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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 enhanced resistance to P. syringae pv. tomato DC3000. Ten-day-old seedlings were infiltrated with agrobacteria carrying TRV-SlSAHH1/2/3, TRV-SlSAHHa or TRV-GUS constructs and were inoculated by vacuum infiltration with Pst DC3000 (OD600 = 0.0002) at 4 weeks after VIGS infiltration. (A) Representative disease symptom on leaves of the TRV-GUS- and TRV-SlSAHH-infiltrated plants. Photos were taken 3 days after inoculation (dpi). (B) Bacterial growth in inoculated leaves of TRV-GUS- and TRV-SlSAHH-infiltrated plants at 0 and 3 dpi. (C) Changes of SAHH activity in TRV-GUS- and TRV-SlSAHHa-infiltrated plants after inoculation with Pst DC3000. (D) SA contents in TRV-GUS- and TRV-SlSAHHa-infiltrated plants without and 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. Similar results were obtained in independent experiments (A) and data presented in (B), (C), and (D) are the means ± SD from three independent experiments. ∗ above the columns in (B), (C), and (D) indicate significant differences at p < 0.05 level between the TRV-SlSAHHa- and TRV-GUS-infiltrated plants.
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Figure 3: Co-silencing of SlSAHHs conferred enhanced resistance to P. syringae pv. tomato DC3000. Ten-day-old seedlings were infiltrated with agrobacteria carrying TRV-SlSAHH1/2/3, TRV-SlSAHHa or TRV-GUS constructs and were inoculated by vacuum infiltration with Pst DC3000 (OD600 = 0.0002) at 4 weeks after VIGS infiltration. (A) Representative disease symptom on leaves of the TRV-GUS- and TRV-SlSAHH-infiltrated plants. Photos were taken 3 days after inoculation (dpi). (B) Bacterial growth in inoculated leaves of TRV-GUS- and TRV-SlSAHH-infiltrated plants at 0 and 3 dpi. (C) Changes of SAHH activity in TRV-GUS- and TRV-SlSAHHa-infiltrated plants after inoculation with Pst DC3000. (D) SA contents in TRV-GUS- and TRV-SlSAHHa-infiltrated plants without and 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. Similar results were obtained in independent experiments (A) and data presented in (B), (C), and (D) are the means ± SD from three independent experiments. ∗ above the columns in (B), (C), and (D) indicate significant differences at p < 0.05 level between the TRV-SlSAHHa- and TRV-GUS-infiltrated plants.

Mentions: To explore the involvement of SlSAHHs in disease resistance, we compared the disease phenotypes between SlSAHH-silenced and non-silenced plants after infection with Pst DC3000 or B. cinerea. Under our experiment condition, typical disease symptom was appeared at 4 days after inoculation (dpi) with Pst DC3000. At this time point, large numbers of small necrotic spots were seen in leaves of the SlSAHH1-, SlSAHH2-, SlSAHH3-silenced and the TRV-GUS-infiltrated control plants; however, almost no necrotic spot was observed in leaves of the TRV-SlSAHHa-infiltrated plants (Figure 3A). This was further confirmed by measurement of the bacterial growth in planta. At 4 dpi, the bacterial populations in leaves of the TRV-GUS-infiltrated control plants and of the SlSAHH1-, SlSAHH2-, SlSAHH3-silenced plants were comparable, accounting for 4.17 × 106 CFU/cm2, 2.82 × 106 CFU/cm2, 1.21 × 106 CFU/cm2 and 1.73 × 106 CFU/cm2, respectively (Figure 3B). However, the bacterial population in leaves of the TRV-SlSAHHa-infiltrated plants at 4 dpi was 1.15 × 104 CFU/cm2, giving ∼360 times lower than that in leaves of the TRV-GUS-infiltrated plants (Figure 3B). Additionally, we also analyzed the changes in SAHH activity in TRV-GUS- and TRV-SlSAHHa-infiltrated plants after infection of Pst DC3000. As shown in Figure 3C, the SAHH activity in TRV-SlSAHHa-infiltrated plants was significantly reduced, accounting for 31% of the activity in the TRV-GUS-infiltrated plants at 0 h after inoculation. However, the SAHH activity in both of the TRV-GUS- and TRV-SlSAHHa-infiltrated plants was decreased with the times during a period of 3 dpi and the activity in TRV-SlSAHHa-infiltrated plants was decreased significantly, as compared with those in the TRV-GUS-infiltrated plants at 1, 2, and 3 dpi (Figure 3C). We also examined whether co-silencing of SlSAHHs affected the endogenous SA levels. As shown in Figure 3D, the SA level in TRV-SlSAHHa-infiltrated plants was significantly increased by 52% compared to that in TRV-GUS-infiltrated plants without inoculation of Pst DC3000; however, the SA level in TRV-SlSAHHa-infiltrated plants showed a further increase of 85% as compared to that in TRV-GUS-infiltrated plants at 24 h after inoculation with Pst DC3000 (Figure 3D). These data indicate that co-silencing of SlSAHHs resulted in an enhanced resistance of tomato plants to Pst DC3000 as revealed by the reduced disease symptom, decreased bacterial population, increased SA level and suppressed the SAHH activity.


