Centre for Resource, Environment and Food Security, Department of Plant Nutrition, Key Laboratory of Plant-Soil Interactions, Ministry of Education, China Agricultural University, Beijing 100193, PR China.
J Plant Physiol. 2013 Sep 15;170(14):1243-50. doi: 10.1016/j.jplph.2013.04.015. Epub 2013 Jun 5.
Acid phosphatases (APases) play a key role in phosphorus (P) acquisition and recycling in plants. White lupin (Lupinus albus L.) forms cluster roots (CRs) and produces large amounts of APases under P deficiency. However, the relationships between the activity of intracellular and extracellular APases (EC 3.1.3.2) and CR development are not fully understood. Here, comparative studies were conducted to examine the spatial variation pattern of APase activity during CR development using the enzyme-labelled fluorescence-97 (ELF-97) and the p-nitrophenyl phosphate methods. The activity of intracellular and extracellular APases was significantly enhanced under P deficiency in the non-CRs and CRs at different developmental stages. These two APases exhibited different spatial distribution patterns during CR development, and these distribution patterns were highly modified by P deficiency. The activity of extracellular APase increased steadily with CR development from meristematic, juvenile, mature to senescent stages under P deficiency. In comparison, P deficiency-induced increase in the activity of intracellular APase remained relatively constant during CR development. Increased activity of intracellular and extracellular APases was associated with enhanced expression of LaSAP1 encoding intracellular APase and LaSAP2 encoding extracellular APase. The expression levels of these two genes were significantly higher at transcriptional level in both mature and senescent CRs. Taken together, these findings demonstrate that both activity and gene expression of intracellular or extracellular APases exhibit a differential response pattern during CR development, depending on root types, CR developmental stages and P supply. Simultaneous in situ determination of intracellular and extracellular APase activity has proved to be an effective approach for studying spatial variation of APases during CR development.
酸性磷酸酶（APases）在植物磷（P）获取和再循环中起着关键作用。白 Lupinus albus L. 在 P 缺乏下形成丛生根（CRs）并产生大量的 APases。然而，细胞内和细胞外 APases（EC 3.1.3.2）的活性与 CR 发育之间的关系尚未完全了解。在这里，使用酶标记荧光-97（ELF-97）和对硝基苯磷酸酯方法，对 CR 发育过程中 APase 活性的空间变化模式进行了比较研究。在非 CR 和不同发育阶段的 CR 中，细胞内和细胞外 APases 的活性在 P 缺乏下显著增强。这两种 APases 在 CR 发育过程中表现出不同的空间分布模式，这些分布模式受到 P 缺乏的高度修饰。在 P 缺乏下，细胞外 APase 的活性随着 CR 从分生组织、幼龄、成熟到衰老阶段的发育而稳定增加。相比之下，P 缺乏诱导的细胞内 APase 活性在 CR 发育过程中保持相对稳定。细胞内和细胞外 APases 活性的增加与编码细胞内 APase 的 LaSAP1 和编码细胞外 APase 的 LaSAP2 的表达增强有关。在成熟和衰老的 CR 中，这两个基因的转录水平表达水平均显著升高。综上所述，这些发现表明，细胞内或细胞外 APases 的活性和基因表达在 CR 发育过程中表现出不同的响应模式，这取决于根类型、CR 发育阶段和 P 供应。同时原位测定细胞内和细胞外 APase 活性已被证明是研究 CR 发育过程中 APases 空间变化的有效方法。
