Spatial and temporal synthesis of Mamestra configurata peritrophic matrix through a larval stadium.

The structure and synthesis of the Mamestra configurata peritrophic matrix (PM) was examined at various time points during a larval stadium. Bright field and confocal fluorescence microscopy revealed major differences between the PM of feeding and molting larvae. The PM from feeding larvae was thinner and composed of approximately 5-10 layers. In contrast, mid-molt larvae had a chitinaceaous PM composed of multiple thick layers which filled most of the midgut lumen. PM synthesis initiates in the anterior midgut, based on the expression of genes encoding chitin synthase-2 (CHS-2), coincident with the incorporation of the major structural PM proteins (McIIM1, McIIM2 and McPM1). This is followed by reinforcement with other PM proteins (McIIM3 and McIIM4) as it moves toward the posterior of the midgut. Chitin deacetylase (McCDA1) was associated only with the anterior PM. Collectively, these findings indicate that the structural properties of the PM differ along the length of the midgut. Genes encoding chitinolytic enzymes (McCHI and McNAG) were expressed and exochitinase activity was present when the PM had degraded (pre-molt) and when the new PM was forming (mid-molt), indicating that they are involved in either PM turnover and/or maintenance dependent upon the stage.