title: GmEXPB2, a Cell Wall β-Expansin, Affects Soybean Nodulation through Modifying Root Architecture and Promoting Nodule Formation and Development.
abstract: Nodulation is an essential process for biological nitrogen (N2) fixation in legumes, but its regulation remains poorly understood. Here, a β-expansin gene, GmEXPB2, was found to be critical for soybean (Glycine max) nodulation. GmEXPB2 was preferentially expressed at the early stage of nodule development. β-Glucuronidase staining further showed that GmEXPB2 was mainly localized to the nodule vascular trace and nodule vascular bundles, as well as nodule cortical and parenchyma cells, suggesting that GmEXPB2 might be involved in cell wall modification and extension during nodule formation and development. Overexpression of GmEXPB2 dramatically modified soybean root architecture, increasing the size and number of cortical cells in the root meristematic and elongation zones and expanding root hair density and size of the root hair zone. Confocal microscopy with green fluorescent protein-labeled rhizobium USDA110 cells showed that the infection events were significantly enhanced in the GmEXPB2-overexpressing lines. Moreover, nodule primordium development was earlier in overexpressing lines compared with wild-type plants. Thereby, overexpression of GmEXPB2 in either transgenic soybean hairy roots or whole plants resulted in increased nodule number, nodule mass, and nitrogenase activity and thus elevated plant N and phosphorus content as well as biomass. In contrast, suppression of GmEXPB2 in soybean transgenic composite plants led to smaller infected cells and thus reduced number of big nodules, nodule mass, and nitrogenase activity, thereby inhibiting soybean growth. Taken together, we conclude that GmEXPB2 critically affects soybean nodulation through modifying root architecture and promoting nodule formation and development and subsequently impacts biological N2 fixation and growth of soybean.
authors.affiliation: Haixia Institute of Science and Technology, Root Biology Center (X.L., H.L.) and College of Life Sciences (R.Z.), Fujian Agriculture and Forestry University, Fuzhou 350002, Chinaand College of Agriculture, South China Agricultural University, Guangzhou 510642, China (X.L., J.Z., Z.T., H.L.).
authors.forename: Xinxin
authors.initials: X
authors.lastname: Li
authors.affiliation: Haixia Institute of Science and Technology, Root Biology Center (X.L., H.L.) and College of Life Sciences (R.Z.), Fujian Agriculture and Forestry University, Fuzhou 350002, Chinaand College of Agriculture, South China Agricultural University, Guangzhou 510642, China (X.L., J.Z., Z.T., H.L.).
authors.forename: Jing
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Haixia Institute of Science and Technology, Root Biology Center (X.L., H.L.) and College of Life Sciences (R.Z.), Fujian Agriculture and Forestry University, Fuzhou 350002, Chinaand College of Agriculture, South China Agricultural University, Guangzhou 510642, China (X.L., J.Z., Z.T., H.L.).
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Tan
authors.affiliation: Haixia Institute of Science and Technology, Root Biology Center (X.L., H.L.) and College of Life Sciences (R.Z.), Fujian Agriculture and Forestry University, Fuzhou 350002, Chinaand College of Agriculture, South China Agricultural University, Guangzhou 510642, China (X.L., J.Z., Z.T., H.L.).
authors.forename: Rensen
authors.identifier: http://orcid.org/0000-0002-6435-3054
authors.initials: R
authors.lastname: Zeng
authors.affiliation: Haixia Institute of Science and Technology, Root Biology Center (X.L., H.L.) and College of Life Sciences (R.Z.), Fujian Agriculture and Forestry University, Fuzhou 350002, Chinaand College of Agriculture, South China Agricultural University, Guangzhou 510642, China (X.L., J.Z., Z.T., H.L.) hliao@scau.edu.cn.
authors.forename: Hong
authors.initials: H
authors.lastname: Liao
mesh_terms: D002473:Cell Wall / Q000235:genetics* / Q000378:metabolism; D020869:Gene Expression Profiling / Q000379:methods; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D018613:Microscopy, Confocal; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D055170:Plant Root Nodulation / Q000235:genetics*; D018517:Plant Roots / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053204:Root Nodules, Plant / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D013025:Glycine max / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism
chemical_list: D010940:Plant Proteins; C095825:expansin protein, plant