analysis. The data revealed a significantly low level of transcript in the aerial parts than the roots. Quantitative analysis using real-time PCR assay revealed induction of transcript in all parts of plants in response to cold stress at 4°C. The transcript abundance was found to increase exponentially with time course from 6 to 24 h after exposure. Further, regulation of transcript accumulation in response to abscisic acid application, polyethylene glycol (100 µM)-induced osmotic stress, or ZnSO(4) (1 µM) foliar spray indicated by Northern hybridization suggests the involvement of CmMet-2 in multiple stress response.