Тяжелые металлы в окружающей среде
Conclusions and future directions
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| Conclusions and future directions
The problem of heavy metal pollution has been worsening for quite some time due to a se- ries of human activities. On the other hand this leads to intensification of the research dealing with the phytotoxicity of these contaminants and with the mechanisms used by plants to counter their harmful effects. This resulted in substantial knowledge gained mostly by studying the behavior of hyperaccumulator plants growing on metalliferous soils. Such plants can accumulate heavy metals in leaves at concentrations several 100-fold higher than other plants. However, in spite of important progress made in recent years by the numerous studies, the complexity of hyperaccumulation is far from being fully understood. A key factor in this process is the complexity of ion uptake and the maintenance of ion homeostasis processes in plant cells. Therefore, the manipulation of membrane transporters in order to reduce the uptake and transport of one particular heavy metal ion is prone to creating imbalances in the homeostasis of other, essential ions. Consequently, it will be important to link the ion specificity of particular transporters to their tissue-specific distributions. Mutational and overexpression approaches that now are becoming widely available through the new biotech tools discussed above should make it possible to target specific transporters of interest in the roots, which are the organs in first contact with potentially harmful ions in the rhizosphere. Because heavy metal treatment activates different metabolic pro- cesses in different developmental parts of the plant, the potential benefits of biotechnological ap- proaches in terms of protecting the most sensitive parts should be evaluated in the context of this metabolic distribution. The ability to protect the growth zones of roots from heavy metal poisoning could potentially greatly reduce the impact of their toxicity on crops. Furthermore, making plants more resistant to heavy metal uptake would minimize the scope for dangerous heavy metal ions to enter the food chain. 70 71 Considerable attention has been given to the possibility of using hyperaccumulators for phy- toremediation/phytomining of contaminated or natural metal-rich soils. Knowledge acquired on genes involved in hyperaccumulation mechanisms will open the opportunity to use biotechnology to transfer specific genes to high-biomass promising species. There is also a need to find and charac- terize more hyperaccumulators, to cultivate them and better assess agronomic practices and man- agement to enhance plant growth and metal uptake by selective breeding and gene manipulation. The newer and emerging biotechnological solutions discussed here open plethora of oppor- tunities to study both effects of specific gene alleles and the outcomes of their modified expression. This becomes possible through the ability of these approaches to tackle either internal to the gene, or other (near or distant) sequences in a variety of manners. The possibility to modify single (or low numbers of) nucleotides, to shuffle their positions in the genome and/or to either block or enhance their specific activity is something geneticists and breeders were craving for a very long time. It is only in the last 5 to 10 years that all this has become possible and widely available. The outcomes of that are poised to be profound and will greatly affect both our understanding and utilization of mechanisms of heavy metal tolerance to a good for humanity. In this respect it has to be pointed out that the interest is rising in the potential exploiting of hyperaccumulators as a rich genetic resource to develop engineered plants with enhanced nutritional value for improving public health or for con- tending with widespread mineral deficiencies in human vegetarian diets. The strategies of food crop biofortification are still in infancy; however their paramount importance for the world‘s population makes this an exciting line of future research in the field of essential elements hyperaccumulation. жүктеу/скачать 6.49 Mb. Достарыңызбен бөлісу:
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