Table 4. Potential roles for nematode PDAs.

TARGET		EFFECT	OUTCOME
Endogenous	Pharyngeal chitin	Facilitates signaling to underlying epithelium;control of length/diameter of chitinous lining	Pharyngeal morphogenesis
		Affects recognition of the pharyngeal liningby other enzymes	Protection of gut from exogenous chitinases
	Eggshell chitin	Alters physical properties of the macromolecule	Hatching or eggshell remodeling
	GAGS or other acetylated hexosamines	Affects various context-specific developmental functions	Morphogenesis
Exogenous	Xylan (Plant hosts)	Permits penetration of host tissues	Virulence
	GAGs (Vertebrate hosts)	Permits penetration of host tissues	Virulence