Ac. Cohen et Ag. Wheeler, ROLE OF SALIVA IN THE HIGHLY DESTRUCTIVE FOURLINED PLANT BUG (HEMIPTERA, MIRIDAE, MIRINAE), Annals of the Entomological Society of America, 91(1), 1998, pp. 94-100
The fourlined plant bug, Poecilocapsus lineatus (F.), is among the mor
e damaging hemipterans, causing immediate and conspicuous lesions at f
eeding sites on leaves. The damage appears histologically to involve c
omplete loss of cellular integrity and removal of the palisade cell la
yer. The ability of P. lineatus to cause such remarkable damage appear
s to reside in the chemical nature of its salivary products; however,
among tests of the salivary enzymes that included assays for pectinase
, cellulase, proteinase, polyphenol oxidase, lipase, and amylase, only
an exopectinase was found. The size of the salivary gland complex in
later instars and adults (approximate to 14-21% of total body mass) wa
s proportionately far greater than that found in other Heteroptera, su
ch as in another mirid, Lygus hesperus Knight (where salivary gland co
mplexes were only 4-7% of total body mass). Ultrastructure analysis of
the salivary glands revealed that the vast majority of the cellular m
ake-up of the glands is rough endoplasmic reticulum. A complex of prot
eins was present in salivary gland extracts with molecular weights of
87, 79, 42, 33, 30, and 21 kDa. Gel filtration chromatography revealed
a major peak of exopectinase activity corresponding to a molecular we
ight of approximate to 30-35 kDa; and ion exchange chromatography reve
aled 2 peaks of exopectinase activity eluting with an ion strength of
approximate to 0.4 and 0.5 M NaCl.