Genetic transformation of Sorghum bicolor (L. Moench) aiming Al+3 tolerance / TransformaÃÃo genÃtica de Sorghum bicolor (L. Moench) visando tolerÃncia ao AlumÃnio.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The genetic transformation has been frequently associated with conventional genetic breeding programs. This technique allows the introduction of exogenous gene(s) into plant genomes, modifying specific characteristics. It can be an important supplementary tool for sorghum conventional breeding programs. However, most of the genetic transformation protocols require a previous establishment of an efficient in vitro regeneration system. Therefore, with the purpose of producing transgenic sorghum plants with increase tolerance to toxic aluminum present in acidic soils, the objectives of this research were (i) to select sorghum cultivars able to efficiently regenerate in vitro via organogenesis or embryogenesis; (ii) to optimize biolistic transformation parameters for sorghum immature inflorescence and (iii) to produce transgenic sorghum plants expressing the malato transporter gene, ALMT1, isolated from wheat. Initially, it was identified three sorghum genotypes, out of 15 tested, able to efficiently regenerate in vitro via organogenesis in MS basal medium supplemented with CuSO4.5H2O, 2,4-D, and BAP. Also, it was established that more than six weeks cultivation in this medium impaired plant regeneration. Sorghum regeneration via embryogenesis was tested using two tissue culture media formulations, MS (CIM medium) and N6 (N6 medium) basal salts supplemented with 2,4-D. Fragments of immature inflorescences of 9 elite sorghum cultivars developed embriogenic calli (EC) efficiently in CIM media, and two cultivars were selected for their highest production of EC. The cultivar CMSXS 102B was used for the optimization of microparticle bombardment parameters throughout the analysis of the transient expression of anthocyanin. The tested parameters included acceleration pressure, microprojectile flying distance and the time of explants on osmoticum prior bombardment. Higher transient expression of reporter gene was attained when embryogenic calli were cultivated in osmotic medium during 4 hours before the bombardment, positioned at 3 cm distant from the microcarrier release platform and shot at 1000 psi of helium accelerating pressure. These parameters were used to generate transgenic sorghum plants, expressing the GUS and bar genes, with a transformation efficiency ranging from 1.01 to 3.33%. Finally, the biolistic parameters established were used to generate transgenic sorghum plants expressing ALMT1 gene. T1 plants showed an increase level of tolerance to Al+3 when grown in hydroponic culture under aluminum stress, compared with untransformed control.

ASSUNTO(S)

transformaÃÃo genÃtica sorgo agronomia embriogÃnese genetic transformation almt1 sorghum almt1 organogÃnese organogenesis embryogenesis

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