Salicylic acid (SA) is an important plant hormone that is best known for mediating host responses upon pathogen infection. Its role in plant defense activation is well established, but its biosynthesis in plants is not fully understood. SA is considered to be derived from two possible pathways; the ICS and PAL pathway, both starting from chorismate. The importance of both pathways for biosynthesis differs between plant species, rendering it hard to make generalizations about SA production that cover the entire plant kingdom. Yet, understanding SA biosynthesis is important to gain insight into how plant pathogen responses function and how pathogens can interfere with them. In this review, we have taken a closer look at how SA is synthesized and the importance of both biosynthesis pathways in different plant species.

Hirschmanniella oryzae is one of the most devastating pests in rice fields worldwide. Because H. oryzae is well adapted to flooded conditions, it is a major problem in flooded rice ecosystems (Babatola, 1981). This migratory nematode penetrates the root and migrates through the aerenchyma, completing its life cycle in about 33 days (Karakas, 2004). Plant-parasitic nematodes are equipped with an arsenal of cell wall-modifying proteins that are secreted through the stylet into the host tissue to hydrolyse cell walls (Davis et al., 2011). Sedentary nematodes establish a feeding site, whereby it is important to remain undetected by the plant to prevent an adequate defence response.