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 enhanced resistance to P. syringae pv. tomato DC3000. Ten-day-old seedlings were infiltrated with agrobacteria carrying TRV-SlSAHH1/2/3, TRV-SlSAHHa or TRV-GUS constructs and were inoculated by vacuum infiltration with Pst DC3000 (OD600 = 0.0002) at 4 weeks after VIGS infiltration. (A) Representative disease symptom on leaves of the TRV-GUS- and TRV-SlSAHH-infiltrated plants. Photos were taken 3 days after inoculation (dpi). (B) Bacterial growth in inoculated leaves of TRV-GUS- and TRV-SlSAHH-infiltrated plants at 0 and 3 dpi. (C) Changes of SAHH activity in TRV-GUS- and TRV-SlSAHHa-infiltrated plants after inoculation with Pst DC3000. (D) SA contents in TRV-GUS- and TRV-SlSAHHa-infiltrated plants without and 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. Similar results were obtained in independent experiments (A) and data presented in (B), (C), and (D) are the means ± SD from three independent experiments. ∗ above the columns in (B), (C), and (D) indicate significant differences at p < 0.05 level between the TRV-SlSAHHa- and TRV-GUS-infiltrated plants.
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Figure 3: Co-silencing of SlSAHHs conferred enhanced resistance to P. syringae pv. tomato DC3000. Ten-day-old seedlings were infiltrated with agrobacteria carrying TRV-SlSAHH1/2/3, TRV-SlSAHHa or TRV-GUS constructs and were inoculated by vacuum infiltration with Pst DC3000 (OD600 = 0.0002) at 4 weeks after VIGS infiltration. (A) Representative disease symptom on leaves of the TRV-GUS- and TRV-SlSAHH-infiltrated plants. Photos were taken 3 days after inoculation (dpi). (B) Bacterial growth in inoculated leaves of TRV-GUS- and TRV-SlSAHH-infiltrated plants at 0 and 3 dpi. (C) Changes of SAHH activity in TRV-GUS- and TRV-SlSAHHa-infiltrated plants after inoculation with Pst DC3000. (D) SA contents in TRV-GUS- and TRV-SlSAHHa-infiltrated plants without and 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. Similar results were obtained in independent experiments (A) and data presented in (B), (C), and (D) are the means ± SD from three independent experiments. ∗ above the columns in (B), (C), and (D) indicate significant differences at p < 0.05 level between the TRV-SlSAHHa- and TRV-GUS-infiltrated plants.
Mentions: To explore the involvement of SlSAHHs in disease resistance, we compared the disease phenotypes between SlSAHH-silenced and non-silenced plants after infection with Pst DC3000 or B. cinerea. Under our experiment condition, typical disease symptom was appeared at 4 days after inoculation (dpi) with Pst DC3000. At this time point, large numbers of small necrotic spots were seen in leaves of the SlSAHH1-, SlSAHH2-, SlSAHH3-silenced and the TRV-GUS-infiltrated control plants; however, almost no necrotic spot was observed in leaves of the TRV-SlSAHHa-infiltrated plants (Figure 3A). This was further confirmed by measurement of the bacterial growth in planta. At 4 dpi, the bacterial populations in leaves of the TRV-GUS-infiltrated control plants and of the SlSAHH1-, SlSAHH2-, SlSAHH3-silenced plants were comparable, accounting for 4.17 × 106 CFU/cm2, 2.82 × 106 CFU/cm2, 1.21 × 106 CFU/cm2 and 1.73 × 106 CFU/cm2, respectively (Figure 3B). However, the bacterial population in leaves of the TRV-SlSAHHa-infiltrated plants at 4 dpi was 1.15 × 104 CFU/cm2, giving ∼360 times lower than that in leaves of the TRV-GUS-infiltrated plants (Figure 3B). Additionally, we also analyzed the changes in SAHH activity in TRV-GUS- and TRV-SlSAHHa-infiltrated plants after infection of Pst DC3000. As shown in Figure 3C, the SAHH activity in TRV-SlSAHHa-infiltrated plants was significantly reduced, accounting for 31% of the activity in the TRV-GUS-infiltrated plants at 0 h after inoculation. However, the SAHH activity in both of the TRV-GUS- and TRV-SlSAHHa-infiltrated plants was decreased with the times during a period of 3 dpi and the activity in TRV-SlSAHHa-infiltrated plants was decreased significantly, as compared with those in the TRV-GUS-infiltrated plants at 1, 2, and 3 dpi (Figure 3C). We also examined whether co-silencing of SlSAHHs affected the endogenous SA levels. As shown in Figure 3D, the SA level in TRV-SlSAHHa-infiltrated plants was significantly increased by 52% compared to that in TRV-GUS-infiltrated plants without inoculation of Pst DC3000; however, the SA level in TRV-SlSAHHa-infiltrated plants showed a further increase of 85% as compared to that in TRV-GUS-infiltrated plants at 24 h after inoculation with Pst DC3000 (Figure 3D). These data indicate that co-silencing of SlSAHHs resulted in an enhanced resistance of tomato plants to Pst DC3000 as revealed by the reduced disease symptom, decreased bacterial population, increased SA level and suppressed the SAHH activity.

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