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Regulation of volatile benzenoid biosynthesis in petunia flowers 总被引:5,自引:0,他引:5
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Funmilayo Adebesin Joshua R. Widhalm Joseph H. Lynch Rachel M. McCoy Natalia Dudareva 《The Plant journal : for cell and molecular biology》2018,93(5):905-916
Peroxisomal β‐oxidative degradation of compounds is a common metabolic process in eukaryotes. Reported benzoyl‐coenzyme A (BA‐CoA) thioesterase activity in peroxisomes from petunia flowers suggests that, like mammals and fungi, plants contain auxiliary enzymes mediating β‐oxidation. Here we report the identification of Petunia hybrida thioesterase 1 (PhTE1), which catalyzes the hydrolysis of aromatic acyl‐CoAs to their corresponding acids in peroxisomes. PhTE1 expression is spatially, developmentally and temporally regulated and exhibits a similar pattern to known benzenoid metabolic genes. PhTE1 activity is inhibited by free coenzyme A (CoA), indicating that PhTE1 is regulated by the peroxisomal CoA pool. PhTE1 downregulation in petunia flowers led to accumulation of BA‐CoA with increased production of benzylbenzoate and phenylethylbenzoate, two compounds which rely on the presence of BA‐CoA precursor in the cytoplasm, suggesting that acyl‐CoAs can be exported from peroxisomes. Furthermore, PhTE1 downregulation resulted in increased pools of cytoplasmic phenylpropanoid pathway intermediates, volatile phenylpropenes, lignin and anthocyanins. These results indicate that PhTE1 influences (i) intraperoxisomal acyl‐CoA/CoA levels needed to carry out β‐oxidation, (ii) efflux of β‐oxidative products, acyl‐CoAs and free acids, from peroxisomes, and (iii) flux distribution within the benzenoid/phenylpropanoid metabolic network. Thus, this demonstrates that plant thioesterases play multiple auxiliary roles in peroxisomal β‐oxidative metabolism. 相似文献
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Floral scent has an important role in the reproductive processes of many plants and a considerable economic value in guaranteeing yield and quality of many crops. It also enhances the aesthetic properties of ornamental plants and cut flowers. Many floral scent volatiles fall into the terpenoid or phenylpropanoid/benzenoid classes of compounds. Although the biochemistry of floral scent is still a relatively new field of investigation, in the past decade investigators have begun to identify 'scent genes'. Several of these genes, most of which, but not all, encode enzymes that directly catalyze the formation of volatile terpenoid or phenylpropanoid/benzenoid compounds, have now been used to manipulate, through genetic engineering techniques, the mix of volatiles emitted from the flowers of several plant species. The outcomes of these experiments, which are discussed here, have indicated that the genetic engineering approach to altering floral scents has potential; however, they have also revealed the limitations that result from our inadequate knowledge of the metabolic pathways responsible for scents and their regulation. 相似文献
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Much effort has been focussed on better understanding the key signals that modulate floral senescence. Although ethylene is one of the most important regulators of floral senescence in several species, Lilium flowers show low sensitivity to ethylene; thus their senescence may be regulated by other hormones. In this study we have examined how (1) endogenous levels of hormones in various floral tissues (outer and inner tepals, androecium and gynoecium) vary throughout flower development, (2) endogenous levels of hormones in such tissues change in cut versus intact flowers at anthesis, and (3) spray applications of abscisic acid and pyrabactin alter flower longevity. Results show that floral tissues behave differently in their hormonal changes during flower development. Cytokinin and auxin levels mostly increased in tepals prior to anthesis and decreased later during senescence. In contrast, levels of abscisic acid increased during senescence, but only in outer tepals and the gynoecium, and during the latest stages. In addition, cut flowers at anthesis differed from intact flowers in the levels of abscisic acid and auxins in outer tepals, salicylic acid in inner tepals, cytokinins, gibberellins and jasmonic acid in the androecium, and abscisic acid and salicylic acid in the gynoecium, thus showing a clear differential response between floral tissues. Furthermore, spray applications of abscisic acid and pyrabactin in combination accelerated the latest stages of tepal senescence, yet only when flower senescence was delayed with Promalin. It is concluded that (1) floral tissues differentially respond in their endogenous variations of hormones during flower development, (2) cut flowers have drastic changes in the hormonal balance not only of outer and inner tepals but also of androecium and gynoecium, and (3) abscisic acid may accelerate the progression of tepal senescence in Lilium. 相似文献
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Underwood BA Tieman DM Shibuya K Dexter RJ Loucas HM Simkin AJ Sims CA Schmelz EA Klee HJ Clark DG 《Plant physiology》2005,138(1):255-266
