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Rapid screening for citrus canker resistance employing pathogen-associated molecular pattern-triggered immunity responses.

Pitino M, Armstrong CM, Duan Y - Hortic Res (2015)

Bottom Line: Here, an inverse correlation between reactive oxygen species (ROS) production by the plant and the ability of Xcc to grow and form lesions on infected plants is reported.Based on this information, a novel screening method that can rapidly identify citrus seedlings that are less susceptible to early infection by Xcc was devised by measuring ROS accumulation triggered by a 22-amino acid sequence of the conserved N-terminal part of flagellin (flg22) from X. citri ssp. citri (Xcc-flg22).Moreover, the differential expression patterns observed amongst the citrus seedlings demonstrated the existence of genetic variations in the PTI response among citrus species/varieties.

View Article: PubMed Central - PubMed

Affiliation: USDA-ARS , 2001 S. Rock Rd., Fort Pierce, FL 34945, USA.

ABSTRACT
Citrus canker, caused by the bacterial pathogen Xanthomonas citri ssp. citri (Xcc), has been attributed to millions of dollars in loss or damage to commercial citrus crops in subtropical production areas of the world. Since identification of resistant plants is one of the most effective methods of disease management, the ability to screen for resistant seedlings plays a key role in the production of a long-term solution to canker. Here, an inverse correlation between reactive oxygen species (ROS) production by the plant and the ability of Xcc to grow and form lesions on infected plants is reported. Based on this information, a novel screening method that can rapidly identify citrus seedlings that are less susceptible to early infection by Xcc was devised by measuring ROS accumulation triggered by a 22-amino acid sequence of the conserved N-terminal part of flagellin (flg22) from X. citri ssp. citri (Xcc-flg22). In addition to limiting disease symptoms, ROS production was also correlated with the expression of basal defense-related genes such as the pattern recognition receptors LRR8 and FLS2, the leucine-rich repeat receptor-like protein RLP12, and the defense-related gene PR1, indicating an important role for pathogen-associated molecular pattern-triggered immunity (PTI) in determining resistance to citrus canker. Moreover, the differential expression patterns observed amongst the citrus seedlings demonstrated the existence of genetic variations in the PTI response among citrus species/varieties.

No MeSH data available.


Related in: MedlinePlus

Seedlings with high ROS accumulation show reduced growth of Xcc. Growth of the Xcc bacterium in seedlings with high levels of ROS (SO53, SO56, and SO57) compared to seedlings with a low production of ROS (SO39, SO63, and SO66) was determined by qPCR for the pthA gene using two pairs of gene-specific primers designed for Xcc. Growth is represented as CFUs per gram of tissue tested. Error bars represent the standard deviation of two independent experiments.
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fig3: Seedlings with high ROS accumulation show reduced growth of Xcc. Growth of the Xcc bacterium in seedlings with high levels of ROS (SO53, SO56, and SO57) compared to seedlings with a low production of ROS (SO39, SO63, and SO66) was determined by qPCR for the pthA gene using two pairs of gene-specific primers designed for Xcc. Growth is represented as CFUs per gram of tissue tested. Error bars represent the standard deviation of two independent experiments.

Mentions: Typically, the level of ROS produced in response to Xcc-flg22 measured via CPS in the sour orange seedlings ranged between 50 and 300; however, a small group of seedlings showed a CPS above 400 whereas another showed a CPS below 50. To determine if the results of the ROS assay correlated with disease suppression, we used the standard deviation of the mean to identify several plants as having high ROS production (SO53, SO56, and SO57) and low ROS production (SO39, SO63, and SO66; Figure 2a) and inoculated their leaves with the Xcc pathogen using both a leaf-infiltration method (Figure 2b) and a leaf dip inoculation (Figure 2c). Autoclaved tap water was used as a control in these experiments. A close correlation between the magnitude of the lesions and the number of lesions was observed. By 20 days post Xcc inoculation, lesions on the leaf surface were both more numerous, larger in size, and more severe in seedlings SO39, SO63, and SO66 compared to SO53, SO56, and SO57 (Figure 2). Moreover, a close correlation between the magnitude of the lesions and the number of Xcc cells was seen despite the leaves being inoculated with the same cell concentration. Differences in bacterial Xcc cell concentrations could be seen in the leaves of the sour orange seedlings by 4 days post Xcc infiltration (Figure 3). Although none of the seedlings were completely resistant to ACC, it was possible to separate the seedlings into two groups, which corresponded with high ROS production or low ROS production, based on the number of cells present 20 days after infiltration (Figure 3). Leaves averaged 104–105 cells for seedlings that showed high ROS production post Xcc-flg22 treatment and 106–107 cells for the seedling with low ROS production post Xcc-flg22 treatment.


