After every run, the column was equilibrated in 20 mM NaOH for 10 min. have a greater impact due to the nutrient losses caused by colonies draining plants and promoting saprophytic fungal growth, thus significantly decreasing crop yields (?stman et al., 2003; Dedryver et al., 2010). Moreover, viruses transmitted by aphids are the most relevant risk factor for the target crop. Indeed, aphids function as vectors for 50% of the 700 known Dutasteride (Avodart) insect-borne viruses (Hooks and Fereres, 2006; Dedryver et al., 2010). Consequently, aphids are one of the most costly pests in terms of pesticide treatments (Murray et al., 2013). The aphid feeding process starts when the stylet penetrates the host and then moves toward the phloem through intercellular pathways, such as cell wall matrices, middle lamellae, and gas spaces, until sieve elements are reached (Kimmins, 1986; Tjallingii and Esch, 1993). Most cells along the stylet pathway are briefly punctured (typically for 5C10 s), but the stylets are always withdrawn from the cells and then continue along Dutasteride (Avodart) the intercellular route until sieve elements are found (Tjallingii and Esch, 1993). Intercellular cell wall polysaccharides are a main component of the intercellular stylet pathway. These macromolecules share common features among vascular plants and consist of cellulose microfibrils anchored to the cell membrane, cross-linked by and embedded in matrices of hemicellulose and pectic polymers (Ridley et al., 2001; Wolf and Greiner, 2012). In this context, homogalacturonan (HG) has been found to participate in different plant developmental and defensive processes (Ridley et al., 2001; Gramegna et al., 2016). HG is a homopolymer of galacturonic acid (GalA) residues, which can be methylesterified at C-6 and may carry acetyl groups on O-2 and O-3 (Ridley et al., 2001). According to the current model of HG synthesis, it has been established that HGs are synthesized in the Golgi apparatus in a highly methylesterified state and then secreted into the cell wall (Ibar and Orellana, 2007). In the cell wall, the methylesterification status may be modified by the action of pectin methylesterases (PMEs), which remove Dutasteride (Avodart) the methylester groups (EC In turn, these reactions of HG demethylesterification are regulated by the proteinaceous PME inhibitors (PMEIs) (Hothorn et al., 2004; Caffall and Mohnen, 2009; Saez-Aguayo et al., 2013; Levesque-Tremblay et al., 2015). The degree and pattern of HG methylesterification are key factors influencing the mechanical properties of cell walls, and BNIP3 hence in controlling plant development (Peaucelle et al., 2008; Levesque-Tremblay et al., 2015). In fact, depending on the methylesterification degree, HG domains can be directed into different fates: (1) polymer breakdown by polygalacturonases (PGs; EC and pectate lyase (PL; EC, causing cell wall loosening, and (2) ionic cross-linking with other demethylesterified HG chains through calcium ion bridges, creating the so-called egg box structures leading to cell wall stiffening and reduced matrix porosity (Braccini et al., 1999; Willats et al., 2001; Levesque-Tremblay et al., 2015). HG modification and degradation are important factors during the attack of pathogens or phytophagous insects possessing cell wall-degrading enzymes such as PMEs, PGs, and PLs as virulence factors (Cantu et al., 2008; Malinovsky et al., 2014). The evidence linking HG to the defensive responses of plants includes the broad spectrum of pathogen resistance or susceptibility phenotypes that are created by altering HG-modifying enzymes in different plant species Dutasteride (Avodart) (Cantu Dutasteride (Avodart) et al., 2008). Although the evidence relating to HG metabolism during aphid feeding is limited, it is thought that the presence of HG-modifying enzymes such as PMEs and PGs, in the saliva of aphids, could facilitate stylet penetration through the intercellular matrix (McAllan and Adams, 1961; Dreyer and Campbell, 1987; Ma et al., 1990). Additionally, by exploring the transcriptional profiles of Arabidopsis ((feeding yet was unchanged during the interaction with other attackers studied. Despite this valuable information, there still.