Poster: Plant Insect/Nematode Interactions

Abs # 685: Is the unique maize 33- kD cysteine proteinase attacking proteins of insect peritrophic matrix?

Presenter:	Pechan, Tibor , pechan@ra.msstate.edu
Authors	Pechan, Tibor  (A)   Ma, Peter  (A)   Williams, Paul  (B)   Luthe, Dawn  (A)
Affiliations:	(A): Mississippi State University (B): USDA-ARS Corn Host Plant Resistance Research Laboratory, Mississippi State

Previous research demonstrated that the 33-kD Mir1 cysteine proteinase accumulates in the whorls of the insect resistant corn genotype Mp708 in response to larval feeding. The growth of Spodoptera frugiperda larvae reared on Mp708, and transgenic Black Mexican Sweet corn callus expressing the Mir1 proteinase was inhibited by approximately 50%. Physiological indices indicated that larvae reared on tissue from resistant plants were unable to convert ingested and digested food into body mass. Scanning electron microscopy (SEM) of larvae peritrophic matrix (PM) showed that larvae reared on resistant corn tissues sustained damage to their PM including holes, cracks, structural voids and abrasions of variable size that penetrated one or more layers of the PM. In all cases there was a negative correlation between larval weight and the extent of PM damage. Proteins of larval PM were extracted, analyzed by 2-D gel electrophoresis, MALDI-TOF mass spectroscopy and 2-D LC/MS/MS. Both in vivo and in vitro effect of Mir1 cysteine proteinase on PM and its proteins were studied. Recombinant Mir1 was expressed in Trichoplusia ni hemolymph, purified by HPLC and used for in vitro studies. In addition, the changes in PM permeability were measured using the apparatus of our design.