SELECTION AND CHARACTERIZATION OF A FEEDBACK-INSENSITIVE TISSUE-CULTURE OF MAIZE
SELECTION AND CHARACTERIZATION OF A FEEDBACK-INSENSITIVE TISSUE-CULTURE OF MAIZE
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DOI：
10.1007/bf00386420
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发表时间：
1980-01-01
期刊：
影响因子：
4.3
通讯作者：
GENGENBACH, BG
中科院分区：
文献类型：
--
作者：
HIBBERD, KA;WALTER, T;GENGENBACH, BG
采用组织培养选择技术分离了玉米（Z. mays L.）突变体D33，该突变体中天冬氨酸家族通路对赖氨酸反馈抑制的敏感性较低。D33是通过在含有抑制生长水平的赖氨酸+苏氨酸的MS （Murashige-Skoog）培养基上连续继代培养获得的。D33在赖氨酸+苏氨酸培养基上生长12个月后仍能保持旺盛的生长能力。从D33再生植株的茎部组织开始的新培养物也对赖氨酸+苏氨酸的抑制具有抗性。在D33中，天冬氨酸的反馈抑制剂赖氨酸的Ki值比未选择培养的天冬氨酸的Ki值高9倍。赖氨酸、苏氨酸、异亮氨酸和蛋氨酸的游离池在D33培养中增加了2 ~ 9倍。这与观察到的天冬氨酸激酶反馈调节的变化是一致的，天冬氨酸激酶是天冬氨酸途径中这些氨基酸生物合成的第一个共同酶。积累的证据包括培养物的抗性稳定性、再生植株的抗性、反馈调节的改变以及游离氨基酸的增加，表明这些性状在D33系中是突变的。
Tissue culture selection techniques were used to isolate a maize (Z. mays L.) variant D33, in which the aspartate family pathway was less sensitive to feedback inhibition by lysine. D33 was recovered by successively subculturing cultures originally derived from immature embryos on MS (Murashige-Skoog) medium containing growth-inhibitory levels of lysine + threonine. The ability of D33 to grow vigorously on lysine + threonine medium was retained after growth for 12 mo. on nonselection medium. New cultures initiated from shoot tissues of plants regenerated from D33 also were resistant to lysine + threonine inhibition. The Ki of aspartokinase for its feedback inhibitor, lysine, was about 9-fold higher in D33 than for the enzyme from unselected cultures. The free pools of lysine, threonine, isoleucine and methionine were increased 2- to 9-fold in D33 cultures. This was consistent with the observed change in feedback regulation of aspartokinase, the 1st enzyme common to the biosynthesis of these amino acids in the aspartate pathway. The accumulated evidence including the stability of resistance in the cultures, the resistance of cultures initiated from regenerated plants, the altered feedback regulation, and the increased free amino acids, indicates a mutational origin for these traits in line D33.