Cellular and ultrastructural alterations of Arabidopsis thaliana roots in response to exogenous trans-aconitic acid

Abstract

In this work, the responses of Arabidopsis thaliana (L.) Heynh to trans-aconitic acid (TAA) were investigated. A. thaliana was grown in the presence of TAA in a concentration range of 400–1200 µM for 7 or 15 days. Changes in the morphoanatomy, cellular ultrastructure, and micromorphology of the roots were evaluated by light and transmission electron (TEM) microscopy. At concentrations below 1000 µM, TAA reduced the length of the primary roots, but induced an early appearance of lateral roots and root hairs. At a concentration of 1200 µM, TAA suppressed the growth of seedlings. The images of longitudinal sections of root tips of seedlings treated with IC50 of TAA (684 µM) revealed a reduced elongation zone with an increased differentiation zone. TEM images showed an increase in the number and volume of vacuoles, an increase in vesicles containing electron-dense material derived from plasmalemma, and electron-dense granules attached to the cell wall. Trans-aconitic acid induced an early differentiation of A. thaliana seedlings suggesting an interference in the auxin action. Changes in the cellular ultrastructure may represent vacuolar and extracellular accumulation of TAA, to remove excess TAA in the cytosol and mitochondria. An inhibition of aconitase and the chelation of intracellular cations may have contributed to cytotoxicity of TAA at 1200 µM concentration.