Respostas celulares, fisiológicas e estruturais induzidas por um Diptera: Cecidomyiidae em Piper arboreum Aubl. (Piperaceae)

Abstract

Galls result from the stimulation of specific inducers, which coordinate tissue changes that provide favorable environment for their development. The specific relationship between host plant-galling herbivore reveals differences, characteristic of each system. Piper arboreum Aubl (Piperaceae) hosts a Diptera: Cecidomyiidae, which induces a lenticular intralaminar morphotype on leaves. The morphological, anatomical and functional design was established by specific food processes linked to the galling herbivore taxa, confirming pre-established patterns. Hypertrophy in anticlinal axis and hyperplasia in periclinal axia were determinant for the lenticular design of the gall. Cell redifferentiation was essential to the tissue neo- functions, such as nutrition and protection. The nutritional requirements of the Cecidomyiidae, and the gall structural development requires nutrient storage and availability via enzymatic activity, especially located in the inner tissues of the gall. The external location of toxic metabolites from the secondary metabolites may protect the gall and galling herbivore against the attack of natural enemies. In Piper arboreum-Cecidomyiidae system spatial compartmentalization, accumulation and availability of carbohydrates produced in response to the gall Cecidomyiidae stimuli, and restrictions imposed by the host plant, modeled specific characteristics of the gall chemical profile. The supply of hexoses designed to fit the metabolic and nutritive demands are associated with the increased oxidative stress at the gall site. The greatest accumulation of reactive oxygen species (ROS) triggers a cascade of cellular signals which may favor or not gall development. Under the stimulation of the galling herbivore, a centrifugal gradient of ROS was established in Piper arboreum, triggering cytological differential responses in the gall tissue layers, which were essential to maintain cell high metabolism. Cytological conservative characteristics in galls denote the potential of the host plant to reduce the impact of the oxidative stress and together with the structural features were essential to maintain the similarity between the photosynthetic profile of non galled leaves and mature galls.