ABSTRACT
A transformação genética, que consiste na introdução controlada de um gene no genoma de uma célula receptora e em sua posterior expressão, assume adicional significância, pois abre novas perspectivas ao melhoramento genético de espécies florestais, disponibilizando novos genes com características desejáveis para serem incorporados em menor espaço de tempo. Através do uso de estratégias com Agrobacterium e biobalística, já foram obtidas plantas transgênicas com maior produção de biomassa, melhor qualidade de madeira, maior resistência a determinados insetos e com tolerância a herbicidas, entre outras características de interesse. Tais exemplos demonstram a relevância dessas ferramentas para o setor florestal. Esta revisão apresenta, de forma resumida, a importância do estabelecimento de um eficiente sistema de regeneração in vitro, as principais estratégias usadas na transformação genética de espécies florestais e algumas das características agroflorestais que já foram incorporadas nessas espécies.
The genetic transformation which consists in a controlled introduction of a gene in the genome of a receive cell and its subsequent expression, assumes additional significance, giving new perspectives to genetic improvement of the forest species, extending and available new genes with desirable characteristics, to be incorporated in a smaller period of time. Through the strategies Agrobacterium and bioballistic, transgenic plants had already been obtained showing higher biomass production, better wood quality, resistance to some insects, tolerance to herbicides, among other desirable characteristics, showing the relevance of these tools to the forest industry. This revision points out in a summarized way, the importance of establishing an efficient in vitro regeneration system, the strategies used in the genetic transformations of forestry species and some agroforestry characteristics that were previously incorporated in these species.
ABSTRACT
A procedure for genetic transformation of the hybrid Eucalyptus grandis × E. urophylla using particle bombardment is described. Cotyledon- and hypocotyl-derived calli growing on SP medium supplemented with 2mthidiazuron or on MS modified (MSM) medium supplemented with 10 m 2,4-dichlorophenoxyacetic acid (2,4-D) and 2.5m6-benzylaminopurine (BAP), were used as target material for bombardment assays. Multiple preincubation and bombardment conditions were tested. Tungsten particles were coated with the plasmid pBI426 harbouring a ß-glucuronidase (gus) and neomycin phosphotransferase II (npt II) gene fusion controlled by a double 35S cauliflower mosaic virus (CaMV) promoter. Four days after bombardment, the transient transformation efficiency was determined by expression of the gus gene. Fully GUS-positive calli were then obtained after 105 d in MSM medium supplemented with 2,4-D, BAP, and the selective agent kanamycin at 200 mg L-1. The presence of the gus gene in these kanamycin-resistant calli was confirmed by polymerase chain reaction analysis. Extensive experiments were performed aiming to identify conditions for the regeneration of these GUS-expressing calli. However, they were unable to regenerate transgenic shoots, suggesting that conditions suitable for regeneration are unsuitable for transformation and vice versa.
