Comparative Physiological Analysis of Lignification, Anthocyanin Metabolism and Correlated Gene Expression in Red Toona sinensis Buds during Cold Storage
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The characteristics of anthocyanin and lignin are important parameters in evaluating the quality of red Toona sinensis buds. Red T. sinensis buds are prone to senescence during postharvest storage, which subsequently affects their quality and sales. However, the mechanism of senescence in red T. sinensis buds under low-temperature conditions remains unclear. In this study, red T. sinensis buds were stored at 4 °C, and their anthocyanin and lignin contents as well as the enzyme activities of PAL (phenylalanine ammonia lyase), 4CL (4-coumarate-CoA ligase), CAD (cinnamyl alcohol dehydrogenase) and POD (peroxidase) were determined at 0, 1, 2 and 3 d after handing. Meanwhile, the cellular structure of postharvest red T. sinensis buds was observed by microscopy. The relative expression of lignin-related and anthocyanin-related genes was analyzed using qRT-PCR. The results show that the anthocyanin content of the leaves was higher than that of the petioles. After 3 d of storage, the anthocyanin content of the leaves was 4.66 times that of the petioles. Moreover, the lignin content of the red T. sinensis buds gradually increased. Compared with 0 d, the lignin content of the leaves and petioles increased by 331.8 and 94.14 mg·g−1, respectively. The enzyme activities of PAL, 4CL, CAD and POD increased during cold storage. The intercellular space and the arrangement of the palisade tissue and sponge tissue in the mesophyll of red T. sinensis buds became smaller and closer, respectively. The secondary cell wall of xylem cells thickened, the number of xylem cells increased, and the arrangement number of the xylem cells became closed in the leaf vein and petioles during red T. sinensis bud storage. The expression levels of anthocyanin-related (Except for TsCHS and TsANS) and lignin-related genes increased during red T. sinensis bud storage and are highly consistent with the accumulation patterns of anthocyanins and lignin. This study may serve as a reference for exploring the molecular mechanisms of senescence, regulating the quality and cultivating new varieties of red T. sinensis buds that have low lignin content but high anthocyanin content after harvest.Keywords:
Cinnamyl-alcohol dehydrogenase
Phenylalanine ammonia-lyase
Phenylpropanoid
Citrus × sinensis
Phenylalanine ammonia-lyase
Phenylpropanoid
Cinnamyl-alcohol dehydrogenase
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We have used high-resolution gas chromatography to determine the levels of trans-cinnamic acid (CA) and trans-4-coumaric acid (4CA) in alfalfa (Medicago sativa L.) cell-suspension cultures to address the role of these phenylpropanoid pathway intermediates as potential negative regulators of phenylalanine ammonia-lyase (PAL) in vivo. Exogenous addition of CA to elicitor-treated cultures resulted in rapid increases in endogenous CA, 4CA, and CA-conjugate levels associated with inhibition of the appearance of PAL transcripts. Treatment of elicited cultures with [alpha]-aminooxy-[beta]-phenylpropionic acid (AOPP), a potent and specific inhibitor of PAL activity in vivo, resulted in reductions of CA and 4CA, with concomitant increases in PAL transcripts and extractable enzyme activity. In contrast, treatment with tetcyclacis, an inhibitor of CA 4-hydroxylase, resulted in increased CA and CA-conjugate levels, decreased 4CA levels, and decreased PAL transcript levels and enzyme activity. In tetcyclasis-treated cells, the inhibition of PAL transcript appearance preceded the increase in the levels of free CA and its conjugates. In elicited cells in which the phenylpropanoid pathway was not perturbed by metabolic inhibitors, PAL transcripts accumulated rapidly and transiently, beginning to decline by 2 h postelicitation. Changes in levels of total free or conjugated CA or 4CA did not consistently correlate with these changes in transcript levels. We propose that regulation of PAL transcript levels by endogenous phenylpropanoid pathway intermediates could involve compartmentalized pools that may exist because of the microsomal localization of cinnamic acid 4-hydroxylase.
