Methylation mediated by an anthocyanin, O-methyltransferase, is involved in purple flower coloration in Paeonia.

Anthocyanins are major pigments in plants. Methylation plays a role in the diversity and stability of anthocyanins. However, the contribution of anthocyanin methylation to flower coloration is still unclear. We identified two homologous anthocyanin O-methyltransferase (AOMT) genes from purple-flowered (PsAOMT) and red-flowered (PtAOMT) Paeonia plants, and we performed functional analyses of the two genes in vitro and in vivo. The critical amino acids for AOMT catalytic activity were studied by site-directed mutagenesis. We showed that the recombinant proteins, PsAOMT and PtAOMT, had identical substrate preferences towards anthocyanins. The methylation activity of PsAOMT was 60 times higher than that of PtAOMT in vitro. Interestingly, this vast difference in catalytic activity appeared to result from a single amino acid residue substitution at position 87 (arginine to leucine). There were significant differences between the 35S::PsAOMT transgenic tobacco and control flowers in relation to their chromatic parameters, which further confirmed the function of PsAOMT in vivo. The expression levels of the two homologous AOMT genes were consistent with anthocyanin accumulation in petals. We conclude that AOMTs are responsible for the methylation of cyanidin glycosides in Paeonia plants and play an important role in purple coloration in Paeonia spp.

Movement of rhizobia inside tobacco and lifestyle alternation from endophytes to free-living rhizobia on leaves.

Rhizobia are well-known for their ability to infect and nodulate legume roots, forming a nitrogen-fixing symbiosis of agricultural importance. In addition, recent studies have shown that rhizobia can colonize roots and aerial plant tissues of rice as a model plant of the Graminaceae family. Here we show that rhizobia can invade tobacco, a model plant belonging to the Solanaceae family. Inoculation of seedling roots with five GFP-tagged rhizobial species followed by microscopy and viable plating analyses indicated their colonization of the surface and interior of the whole vegetative plant. Blockage of ascending epiphytic migration by coating the hypocotyls with Vaseline showed that the endophytic rhizobia can exit the leaf interior through stomata and colonize the external phyllosphere habitat. These studies indicate rhizobia can colonize both below and above-ground tissues of tobacco using a dynamic invasion process that involves both epiphytic and endophytic lifestyles.

Analysis of active compounds and antioxidant activity assessment of six popular Chinese Juhua teas.

Chrysanthemum is an important traditional Chinese medicine and is drunk daily as a herbal tea. Chlorogenic acids and flavonoids are generally considered as the bioactive compounds. In this work, six kinds of Juhua Tea were analyzed and their active compounds and antioxidant activities were compared. In total, 32 phenolic compounds were profiled and identified using HPLC-DAD/ESI-MSn, composed of chlorogenic acids (10), flavones (8), chalcones (8), flavanones (4) and flavonols (2). Chalcones were the main flavonoids in Kunlun Xueju (Coreopsis tinctoria) extract, while flavones and chlorogenic acids were dominant in the five Chrysanthemum teas. Total chlorogenic acids content (TCA) was highest in Tai Ju (Chrysanthemum morifolium cv. 'Tai Ju') (8.59 ± 0.87 mg/g DW), and total flavonoids content (TF) was highest in Kunlun Xueju (87.2 ± 7.0 mg/g DW), which were both lowest in Ganye Ju (Chrysanthemum eticuspe) (TCA 0.86 ± 0.26 mg/g DW, TF 1.43 ± 0.41 mg/g DW). Huangin Ju (Anthemis tinctoria) possessed the most flavones (19.7 ± 0.6 mg/g DW). Antioxidant capacity of each drink, assessed by Folin-Ciocalteu, DPPH, ABTS and FRAP assays, consistently showed that Kunlun Xueju extract possessed stronger antioxidant activity than the other five, suggesting that the flavonoids content accounted for the free radical scavenging. The present work provides a method for the characterization and quality control of Juhua Tea. Moreover, it is a guideline for consuming choice, due to the different biological functions resulting from chalcones, chlorogenic acids, and flavones.

Polyphenols and triterpenes from Chaenomeles fruits: chemical analysis and antioxidant activities assessment.

Mugua, fruit of the genus Chaenomeles, is a valuable source of health food and Chinese medicine. To elucidate the bioactive compounds of five wild Chaenomeles species, extracts from fresh fruits were investigated by HPLC-DAD/ESI-MS/MS. Among the 24 polyphenol compounds obtained, 20 were flavan-3-ols (including catechin, epicatechin and procyanidin oligomers). The mean polymerisation degree (mDP) of procyanidins was examined by two acid-catalysed cleavage reactions; the mDP value was the highest in Chaenomeles sinensis and the lowest in Chaenomeles japonica. Total polyphenol content (TPC) reached 46.92 and 46.28 mg/g gallic acid equivalents (GAE) in Chaenomeles speciosa and Chaenomeles thibetica, respectively, although their main bioactive compounds were different (being epicatechin and procyanidin B2 in the former, and catechin and procyanidin B1 in the latter). These two species also exhibited equally strong free radical scavenging activities. Our results further showed that the antioxidant ability of Chaenomeles fruits was significantly correlated to their total polyphenol contents. Two triterpenes (oleanolic acid and ursolic acid) were the highest quantity in Chaenomeles cathayensis and C. thibetica, respectively.