THE INFLUENCE OF BACTERIAL SPECIES AND INTENSITY OF INFECTIONS ON NODULE FORMATION IN INSECTS

Nodulation is the predominant cellular immune reaction to bacterial in fection in insects. Nodulation is a complex process involving an unkno wn number of discrete cellular actions, Currently, there is only limit ed information on the signal transduction mechanisms that result in no dulation, In older larvae of the tobacco hornworm, Manduca sexta, and of the tenebrionid beetle, Zophobas atratus, eicosanoids are involved in one or more steps in the overall process, and treating these insect s with inhibitors of eicosanoid biosynthesis prior to bacterial infect ion severely impairs their ability to form nodules, In this paper we a ddress more detailed questions on eicosanoid-mediated nodulation. The nodulation reaction to bacterial infection occurs in all larval stages we examined, specifically, second, third, and fourth instars of M. se xta. In both species, the number of nodules formed in response to bact erial infection is related in an exponential way to the number of bact erial cells in the infection. Nodulation is also not related to larval size. We also found that nodulation intensity varies according to the species of infecting bacteria. (C) 1998 Elsevier Science Ltd. All rig hts reserved.