Tomato SlMPK4 is required for resistance against Botrytis cinerea and tolerance to drought stress

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ORIGINAL PAPER

Tomato SlMPK4 is required for resistance against Botrytis cinerea and tolerance to drought stress Nasar Virk • Bo Liu • Huijuan Zhang • Xiaohui Li Yafen Zhang • Dayong Li • Fengming Song



Received: 28 June 2012 / Revised: 25 September 2012 / Accepted: 13 November 2012 / Published online: 27 November 2012 Ó Franciszek Go´rski Institute of Plant Physiology, Polish Academy of Sciences, Krako´w 2012

Abstract Mitogen-activated protein kinases (MPKs) play important roles in biotic and abiotic stress responses. In the present study, we identified a tomato MPK gene, SlMPK4, a possible homolog of Arabidopsis AtMPK4, and performed functional analysis to examine its possible roles in biotic and abiotic responses. Expression of SlMPK4 was induced by infection with Botrytis cinerea and by exogenous application of jasmonic acid and ethylene precursor 1-amino cyclopropane-1-carboxylic acid. Knockdown of the endogenous SlMPK4 expression through virus-induced gene silencing in tomato plants (TRV-SlMPK4) resulted in increased susceptibility to B. cinerea. Expression of defense-related genes SlPR1a and SlPR1b were up-regulated in the SlMPK4-silenced plants. Furthermore, silencing of the SlMPK4 gene also resulted in reduced tolerance against drought stress, leading to earlier wilting symptom under drought stress condition, as compared with the control plants. These results suggest important roles for SlMPK4 in disease resistance against B. cinerea and tolerance to drought stress. Keywords Mitogen-activated protein kinase (MPK)  SlMPK4  Disease resistance  Drought tolerance  Tomato (Solanum lycopersicum)

Communicated by B. Barna. N. Virk  B. Liu  H. Zhang  X. Li  Y. Zhang  D. Li  F. Song (&) National Key Laboratory for Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, Zhejiang, China e-mail: [email protected]

Introduction Plants are vulnerable to various biotic and abiotic stresses that can harden plant’s ability to survive. However, plants have developed sophisticated signaling networks to precisely regulate defense responses against pathogen attack and abiotic stress. In case of pathogens, two innate immune systems, pathogen-associated molecular pattern (PAMP)triggered immunity (PTI) and effector-triggered immunity (ETI), have been identified in plants that trigger defense response against different types of pathogens (Jones and Dangl 2006; Boller and He 2009). In both PTI and ETI, recognition of PAMPs or pathogen-secreted effectors can activate a complex immune response against pathogen infection (Jones and Dangl 2006), and the immune response activated in ETI results in disease resistance and hypersensitive response (HR), which is characterized by a rapid, localized death of tissues at the site of infection, limiting further pathogen multiplication and spread. Generally, HR is the outcome of gene-for-gene interactions between plants and biotrophic pathogens, in which a specific resistance protein from plant recognizes an avirulence effector from the pathogen, ultimately le