Investigating the tomato tolerance to cadmium (Cd) via high throughput proteomics

Abstract

Investigating the tomato tolerance to cadmium (Cd) via high throughput proteomics The problem of cadmium (Cd) toxicity aggravates every year. However, the amount of plant species presenting some degree of tolerance to this metal is low. Therefore, it is of utmost importance to understand the Cd tolerance mechanisms. Two tomato cultivars exhibiting distinct levels of tolerance to Cd were investigated by exposing them to 35 µm CdCl2 for eight days. The samples (roots, stems, and leaves) were collected at 0, 2, 4, 6 and 8 days. The root length and surface area were obtained using a WinRhizo PRO 2009c image analyzer. The ICP OES method was used for the quantification of metals in the different tissues. The translocation index (TrI), metal uptake and Cd distribution nutrient absorbed (NA), and nutrient efficiency (NUE) were calculated. The plant material used for stress indicators and proteomics analysis were collected in liquid nitrogen. Lipid peroxidation and H2O2 contents were obtained by spectrometry. For the proteomics data the gel-free method was used. The stress indicators showed the variation in both cultivars, evidencing the stress caused by the Cd. Chlorosis and necrotic spots were observed in plants exposed to Cd less significant way in the first days of exposure and more evident in the less tolerant cultivar (TTO) in the last days. The growth reduction can be observed in both cultivars, more evident in TTO. Regarding the Cd distribution, the two cultivars showed similar behavior, with the highest percentage of Cd in the roots. The Cd absorption could interfere with both cultivars in the accumulation absorption and efficiency in the use of most nutrients assessed. In general, the Cd interference was more evident at TTO than at YOSH. Highest percentages of TrI were also observed in TTO cultivar. Identification and evaluation of the differentially accumulated protein (DAP) in the two cultivars roots it is possible to observe that in the presence of Cd the cultivar TTO generates a more significant alteration in the amplitude of the accumulation and the number of proteins. These results suggest that the cultivar, which presents a higher degree of tolerance, has some form to make the Cd unavailable or a mechanism that makes the Cd transportation to the leaves more difficult.