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Co-silencing of tomato S-adenosylhomocysteine hydrolase genes confers increased immunity against Pseudomonas syringae pv. tomato DC3000 and enhanced tolerance to drought stress.

Li X, Huang L, Hong Y, Zhang Y, Liu S, Li D, Zhang H, Song F - Front Plant Sci (2015)

Bottom Line: Virus-induced gene silencing-based knockdown of individual SlSAHH gene did not affect the growth performance and the response to Pst DC3000.The SlSAHH-co-silenced plants displayed increased resistance to Pst DC3000 but did not alter the resistance to B. cinerea.Co-silencing of SlSAHHs resulted in constitutively activated defense responses including elevated SA level, upregulated expression of defense-related and PAMP-triggered immunity marker genes and increased callose deposition and H2O2 accumulation.

View Article: PubMed Central - PubMed

Affiliation: National Key Laboratory for Rice Biology, Institute of Biotechnology, Zhejiang University Hangzhou, China.

ABSTRACT
S-adenosylhomocysteine hydrolase (SAHH), catalyzing the reversible hydrolysis of S-adenosylhomocysteine (SAH) to adenosine and homocysteine, is a key enzyme that maintain the cellular methylation potential in all organisms. We report here the biological functions of tomato SlSAHHs in stress response. The tomato genome contains three SlSAHH genes that encode SlSAHH proteins with high level of sequence identity. qRT-PCR analysis revealed that SlSAHHs responded with distinct expression induction patterns to Pseudomonas syringae pv. tomato (Pst) DC3000 and Botrytis cinerea as well as to defense signaling hormones such as salicylic acid, jasmonic acid and a precursor of ethylene. Virus-induced gene silencing-based knockdown of individual SlSAHH gene did not affect the growth performance and the response to Pst DC3000. However, co-silencing of three SlSAHH genes using a conserved sequence led to significant inhibition of vegetable growth. The SlSAHH-co-silenced plants displayed increased resistance to Pst DC3000 but did not alter the resistance to B. cinerea. Co-silencing of SlSAHHs resulted in constitutively activated defense responses including elevated SA level, upregulated expression of defense-related and PAMP-triggered immunity marker genes and increased callose deposition and H2O2 accumulation. Furthermore, the SlSAHH-co-silenced plants also exhibited enhanced drought stress tolerance although they had relatively small roots. These data demonstrate that, in addition to the functions in growth and development, SAHHs also play important roles in regulating biotic and abiotic stress responses in plants.

No MeSH data available.


Related in: MedlinePlus

Co-silencing of SlSAHHs conferred a constitutively activated immune response. Ten-day-old seedlings were infiltrated with agrobacteria carrying TRV-SlSAHHa or TRV-GUS construct and leaf samples were collected at 4 weeks after agroinfiltration for analyzing expression of defense-related genes and staining of H2O2 accumulation. (A) Expression patterns of defense-related and PTI marker genes in TRV-GUS- and TRV-SlSAHHa-infiltrated plants. (B) Expression patterns of ROS-generating and scavenging genes in TRV-GUS- and TRV-SlSAHHa-infiltrated plants. (C) and (D) Callose deposition and H2O2 accumulation in TRV-GUS- and TRV-SlSAHHa-infiltrated plants without or with inoculation with Pst DC3000. Leaf samples were collected at 24 h after inoculation with Pst DC3000 or with 10 mM MgCl2 as mock inoculation controls. Data presented in (A) and (B) are the means ± SD from three independent experiments and ∗ above the columns indicate significant differences at p < 0.05 level between the TRV-SlSAHHa- and TRV-GUS-infiltrated plants. Similar results in (C) and (D) were obtained in independent experiments.
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Figure 5: Co-silencing of SlSAHHs conferred a constitutively activated immune response. Ten-day-old seedlings were infiltrated with agrobacteria carrying TRV-SlSAHHa or TRV-GUS construct and leaf samples were collected at 4 weeks after agroinfiltration for analyzing expression of defense-related genes and staining of H2O2 accumulation. (A) Expression patterns of defense-related and PTI marker genes in TRV-GUS- and TRV-SlSAHHa-infiltrated plants. (B) Expression patterns of ROS-generating and scavenging genes in TRV-GUS- and TRV-SlSAHHa-infiltrated plants. (C) and (D) Callose deposition and H2O2 accumulation in TRV-GUS- and TRV-SlSAHHa-infiltrated plants without or with inoculation with Pst DC3000. Leaf samples were collected at 24 h after inoculation with Pst DC3000 or with 10 mM MgCl2 as mock inoculation controls. Data presented in (A) and (B) are the means ± SD from three independent experiments and ∗ above the columns indicate significant differences at p < 0.05 level between the TRV-SlSAHHa- and TRV-GUS-infiltrated plants. Similar results in (C) and (D) were obtained in independent experiments.

