Ontogenetic differences in sun and shade galls of Clinodiplosis profusa on Eugenia uniflora leaves and the cytological antioxidant mechanisms in gall cells.

ABSTRACT

The gall-host Eugenia uniflora (Myrtaceae) is adaptable to different light conditions, enabling leaf production and survival in both sun and shade. Leaves of E. uniflora in shaded environments have more mesophyll layers, and galls of Clinodiplosis profusa (Cecidomyiidae) are larger and wider. Based on these previous observations, this study investigated the morphogenesis of galls induced by C. profusa on leaves of E. uniflora in different light conditions, revealing if the galls have a potential for acclimation, as observed with leaves. For this purpose, we compared the anatomical, histometric, and histochemical development of leaves and galls at different stages of development in sun and shade environments. Additionally, we analyzed the cytological features of the tissues composing the mature gall walls. Cells of shade galls expanded more toward the end of the developmental phase, which may explain the larger volume found for shade galls in a previous study. However, during the mature phase, these galls showed no significant differences in tissue thickness and final cell elongation in the contrasting light conditions. In the ultrastructural analyses, mature galls showed a gradient distinguishing the outer and inner parenchyma cells. The inner parenchyma had nutritive cells, with dense cytoplasm and abundant organelles. A higher accumulation of starch grains in nutritive cells, with evidence of hydrolysis of starch grains detected in the innermost layers leads to the accumulation of reducing sugars, which, with the presence of plastoglobules and protein bodies, are important mechanisms of oxidative stress dissipation in the cells in contact with the gall inducer.