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OPINION ARTICLE
published: 06 December 2012 doi: 10.3389/fgene.2012.00256

Biotic stress in plants: life lessons from your parents and grandparents
A. E. Dorantes-Acosta1 , C. V. Sánchez-Hernández 2 and M. A. Arteaga-Vázquez1*
Laboratorio de Epigenética y Biología del Desarrollo, Instituto de Biotecnología y Ecología Aplicada (INBIOTECA), Universidad Veracruzana. Xalapa, Veracruz. México 2Departamento de Producción Agrícola, Centro Universitario de Ciencias Biológicas y Agropecuarias, Universidad de Guadalajara, Guadalajara, Jalisco, Mexico *correspondence: maarteaga@uv.mx Edited by: Bernie Carroll, The University of Queensland, Australia Reviewed by: Bernie Carroll, The University of Queensland, Australia
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Epigenetic regulation is essential for growth and development ineukaryotic organisms (Henikoff et al., 2008; Suzuki and Bird, 2008) and is also responsible for the establishment, maintenance, and reversal of non-genetic cellular memory that records developmental and environmental cues, including those arising from biotic and abiotic stress (Bonasio et al., 2010). A series of recent stimulating papers, show that biotic stress can trigger a transgenerationalepigenetic response in plants, where DNA methylation seems to play a central role. Plants sense and respond to environmental cues by a repertoire of mechanisms that regulate gene expression in order to maximize chances of survival in hostile environments. In addition to preformed defense traits, plants have evolved inducible defenses against microbial pathogens, herbivores, and even other plants thatinvolve the regulation of gene expression for the synthesis of defensive secondary metabolites and specific proteins (Walling, 2000; Howe and Jander, 2008; Mithofer and Boland, 2012). Plants rely on the innate immunity of each cell and on systemic signals emanating from infection sites (Jones and Dangl, 2006). Plant hormones play essential roles during systemic defense signaling (RobertSeilaniantz etal., 2011). Salicylic acid (SA) primarily triggers resistance against biotrophic and hemibiotrophic pathogens whereas a combination of jasmonic acid (JA) and ethylene (ET) signaling activates resistance against necrotrophic pathogens (Glazebrook, 2005; Robert-Seilaniantz et al., 2011). SA acts as an endogenous signal involved in systemic acquired resistance (SAR), an inducible resistance

againsta broad spectrum of pathogens including viruses, bacteria, and fungi that cause necrosis through rapid programmed cell death of infected cells, known as the hypersensitive response (Durrant and Dong, 2004). SAR induces resistance in the systemic (uninoculated) plant organs in response to local infection (Vlot et al., 2009). Recent evidence shows that NON-EXPRESSOR of PATHOGENESISRELATED GENES 3(NPR3) and NPR4 are SA receptors that bind SA with different affinities and regulate degradation of the transcription cofactor NPR1 in a SA-dependent manner (Fu et al., 2012). In addition to their role during plant development, JA and JA-related compounds, including methyl-jasmonate (MeJA) and jasmonate-isoleucine conjugate (JA-Ile), play essential roles during endogenous regulation of plantresistance to mechanical wounding and herbivory by modulating global changes in gene expression (Creelman and Mullet, 1997; Sheard et al., 2010). Priming (or sensitization) refers to the enhanced ability for the quicker and more effective activation of specific cellular defense responses upon previous exposure to biotic or abiotic stress (Conrath et al., 2002, 2006). Defense pathways and priming can alsobe induced by application of chemical stimuli including the non-protein amino acid beta-amino-butyric acid (BABA) (Zimmerli et al., 2000). In addition to plant hormones, small RNAs and genes involved in the biogenesis of small RNAs are also components of the plant defense strategies against herbivory and microbial pathogens (Pandey et al., 2008; RuizFerrer and Voinnet, 2009; Katiyar-Agarwal and...