The Miniature1 seed locus of maize encodes a cell wall invertase required for normal development of endosperm and maternal cells in the pedicel
The Miniature1 seed locus of maize encodes a cell wall invertase required for normal development of endosperm and maternal cells in the pedicel
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DOI：
10.1105/tpc.8.6.971
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发表时间：
1996-06-01
期刊：
影响因子：
11.6
通讯作者：
Chourey, PS
中科院分区：
文献类型：
--
作者：
Cheng, WH;Taliercio, EW;Chourey, PS
大量证据表明，玉米的Miniature1(Mn1)种子位点编码一种胚乳特有的细胞壁转化酶同工酶CWI-2。证据包括(1)分离和鉴定甲烷磺酸乙酯诱导的酶活性改变的mn1突变株；(2)基因剂量和转化酶活性与CWI-2蛋白之间的近线性关系。此外，分子分析表明，CBNA克隆incw2定位于mn1基因，并在RNA凝胶印迹分析中将6个独立来源的mn1突变体区分为两类。我们还报告了两个意想不到的观察，这为蔗糖酶在种子发育中的生理作用及其调节提供了重要的新见解。首先，很大比例的总酶活性(类似于90%)是可有可无的(即非限制性的)。然而，在接近野生型活性6%的阈值水平下，胚乳酶以限速方式控制着发育中的胚乳的库强度和花梗中母细胞的发育稳定性。我们的数据还表明，转化酶的细胞壁结合形式和可溶性形式之间存在异常紧密的协调控制，很可能是由两个独立的基因编码的，可能是通过糖介导的新陈代谢控制。
Collective evidence demonstrates that the Miniature1 (Mn1) seed locus in maize encodes an endosperm-specific isozyme of cell wall invertase, CWI-2. The evidence includes (1) isolation and characterization of ethyl methanesulfonate-induced mn1 mutants with altered enzyme activity and (2) a near-linear relationship between geneldose and invertase activity and the CWI-2 protein. In addition, molecular analyses showed that the cBNA clone incw2 maps to the Mn1 locus and differentiates the six ethyl methanesulfonate-induced mn1 mutants of independent origin into two classes when RNA gel blot analyses were used. We also report two unexpected observations that provide significant new insight into the physiological role of invertase and its regulation in a developing seed. First, a large proportion of total enzyme activity (similar to 90%) was dispensable (i.e., nonlimiting). However, below the threshold level of similar to 6% of wild-type activity, the endosperm enzyme controlled both the sink strength of the developing endosperm as well as the developmental stability of maternal cells in the pedicel in a rate-limiting manner. Our data also suggest an unusually tight coordinate control between the cell wall-bound and the soluble forms of invertase, which are most likely encoded by two separate genes, presumably through metabolic controls mediated by the sugars.