Phenylpropanoid
Phenylalanine ammonia-lyase
Cinnamic acid
Metabolic pathway
Lyase
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Phenylpropanoid
Phenylalanine ammonia-lyase
Lyase
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Abstract A major quantitative trait locus ( QTL ) influencing seed fibre and colour in Brassica napus was dissected by marker saturation in a doubled haploid ( DH ) population from the black‐seeded oilseed rape line ‘Express 617’ crossed with a yellow‐seeded B. napus line, ‘1012–98’. The marker at the peak of a sub‐ QTL with a strong effect on both seed colour and acid detergent lignin content lay only 4 kb away from a Brassica (H+)‐ ATP ase gene orthologous to the transparent testa gene AHA 10 . Near the peak of a second sub‐ QTL , we mapped a copy of the key phenylpropanoid biosynthesis gene cinnamyl alcohol dehydrogenase, while another key phenylpropanoid biosynthesis gene, cinnamoyl co‐a reductase 1, was found nearby. In a cross between ‘Express 617’ and another dark‐seeded parent, ‘V8’, Bna . CCR 1 was localized in silico near the peak of a corresponding seed fibre QTL , whereas in this case Bna . CAD 2/ CAD 3 lay nearby. Re‐sequencing of the two phenylpropanoid genes via next‐generation amplicon sequencing revealed intragenic rearrangements and functionally relevant allelic variation in the three parents.
Cinnamyl-alcohol dehydrogenase
Phenylpropanoid
Doubled haploidy
Candidate gene
Flavonoid Biosynthesis
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Medicago sativa
Phenylpropanoid
Medicago
Suspension culture
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Phenylpropanoid
Phenylalanine ammonia-lyase
Cocos nucifera
Coumaric acid
p-Coumaric acid
Cinnamyl-alcohol dehydrogenase
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Phenylpropanoid
Phenylalanine ammonia-lyase
Cucumis
Cinnamic acid
Cinnamyl-alcohol dehydrogenase
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Abstract The phenylalanine ammonia‐lyase (PAL) enzyme catalyses the conversion of l ‐phenylalanine to trans ‐cinnamic acid. This conversion is the first step in phenylpropanoid biosynthesis in plants. The phenylpropanoid pathway produces diverse plant metabolites that play essential roles in various processes, including structural support and defence. Previous studies have shown that mutation of the PAL genes enhances disease susceptibility. Here, we investigated the functions of the rice PAL genes using 2‐aminoindan‐2‐phosphonic acid (AIP), a strong competitive inhibitor of PAL enzymes. We show that the application of AIP can significantly reduce the PAL activity of rice crude protein extracts in vitro. However, when AIP was applied to intact rice plants, it reduced infection of the root‐knot nematode Meloidogyne graminicola . RNA‐seq showed that AIP treatment resulted in a rapid but transient upregulation of defence‐related genes in roots. Moreover, targeted metabolomics demonstrated higher levels of jasmonates and antimicrobial flavonoids and diterpenoids accumulating after AIP treatment. Furthermore, chemical inhibition of the jasmonate pathway abolished the effect of AIP on nematode infection. Our results show that disturbance of the phenylpropanoid pathway by the PAL inhibitor AIP induces defence in rice against M. graminicola by activating jasmonate‐mediated defence.
Phenylpropanoid
Phenylalanine ammonia-lyase
Methyl jasmonate
Graminicola
Metabolic pathway
Root-knot nematode
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It has been proposed that natural products synthesized by plants contribute to their resistance to pests and pathogens. We show here that transgenic tobacco plants with suppressed levels of the phenylpropanoid biosynthetic enzyme phenylalanine ammonia-lyase (L-phenylalanine ammonia-lyase, EC 4.3.1.5) and correspondingly low levels of chlorogenic acid, the major soluble leaf phenylpropanoid product, exhibit more rapid and extensive lesion development than wild-type plants after infection by the virulent fungal pathogen Cercospora nicotianae. These observations provide direct evidence that phenylpropanoid products contribute to disease limitation. No induction of transcripts encoding phenylalanine ammonia-lyase or the lignin branch pathway enzyme caffeic acid O-methyltransferase was observed during the infection and there was no perturbation in the pattern of soluble phenylpropanoids. Hence, increased disease susceptibility does not involve inhibition of a pathogen-induced response but likely reflects inhibition of the developmental accumulation of chlorogenic acid. Demonstration of the contribution of such preformed protectants to plant health identifies attractive targets for manipulation by breeding or gene transfer to reduce the quantitative impact of disease.
Phenylpropanoid
Phenylalanine ammonia-lyase
Lyase
Chlorogenic Acid
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Gene silencing of phenylalanine ammonia‐lyase (PAL) in transgenic tobacco ( Nicotiana tabacum L.) is manifested phenotypically by reduced growth, altered leaf morphology, and reduced levels of phenylpropanoid compounds. Here we report the rare event of somatic reversion from silencing to PAL over‐expression in tobacco harboring the bean PAL2 gene. This phenomenon allows the comparison of the effects of PAL under‐ and over‐expression in the same plant. A comparison of gene silenced and revertant tissues reveals striking differences in lignin content and monomer composition, and both qualitative and quantitative differences in soluble and cell wall bound phenylpropanoid compounds in the recovered sector.
Phenylpropanoid
Phenylalanine ammonia-lyase
Reversion
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Citations (27)