Uma das principais dificuldades nos trabalhos visando a seleção de plantas tolerantes a metais pesados é a própria metodologia para avaliação eficiente de grande número de plantas, gerando poucos resíduos para o meio ambiente. Por esse motivo, propomos uma metodologia simples e eficaz que pode ser aplicada a metais ou outros elementos químicos, partindo de um estudo de caso, no qual selecionamos dois mutantes de tomateiro (cv Micro-Tom) tolerantes ao Cádmio, obtidos por mutagênese com etanosulfonato de metila (EMS). Além destes dois novos mutantes, selecionamos outros 21 com alterações potenciais quanto a respostas a este metal. Por fim, chegamos à conclusão de que o sistema proposto é ideal para trabalhos de seleção de plantas tolerantes a metais pesados e possivelmente a outros elementos, devido à facilidade de montagem da estrutura, baixo custo de implantação, minimização de geração de resíduos e possibilidade de uso em várias espécies e diferentes metais pesados.

One of the major difficulties in studies on the selection of heavy metal tolerant plants is the proper methodology that must ensure an efficient evaluation of a large number of plants, but reducing environmental contamination. For this reason, we propose a simple and effective method that can be applied to metals or other chemicals by means of a case study, in which we selected two cadmium-tolerant mutants of tomato (cv Micro-Tom) obtained by mutagenesis with methyl ethanesulfonate (MES). Aside from these two new mutants, we selected 21 others with possible alterations in the response to this metal. Finally, it was concluded that the proposed system is ideal for selection studies on plants tolerant to heavy metals and possibly to other elements, due to the ease of assembly of the structure, low installation cost, minimal waste generation and the possibility of using different species and heavy metals.

UDP-glucose dehydrogenase (UGDH) catalyzes the oxidation of UDP-glucose (UDP-Glc) to UDP-glucuronate (UDP-GlcA), a key sugar nucleotide involved in the biosynthesis of plant cell wall polysaccharides. A full-length cDNA fragment coding for UGDH was cloned from the cambial region of 6-month-old E. grandis saplings by RT-PCR. The 1443-bp-ORF encodes a protein of 480 amino acids with a predicted molecular weight of 53 kDa. The recombinant protein expressed in Escherichia coli catalyzed the conversion of UDP-Glc to UDP-GlcA, confirming that the cloned cDNA encodes UGDH. The deduced amino acid sequence of the cDNA showed a high degree of identity with UGDH from several plant species. The Southern blot assay indicated that more than one copy of UGDH is present in Eucalyptus. These results were also confirmed by the proteomic analysis of the cambial region of 3- and 22-year-old E. grandis trees by 2-DE and LC-MS/MS, showing that at least two isoforms are present. The cloned gene is mainly expressed in roots, stem and bark of 6-month-old saplings, with a lower expression in leaves. High expression levels were also observed in the cambial region of 3- and 22-year-old trees. The results described in this paper provide a further view of the hemicellulose biosynthesis during wood formation in E. grandis.