Analysis of the contribution of acid phosphatase to P efficiency in Brassica napus under low phosphorus conditions.

National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430070, China.
Science China. Life sciences (Impact Factor: 1.51). 06/2010; 53(6):709-17. DOI: 10.1007/s11427-010-4008-2
Source: PubMed

ABSTRACT To understand whether genotypic variation in acid phosphatase (APase) activity in rapeseed (Brassica napus L.) induced by phosphorus (P) deficiency has impact on P efficiency, soil APase activity in the rhizosphere for rapeseed P-efficient genotype 102 and P-inefficient genotype 105 was measured against organic and inorganic P sources in the pot experiment, and the activities of root-secreted APase and leaf intracellular APase were investigated in different P-starvation periods in the nutrient solution. Higher activity of root-secreted APase in B. napus was induced under low P conditions. However, P nutrition and P uptake efficiency of the plants supplied with organic P were not directly related to the activity of root-secreted APase due to several confounding factors affecting APase availability. The higher activity of leaf APase improved P remobilization in plants and played important roles in enhancing P use efficiency, shown by the significant correlation between leaf APase activity and P use efficiency in a rapeseed recombinant inbred population of 135 lines.

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    ABSTRACT: Brassicas are among the most widely grown and important crops worldwide. Phosphorus (P) is a key mineral element in the growth of all plants and is largely supplied as inorganic rock-phosphate, a dwindling resource, which is likely to be an increasingly significant factor in global agriculture. In order to develop crops which can abstract P from the soil, utilize it more efficiently, require less of it or obtain more from other sources such as soil organic P reservoirs, a detailed understanding the factors that influence P metabolism and cycling in plants and associated soil is required. This review focuses on the current state of understanding of root traits, rhizodeposition and rhizosphere community interaction as it applies to P solubilization and acquisition, with particular reference to Brassica species. Physical root characteristics, exudation of organic acids (particularly malate and citrate) and phosphatase enzymes are considered and the potential mechanisms of control of these responses to P deficiency examined. The influence of rhizodeposits on the development of the rhizosphere microbial community is discussed and the specific features of this community in response to P deficiency are considered; specifically production of phosphatases, phytases and phosphonate hydrolases. Finally various potential approaches for improving overall P use efficiency in Brassica production are discussed.
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    ABSTRACT: Acid phosphatase (APase) is very important in phosphorus (P) scavenging and remobilization in plants. The aim of this study was the fine mapping of quantitative trait loci (QTL) for APase activity (APA) in maize (Zea mays L.) leaf. The QTL for APA were studied in the F2:3 population derived from the cross 082 × Ye107 under low P stress in two sites. A significant difference in APA was found between 082 (P-efficient genotype) and Ye107 (P-deficient genotype). Each environment was analyzed to identify the QTL. Six QTL for APA were found, comprising two QTL at Beibei (BB) and four QTL at Hechuan (HC), China. A QTL denoted as AP9 showed a stable expression under different environments on chromosome 9, and explained 10.21 and 16.81 % of phenotypic variation at BB and HC, respectively. For the fine mapping of this QTL, seven individuals selected via marker-assisted selection in the BC3F1 population were used to produce the BC3F2 lines by selfing and to allow recombination within the region containing the target QTL. High-resolution genetic and physical maps were further constructed for the fine mapping of AP9 using 12 simple sequence repeat markers and the BC3F2 population consisting of 1,441 individuals. As a result, the location of AP9 was narrowed down to a 546-kb fragment on chromosome 9.
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    ABSTRACT: Background and aims Cytokinins are known to nega-tively regulate plant root development and phosphorus (P) starvation responses. In this study, two Brassica napus root mutants insensitive to exogenous cytokinin, prl1 (a mutant with an elongated primary root) and lrn1 (a mutant with more lateral roots), were identified and used to evaluate P efficiency, alongside wild type (WT) plants. Methods Solution and pot culture, RNA isolation, RT-PCR were used. Results lrn1 produced the highest shoot dry weight (SDW) and root dry weight (RDW) among the three genotypes at both low P (LP) and high P (HP) con-ditions. prl1 had higher SDW at both P conditions, and higher RDW at LP, in contrast to WT plants. lrn1 not only accumulated more P from the culture medium but utilized it effectively in shoot growth, whilst prl1 just showed higher P use efficiency compared to WT at LP. Trans-zeatin riboside (tZR) and isopentenyl adenosine (iPA) concentration in lrn1 roots were both signifi-cantly lower than that in WT roots at both P con-ditions. Root iPA concentration in prl1 was lower than that in WT under both P conditions, however, root tZR concentration was greater in prl1 than WT under LP condition. Transcription of the P starva-tion induced genes BnSPX3;1 and BnSPX3;2 were up-regulated in the roots of mutants under both P conditions. Conclusions These results suggested that an improved root system might be associated with the reduced cytokinin concentration and lead to a significant increase in acquisition and utilization of P nutrient for lrn1.
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