In many flowering plants, such as petunia (Petunia x hybrida), ethylene produced in floral organs after pollination elicits a series of physiological and biochemical events, ultimately leading to senescence of petals and successful fertilization. Here, we demonstrate, using transgenic ethylene insensitive (44568) and Mitchell Diploid petunias, that multiple components of emission of volatile organic compounds (VOCs) are regulated by ethylene. Expression of benzoic acid/salicylic acid carboxyl methyltransferase (PhBSMT1 and 2) mRNA is temporally and spatially down-regulated in floral organs in a manner consistent with current models for post-pollination ethylene synthesis in petunia corollas. Emission of methylbenzoate and other VOCs after pollination and exogenous ethylene treatment parallels a reduction in PhBSMT1 and 2 mRNA levels. Under cyclic light conditions (day/night), PhBSMT mRNA levels are rhythmic and precede emission of methylbenzoate by approximately 6 h. When shifted into constant dark or light conditions, PhBSMT mRNA levels and subsequent methylbenzoate emission correspondingly decrease or increase to minimum or maximum levels observed during normal conditions, thus suggesting that light may be a more critical influence on cyclic emission of methylbenzoate than a circadian clock. Transgenic PhBSMT RNAi flowers with reduced PhBSMT mRNA levels show a 75% to 99% decrease in methylbenzoate emission, with minimal changes in other petunia VOCs. These results implicate PhBSMT1 and 2 as genes responsible for synthesis of methylbenzoate in petunia. 相似文献
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Ethylene Synthesis and Floral Senescence following Compatible and Incompatible Pollinations in Petunia inflata 总被引:6,自引:2,他引:4 下载免费PDF全文
Ethylene production and floral senescence following compatible and incompatible pollinations were studied in a self-incompatible species, Petunia inflata. Both compatible and incompatible pollinations resulted in a burst of ethylene synthesis that peaked 3 hours after pollination. P. inflata pollen was found to carry large amounts of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC). The amount of pollen-held ACC varied in different genetic backgrounds, and the magnitude of the peak correlated with the amount of ACC borne by the pollen. Aminooxyacetic acid (AOA), an inhibitor of ACC synthesis, had no inhibitory effect on this ethylene response, indicating that pollen-borne ACC was largely responsible for the early synthesis of ethylene. After compatible pollination, a second increase in ethylene synthesis began at 18 hours, and the first sign of senescence appeared at 36 hours. Upon treatment with AOA, the second phase of ethylene production was reduced by 95%, indicating that endogenous ACC synthesis was required for this phase of ethylene synthesis. AOA treatment also delayed senescence to 6 days after anthesis. After incompatible pollination, a second increase in ethylene production did not occur until 3 days, and the first sign of senescence occurred 12 hours later. Unpollinated flowers showed an increase in ethylene production 3 to 4 days after anthesis and displayed signs of senescence 1 day later. The significance of the early and late phases of pollination-induced ethylene synthesis is discussed. 相似文献
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Alice Trivellini Antonio Ferrante Paolo Vernieri Anna Mensuali-Sodi Giovanni Serra 《Journal of Plant Growth Regulation》2011,30(2):175-184
Hibiscus rosa-sinensis L. flowers (cv La France) senesce and die over a 12-h period after opening. The aim of this study was to examine the physiological
mechanisms regulating the senescence process of ephemeral hibiscus flowers. Different flower stages and floral organs were
used to determine whether any interaction existed during flower senescence between endogenous abscisic acid (ABA) and the
predisposition of the tissue to ethylene synthesis. This was carried out on whole flowers treated with promoters and inhibitors
of ethylene and ABA synthesis or a combination of them. Treatments with 1-aminocyclopropane-1-carboxylic acid (ACC), a precursor
of ethylene biosynthesis, enhanced flower senescence, whereas amino-oxyacetic acid (AOA) and fluridone, an ethylene and an
ABA inhibitor, respectively, extended flower longevity. These effects were more significant when applied before anthesis.
Ethylene evolution was substantially reduced in all organs from open and senescent flowers treated with fluridone and AOA.
Similarly, endogenous ABA accumulation was negatively affected by AOA and fluridone treatments. Application of fluridone plus
ACC reduced ethylene evolution and increased ABA content in a tissue-specific manner but did not overcome the inhibitor effect
on flower longevity. AOA plus fluridone treatment slightly accelerated flower longevity compared to AOA-treated flowers. Application
of ABA alone promoted senescence, suppressed ethylene production, and, when applied with fluridone, countered the fluridone-induced
increase in flower longevity. Taken together, these results suggest that the senescence of hibiscus flowers is an endogenously
regulated ethylene- and ABA-dependent process. 相似文献
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