Differential cell wall composition in eriococcid-induced galls: unraveling the influence of sexual dimorphism.

Abstract

Eriococcid-induced galls exhibit many unusual features, such as sexual dimorphism and differences in life cycle duration, which are reflected in the morphology, anatomy, and metabolism of female- and male-induced galls. These sex-based distinctions between the galls result from differential developmental processes related to the time female and male insects remain inside the gall, their feeding activity, and the degree of stress imposed on the host plant cellular machinery. We assessed the immunocytochemical and Raman spectroscopy profiles of two host plant-gall inducer systems: Annona dolabripetala (Annonaceae)-Pseudotectococccus rolliniae Hodgson and Gonçalves, and Pseudobombax grandiflorum (Malvaceae)-Eriogallococcus isaias Hodgson and Magalhães. We expected differences in the dynamics of cell wall chemical components between male and female galls, with particular effects on gall structural and functional profiles, also regarding specific constraints in each system. The epitopes of xylogalacturonans and homogalacturonans, as well as their degree of methylesterification, are affected by the sex of the gall inducers, conferring a rigid structure to the cell walls of female-induced galls in comparison with those of the male-induced galls. Raman spectroscopy detected cellulose peaks in both female- and male-induced galls, with pronounced lignin bands in female-induced galls. The sex-based chemical distinctions between female- and male-induced galls imply in differences in terms of higher rigid cell walls in the female-induced galls, which was similar for both host plants.