Plant-parasitic nematode effectors — insights into their diversity and new tools for their identification

Plant-parasitic nematodes (PPNs) are a large group of obligate biotrophic pathogens that secrete molecules, called effectors, involved in parasitism. The majority of work in molecular phytonematology has focused on the root-knot and cyst nematodes, which are both sedentary endoparasitic nematodes. More recently, inexpensive sequencing technology has facilitated effector searches in PPNs with different parasitic lifestyles. Work in different PPN species suggests that effectors are diverse, and selection pressure from plant hosts has contributed to the presence of large, expanded effector gene families. The identification of promoter elements/motifs preceding effector gene sequences suggests that promoter analysis can computationally predict new putative effectors. However, until a method of genetic transformation is available for PPNs, work on characterizing effectors will be hindered.