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An HPLC-MS characterization of the changes in sweet orange leaf metabolite profile following infection by the bacterial pathogen Candidatus Liberibacter asiaticus.

Hijaz FM, Manthey JA, Folimonova SY, Davis CL, Jones SE, Reyes-De-Corcuera JI - PLoS ONE (2013)

Bottom Line: Included among these compounds are flavonoid glycosides, polymethoxylated flavones, and hydroxycinnamates.Four structurally related hydroxycinnamate compounds increased more than 10-fold in leaves from 'Hamlin' and 'Valencia' sweet orange trees in response to Clas infection.Possible roles of these hydroxycinnamates as plant defense compounds against the Clas infection are discussed.

View Article: PubMed Central - PubMed

Affiliation: IFAS, Citrus Research and Education Center, University of Florida, Lake Alfred, Florida, United States of America.

ABSTRACT
Huanglongbing (HLB) presumably caused by Candidatus Liberibacter asiaticus (CLas) threatens the commercial U.S. citrus crop of an annual value of $3 billion. The earliest shift in metabolite profiles of leaves from greenhouse-grown sweet orange trees infected with Clas, and of healthy leaves, was characterized by HPLC-MS concurrently with PCR testing for the presence of Clas bacteria and observation of disease symptoms. Twenty, 8-month-old 'Valencia' and 'Hamlin' trees were grafted with budwood from PCR-positive HLB source trees. Five graft-inoculated trees of each variety and three control trees were sampled biweekly and analyzed by HPLC-MS and PCR. Thirteen weeks after inoculation, Clas was detected in newly growing flushes in 33% and 55% of the inoculated 'Hamlin' and 'Valencia' trees, respectively. Inoculated trees remained asymptomatic in the first 20 weeks, but developed symptoms 30 weeks after grafting. No significant differences in the leaf metabolite profiles were detected in Clas-infected trees 23 weeks after inoculation. However, 27 weeks after inoculation, differences in metabolite profiles between control leaves and those of Clas-infected trees were evident. Affected compounds were identified with authentic standards or structurally classified by their UV and mass spectra. Included among these compounds are flavonoid glycosides, polymethoxylated flavones, and hydroxycinnamates. Four structurally related hydroxycinnamate compounds increased more than 10-fold in leaves from 'Hamlin' and 'Valencia' sweet orange trees in response to Clas infection. Possible roles of these hydroxycinnamates as plant defense compounds against the Clas infection are discussed.

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Relative amounts versus time (week) of different citrus leaf metabolites from controls and CLas-inoculated trees.A) unknown 29 in ‘Valencia’ leaves; B) unknown 29 in ‘Hamlin’ leaves; C) unknown 39 in ‘Valencia’ leaves; D) unknown 39 in ‘Hamlin’ leaves.
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pone-0079485-g005: Relative amounts versus time (week) of different citrus leaf metabolites from controls and CLas-inoculated trees.A) unknown 29 in ‘Valencia’ leaves; B) unknown 29 in ‘Hamlin’ leaves; C) unknown 39 in ‘Valencia’ leaves; D) unknown 39 in ‘Hamlin’ leaves.

Mentions: In ‘Hamlin’ trees, compounds 5, 16, 22, 27, and 32 occurred at significantly higher levels at week 3 in leaves of Clas-inoculated trees than in control leaves (Table 6). Because the ratios of these compounds in Clas-inoculated trees were slightly higher than those from the control and none of these compounds was significantly higher at 23 weeks after inoculation, these differences are not likely to be caused by Clas infection. Slight variation in leaf metabolite levels could result from differences in leaf maturity and leaf age. At week 23, there was no significant difference in any leaf metabolite, and only a slight increase (20%) in the relative amount of compound 2 in leaves from Clas-inoculated ‘Hamlin’ trees was observed 2 weeks later. At week 38, where the leaf symptoms were clearly evident, dramatic increases in the numbers of compounds with significantly different means between the HLB-affected and control leaves occurred. The number of compounds that was induced in the HLB-affected ‘Hamlin’ leaves was less than those induced in the HLB-affected ‘Valencia’ leaves, yet those compounds observed in the HLB-affected ‘Hamlin’ leaves matched the compounds found at earlier dates in ‘Valencia’ trees. In agreement with the later development of visual leaf symptom in the Clas-infected trees, changes in metabolite profiles appeared later in ‘Hamlin’ leaves than those in ‘Valencia’. Table 6 highlights the metabolites that were higher in leaves from Clas-infected ‘Hamlin’ plants than in leaves from controls. The flavone glycoside (17) was 32 times more concentrated at week 35, and the putative HCAs (6 and 7) were more than 10 times in leaves from HLB-infected ‘Hamlin’ trees 38 weeks after inoculation. A number of the PMFs and PMF-derivatives, 29, 36, and 39 occurred at significantly lower levels in leaves of the HLB-affected trees at week 27, and compounds 29, 33, 36 , and 39 occurred at significantly lower levels in leaves of HLB-affected trees at week 38 (Table 6). The abundance of compounds 29 and 39 against time in control and Clas-inoculated trees is shown in Figure 5. Decreased levels of PMFs were similarly reported in field-grown HLB-symptomatic ‘Valencia’ and ‘Midsweet’ orange leaves [14].


