title: Spatial distribution and expression of intracellular and extracellular acid phosphatases of cluster roots at different developmental stages in white lupin.
abstract: 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.
authors.affiliation: 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.
authors.forename: Hongliang
authors.initials: H
authors.lastname: Tang
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Li
authors.forename: Chao
authors.initials: C
authors.lastname: Zu
authors.forename: Fusuo
authors.initials: F
authors.lastname: Zhang
authors.forename: Jianbo
authors.initials: J
authors.lastname: Shen
mesh_terms: D000135:Acid Phosphatase / Q000235:genetics* / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D031297:Lupinus / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D009596:Nitrophenols / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000378:metabolism; D010758:Phosphorus / Q000172:deficiency*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000378:metabolism
chemical_list: D005456:Fluorescent Dyes; D009596:Nitrophenols; D009943:Organophosphorus Compounds; D010940:Plant Proteins; D010758:Phosphorus; C008644:nitrophenylphosphate; D000135:Acid Phosphatase
keywords: 4-MU; 4-MUP; 4-methylumbelliferone; 4-methylumbelliferone phosphate; APase; Acid phosphatase; CRs; Cluster roots; ELF-97; Fluorescent labelling; P; Phosphorus deficiency; Pi; White lupin; acid phosphatase; cluster roots; enzyme-labelled fluorescence-97; non-CRs; non-cluster roots; orthophosphate; p-NPP; p-nitrophenyl phosphate; phosphorus