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The catabolism of fatty acid (FA) is regarded as a key pathway of aroma volatile compounds in oriental sweet melon (Cucumis melo var. makuwa). In our research, two cultivars of oriental sweet melon, Caihong7 and Tianbao, were employed to illuminate which step of the biosynthetic pathway of aroma compounds could be regulated by ethylene (ETH). The role of ETH in determining the profiles of straight-chain aroma volatile compounds, levels of FA as aroma precursors, activities of aroma-related enzymes derived from FA pathway, and expression patterns of key enzymes were investigated. Overall, exogenous application of ETH increased the production rates of endogenous ETH and levels of FA. Compared with control, the level of straight-chain esters, especially the acetate, hexanoate, and hexyl esters, was significantly increased by ETH, whereas the content of alcohol and aldehyde reduced. In addition, the metabolism of free FA included linoleic acid (LA), linolenic acid (LeA), and oleic acid (OA) appeared to be ETH-dependent. The activities of lipoxygenase (LOX), alcohol dehydrogenase (ADH), and alcohol acetyltransferase (AAT) as well as the expression patterns of Cm-ADH1, Cm-ADH2, Cm-AAT1, and Cm-AAT4 were positively regulated by ETH. In contrast, hydroperoxide lyase (HPL) and Cm-AAT2 and Cm-AAT3 seemed to be independent of ETH modulation. These results suggested that the dissimilation of FA included LA, LeA, and OA into the acetate, hexanoate, and hexyl esters mainly through ETH regulating the LOX pathway by enhancing the expression of particular members of aroma-related key enzyme gene families as well as the activities of dehydrogenation and esterification.
Salvia miltiorrhiza (commonly known in China as Danshen) is widely used in traditional Chinese medicine, and it is applied in the treatment of many diseases, particularly cardiovascular disease. Commercial propagation of Danshen is carried out either through seed germination or in vitro regeneration (micropropagation). However, it is not clear if the different propagation methods affect the chemical properties of the derived plants. In the present study, we first established a highly efficient tissue culture system for Danshen propagation. The addition of 1.0 mg·L−1 6-benzyladenine (BA) and 0.1 mg·L−1 α-naphthalene acetic acid (NAA) to Murashige and Skoog (MS) medium was optimal for inducing adventitious shoots; the highest rate of rooting was recorded on MS medium with 0.2 mg·L−1 NAA, on which the survival rate of transplanted plantlets was 95%. Next, we assessed antioxidant properties in the different tissues of plants of the same age, derived from micropropagation or seed germination, and measured tanshinone, total phenol, and total flavonoid contents. Our results showed that tissues of micropropagated plantlets had higher antioxidant activities than tissues of seed-derived plantlets; the micropropagated plantlets also had higher tanshinone contents in their roots. Thus, a rapid and efficient micropropagation system was established for Danshen, and it can be used for cultivating this plant to obtain therapeutic compounds.
The structure and chemical properties of strontium and calcium are similar. To study the interplay between calcium and strontium in plants, different concentrations of SrCl2 (0, 1, 4, and 10 mmol·L−1) were added to the Hoagland nutrient solution with 4 mmol·L−1 Ca2+ (normal level Ca2+) or 0.4 mmol·L−1 Ca2+ (low-level Ca2+), which were used to cultivate Chinese cabbage seedlings. Under the low-level calcium condition, strontium not only did not promote the growth of Chinese cabbage but showed more severe toxicity compared with that under the normal calcium condition. Under normal calcium condition, although the growth of Chinese cabbage was significantly inhibited by 4 mmol·L−1 strontium, strontium did not show significant toxicity. However, under the low-level calcium condition, 1 mmol·L−1 strontium caused a significant decline of plant biomass and photosynthetic activity. Sr2+ showed a competitive inhibitory effect on the absorption of Ca2+, and strontium was more easily absorbed by Chinese cabbage. Under the low-level calcium condition, strontium aggravated the inhibition of calcium absorption. The inhibitory effect of strontium on plant growth was significantly related to the calcium content in Chinese cabbage. Strontium cannot replace the function of calcium in plants under calcium-deficient conditions.
Roses are one of the economically most important groups of ornamental plants. The internal transcribed spacers (ITS) of the nuclear ribosomal DNA and the chloroplast gene matK were used to investigate the genetic diversity and genetic relationships among Rosa germplasm including 39 wild species, 21 old garden roses, and 29 modern cultivars. Three dendrograms based on ITS and matK clustering data indicated that 1) 39 wild genotypes were consistent with their classification into botanical sections with only a few exceptions; 2) most of the wild genotypes were separated from rose cultivars. However, three sections, Synstylae, Chinenses, and Rosa, that contributed to the modern roses generally gathered together with almost all old garden and modern roses on the molecular level; and 3) the relationships between cultivated roses as inferred by ITS and matK sequences do not correlate with horticultural groups. Results demonstrated that both sequence techniques can contribute to clarifying the genetic relationships of rose accessions and germplasm conservation to enhance the ornamental and economic value of rose.
Rose (Rosa L.) is an economically important ornamental genus that has been cultivated for its scent for the perfume industry since antiquity. However, most modern roses have lost their fragrance during the later stages of the breeding process. Here, 59 species of Rosa, including 24 wild Rosa species, 20 Chinese old garden roses, and 15 modern roses, were examined by headspace solid-phase microextraction and gas chromatography–mass spectrometry. Fifty-three volatile organic compounds (VOCs), including terpenoids, benzenoids/phenylpropanoids, and fatty acid derivatives, were detected with qualitative and quantitative analyses. Thirteen common components, including geraniol, citronellol, 2-phenylethanol, 3,5-dimethoxytoluene, 1,3,5-trimethoxybenzene, germacrene D, and cis-3-hexenyl acetate, were found. Furthermore, different wild species or cultivars showed different characteristic compounds. 3,5-Dimethoxytoluene and 1,3,5-trimethoxybenzene were the main compounds in Rosa odorata and Rosa chinensis, which are the original parents of modern roses. 2-Phenylethanol, citronellol, and geraniol were the main aromatic compounds in Rosa damascene and Rosa centifolia. Methyl salicylate, eugenol, methyl eugenol, and benzyl acetate were lost during domestication and breeding of wild Rosa species to Chinese old garden roses and then to modern cultivars. Geranyl acetate, neryl acetate, and dihydro-β-ionol were gained during this time and showed higher amounts across the rose breeding process. Natural and breeding selection may have caused volatile compound gains and losses. These findings provide a platform for mining scent-related genes and for breeding improved ornamental plants with enhanced flower characteristics to develop new essential oil–producing plants.