Retenção de clorofila em sementes de soja (Glycine max (L.) Merr.): estudos fisiológicos, bioquímicos e moleculares

• Ano de defesa: 2014
• Autor(a) principal: Teixeira, Renake Nogueira [UNESP]
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Estadual Paulista (Unesp)
• Palavras-chave em Português: Expressão gênica; Sementes - Qualidade; Sementes oleaginosas - Fisiologia; Stress (Fisiologia); Gene expression
• Link de acesso: http://hdl.handle.net/11449/132235; http://www.athena.biblioteca.unesp.br/exlibris/bd/cathedra/13-10-2015/000851990.pdf

Brazil is the second largest soybean producer in the world and most of its production is located in the tropical area of the country which is prone to drought and high temperature. Under such stressful conditions it is common to observe the retention of chlorophyll at the end of seed maturation. Very little is known about the role of chlorophyll in developing seeds, but its presence in oilseeds enhances oxidation of the extracted oil, resulting in reduced shelf life, unappealing appearance and a lower price for the producer. Also seed quality for propagation is severely affected by chlorophyll retention. Besides environmental conditions, there are also genetic components controlling the sensitivity of different cultivars to retain chlorophyll. A detailed characterization of green seed production by two different cultivars under stressed conditions and its effect on seed lot quality was carried out. In an attempt to determine the molecular basis of chlorophyll degradation and, consequently, its retention, a transcriptome analysis was performed using stressed (green) and non-stressed (yellow) soybean seeds at three stages of maturation: R6, R7 and R8. Multiple ontologies were enriched in soybean seeds produced under stress. Among the top-ranking was the photosynthetic process, particularly the photosystem (PS) II category. The expression analysis suggests higher levels of the proteins D1 (psbA), D2 (psbD), A1 (psaA) and A2 (psaB) core subunits of PSII and PSI, in stressed/green seeds. Special attention was also given to chlorophyll catabolic enzymes and to stay-green genes, among which, disturbances in expression of PPH2, D1 and D2 caused by environmental stresses appears to be the major cause for chlorophyll retention in soybean seeds.