Jasmonic Acid-Involved OsEDS1 Signaling in Rice-Bacteria Interactions

Abstract

Background: The function of Arabidopsis enhanced disease susceptibility 1 (AtEDS1) and its sequence homologs in other dicots have been extensively studied. However, it is unknown whether rice EDS1 homolog (OsEDS1) plays a role in regulating the rice-pathogen interaction.

Results: In this study, a OsEDS1-knouckout mutant (oseds1) was characterized and shown to have increased susceptibility to Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc), suggesting the positive role of OsEDS1 in regulating rice disease resistance. However, the following evidence suggests that OsEDS1 shares some differences with AtEDS1 in its way to regulate the host-pathogen interactions. Firstly, OsEDS1 modulates the rice-bacteria interactions involving in jasmonic acid (JA) signaling pathway, while AtEDS1 regulates Arabidopsis disease resistance against biotrophic pathogens depending on salicylic acid (SA) signaling pathway. Secondly, introducing AtEDS1 could reduce oseds1 mutant susceptibility to Xoo rather than to Xoc. Thirdly, exogenous application of JA and SA cannot complement the susceptible phenotype of the oseds1 mutant, while exogenous application of SA is capable of complementing the susceptible phenotype of the ateds1 mutant. Finally, OsEDS1 is not required for R gene mediated resistance, while AtEDS1 is required for disease resistance mediated by TIR-NB-LRR class of R proteins.

Conclusion: OsEDS1 is a positive regulator in rice-pathogen interactions, and shares both similarities and differences with AtEDS1 in its way to regulate plant-pathogen interactions.

Keywords: Bacterial blight; Bacterial leaf streak; Enhanced disease susceptibility 1; Jasmonic acid; Oryza sativa; Salicylic acid; Xanthomonas oryzae.

Fig. 1

OsPAD4 directly interacted with OsEDS1. a OsPAD4 interacts with OsEDS1. BiFC analysis of OsEDS1 and OsPAD4 interaction. Fluorescence can be observed only in tobacco (Nicotiana benthamiana) cells co-transfected with OsPAD4-nYFP and OsEDS1-cYFP plasmids. Bars indicate 50 μm. b Protein pull-down assay for detection of His-TF-OsPAD4 and MBP-OsEDS1 interaction. Ten micrograms of His-TF-OsPAD4 coupled beads were used to pull down 5 μg MBP or MBP-OsEDS1 protein. Anti-MBP antibody was used to detect output protein. Anti-His antibody was used to detect input protein

Fig. 2

The increased susceptibility of oseds1 mutant to X. oryzae was associated with insertion of T-DNA. Two-tail student’s t-test. The “a” and “b” above bar indicate significant differences between wild-type (WT) and oseds1 plants at P < 0.01 and P < 0.05, respectively. a T-DNA insertion site in oseds1 mutant. T-DNA was inserted at position 587 of OsEDS1, counting the first nucleotide of translation start codon (ATG) as 1. TAA, translation stop codon. Arrows were PCR primers used for examination of the mutant. F9 + R, OsEDS1 primers; LSP2 + R, T-DNA, and OsEDS1 primers. b Homozygous oseds1 mutant was more susceptible to Xoo than heterozygotes and WT siblings (WT1). Data represent mean ± SE (n = 4 to 5). Plants 4, 6, 7 and 16 were homozygous oseds1 mutants, 1, 2, 5, 10, 11, 13, 14 and 15 were heterozygotes, and 3, 8, 9, and 12 were WT1. c Bacterial growth was analyzed at 12 days and disease symptoms at 14 days after Xoo infection. Data represent mean ± SE (n = 3). d oseds1 was more susceptible to Xoc. Lesion length and disease symptom were analyzed at seven days after Xoc infection. Data represent mean ± SE (n = 10 to 15). e oseds1 had a similar level of susceptibility to M. oryzae to that of WT plants. Disease index and disease symptom were analyzed at seven days after X. oryzae infection. Data represent mean ± SE (n = 23 to 28). f oseds1 affected a set of defense-related genes expression. Data represent mean ± SE (n = 3)

Fig. 3

Introduction of E^WT and E^S143L constructs complemented oseds1 mutant phenotype. Two-tail student’s t-test. ** and * above bar indicate significant differences compared to oseds1 at P < 0.01 and P < 0.05, respectively. The “a” and “b” above bar indicate significant differences compared to wild-type (WT) at P < 0.01 and P < 0.05, respectively. a Introduction of E^WT and E^S143L to oseds1 mutant restored plants showing reduced susceptibility. Data represent mean ± SE (n = 10 to 69). b Introducing E^WT and E^S143L to oseds1 mutant restored PR1a, PR5, and JAZ8 expression. Data represent mean ± SE (n = 3)

Fig. 4

Introduction of E^At partially complemented oseds1 mutant phenotype. Data represent mean ± SE (n = 10 to 56, and 3 for gene expression). Two-tail student’s t-test. ** and * indicate significant differences compared to oseds1 at P < 0.01 and P < 0.05, respectively. The “a” and “b” above bar indicate significant differences compared to wild-type (WT) at P < 0.01 and P < 0.05, respectively. a Introducing E^At to oseds1 mutant restored plants with partially reduced susceptibility to Xoo. b Introducing E^At to oseds1 mutant restored PR5, JAZ8, and PR1a expression

Fig. 5

OsEDS1 was not required for R-mediated resistance to Xoo. Data represent mean ± SE (n = 11 to 15 for lesion length, and 3 for bacterial growth and gene expression). WT, wild-type Zhonghua 11; MKbZH1, transgenic line carrying R gene Xa3/Xa26 with the genetic background of Zhonghua 11. a The oseds1 did not influence Xa3/Xa26-mediated resistance. Bacterial growth were analyzed at 12 days after Xoo inoculation. Different letters above bars indicate significant differences at P < 0.01 by the one-way ANOVA test. b OsEDS1 showed similar expression patterns in both resistant and susceptible reactions. Two-tail student’s t-test. The “a” or “b” above bar indicate significant differences between non-inoculated control (ck) plants and inoculated plants at P < 0.01 or P < 0.05, respectively. The ** above bar indicate significant differences between WT and MKbZH1 plants after the same treatment at P < 0.01

Fig. 6

The oseds1 mutant performance response to Xoo inoculation and hormone treatment. Two-tail student’s t-test. ** and * above bar indicate significant differences between oseds1 and wild-type (WT) plants after the same treatment at P < 0.01 and P < 0.05, respectively. The “a” and “b” above bar indicate significant differences between un-infection (ck) and infection plants at P < 0.01 and P < 0.05, respectively. FW, fresh weight. a Hormone content in oseds1. Bars represent mean ± SE (n = 3). b Genes expression in oseds1. Bars represent mean ± SE (n = 3). c Exogenous application of JA or SA did not reduce the susceptibility of oseds1 mutant to Xoo invasion. Bacterial growth was analyzed at 12 days after Xoo infection. Bars represent mean ± SE (n = 30 to 38 for lesion length, and 3 for bacterial growth)