2-Phenylethanol (2PE) is a prominent scent compound released from flowers of Damask roses (Rosa×damascena) and some hybrid roses (Rosa 'Hoh-Jun' and Rosa 'Yves Piaget'). 2PE is biosynthesized from l-phenylalanine (l-Phe) via the intermediate phenylacetaldehyde (PAld) by two key enzymes, aromatic amino acid decarboxylase (AADC) and phenylacetaldehyde reductase (PAR). Here we describe substrate specificity and cofactor preference in addition to molecular characterization of rose-PAR and recombinant PAR from R.×damascena. The deduced amino acid sequence of the full-length cDNA encoded a protein exhibiting 77% and 75% identity with Solanum lycopersicum PAR1 and 2, respectively. The transcripts of PAR were higher in petals than calyxes and leaves and peaking at the unfurling stage 4. Recombinant PAR and rose-PAR catalyzed reduction of PAld to 2PE using NADPH as the preferred cofactor. Reductase activity of rose-PAR and recombinant PAR were higher for aromatic and aliphatic aldehydes than for keto-carbonyl groups. Both PARs showed that (S)-[4-(2)H] NADPH was preferentially used over the (R)-[4-(2)H] isomer to give [1-(2)H]-2PE from PAld, indicating that PAR can be classified as short-chain dehydrogenase reductase (SDR).
Miscanthus has been proposed as a promising crop for phytoremediation due to its high biomass yield and remarkable adaptability to different environments. However, little is known about the resistance of Miscanthus spp. to cadmium (Cd). To determine any differences in resistance of Miscanthus to Cd, we examined plant growth, net photosynthetic rate (Pn), activities of anti-oxidant and C4 photosynthetic enzymes, concentrations of Cd in leaves and roots, and observed the chloroplast structure in three Miscanthus species treated with 0, 10, 50, 100 or 200 μM Cd in solutions. Miscanthus sinensis showed more sensitivity to Cd, including sharp decreases in growth, Pn, PEPC activity and damage to chloroplast structure, and the highest H2O2 and Cd concentrations in leaves and roots after Cd treatments. Miscanthus sacchariflorus showed higher resistance to Cd and better growth, had the highest Pn and phosphoenolpyruvate carboxylase (PEPC) activities and integrative chloroplast structure and the lowest hydrogen peroxide (H2O2) and leaf and root Cd concentrations. The results could play an important role in understanding the mechanisms of Cd tolerance in plants and in application of phytoremediation.
Drought stress is one of the main environmental stresses that have effect on plant growth and development. Spermidine (SPD) plays an important role in the defense responses to drought stress in plants. In this study, we investigated the effects of exogenous SPD on plant growth, net photosynthetic rate (Pn), antioxidant enzyme activities, chlorophyll, malondialdehyde (MDA) and phytohormone contents in leaves of blueberry (Vaccinium corymbosum 'Misty') seedlings under drought stress. Drought stress severely reduced the relative water content (RWC), chlorophyll, Pn, specific leaf weight (SLW), indole-3acetic acid, gibberellic acid and polyamine contents, while increased relative electrolyte conductivity (REC), MDA, total soluble sugar and abscisic acid (ABA) contents, the activities of SOD and POD. Compared with seedlings without SPD treatment, SPD increased the RWC, chlorophyll content, Pn, SLW, SOD and POD activities and decreased REC, MDA, total soluble sugar and ABA contents in seedlings. These results signified the role of SPD in alleviating the negative effects of drought stress on plants and suggested that SPD could be used as a potential growth regulator for improving plant growth under drought stress.
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