Mentions: To gain insight into the mechanism of the enhanced Pst DC3000 resistance in TRV-SlSAHHa-infiltrated plants, we examined and compared the expression patterns of some well-known defense-related and PAMP-triggered immunity (PTI) marker genes in TRV-GUS- and TRV-SlSAHHa-infiltrated plants. As shown in Figure 5A, the expression levels of SlPR1b, SlPR-P2, and SlPR5, three defense-related genes that are thought to be regulated through the SA-mediated signaling pathway, and SlCHI9, a known defense-related gene, were dramatically upregulated in the TRV-SlSAHHa-infiltrated plants, giving >100 folds of increases for SlPR1b, SlPR-P2, and SlPR5 and 8.2 folds for SlCHI9 over those in the TRV-GUS-infiltrated plants. However, the expression levels of SlLapA and SlPIN2, two defense-related genes that are believed to be modulated via the JA-ET signaling pathway, were comparable to those in the TRV-GUS-infiltrated plants (Figure 5A). By contrast, the expression level of SlPR7, another JA/ET signaling pathway-regulated defense-related gene, in TRV-SlSAHHa-infiltrated plants was significantly downregulated by 2.2 folds as compared with that in the TRV-GUS-infiltrated plants (Figure 5A). Notably, the expression of SlPti5 and SlLrr22, two PTI marker genes in tomato (Taylor et al., 2012), in TRV-SlSAHHa-infiltrated plants were markedly upregulated, leading to 7.3 and 2.8 folds of increases over those in TRV-GUS-infiltrated plants (Figure 5A). Furthermore, the expression levels of SlRbohB and SlWfi1, two genes for NADPH oxidases involved in generation of ROS (Sagi et al., 2004), and SlCAT, a gene for catalase involved in scavenging of H2O2, were significantly increased, while the expression of SlSOD, a gene for superoxide dismutase involved in scavenging of superoxide anion, was downregulated in TRV-SlSAHHa-infiltrated plants, as compared with those in TRV-GUS-infiltrated plants (Figure 5B). These results indicate that co-silencing of SlSAHHs led to upregulated expression of some SA signaling pathway-modulated defense-related genes, PTI-related genes and ROS-related genes.


Co-silencing of tomato S-adenosylhomocysteine hydrolase genes confers increased immunity against Pseudomonas syringae pv. tomato DC3000 and enhanced tolerance to drought stress.

Li X, Huang L, Hong Y, Zhang Y, Liu S, Li D, Zhang H, Song F - Front Plant Sci (2015)

Co-silencing of SlSAHHs conferred a constitutively activated immune response. Ten-day-old seedlings were infiltrated with agrobacteria carrying TRV-SlSAHHa or TRV-GUS construct and leaf samples were collected at 4 weeks after agroinfiltration for analyzing expression of defense-related genes and staining of H2O2 accumulation. (A) Expression patterns of defense-related and PTI marker genes in TRV-GUS- and TRV-SlSAHHa-infiltrated plants. (B) Expression patterns of ROS-generating and scavenging genes in TRV-GUS- and TRV-SlSAHHa-infiltrated plants. (C) and (D) Callose deposition and H2O2 accumulation in TRV-GUS- and TRV-SlSAHHa-infiltrated plants without or with inoculation with Pst DC3000. Leaf samples were collected at 24 h after inoculation with Pst DC3000 or with 10 mM MgCl2 as mock inoculation controls. Data presented in (A) and (B) are the means ± SD from three independent experiments and ∗ above the columns indicate significant differences at p < 0.05 level between the TRV-SlSAHHa- and TRV-GUS-infiltrated plants. Similar results in (C) and (D) were obtained in independent experiments.
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Related In: Results  -  Collection

