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  • Author or Editor: Qi Zhang x
  • Journal of the American Society for Horticultural Science x
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More axillary buds 1 (MAX1), initially identified in arabidopsis (Arabidopsis thaliana), is a key regulatory gene in strigolactone synthesis. CmMAX1, an ortholog of MAX1 was cloned from chrysanthemum (Chrysanthemum morifolium cv. Jinba). It had an open reading frame of 1611 bp and encoded 536 amino acid of P450 protein, with a conserved heme-binding motif of PFG × GPR × C × G, as well as PERF and KExxR motifs. The predicted amino acid sequence of CmMAX1 was most closely related to the MAX1 ortholog identified in lotus (Nelumbo nucifera), NnMAX1, with 55.33% amino acid sequence similarity. Expression analysis revealed there was no significant difference of CmMAX1 expression among various tissues. Phosphorus (P) deficiency significantly improved the expression levels of CmMAX1. Strigolactone, auxin, and cytokinin negatively regulated the expression of CmMAX1. Overexpression of CmMAX1 reduced the branch numbers of arabidopsis max1-1. These results suggest that CmMAX1 may be a candidate gene for reducing the shoot branching of chrysanthemum.

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Floral scents emitted from eight cultivars of cut lily flowers (Lilium) were analyzed. Floral volatiles were collected by headspace adsorption on sorbent tubes and analyzed by gas chromatography–mass spectrometry (GC/MS) using a direct thermal desorption. Fifty volatile compounds were identified. Nine compounds were detected in all lilies, whereas 20 compounds were detected in all scented lilies. The results revealed that non-scented lilies emitted trace amounts of volatile compounds, whereas scented lilies emitted high levels of volatile compounds. Monoterpenoids and benzenoids were the dominant compound classes of volatiles emitted from scented lilies. Myrcene, (E)-β-ocimene, linalool, methyl benzoate, and ethyl benzoate were the major compounds of the aroma of scented lilies; 1,8-cineole was also a major compound in the two scented oriental × trumpet hybrid lilies. Scent emissions occurred in a circadian rhythm with higher levels of volatiles emitted during the night. Lilium ‘Siberia’ was selected as a model to investigate the source of the emissions. GC/MS analysis of four flower parts and neutral red staining revealed that tepals were the source of floral scent.

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Monoecious cucumber (Cucumis sativus L.) parents with high, medium, and low percentage of nodes with distillate flowers had a stronger effect on the percentage of gynoecious plants in F1 and F2 progenies than did degree of gynoecious expression in incompletely gynoecious parents. Highest percentages of gynoecious plants were obtained by using both gynoecious and monoecious parents with the highest level of distillate flowering tendency. According to our data, monoecious parents with a low percentage of distillate flowering nodes should be avoided when gynoeciousness is transferred to monoecious cultivars. Self-pollination of gynoecious F2 plants, requiring induction of staminate flowers by chemical treatment, was more effective in obtaining a high percentage of gynoecious plants in F3 progenies than selfing predominately gynoecious plants, or sibmating predominately gynoecious plants.

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A new sterile mutant designated pollen sterile (PS) found in pickling cucumber (Cucumis sativus L.) is characterized by normal corolla in staminate and pistillate flowers, normal fertility in the female, and absence of pollen in otherwise normal-appearing staminate flowers. All F1 plants from PS × male fertile (MF) sib-matings were MF, and F2 progeny segregated 3 MF: 1 PS. Sib-matings of PS segregates with sister MF segregates produced either 1 MF: 1 PS ratios or all normal plants. Thus, PS is controlled by a single recessive gene. The PS gene is not allelic to apetalous (ap), but was shown to be allelic to male sterile-2 (ms-2) and is designated ms-2 PS. It was not possible to determine possible allelic relationships between ms-2 PS and ms-1 because of strong male and female sterility of the available ms-1 material. F1 generations from gynoecious-PS and monoecious-PS crossed with monoecious, gynoecious (silver-ion treated), and hermaphroditic parents produced no PS plants and sex types did not influence PS levels in F2 progenies, indicating it is not possible to maintain the PS mutants through crosses with different cucumber sex types. It was not possible to change the expression of PS by applying cytokinin, IAA, or GA3, and there were no changes in response to temperature and fertilizer treatment. Unlike gynoecy, which is responsive to some external factors, PS is unresponsive. The results suggest that the use of PS in cucumber F1 hybrid seed production is not practical. Chemical names used: indole acetic acid (IAA), gibberellin (GA3).

