Trehalose phosphate synthase 5‐dependent trehalose metabolism modulates basal defense responses in
            Arabidopsis thaliana

Xanthomonas oryzae pv. oryzae is the causal agent of bacterial blight of rice. The XopR protein, secreted into plant cells through the type III secretion apparatus, is widely conserved in xanthomonads and is predicted to play important roles in bacterial pathogenicity. Here, we examined the function of XopR by constructing transgenic Arabidopsis thaliana plants expressing it under control of the dexamethasone (DEX)-inducible promoter. In the transgenic plants treated with DEX, slightly delayed growth and variegation on leaves were observed. Induction of four microbe-associated molecular pattern (MAMP)-specific early-defense genes by a nonpathogenic X. campestris pv. campestris hrcC deletion mutant were strongly suppressed in the XopR-expressing plants. XopR expression also reduced the deposition of callose, an immune response induced by flg22. When transiently expressed in Nicotiana benthamiana, a XopR::Citrine fusion gene product localized to the plasma membrane. The deletion of XopR in X. oryzae pv. oryzae resulted in reduced pathogenicity on host rice plants. Collectively, these results suggest that XopR inhibits basal defense responses in plants rapidly after MAMP recognition.

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The Role of TIR-NBS and TIR-X Proteins in Plant Basal Defense Responses

PLANT PHYSIOLOGY ◽

10.1104/pp.113.219162 ◽

2013 ◽

Vol 162 (3) ◽

pp. 1459-1472 ◽

Cited By ~ 68

Author(s):

R. S. Nandety ◽

J. L. Caplan ◽

K. Cavanaugh ◽

B. Perroud ◽

T. Wroblewski ◽

...

Keyword(s):

Defense Responses ◽

Basal Defense

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Hormone-regulated defense and stress response networks contribute to heterosis in Arabidopsis F1 hybrids

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1519926112 ◽

2015 ◽

Vol 112 (46) ◽

pp. E6397-E6406 ◽

Cited By ~ 56

Author(s):

Michael Groszmann ◽

Rebeca Gonzalez-Bayon ◽

Rebecca L. Lyons ◽

Ian K. Greaves ◽

Kemal Kazan ◽

...

Keyword(s):

Stress Response ◽

Pseudomonas Syringae ◽

Defense Responses ◽

Gene Activity ◽

Hybrid Vigor ◽

Superior Performance ◽

F1 Hybrids ◽

Biosynthesis Pathway ◽

Leaf Cell ◽

Basal Defense

Plant hybrids are extensively used in agriculture to deliver increases in yields, yet the molecular basis of their superior performance (heterosis) is not well understood. Our transcriptome analysis of a number of Arabidopsis F1 hybrids identified changes to defense and stress response gene expression consistent with a reduction in basal defense levels. Given the reported antagonism between plant immunity and growth, we suggest that these altered patterns of expression contribute to the greater growth of the hybrids. The altered patterns of expression in the hybrids indicate decreases to the salicylic acid (SA) biosynthesis pathway and increases in the auxin [indole-3-acetic acid (IAA)] biosynthesis pathway. SA and IAA are hormones known to control stress and defense responses as well as plant growth. We found that IAA-targeted gene activity is frequently increased in hybrids, correlating with a common heterotic phenotype of greater leaf cell numbers. Reduced SA concentration and target gene responses occur in the larger hybrids and promote increased leaf cell size. We demonstrated the importance of SA action to the hybrid phenotype by manipulating endogenous SA concentrations. Increasing SA diminished heterosis in SA-reduced hybrids, whereas decreasing SA promoted growth in some hybrids and phenocopied aspects of hybrid vigor in parental lines. Pseudomonas syringae infection of hybrids demonstrated that the reductions in basal defense gene activity in these hybrids does not necessarily compromise their ability to mount a defense response comparable to the parents.

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Bacillus cereus AR156 Activates Defense Responses to Pseudomonas syringae pv. tomato in Arabidopsis thaliana Similarly to flg22

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-10-17-0240-r ◽

2018 ◽

Vol 31 (3) ◽

pp. 311-322 ◽

Cited By ~ 9

Author(s):

Shune Wang ◽

Ying Zheng ◽

Chun Gu ◽

Chan He ◽

Mengying Yang ◽

...

Keyword(s):

Arabidopsis Thaliana ◽

Bacillus Cereus ◽

Pseudomonas Syringae ◽

Transcriptional Profiling ◽

Quantitative Polymerase Chain Reaction ◽

Polymerase Chain Reaction Analysis ◽

Defense Responses ◽

Systemic Resistance ◽

Callose Deposition ◽

Plant Growth Promoting

Bacillus cereus AR156 (AR156) is a plant growth–promoting rhizobacterium capable of inducing systemic resistance to Pseudomonas syringae pv. tomato in Arabidopsis thaliana. Here, we show that, when applied to Arabidopsis leaves, AR156 acted similarly to flg22, a typical pathogen-associated molecular pattern (PAMP), in initiating PAMP-triggered immunity (PTI). AR156-elicited PTI responses included phosphorylation of MPK3 and MPK6, induction of the expression of defense-related genes PR1, FRK1, WRKY22, and WRKY29, production of reactive oxygen species, and callose deposition. Pretreatment with AR156 still significantly reduced P. syringae pv. tomato multiplication and disease severity in NahG transgenic plants and mutants sid2-2, jar1, etr1, ein2, npr1, and fls2. This suggests that AR156-induced PTI responses require neither salicylic acid, jasmonic acid, and ethylene signaling nor flagella receptor kinase FLS2, the receptor of flg22. On the other hand, AR156 and flg22 acted in concert to differentially regulate a number of AGO1-bound microRNAs that function to mediate PTI. A full-genome transcriptional profiling analysis indicated that AR156 and flg22 activated similar transcriptional programs, coregulating the expression of 117 genes; their concerted regulation of 16 genes was confirmed by real-time quantitative polymerase chain reaction analysis. These results suggest that AR156 activates basal defense responses to P. syringae pv. tomato in Arabidopsis, similarly to flg22.

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