Pyrophosphate-Dependent Fructose-6-Phosphate 1-Phosphotransferase Induction and Attenuation of Hsp Gene Expression during Endosperm Modification in Quality Protein Maize
Pyrophosphate-Dependent Fructose-6-Phosphate 1-Phosphotransferase Induction and Attenuation of Hsp Gene Expression during Endosperm Modification in Quality Protein Maize
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DOI：
10.1104/pp.111.191163
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发表时间：
2012-02-01
期刊：
影响因子：
7.4
通讯作者：
Holding, David R.
中科院分区：
文献类型：
--
作者：
Guo, Xiaomei;Ronhovde, Kyla;Holding, David R.
优质蛋白玉米（QPM）是高赖氨酸不透明2（o2）玉米（Zea mays）突变体的硬胚乳版本，但涉及软o2胚乳修饰的基因在很大程度上是未知的。焦磷酸依赖性果糖-6-磷酸1-磷酸转移酶（PFP）催化糖酵解中果糖-6-磷酸向果糖-1，6-二磷酸的非ATP依赖性转化。我们发现QPM胚乳中PFP α调节亚基（PFP α）的转录本和蛋白质水平大幅增加。在体外酶试验表明，在发展中的胚乳提取物的QPM相对于野生型和O2的正向PFP活性显着增加。还鉴定了在QPM中未上调的未知功能的PFP α的表达逆转录基因版本。QPM改善了o_2胚乳中大量ATP需要热激蛋白（Hsps）的表达水平。在玉米根中，PFP α也与热休克蛋白共诱导，以响应热、冷和未折叠蛋白反应应激。我们建议，减少ATP的可用性，除了减少丙酮酸，正磷酸二激酶的活性在o2胚乳的广义热休克蛋白的反应是补偿部分增加PFP活性在QPM。
Quality Protein Maize (QPM) is a hard-endosperm version of the high-lysine opaque2 (o2) maize (Zea mays) mutant, but the genes involved in modification of the soft o2 endosperm are largely unknown. Pyrophosphate-dependent fructose-6-phosphate 1-phosphotransferase (PFP) catalyzes the ATP-independent conversion of fructose-6-phosphate to fructose-1,6-bisphosphate in glycolysis. We found a large increase in transcript and protein levels of the alpha-regulatory subunit of PFP (PFP alpha) in QPM endosperm. In vitro enzyme assays showed a significant increase in forward PFP activity in developing endosperm extracts of QPM relative to the wild type and o2. An expressed retrogene version of PFP alpha of unknown function that was not up-regulated in QPM was also identified. The elevated expression levels of a number of ATP-requiring heat shock proteins (Hsps) in o2 endosperm are ameliorated in QPM. PFP alpha is also coinduced with Hsps in maize roots in response to heat, cold, and the unfolded protein response stresses. We propose that reduced ATP availability resulting from the generalized Hsp response in addition to the reduction of pyruvate, orthophosphate dikinase activity in o2 endosperm is compensated in part by increased PFP activity in QPM.