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The dynamics of cell wall components during gall development are related to structural specialization to meet the defensive or nutritional requirements of gall tissues. Cell wall features have been studied mostly in galls induced by hemipterans (Psylloidea), while galls induced by Cecidomyiidae have been little explored. We applied monoclonal antibodies to epitopes of proteins and pectins in the cell walls of non-galled leaves and galls induced by Clinodiplosis sp. (Diptera; Cecidomyiidae) on Croton floribundus Spreng. (Euphorbiaceae). The complexity of tissue zonation in Clinodiplosis galls reflected the impairment of the activity of the pectin-methylesterases during development. The labeling of the epitopes of extensins in young galls denoted cell enlargement with resistant cell walls, while the labeling of epitopes of the arabinogalactan proteins in senescent galls indicated the involvement of these proteins with programmed cell death, at the end of cell cycles at the gall development site. We conclude that the cell wall profile in Clinodiplosis galls implies an imbalance between tissue porosity, cell-to-cell signaling, and resistance linked to tissue structural and functional compartments. Current data confirm the presence of the epitopes of extensins in young galls, and the compartmentalization of homogalacturonans and rhamnogalacturonan I in galls as an independent taxon feature.

Gall-inducing insects manipulate the structural, histochemical and physiological profiles of host-plant tissues to develop galls. We evaluated galls induced by Eugeniamyia dispar on the leaves of Eugenia uniflora in an attempt to answer the following questions: (i) How does this gall-inducing insect change the structural and histochemical profiles of the host-plant organ? (ii) Despite structural changes, can gall tissues maintain photosynthetic activity? Starch, proteins, reducing sugars and reactive oxygen species were detected mainly in the nutritive tissue surrounding the larval chamber. Despite structural changes, the galls induced by E. dispar on E. uniflora retain chlorophyllous tissue, although its amount and photosynthetic activity are less than that of non-galled leaves. This reduced photosynthetic activity, in association with the presence of large intercellular spaces, could improve gas diffusion and, consequently, avoid hypoxia and hypercarbia in gall tissue.

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