Label-free shotgun proteomics and metabolite analysis reveal a significant metabolic shift during citrus fruit development.

Label-free LC-MS/MS-based shot-gun proteomics was used to quantify the differential protein synthesis and metabolite profiling in order to assess metabolic changes during the development of citrus fruits. Our results suggested the occurrence of a metabolic change during citrus fruit maturation, where the organic acid and amino acid accumulation seen during the early stages of development shifted into sugar synthesis during the later stage of citrus fruit development. The expression of invertases remained unchanged, while an invertase inhibitor was up-regulated towards maturation. The increased expression of sucrose-phosphate synthase and sucrose-6-phosphate phosphatase and the rapid sugar accumulation suggest that sucrose is also being synthesized in citrus juice sac cells during the later stage of fruit development

Interlinking showy traits: co-engineering of scent and colour biosynthesis in flowers

The phenylpropanoid pathway gives rise to metabolites that determine floral colour and fragrance. These metabolites are one of the main means used by plants to attract pollinators, thereby ensuring plant survival. A lack of knowledge about factors regulating scent production has prevented the successful enhancement of volatile phenylpropanoid production in flowers. In this study, the Production of Anthocyanin Pigment1 ( Pap1 ) Myb transcription factor from Arabidopsis thaliana , known to regulate the production of non-volatile phenylpropanoids, including anthocyanins, was stably introduced into Petunia hybrida . In addition to an increase in pigmentation, Pap1 -transgenic petunia flowers demonstrated an increase of up to tenfold in the production of volatile phenylpropanoid/benzenoid compounds. The dramatic increase in volatile production corresponded to the native nocturnal rhythms of volatile production in petunia. The application of phenylalanine to Pap1 -transgenic flowers led to an increase in the otherwise negligible levels of volatiles emitted during the day to nocturnal levels. On the basis of gene expression profiling and the levels of pathway intermediates, it is proposed that both increased metabolic flux and transcriptional activation of scent and colour genes underlie the enhancement of petunia flower colour and scent production by Pap1 . The co-ordinated regulation of metabolic steps within or between pathways involved in vital plant functions, as shown here for two showy traits determining plant–pollinator interactions, provides a clear advantage for plant survival. The use of a regulatory factor that activates scent production creates a new biotechnological strategy for the metabolic architecture of fragrance, leading to the creation of novel genetic variability for breeding purposes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75040/1/j.1467-7652.2008.00329.x.pd

Distinct Roles of Jasmonates and Aldehydes in Plant-Defense Responses

BACKGROUND: Many inducible plant-defense responses are activated by jasmonates (JAs), C(6)-aldehydes, and their corresponding derivatives, produced by the two main competing branches of the oxylipin pathway, the allene oxide synthase (AOS) and hydroperoxide lyase (HPL) branches, respectively. In addition to competition for substrates, these branch-pathway-derived metabolites have substantial overlap in regulation of gene expression. Past experiments to define the role of C(6)-aldehydes in plant defense responses were biased towards the exogenous application of the synthetic metabolites or the use of genetic manipulation of HPL expression levels in plant genotypes with intact ability to produce the competing AOS-derived metabolites. To uncouple the roles of the C(6)-aldehydes and jasmonates in mediating direct and indirect plant-defense responses, we generated Arabidopsis genotypes lacking either one or both of these metabolites. These genotypes were subsequently challenged with a phloem-feeding insect (aphids: Myzus persicae), an insect herbivore (leafminers: Liriomyza trifolii), and two different necrotrophic fungal pathogens (Botrytis cinerea and Alternaria brassicicola). We also characterized the volatiles emitted by these plants upon aphid infestation or mechanical wounding and identified hexenyl acetate as the predominant compound in these volatile blends. Subsequently, we examined the signaling role of this compound in attracting the parasitoid wasp (Aphidius colemani), a natural enemy of aphids. PRINCIPAL FINDINGS: This study conclusively establishes that jasmonates and C(6)-aldehydes play distinct roles in plant defense responses. The jasmonates are indispensable metabolites in mediating the activation of direct plant-defense responses, whereas the C(6)-aldehyes are not. On the other hand, hexenyl acetate, an acetylated C(6)-aldehyde, is the predominant wound-inducible volatile signal that mediates indirect defense responses by directing tritrophic (plant-herbivore-natural enemy) interactions. SIGNIFICANCE: The data suggest that jasmonates and hexenyl acetate play distinct roles in mediating direct and indirect plant-defense responses. The potential advantage of this "division of labor" is to ensure the most effective defense strategy that minimizes incurred damages at a reduced metabolic cost

Molecular cloning, characterization, and expression analysis of a gene encoding a Ran binding protein (RanBP) in Cucumis melo L.

Ran binding proteins (RanBPs) are highly conserved members of the GTP-binding protein family that are involved in nuclear protein export between the nucleus and the cytoplasm. In this study, a CmRanBP gene from a melon was isolated (Cucumis melo L.) using the RACE (rapid amplification of cDNA ends) method. The 778 basepair long melon, with a RanBP cDNA encoding consisting of 197 amino acids (22.2 kDa protein), was characterized (GenBank accession no: EU853459). The predicted amino acid sequence of CmRanBP was found to be 70% identical to VvRanBP, PtRanBP, and RcRanBP from Vitis vinifera, Populus trichocarpa, and Ricinus communis, respectively. Within the RanBD (Ran binding domain), 5 highly conserved motifs and 1 Ran binding motif were found in all members of the RanBP gene family from various plant species. Expression profiles of the CmRanBP gene in different tissues under high temperature stress were also investigated by semiquantitative RT-PCR. The CmRanBP gene was expressed in a similar manner in the roots, leaves, and stems at 25 degrees C as a control environment. However, when the temperature was raised to 38 degrees C and 40 degrees C, expression levels of the CmRanBP gene were significantly (P < 0.05) increased in the root, leaf, and stem tissues. We show here for the first time that the CmRanBP gene expression was correlated with heat stress responses

Distinct roles of jasmonates and aldehydes in plant-defense responses.