Rapid screening for citrus canker resistance employing pathogen-associated molecular pattern-triggered immunity responses.

Pitino M, Armstrong CM, Duan Y - Hortic Res (2015)

Seedlings with high ROS accumulation show reduced growth of Xcc. Growth of the Xcc bacterium in seedlings with high levels of ROS (SO53, SO56, and SO57) compared to seedlings with a low production of ROS (SO39, SO63, and SO66) was determined by qPCR for the pthA gene using two pairs of gene-specific primers designed for Xcc. Growth is represented as CFUs per gram of tissue tested. Error bars represent the standard deviation of two independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4595992&req=5

fig3: Seedlings with high ROS accumulation show reduced growth of Xcc. Growth of the Xcc bacterium in seedlings with high levels of ROS (SO53, SO56, and SO57) compared to seedlings with a low production of ROS (SO39, SO63, and SO66) was determined by qPCR for the pthA gene using two pairs of gene-specific primers designed for Xcc. Growth is represented as CFUs per gram of tissue tested. Error bars represent the standard deviation of two independent experiments.
Mentions: Typically, the level of ROS produced in response to Xcc-flg22 measured via CPS in the sour orange seedlings ranged between 50 and 300; however, a small group of seedlings showed a CPS above 400 whereas another showed a CPS below 50. To determine if the results of the ROS assay correlated with disease suppression, we used the standard deviation of the mean to identify several plants as having high ROS production (SO53, SO56, and SO57) and low ROS production (SO39, SO63, and SO66; Figure 2a) and inoculated their leaves with the Xcc pathogen using both a leaf-infiltration method (Figure 2b) and a leaf dip inoculation (Figure 2c). Autoclaved tap water was used as a control in these experiments. A close correlation between the magnitude of the lesions and the number of lesions was observed. By 20 days post Xcc inoculation, lesions on the leaf surface were both more numerous, larger in size, and more severe in seedlings SO39, SO63, and SO66 compared to SO53, SO56, and SO57 (Figure 2). Moreover, a close correlation between the magnitude of the lesions and the number of Xcc cells was seen despite the leaves being inoculated with the same cell concentration. Differences in bacterial Xcc cell concentrations could be seen in the leaves of the sour orange seedlings by 4 days post Xcc infiltration (Figure 3). Although none of the seedlings were completely resistant to ACC, it was possible to separate the seedlings into two groups, which corresponded with high ROS production or low ROS production, based on the number of cells present 20 days after infiltration (Figure 3). Leaves averaged 104–105 cells for seedlings that showed high ROS production post Xcc-flg22 treatment and 106–107 cells for the seedling with low ROS production post Xcc-flg22 treatment.

Bottom Line: Here, an inverse correlation between reactive oxygen species (ROS) production by the plant and the ability of Xcc to grow and form lesions on infected plants is reported.Based on this information, a novel screening method that can rapidly identify citrus seedlings that are less susceptible to early infection by Xcc was devised by measuring ROS accumulation triggered by a 22-amino acid sequence of the conserved N-terminal part of flagellin (flg22) from X. citri ssp. citri (Xcc-flg22).Moreover, the differential expression patterns observed amongst the citrus seedlings demonstrated the existence of genetic variations in the PTI response among citrus species/varieties.

View Article: PubMed Central - PubMed

Affiliation: USDA-ARS , 2001 S. Rock Rd., Fort Pierce, FL 34945, USA.

ABSTRACT
Citrus canker, caused by the bacterial pathogen Xanthomonas citri ssp. citri (Xcc), has been attributed to millions of dollars in loss or damage to commercial citrus crops in subtropical production areas of the world. Since identification of resistant plants is one of the most effective methods of disease management, the ability to screen for resistant seedlings plays a key role in the production of a long-term solution to canker. Here, an inverse correlation between reactive oxygen species (ROS) production by the plant and the ability of Xcc to grow and form lesions on infected plants is reported. Based on this information, a novel screening method that can rapidly identify citrus seedlings that are less susceptible to early infection by Xcc was devised by measuring ROS accumulation triggered by a 22-amino acid sequence of the conserved N-terminal part of flagellin (flg22) from X. citri ssp. citri (Xcc-flg22). In addition to limiting disease symptoms, ROS production was also correlated with the expression of basal defense-related genes such as the pattern recognition receptors LRR8 and FLS2, the leucine-rich repeat receptor-like protein RLP12, and the defense-related gene PR1, indicating an important role for pathogen-associated molecular pattern-triggered immunity (PTI) in determining resistance to citrus canker. Moreover, the differential expression patterns observed amongst the citrus seedlings demonstrated the existence of genetic variations in the PTI response among citrus species/varieties.

No MeSH data available.


Related in: MedlinePlus