Mutantes da via metabolica do acido aspartico em milho, obtidos atraves de cultura de tecidos

AUTOR(ES)

Ricardo Antunes de Azevedo

DATA DE PUBLICAÇÃO

1988

RESUMO

The essential amino acids lysine, threonine and methionine are derived from the aspartate family of amino acids in pIants. Since the cereaIs are devoid in at least one of these amino acids, the aspartate pathway has received great attention in the last recent years. Biochemical, moIecular and genetic studies has lead to a deep understand of the regulation of the aspartate family showing that many branch poiny enzymes are positively or negatively regulated by feedback. Many investigators have proved the regulation of the key points by finding mutants with aItered regulation of aspartate pathway. Several studies showed that the regulatory mutants has leveIs of some of the amino acids and products. With the advance of the tissue culture and technics and plants regeneration selection of biochemical mutants became as an important system to study mutants can be with altered regulation of amino acid biosynthesis. Such mutants can be easily selected in a petridish containing millions of cells pIated on selective medium added of combinations of the amino acids and products or amino acids analogs. In this study maize tissue culture was used select plants resistant to the lysine analog aminoethylcysteine. In addition, mutant resistant to lysine plus threonine which selected by Hibberd and Green, (1982), was included in the studies. Combinations of the lysines plus trheonine resistant mutant, with the maize endosperrn mutants opaque-2, brittle-1 and shrunken-2 were performed to study the effect of such combination on the biosynthesis of amino acid and proteins in the seeds. Resistance embriogenic cali of a maize inbred line were selected in medium containing from 0,25 to 0,5mM of aminoethylcysteine. These cali were used for plant regeneration. From 63 regenerated plants two presented R1 progenies which when selfed polinated segregates resistant and sensitive plants. The resistance of one R0 plants showed to be determined by a singIe dominant gene while the other showed to be determined by a single recessive gene. Both resistant mutant presented increased free lysine leveI when compared with sensitive plants.The resistance of the lysine plus threonine mutant is determined by a single dominant gene, named Ltr*i9. 1his gene was transferred to two maize inbred lines containig normal, opaque-2, brittle-1 and shrunken-2 endosperms by successive backcrosses. The genetic analysis of single an double mutants revealed that the Ltr*19 gene is located in the short arm of cromossome 7, at 10.57+ - 1,38 centimorgans of the opaque-2 gene. The presence of the Ltr*19 gene increase 8 times the free threonine leveI in the normal endosperm. A synergistic effect on the increase of free threonine was observed when the Ltr*19 gene was combined in a double mutant with the opaque-2 gene. It was observed also that the Ltr*19 gene intensify the effect of opaque-2 gene on amino acid and protein synthesis in the endosperm. SDS-PAGE and IEF analysis of single and double mutants containing the Ltr*19 and end endosperm mutant did not show any difference in the polypeptide profile which could be attributed to the Ltr*19 gene

ASSUNTO(S)

biologia - genetica vegetal

Documentos Relacionados

• Caracterização de mutantes ADH-O em milho (Zea mays L.) obtidos atraves de variação somaclonal
• Propagacao Vegetativa do Coqueiro Atraves da Cultura de Tecidos.
• Erosão hídrica, em três momentos da cultura do milho, influenciada por métodos de preparo do solo e semeadura
• Efeito do herbicida glifosato em cultura de tecidos de milho (Zea mays L.)
• Eficiência de Cerrospora caricis no controle de tiririca, em cultura do milho, sob condições de campo.