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The branch number of plants is an important agronomic trait that directly influences the ornamental characters and production costs of ornamental plants. Shoot branching has always been a hot topic for Petunia hybrida. During our research, we isolated the homologous gene of narrow-leaf 1 (NAL1), denoted as PhNAL1. The expression level of PhNAL1 was higher in leaves and axils than in roots, stems, and flowers. Pertinent to shoot apex removal and 6-benzyladenine treatments, both interventions demonstrated a suppressive effect on the expression of PhNAL1. Through subcellular localization analysis, we found that PhNAL1 predominantly localized in the nucleus. By using RNA interference targeting PhNAL1, we induced a noticeable increase in branch number while concurrently reducing plant height of petunia. These findings demonstrate that PhNAL1 is involved in regulating branch development within petunia. This study provides genetic resources for the subsequent cultivation of new cultivars of petunia endowed with distinct branching characteristics.

Open Access

Leaves of Begonia semperflorens accumulate anthocyanins and turn red under low temperature (LT). In the present work, LT increased H2O2 content and superoxide anions production rate, causing significant increases in the activities of enzymes and contents of reduced components involved in the ascorbate-glutathione cycle (AsA-GSH cycle). As a result, LT-exposed seedlings increased the expression of genes involved in anthocyanin biosynthesis, and accumulated anthocyanin. Based on LT condition, application of N,N'-dimethylthiourea (DMTU) decreased reactive oxygen species (ROS) content, and unbalanced the AsA-GSH-controlled redox homeostasis. As a result, seedlings in the LT + DMTU group did not accumulate anthocyanin. Our results suggest that ROS may act as an important inducer in LT-induced anthocyanin biosynthesis.

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Cold stress is one of the most important environmental factors affecting crop growth and agricultural production. Induced changes of gene expression and metabolism are critical for plants responding and acclimating to cold stress. Banana (Musa sp.) is one of the most important food crops in the tropical and subtropical countries of the world. Banana, which originated from tropical regions, is sensitive to cold, which can result in serious losses in commercial banana production. To investigate the response of the banana to cold stress conditions, changes in protein expression were analyzed using a comparative proteomics approach. ‘Brazil’ banana (Musa acuminata AAA group) is a common banana cultivar in southern China. ‘Brazil’ banana plantlets were exposed to 5 °C for 24 hours and then total crude protein was extracted from treatment and control leaves by phenol extraction, separated with two-dimensional gel electrophoresis, and subsequently identified by mass spectrometry (MS). Out of the more than 400 protein spots reproducibly detected, only 41 protein spots exhibited a change in intensity by at least 2-fold, with 26 proteins increasing and 15 proteins decreasing expression. Of these, 28 differentially expressed proteins were identified by MS. The identified proteins, including well-known and novel cold-responsive proteins, are involved in several cellular processes, including antioxidation and antipathogen, photosynthesis, chaperones, protein synthesis, signal transduction, energy metabolism, and other cellular functions. Proteins related to antioxidation, pathogen resistance, molecular chaperones, and energy metabolism were up-regulated, and proteins related to ethylene synthesis, protein synthesis, and epigenetic modification were down-regulated in response to cold temperature treatment. The banana plantlets incubated at cold temperatures demonstrated major changes in increased reactive oxygen species (ROS) scavenging, defense against diseases, and energy supply. Increased antioxidation capability in banana was also discovered in plantain, which has greater cold tolerance than banana in response to cold stress conditions. Therefore, we hypothesized that an increased antioxidation ability could be a common characteristic of banana and plantain in response to cold stress conditions. These findings may provide a better understanding of the physiological processes of banana in response to cold stress conditions.

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Wild Rosa species, which are highly variable and locally adapted, are widely distributed in the Xinjiang Uygur autonomous region of China. These species possess many important horticultural traits that are not found in the gene pool of modern cultivated roses. However, little is known about their cytological characteristics, because few of them have been karyologically analyzed. Karyological data of 13 samples of seven wild Rosa taxa, including R. berberifolia, two botanical varieties of R. spinosissima, R. platyacantha, R. beggeriana, R. acicularis, and R. laxa, were investigated by means of squashes of shoot tips. The results showed that seven samples were diploid (2n = 2x = 14), whereas the other six samples were tetraploid (2n = 4x = 28). The karyotypes of all the test samples were composed of m and sm chromosomes, which include 1A, 2A, 1B, and 2B. There were differences in asymmetry index, centromere index, and distribution of relative lengths. The karyotype of the tetraploid R. laxa var. laxa sample from Aksu easily distinguished from the other R. laxa var. laxa samples tested in having the highest asymmetry index and the most evolved karyotype. This Aksu population merits recognition as a new botanical variety of R. laxa. The karyological data, most of which are first reports for their taxa, provide a comprehensive cytogenetic resource that can be used to better understand the taxonomy, evolution, and speciation in the genus Rosa and to identify candidate species for breeding programs.

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