BackgroundMany inducible plant-defense responses are activated by jasmonates (JAs), C(6)-aldehydes, and their corresponding derivatives, produced by the two main competing branches of the oxylipin pathway, the allene oxide synthase (AOS) and hydroperoxide lyase (HPL) branches, respectively. In addition to competition for substrates, these branch-pathway-derived metabolites have substantial overlap in regulation of gene expression. Past experiments to define the role of C(6)-aldehydes in plant defense responses were biased towards the exogenous application of the synthetic metabolites or the use of genetic manipulation of HPL expression levels in plant genotypes with intact ability to produce the competing AOS-derived metabolites. To uncouple the roles of the C(6)-aldehydes and jasmonates in mediating direct and indirect plant-defense responses, we generated Arabidopsis genotypes lacking either one or both of these metabolites. These genotypes were subsequently challenged with a phloem-feeding insect (aphids: Myzus persicae), an insect herbivore (leafminers: Liriomyza trifolii), and two different necrotrophic fungal pathogens (Botrytis cinerea and Alternaria brassicicola). We also characterized the volatiles emitted by these plants upon aphid infestation or mechanical wounding and identified hexenyl acetate as the predominant compound in these volatile blends. Subsequently, we examined the signaling role of this compound in attracting the parasitoid wasp (Aphidius colemani), a natural enemy of aphids.Principal findingsThis study conclusively establishes that jasmonates and C(6)-aldehydes play distinct roles in plant defense responses. The jasmonates are indispensable metabolites in mediating the activation of direct plant-defense responses, whereas the C(6)-aldehyes are not. On the other hand, hexenyl acetate, an acetylated C(6)-aldehyde, is the predominant wound-inducible volatile signal that mediates indirect defense responses by directing tritrophic (plant-herbivore-natural enemy) interactions.SignificanceThe data suggest that jasmonates and hexenyl acetate play distinct roles in mediating direct and indirect plant-defense responses. The potential advantage of this "division of labor" is to ensure the most effective defense strategy that minimizes incurred damages at a reduced metabolic cost

Label-free shotgun proteomics and metabolite analysis reveal a significant metabolic shift during citrus fruit development

Label-free LC-MS/MS-based shot-gun proteomics was used to quantify the differential protein synthesis and metabolite profiling in order to assess metabolic changes during the development of citrus fruits. Our results suggested the occurrence of a metabolic change during citrus fruit maturation, where the organic acid and amino acid accumulation seen during the early stages of development shifted into sugar synthesis during the later stage of citrus fruit development. The expression of invertases remained unchanged, while an invertase inhibitor was up-regulated towards maturation. The increased expression of sucrose-phosphate synthase and sucrose-6-phosphate phosphatase and the rapid sugar accumulation suggest that sucrose is also being synthesized in citrus juice sac cells during the later stage of fruit development

Function of JAs and C₆-aldehydes in plant protection against necrotrophic fungus, <i>Botrytis cinerea.</i>

<p>Lesion development was monitored and compared between leaves isolated from (A) <i>HPL-OE</i> vs. Col, (B) <i>aos</i>-<i>hpl</i> vs. <i>aos-HPL-OE</i>, (C) <i>gl-1</i> vs. <i>aos-hpl</i>, at 48, 72 or 96 hours post inoculation (hpi) with <i>B. cinerea</i> conidia. Each bar graph represents average lesion diameter±SD of 24 inoculated leaves. All leaves lacking jasmonates (<i>aos-hpl</i>, <i>aos-HPL-OE)</i> show larger lesions as compared to those with a functional AOS (Col, <i>HPL-OE</i>, <i>gl-1</i>). The lesion sizes were not affected by the presence or absence of HPL-derived metabolites. For comparison, representative photographs of each genotype 72 hpi is shown. Graphs are the means±SD of 24 replicates for each genotype. Bar = 1 cm. (D) Analyses of camalexin accumulation levels for leaves collected at 72 hpi (<i>gl-1</i>, <i>aos-hpl</i> and <i>aos-HPL-OE</i>) or 96 hpi (Col and <i>HPL-OE</i>) show negligible levels of camalexin in all plant genotypes with dysfunctional <i>AOS.</i> The <i>HPL-OE</i> lines contain 30% less camalexin than that in Col lines, potentially because of the reduced JA levels in these plants. Graphs are the means±SD of 24 replicates for each genotype. Within any given treatment, bars with different letters indicate significant differences (<i>P</i><0.005, Tukey's test).</p

Choice and no choice tests with the green peach aphid (<i>Myzus persicae</i>).

<p>(A) Choice bioassays performed on pairs of plant genotypes where a single <i>M. persicae</i> alate female was released in each cage containing the most comparable pair of genotypes. The initial nymph deposition preference was determined within 2 days of aphid release. Bar graphs represent the actual numbers of alates. One-tailed binomial tests were used to determine significance (<i>P</i><0.05). (B) Population increase of aphids (fecundity) upon the release of a newly deposited nymph on a single plant of indicated genotype during 15 days of reproduction. The graphs indicate the mean numbers of aphids per plant±SE. Each of the above-described tests was performed on ∼30 individual plants per genotype.</p