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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

Induction of PTI-related resistance genes in seedlings with high ROS production. The relative quantity of PTI-related genes in SO53, SO56, and SO57 compared to SO39, SO63, and SO66 seedlings at 12 and 24 hours post-infiltration with the Xcc-flg22 peptide. The relative quantity of genes was determined using reverse transcriptase real-time PCR with primers specific for the PR1, LRR8, FLS2, RLP12, and GSL07 genes. Error bars represent the standard deviation of two independent experiments.
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fig4: Induction of PTI-related resistance genes in seedlings with high ROS production. The relative quantity of PTI-related genes in SO53, SO56, and SO57 compared to SO39, SO63, and SO66 seedlings at 12 and 24 hours post-infiltration with the Xcc-flg22 peptide. The relative quantity of genes was determined using reverse transcriptase real-time PCR with primers specific for the PR1, LRR8, FLS2, RLP12, and GSL07 genes. Error bars represent the standard deviation of two independent experiments.

Mentions: To examine whether PTI was activated in those seedlings that displayed an increased level of ROS and a decreased level of pathogen, we analyzed the transcript levels of a set of known PTI marker genes. To do so, RT-PCR was performed on RNA isolated from sour orange leaves that had been syringe-infiltrated with either the Xcc pathogen or autoclaved tap water. Overall, the group of seedlings with high ROS production (SO53, SO56, and SO57) showed an increase in the level of transcript of the PTI-related genes in response to the bacterial pathogen Xcc (Figure 4). In particular, the genes that showed increased expression were as follows: the PRR LRR8, which is similar to a LRR receptor-like protein kinase in Arabidopsis; the LRR receptor-like protein RLP12, which is associated mainly with disease resistance;48–50 and the defense-related gene PR1. Upregulation of these genes suggests that PAMPs from Xcc might be perceived by PRRs in the sour orange seedlings and could trigger the PTI response. Since callose deposition also plays an important role in a plants defense response, it is worth mentioning that the callose synthase gene GSL07 was also induced in seedlings with high ROS (Figure 4).


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

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

Induction of PTI-related resistance genes in seedlings with high ROS production. The relative quantity of PTI-related genes in SO53, SO56, and SO57 compared to SO39, SO63, and SO66 seedlings at 12 and 24 hours post-infiltration with the Xcc-flg22 peptide. The relative quantity of genes was determined using reverse transcriptase real-time PCR with primers specific for the PR1, LRR8, FLS2, RLP12, and GSL07 genes. 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

fig4: Induction of PTI-related resistance genes in seedlings with high ROS production. The relative quantity of PTI-related genes in SO53, SO56, and SO57 compared to SO39, SO63, and SO66 seedlings at 12 and 24 hours post-infiltration with the Xcc-flg22 peptide. The relative quantity of genes was determined using reverse transcriptase real-time PCR with primers specific for the PR1, LRR8, FLS2, RLP12, and GSL07 genes. Error bars represent the standard deviation of two independent experiments.
Mentions: To examine whether PTI was activated in those seedlings that displayed an increased level of ROS and a decreased level of pathogen, we analyzed the transcript levels of a set of known PTI marker genes. To do so, RT-PCR was performed on RNA isolated from sour orange leaves that had been syringe-infiltrated with either the Xcc pathogen or autoclaved tap water. Overall, the group of seedlings with high ROS production (SO53, SO56, and SO57) showed an increase in the level of transcript of the PTI-related genes in response to the bacterial pathogen Xcc (Figure 4). In particular, the genes that showed increased expression were as follows: the PRR LRR8, which is similar to a LRR receptor-like protein kinase in Arabidopsis; the LRR receptor-like protein RLP12, which is associated mainly with disease resistance;48–50 and the defense-related gene PR1. Upregulation of these genes suggests that PAMPs from Xcc might be perceived by PRRs in the sour orange seedlings and could trigger the PTI response. Since callose deposition also plays an important role in a plants defense response, it is worth mentioning that the callose synthase gene GSL07 was also induced in seedlings with high ROS (Figure 4).

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