An HPLC-MS characterization of the changes in sweet orange leaf metabolite profile following infection by the bacterial pathogen Candidatus Liberibacter asiaticus.

Hijaz FM, Manthey JA, Folimonova SY, Davis CL, Jones SE, Reyes-De-Corcuera JI - PLoS ONE (2013)

Relative amounts versus time (week) of different citrus leaf metabolites from controls and CLas-inoculated trees.A) unknown 29 in ‘Valencia’ leaves; B) unknown 29 in ‘Hamlin’ leaves; C) unknown 39 in ‘Valencia’ leaves; D) unknown 39 in ‘Hamlin’ leaves.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3818228&req=5

pone-0079485-g005: Relative amounts versus time (week) of different citrus leaf metabolites from controls and CLas-inoculated trees.A) unknown 29 in ‘Valencia’ leaves; B) unknown 29 in ‘Hamlin’ leaves; C) unknown 39 in ‘Valencia’ leaves; D) unknown 39 in ‘Hamlin’ leaves.
Mentions: In ‘Hamlin’ trees, compounds 5, 16, 22, 27, and 32 occurred at significantly higher levels at week 3 in leaves of Clas-inoculated trees than in control leaves (Table 6). Because the ratios of these compounds in Clas-inoculated trees were slightly higher than those from the control and none of these compounds was significantly higher at 23 weeks after inoculation, these differences are not likely to be caused by Clas infection. Slight variation in leaf metabolite levels could result from differences in leaf maturity and leaf age. At week 23, there was no significant difference in any leaf metabolite, and only a slight increase (20%) in the relative amount of compound 2 in leaves from Clas-inoculated ‘Hamlin’ trees was observed 2 weeks later. At week 38, where the leaf symptoms were clearly evident, dramatic increases in the numbers of compounds with significantly different means between the HLB-affected and control leaves occurred. The number of compounds that was induced in the HLB-affected ‘Hamlin’ leaves was less than those induced in the HLB-affected ‘Valencia’ leaves, yet those compounds observed in the HLB-affected ‘Hamlin’ leaves matched the compounds found at earlier dates in ‘Valencia’ trees. In agreement with the later development of visual leaf symptom in the Clas-infected trees, changes in metabolite profiles appeared later in ‘Hamlin’ leaves than those in ‘Valencia’. Table 6 highlights the metabolites that were higher in leaves from Clas-infected ‘Hamlin’ plants than in leaves from controls. The flavone glycoside (17) was 32 times more concentrated at week 35, and the putative HCAs (6 and 7) were more than 10 times in leaves from HLB-infected ‘Hamlin’ trees 38 weeks after inoculation. A number of the PMFs and PMF-derivatives, 29, 36, and 39 occurred at significantly lower levels in leaves of the HLB-affected trees at week 27, and compounds 29, 33, 36 , and 39 occurred at significantly lower levels in leaves of HLB-affected trees at week 38 (Table 6). The abundance of compounds 29 and 39 against time in control and Clas-inoculated trees is shown in Figure 5. Decreased levels of PMFs were similarly reported in field-grown HLB-symptomatic ‘Valencia’ and ‘Midsweet’ orange leaves [14].

Bottom Line: Included among these compounds are flavonoid glycosides, polymethoxylated flavones, and hydroxycinnamates.Four structurally related hydroxycinnamate compounds increased more than 10-fold in leaves from 'Hamlin' and 'Valencia' sweet orange trees in response to Clas infection.Possible roles of these hydroxycinnamates as plant defense compounds against the Clas infection are discussed.

View Article: PubMed Central - PubMed

Affiliation: IFAS, Citrus Research and Education Center, University of Florida, Lake Alfred, Florida, United States of America.

ABSTRACT
Huanglongbing (HLB) presumably caused by Candidatus Liberibacter asiaticus (CLas) threatens the commercial U.S. citrus crop of an annual value of $3 billion. The earliest shift in metabolite profiles of leaves from greenhouse-grown sweet orange trees infected with Clas, and of healthy leaves, was characterized by HPLC-MS concurrently with PCR testing for the presence of Clas bacteria and observation of disease symptoms. Twenty, 8-month-old 'Valencia' and 'Hamlin' trees were grafted with budwood from PCR-positive HLB source trees. Five graft-inoculated trees of each variety and three control trees were sampled biweekly and analyzed by HPLC-MS and PCR. Thirteen weeks after inoculation, Clas was detected in newly growing flushes in 33% and 55% of the inoculated 'Hamlin' and 'Valencia' trees, respectively. Inoculated trees remained asymptomatic in the first 20 weeks, but developed symptoms 30 weeks after grafting. No significant differences in the leaf metabolite profiles were detected in Clas-infected trees 23 weeks after inoculation. However, 27 weeks after inoculation, differences in metabolite profiles between control leaves and those of Clas-infected trees were evident. Affected compounds were identified with authentic standards or structurally classified by their UV and mass spectra. Included among these compounds are flavonoid glycosides, polymethoxylated flavones, and hydroxycinnamates. Four structurally related hydroxycinnamate compounds increased more than 10-fold in leaves from 'Hamlin' and 'Valencia' sweet orange trees in response to Clas infection. Possible roles of these hydroxycinnamates as plant defense compounds against the Clas infection are discussed.

Show MeSH
Related in: MedlinePlus