Abscisic acid-deficient sit tomato mutant responses to cadmium-induced stress

Abstract

There is a very effective cross-talk between signals triggered by reactive oxygen species and hormonal responses in plants, activating proteins/enzymes likely to be involved in stress tolerance. Abscisic acid (ABA) is known as a stress hormone that takes part in the integration of signals. This work aimed to characterize the biochemical response and ultrastructural changes induced by cadmium (Cd) in the Micro-Tom (MT) sitiens ABA-deficient mutant (sit) and its wild-type (MT) counterpart. MT and sit plants were grown over a 96-h period in the presence of Cd (0, 10, and 100 μM CdCl). The overall results indicated increases in lipid peroxidation, hydrogen peroxide content and in the activities of the key antioxidant enzymes such as catalase, glutathione reductase, and ascorbate peroxidase in both genotypes. On the other hand, no alteration was observed in chlorophyll content, while the activity of another antioxidant enzyme, superoxide dismutase, remained constant or even decreased in the presence of Cd. Roots and shoots of the sit mutant and MT were analyzed by light and transmission electron microscopy in order to characterize the structural changes caused by the exposure to this metal. Cd caused a decrease in intercellular spaces in shoots and a decrease in cell size in roots of both genotypes. In leaves, Cd affected organelle shape and internal organization of the thylakoid membranes, whereas noticeable increase in the number of mitochondria and vacuoles in MT and sit roots were observed. These results add new information that should help unravel the relative importance of ABA in regulating the cell responses to stressful conditions induced by Cd apart from providing the first characterization of this mutant to oxidative stress.

Potential of hydrogen (pH) differentially modulates cadmium stress response in abscisic acid-deficient sitiens tomato mutant

“…For example, sit plants submitted to 100 µM CdCl 2 at pH 6 for 96 h accumulated more Cd in the roots when compared to MT plants. However, an increase in vacuole number in MT roots was observed in the presence of Cd (Pompeu et al 2017). Thus, the important role of ABA appears to be related to a reduction in Cd accumulation in tomato (Pompeu et al 2017).…”

“…In a recent study, the sit tomato mutant exhibited altered biochemical and morpho-anatomical responses to Cd exposure (Pompeu et al 2017). For example, sit plants submitted to 100 µM CdCl 2 at pH 6 for 96 h accumulated more Cd in the roots when compared to MT plants.…”

“…The pH 6 was used in studies on Cd toxicity in tomato in hydroponic systems (Piotto et al 2014;. The Cd-concentration chosen was based on previous results with MT (Gratão et al 2012(Gratão et al , 2015Pompeu et al 2017). Forty-eight hours after Cd addition, roots and shoots were collected and stored for further biochemical analysis.…”

“…Cd-induced oxidative stress can be modulated by phytohormones such as auxin (Alves et al 2017), gibberellin (Cai et al 2015), cytokinin (Bezrukova et al 2016), ethylene (Gratão et al 2015), jasmonic acid (Yan et al 2015) and abscisic acid (Pompeu et al 2017). Abscisic acid (ABA) regulates a wide range of processes in plants, including seed development and dormancy, transition from the vegetative to the reproductive phase, stomatal closure, and responses to a variety of environmental stresses (Galpaz et al 2008;Harrison et al 2011;Akpinar et al 2012;Harrison 2012).…”

New insights about cadmium impacts on tomato: Plant acclimation, nutritional changes, fruit quality and yield

“…In soil, most of the Cd (55%-90%) is presented as a free metal ion that is readily available to plants, being absorbed through roots and translocated to shoots after a short period of exposure (Gratão et al, 2015;Kabata-Pendias, 2011;Pompeu et al, 2017). Physicochemical characteristics of the soil, such as pH, texture, and organic matter content, affect Cd availability for plant absorption, which is particularly enhanced under acidic conditions (Castaldi & Melis, 2004;Kabata-Pendias, 2011;Kibria, Osman, & Ahmed, 2006;Manciulea & Ramsey, 2006;Melo, Alleoni, Carvalho, & Azevedo, 2011;Nogueirol, Monteiro, Gratão, Silva, & Azevedo, 2016).…”