The kinetics associated with phosphate absorption by Arabidopsis and its regulation by phosphorus status
The kinetics associated with phosphate absorption by Arabidopsis and its regulation by phosphorus status
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DOI：
10.1071/pp96137
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发表时间：
1997-01-01
期刊：
影响因子：
--
通讯作者：
White, DWR
中科院分区：
文献类型：
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作者：
Dunlop, J;Phung, HT;White, DWR
磷状态对 3 日龄拟南芥 (L.) Heynh 磷吸收动力学的影响。对幼苗进行了研究。种子在含有不同量磷酸盐的琼脂糖凝胶上发芽3天，并在一系列磷酸盐浓度下测量这些幼苗对P-32标记的磷酸盐的吸收。在没有磷酸盐的情况下发芽的种子的吸收速率比在含有 1、5 或 10 mM 磷酸盐的凝胶上发芽的幼苗的吸收速率快四倍。动力学常数 K-m 和 V-max 通过将数据拟合到具有一种和两种并行操作的机制的模型来确定。需要具有两种机制的模型才能很好地拟合 0.5 μM 至 5 mM 浓度范围的数据。对于高亲和力机制，K-m，K-1（平均值12.3μM）不受影响，因为磷状态增加，但V-max，V-1减少。对于低亲和力机制，K-m,K-2 (5697-16547 mu M) 和 V-max,V-2 的值随着磷状态的增加而增加。砷酸盐会抑制磷酸盐的吸收，但效果有限。在 4.8 至 7.3 范围内改变 pH 值不会影响吸收速率。结论是，除非常数 K-m 或 V-max 存在较大的数量差异，否则动力学方法可能没有足够的分辨率来区分不同的机制。
The effects of phosphorus status on the kinetics of phosphate absorption by 3-day-old Arabidopsis thaliana (L.) Heynh. seedlings were studied. Seeds were germinated for 3 days on agarose gel containing different amounts of phosphate and the absorption of P-32-labelled phosphate by these seedlings was measured at a range of phosphate concentrations. The absorption rates for seeds germinated in the absence of phosphate were up to four times faster than for seedlings germinated on gels containing 1, 5 or 10 mM phosphate. The kinetic constants K-m and V-max were determined by fitting the data to models with one and two mechanisms operating in parallel. A model with two mechanisms was needed to provide a good fit to the data for concentrations ranging from 0.5 mu M to 5 mM. For the high affinity mechanism, K-m,K-1 (mean value 12.3 mu M) was not affected as phosphorus status increased but V-max,V-1 decreased. For the low affinity mechanism the values for both K-m,K-2 (5697-16547 mu M) and V-max,V-2 increased with increasing phosphorus status. Arsenate inhibited phosphate absorption but only moderately. Varying the pH over the range 4.8 to 7.3 did not affect the rate of absorption. It is concluded that a kinetic approach may not have sufficient resolution to discriminate between different mechanisms unless there are large quantitative differences in the constants K-m or V-max.