purple acid phosphatase plays a role in nodule formation and nitrogen fixation in Astragalus sinicus

• Published in: Plant molecular biology 2015-08, Vol.88 (6), p.515-529
• Main Authors: Wang, Jianyun, Si, Zaiyong, Li, Fang, Xiong, Xiaobo, Lei, Lei, Xie, Fuli, Chen, Dasong, Li, Yixing, Li, Youguo
• Format: Article
• Language: English
• Subjects: acid phosphatase; Acid Phosphatase - genetics; Acid Phosphatase - metabolism; Acids; Adenosine diphosphate; adenosine triphosphate; Amino Acid Sequence; Astragalus Plant - enzymology; Astragalus Plant - metabolism; Astragalus Plant - microbiology; Astragalus sinicus; ATP; Biochemistry; Biomedical and Life Sciences; Cloning, Molecular; DNA, Complementary; DNA, Plant; energy; Enzymatic activity; enzyme activity; Gene expression; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant - physiology; gene overexpression; Gene Silencing; genes; Glycoproteins - genetics; Glycoproteins - metabolism; high performance liquid chromatography; Legumes; Life Sciences; Liquid chromatography; Mesorhizobium - physiology; Molecular Sequence Data; Mutation; Nitrogen; Nitrogen fixation; Nitrogen Fixation - physiology; nitrogenase; nodulation; organogenesis; phenotype; Phosphatase; phosphates; Pichia pastoris; Plant biology; Plant Pathology; Plant Root Nodulation - physiology; Plant Roots - enzymology; Plant Roots - microbiology; Plant Roots - physiology; Plant Sciences; plasma membrane; Ribonucleic acid; RNA; RNA interference; root nodules; Roots; Symbiosis; Time Factors; Up-Regulation - physiology
• ISSN: 0167-4412; 1573-5028
• DOI: 10.1007/s11103-015-0323-0

The AsPPD1 gene from Astragalus sinicus encodes a purple acid phosphatase. To address the functions of AsPPD1 in legume-rhizobium symbiosis, its expression patterns, enzyme activity, subcellular localization, and phenotypes associated with its over-expression and RNA interference (RNAi) were investigated. The expression of AsPPD1 was up-regulated in roots and nodules after inoculation with rhizobia. Phosphate starvation reduced the levels of AsPPD1 transcripts in roots while increased those levels in nodules. We confirmed the acid phosphatase and phosphodiesterase activities of recombinant AsPPD1 purified from Pichia pastoris, and demonstrated its ability to hydrolyze ADP and ATP in vitro. Subcellular localization showed that AsPPD1 located on the plasma membranes in hairy roots and on the symbiosomes membranes in root nodules. Over-expression of AsPPD1 in hairy roots inhibited nodulation, while its silencing resulted in nodules early senescence and significantly decreased nitrogenase activity. Furthermore, HPLC measurement showed that AsPPD1 overexpression affects the ADP levels in the infected roots and nodules, AsPPD1 silencing affects the ratio of ATP/ADP and the energy charge in nodules, and quantitative observation demonstrated the changes of AsPPD1 transcripts level affected nodule primordia formation. Taken together, it is speculated that AsPPD1 contributes to symbiotic ADP levels and energy charge control, and this is required for effective nodule organogenesis and nitrogen fixation.