A proteína BiP exerce função protetora contra o déficit hídrico em plantas de soja

• Autor(a) principal: Valente, Maria Anete Santana
• Data de Publicação: 2008
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/324
• topic: BIP; Soja; Déficit hídrico; BIP; Soybean; Water deficit; CNPQ::CIENCIAS BIOLOGICAS::BIOQUIMICA::BIOLOGIA MOLECULAR

The plants are under continuous biotic and abiotic stress conditions, and drought is the major abiotic factors which limits agricultural production, triggering biochemical, physiological and molecular changes in plants. Based on the capacity of BiP to increase drought tolerance in Nicotiana tabacum, it was aimed in this research to analyze if such molecular strategy for increasing the tolerance would be effective in soybean. Soybean plants, belonging to the consquista variety, were initially transformed with the soyBiPD gene under control of the 35S constitutive promoter. The transgenic analysis was evaluated in segregating populations until the T6 generation. The transgene expression was analyzed in six transformants called 35S:BiP-1, 35S:BiP-2, 35S:BiP-3, 35S:BiP-4, 35S:BiP-5, 35S:BiP-6. On T6 generation, homozygous plants of the 35S:BiP-4 lineage that were overexpressing BiP were selected. Higher BiP protein accumulation was found in the endoplasmatic reticulum of the transgenic plants, indicating a right cellular addressing of the recombinant protein. T3 soybean plants overexpressing BiP were subjected to hydric stress. After hydric restriction, a tolerant phenotype was observed in plants sense which kept leaf turgescence level without accumulating high levels of sucrose, while soybean control plants did not have the same leaf turgescence level and they accumulated higher levels of sucrose. Under hydric restriction, transformed plants significantly showed higher photosynthetic ability and stomatic conductance than non-transformed plants. T4 and T5 soybean plants were also subjected to severe hydric deficit by complete watering interruption and the transgenic plants revealed higher drought resistance. Nontransformed plants significantly showed lower photosynthetic, stomatic conductance and transpiration rates in this water stress. Proline concentration increased significantly in plants that underwent drought, being noticeably higher in the wild type plants. The stress condition increased malondialdehyde (MDA) contents in soybean plants, occurring peroxidation in the membrane lipids of both plants, but it was significantly higher in the controls. It was also found that control plant roots under osmotic stress showed greater branching. Under conditions of water stress, genes were differentially expressed in transgenic lineages and control plants, standing out the induction of drought responsive genes, such as LEA, antiquitin and GST, in non-transformed plants. BiP superexpression delayed leaf senescence induction, being chlorophyll and protein percentages significantly lower in the control plants. Altogether, these results suggest that BiP protein has a protector function against the water deficit in plants.