Wang Xiurong, Wang Yingxiang, Tian Jiang, Lim Boon Leong, Yan Xiaolong, Liao Hong
Root Biology Center, South China Agricultural University, Guangzhou 510642, China.
Plant Physiol. 2009 Sep;151(1):233-40. doi: 10.1104/pp.109.138891. Epub 2009 Jul 8.
Low phosphorus (P) availability is a major constraint to crop growth and production, including soybean (Glycine max), on a global scale. However, 50% to 80% of the total P in agricultural soils exists as organic phosphate, which is unavailable to plants unless hydrolyzed to release inorganic phosphate. One strategy for improving crop P nutrition is the enhanced activity of acid phosphatases (APases) to obtain or remobilize inorganic phosphate from organic P sources. In this study, we overexpressed an Arabidopsis (Arabidopsis thaliana) purple APase gene (AtPAP15) containing a carrot (Daucus carota) extracellular targeting peptide in soybean hairy roots and found that the APase activity was increased by 1.5-fold in transgenic hairy roots. We subsequently transformed soybean plants with AtPAP15 and studied three homozygous overexpression lines of AtPAP15. The three transgenic lines exhibited significantly improved P efficiency with 117.8%, 56.5%, and 57.8% increases in plant dry weight, and 90.1%, 18.2%, and 62.6% increases in plant P content, respectively, as compared with wild-type plants grown on sand culture containing phytate as the sole P source. The transgenic soybean lines also exhibited a significant level of APase and phytase activity in leaves and root exudates, respectively. Furthermore, the transgenic lines exhibited improved yields when grown on acid soils, with 35.9%, 41.0%, and 59.0% increases in pod number per plant, and 46.0%, 48.3%, and 66.7% increases in seed number per plant. Taken together, to our knowledge, our study is the first report on the improvement of P efficiency in soybean through constitutive expression of a plant APase gene. These findings could have significant implications for improving crop yield on soils low in available P, which is a serious agricultural limitation worldwide.
在全球范围内，低磷有效性是包括大豆（Glycine max）在内的作物生长和产量的主要限制因素。然而，农业土壤中总磷的50%至80%以有机磷酸盐的形式存在，除非水解释放无机磷酸盐，否则植物无法利用。提高作物磷营养的一种策略是增强酸性磷酸酶（APases）的活性，以便从有机磷源中获取或重新利用无机磷酸盐。在本研究中，我们在大豆毛状根中过表达了一个含有胡萝卜（Daucus carota）细胞外靶向肽的拟南芥（Arabidopsis thaliana）紫色APase基因（AtPAP15），发现转基因毛状根中的APase活性提高了1.5倍。随后，我们用AtPAP15转化大豆植株，并研究了AtPAP15的三个纯合过表达株系。与在以植酸为唯一磷源的砂培中生长的野生型植株相比，这三个转基因株系的磷效率显著提高，植株干重分别增加了117.8%、56.5%和57.8%，植株磷含量分别增加了90.1%、18.2%和62.6%。转基因大豆株系在叶片和根系分泌物中也分别表现出显著水平的APase和植酸酶活性。此外，转基因株系在酸性土壤中生长时产量提高，单株荚数分别增加了35.9%、41.0%和59.0%，单株种子数分别增加了46.0%、48.3%和66.7%。据我们所知，本研究是通过植物APase基因的组成型表达提高大豆磷效率的首次报道。这些发现对于提高全球范围内有效磷含量低的土壤上的作物产量可能具有重要意义，而有效磷含量低是一个严重的农业限制因素。
