Cell wall epitope distribution in the functional compartments of galls induced by Palaeomystella oligophaga (Lepidoptera) in Macairea radula (Melastomataceae)

Context

The parasitic interaction between the galling insect Palaeomystella oligophaga (Lepidoptera) and the host plant tissues of Macairea radula (Melastomataceae) leads to the formation of globoid galls. These galls have storage and typical nutritive tissues (outer and inner compartments, respectively), whose functions may be related to differential cell wall component distributions and to the stage of development of the gall inducer.

Aims

We evaluated whether the cell wall composition of the gall compartments (storage and nutritive tissues) changes according to the developmental stage of the gall inducer P. oligophaga.

Methods

The galls occupied by the gall inducer in different stages of development (i.e. larval and pupal stages, as well as empty galls) were collected and submitted to histological examination, immunocytochemical analyses using monoclonal antibodies for pectins, hemicelluloses, and glycoproteins, and histochemical analyses using phloroglucinol for lignins.

Key results

The histological results showed that nutritive tissues have smaller cells compared with storage ones when the galling insect is in the larval stage. Immunocytochemical analyses also showed the occurrence of both methyl-esterified and unesterified pectins, as well hemicelluloses in the nutritive tissue during the larval stage. The dynamic of some cell wall components changes when the gall inducer is in the pupal stage, or the galls are empty.

Conclusions

The changes in the composition of the cell walls, especially regarding homogalacturonans and xyloglucans, support the high metabolism and resource availability in cell walls of nutritive tissue for the gall inducer.

Implications

The cell wall composition may indicate important metabolic steps during gall formation and galling insect diet.