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Figure 5: Co-silencing of SlSAHHs conferred a constitutively activated immune response. Ten-day-old seedlings were infiltrated with agrobacteria carrying TRV-SlSAHHa or TRV-GUS construct and leaf samples were collected at 4 weeks after agroinfiltration for analyzing expression of defense-related genes and staining of H2O2 accumulation. (A) Expression patterns of defense-related and PTI marker genes in TRV-GUS- and TRV-SlSAHHa-infiltrated plants. (B) Expression patterns of ROS-generating and scavenging genes in TRV-GUS- and TRV-SlSAHHa-infiltrated plants. (C) and (D) Callose deposition and H2O2 accumulation in TRV-GUS- and TRV-SlSAHHa-infiltrated plants without or with inoculation with Pst DC3000. Leaf samples were collected at 24 h after inoculation with Pst DC3000 or with 10 mM MgCl2 as mock inoculation controls. Data presented in (A) and (B) are the means ± SD from three independent experiments and ∗ above the columns indicate significant differences at p < 0.05 level between the TRV-SlSAHHa- and TRV-GUS-infiltrated plants. Similar results in (C) and (D) were obtained in independent experiments.
Mentions: To gain insight into the mechanism of the enhanced Pst DC3000 resistance in TRV-SlSAHHa-infiltrated plants, we examined and compared the expression patterns of some well-known defense-related and PAMP-triggered immunity (PTI) marker genes in TRV-GUS- and TRV-SlSAHHa-infiltrated plants. As shown in Figure 5A, the expression levels of SlPR1b, SlPR-P2, and SlPR5, three defense-related genes that are thought to be regulated through the SA-mediated signaling pathway, and SlCHI9, a known defense-related gene, were dramatically upregulated in the TRV-SlSAHHa-infiltrated plants, giving >100 folds of increases for SlPR1b, SlPR-P2, and SlPR5 and 8.2 folds for SlCHI9 over those in the TRV-GUS-infiltrated plants. However, the expression levels of SlLapA and SlPIN2, two defense-related genes that are believed to be modulated via the JA-ET signaling pathway, were comparable to those in the TRV-GUS-infiltrated plants (Figure 5A). By contrast, the expression level of SlPR7, another JA/ET signaling pathway-regulated defense-related gene, in TRV-SlSAHHa-infiltrated plants was significantly downregulated by 2.2 folds as compared with that in the TRV-GUS-infiltrated plants (Figure 5A). Notably, the expression of SlPti5 and SlLrr22, two PTI marker genes in tomato (Taylor et al., 2012), in TRV-SlSAHHa-infiltrated plants were markedly upregulated, leading to 7.3 and 2.8 folds of increases over those in TRV-GUS-infiltrated plants (Figure 5A). Furthermore, the expression levels of SlRbohB and SlWfi1, two genes for NADPH oxidases involved in generation of ROS (Sagi et al., 2004), and SlCAT, a gene for catalase involved in scavenging of H2O2, were significantly increased, while the expression of SlSOD, a gene for superoxide dismutase involved in scavenging of superoxide anion, was downregulated in TRV-SlSAHHa-infiltrated plants, as compared with those in TRV-GUS-infiltrated plants (Figure 5B). These results indicate that co-silencing of SlSAHHs led to upregulated expression of some SA signaling pathway-modulated defense-related genes, PTI-related genes and ROS-related genes.

Bottom Line: Virus-induced gene silencing-based knockdown of individual SlSAHH gene did not affect the growth performance and the response to Pst DC3000.The SlSAHH-co-silenced plants displayed increased resistance to Pst DC3000 but did not alter the resistance to B. cinerea.Co-silencing of SlSAHHs resulted in constitutively activated defense responses including elevated SA level, upregulated expression of defense-related and PAMP-triggered immunity marker genes and increased callose deposition and H2O2 accumulation.

View Article: PubMed Central - PubMed

Affiliation: National Key Laboratory for Rice Biology, Institute of Biotechnology, Zhejiang University Hangzhou, China.

ABSTRACT
S-adenosylhomocysteine hydrolase (SAHH), catalyzing the reversible hydrolysis of S-adenosylhomocysteine (SAH) to adenosine and homocysteine, is a key enzyme that maintain the cellular methylation potential in all organisms. We report here the biological functions of tomato SlSAHHs in stress response. The tomato genome contains three SlSAHH genes that encode SlSAHH proteins with high level of sequence identity. qRT-PCR analysis revealed that SlSAHHs responded with distinct expression induction patterns to Pseudomonas syringae pv. tomato (Pst) DC3000 and Botrytis cinerea as well as to defense signaling hormones such as salicylic acid, jasmonic acid and a precursor of ethylene. Virus-induced gene silencing-based knockdown of individual SlSAHH gene did not affect the growth performance and the response to Pst DC3000. However, co-silencing of three SlSAHH genes using a conserved sequence led to significant inhibition of vegetable growth. The SlSAHH-co-silenced plants displayed increased resistance to Pst DC3000 but did not alter the resistance to B. cinerea. Co-silencing of SlSAHHs resulted in constitutively activated defense responses including elevated SA level, upregulated expression of defense-related and PAMP-triggered immunity marker genes and increased callose deposition and H2O2 accumulation. Furthermore, the SlSAHH-co-silenced plants also exhibited enhanced drought stress tolerance although they had relatively small roots. These data demonstrate that, in addition to the functions in growth and development, SAHHs also play important roles in regulating biotic and abiotic stress responses in plants.

No MeSH data available.


Related in: MedlinePlus