Altered disease development in the eui mutants and Eui overexpressors indicates that gibberellins negatively regulate rice basal disease resistance.

National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.
Molecular Plant (Impact Factor: 6.13). 05/2008; 1(3):528-37. DOI:10.1093/mp/ssn021
Source: PubMed

ABSTRACT Gibberellins (GAs) form a group of important plant tetracyclic diterpenoid hormones that are involved in many aspects of plant growth and development. Emerging evidence implicates that GAs also play roles in stress responses. However, the role of GAs in biotic stress is largely unknown. Here, we report that knockout or overexpression of the Elongated uppermost internode (Eui) gene encoding a GA deactivating enzyme compromises or increases, respectively, disease resistance to bacterial blight (Xanthomonas oryzae pv. oyrzae) and rice blast (Magnaporthe oryzae). Exogenous application of GA(3) and the inhibitor of GA synthesis (uniconazol) could increase disease susceptibility and resistance, respectively, to bacterial blight. Similarly, uniconazol restored disease resistance of the eui mutant and GA(3) decreased disease resistance of the Eui overexpressors to bacterial blight. Therefore, the change of resistance attributes to GA levels. In consistency with this, the GA metabolism genes OsGA20ox2 and OsGA2ox1 were down-regulated during pathogen challenge. We also found that PR1a induction was enhanced but the SA level was decreased in the Eui overexpressor, while the JA level was reduced in the eui mutant. Together, our current study indicates that GAs play a negative role in rice basal disease resistance, with EUI as a positive modulator through regulating the level of bioactive GAs.

0 0
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: The plant hormone abscisic acid (ABA) is involved in a wide variety of plant processes, including the initiation of stress-adaptive responses to various environmental cues. Recently, ABA also emerged as a central factor in the regulation and integration of plant immune responses, although little is known about the underlying mechanisms. Aiming to advance our understanding of ABA-modulated disease resistance, we have analyzed the impact, dynamics and interrelationship of ABA and the classic defense hormone salicylic acid (SA) during progression of rice infection by the leaf blight pathogen Xanthomonas oryzae pv. oryzae (Xoo). Consistent with ABA negatively regulating resistance to Xoo, we found that exogenously administered ABA renders rice hypersusceptible to infection, whereas chemical and genetic disruption of ABA biosynthesis and signaling, respectively, led to enhanced Xoo resistance. In addition, we found successful Xoo infection to be associated with extensive reprogramming of ABA biosynthesis and response genes, suggesting that ABA functions as a virulence factor for Xoo. Interestingly, several lines of evidence indicate that this immune-suppressive effect of ABA is due at least in part to suppression of SA-mediated defenses that normally serve to limit pathogen growth. Resistance induced by the ABA biosynthesis inhibitor fluridone, however, appears to operate in a SA-independent manner and is likely due to induction of non-specific physiological stress. Collectively, our findings favor a scenario whereby virulent Xoo hijacks the rice ABA machinery to cause disease and highlight the importance of ABA and its crosstalk with SA in shaping the outcome of rice-Xoo interactions.
    PLoS ONE 01/2013; 8(6):e67413. · 3.73 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: BACKGROUND: Workarounds circumvent or temporarily 'fix' perceived workflow hindrances to meet a goal or to achieve it more readily. Behaviours fitting the definition of workarounds often include violations, deviations, problem solving, improvisations, procedural failures and shortcuts. Clinicians implement workarounds in response to the complexity of delivering patient care. One imperative to understand workarounds lies in their influence on patient safety. This paper assesses the peer reviewed empirical evidence available on the use, proliferation, conceptualisation, rationalisation and perceived impact of nurses' use of workarounds in acute care settings. METHODS: A literature assessment was undertaken in 2011--2012. Snowballing technique, reference tracking, and a systematic search of twelve academic databases were conducted to identify peer reviewed published studies in acute care settings examining nurses' workarounds. Selection criteria were applied across three phases. 58 studies were included in the final analysis and synthesis. Using an analytic frame, these studies were interrogated for: workarounds implemented in acute care settings by nurses; factors contributing to the development and proliferation of workarounds; the perceived impact of workarounds; and empirical evidence of nurses' conceptualisation and rationalisation of workarounds. RESULTS: The majority of studies examining nurses' workarounds have been published since 2008, predominantly in the United States. Studies conducted across a variety of acute care settings use diverse data collection methods. Nurses' workarounds, primarily perceived negatively, are both individually and collectively enacted. Organisational, work process, patient-related, individual, social and professional factors contribute to the proliferation of workarounds. Group norms, local and organisational culture, 'being competent', and collegiality influence the implementation of workarounds. CONCLUSION: Workarounds enable, yet potentially compromise, the execution of patient care. In some contexts such improvisations may be deemed necessary to the successful implementation of quality care, in others they are counterproductive. Workarounds have individual and cooperative characteristics. Few studies examine nurses' individual and collective conceptualisation and rationalisation of workarounds or measure their impact. The importance of displaying competency (image management), collegiality and organisational and cultural norms play a role in nurses' use of workarounds.
    BMC Genomics 05/2013; 14(1):322. · 4.40 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: Recent advances in plant immunity research underpin the pivotal role of small-molecule hormones in regulating the plant defense signaling network. Although most of our understanding comes from studies of dicot plants such as Arabidopsis thaliana, new studies in monocots are providing additional insights into the defense-regulatory role of phytohormones. Here, we review the roles of both classical and more recently identified stress hormones in regulating immunity in the model monocot rice (Oryza sativa) and highlight the importance of hormone crosstalk in shaping the outcome of rice-pathogen interactions. We also propose a defense model for rice that does not support a dichotomy between the pathogen lifestyle and the effectiveness of the archetypal defense hormones salicylic acid (SA) and jasmonic acid (JA).
    Trends in Plant Science 07/2013; · 11.81 Impact Factor