The Effect Of Pectin Content In Root Cell Wall Of Arabidopsis On Its Resistant To Cadmium Stress

Heavy metals are a series of trace elements with a small stock on the earth. Some of them are useful for creatures, but most of them have an obvious toxic effect on organisms. Since more and more concern is given to the ecological environment, organisms and human health, the researches about heavy metal toxicity and tolerance to lives have made enormous progress in recent years. However, most of these researches are focused on transporters and gene expression in the internal cell level, while the function of apoplast in the resistance to heavy metal toxicity lacks adequate understanding.In order to further understand the effect of apoplast of cell wall on heavy metal toxicity and tolerance, we adopted the most typical heavy metal pollutant—cadmium (Cd) as object and the mutants of cell wall (cellulose and pectin) of Arabidopsis as plant materials. We investigated the growth condition, the accumulation of Cd in the shoots, roots and root cell wall of Arabidopsis and the changes of monosaccharide composition of root cell wall, and also measured the absorption to other nutrient elements Under the Cd treatment.The results showed that:1. Under the Cd treatment, the root growth showed a significant inhibition. In cs6354 with rich pectin, compared with its wild type, relative root elongation had substantially improvement, but qua1-2 of lacking pectin did not show significant difference of relative root elongation with the wild type.2. Under the Cd treatment, the content of Cd in the root of cs6354 increased by about 50% compared with the wild type. In the root of mutant qua1-2, the content of Cd decreased, but the shoot showed a higher accumulation. In cs6354, the ratio of Cd distributed in roots was 25% but 10% in qual-2, which indicated better transfer of Cd to shoots with lower content of Cd.3. The Cd content in cell wall extracted was measured. cs6354 showed 15% increase of Cd content compared with wild type, but it had no difference in qual-2. The cell wall of untreated cultivars was emerged in Cd solution, 93% Cd was adsorbed in cs6354 in 10min, but the ratio of wild type was 87%. After 120min adsorption, the cell wall of cs6354 nearly completely adsorbed Cd in solution. It indicated cs6354 with more pectin in cell wall could adsorb Cd rapidly.4. The pectin in root cell wall of cs6354 increased by 20% compared with the wild type, while in qua1-2, the pectin content decreased by 40%.5. The monosaccharide composition in root cell wall had changed under the treatment of Cd. Arabinose and xylose had a certain degree of increase in the total proportion of sugar under the stress, which may be caused by the reduction of the amount of pectin.6. After Cd treatment, the content of Ca and Zn in the roots of Arabidopsis was significantly reduced, but the content of Mg wasn't influenced by the stress of Cd.