P and N deficiency change the relative abundance and function of rhizosphere microorganisms during cluster root development of white lupin (Lupinus albus L.)

• Published in: Soil science and plant nutrition (Tokyo) 2018-11, Vol.64 (6), p.686-696
• Main Authors: Wasaki, Jun, Sakaguchi, Junya, Yamamura, Takuya, Ito, Susumu, Shinano, Takuro, Osaki, Mitsuru, Kandeler, Ellen
• Format: Article
• Language: English
• Subjects: Abundance; Biodegradation; Citric acid; cluster roots; Clusters; Communities; Community structure; Cultivation; Cycles; Electrophoresis; Enzymes; Fingerprinting; Gel electrophoresis; Microorganisms; N deficiency; Nodules; Nutrition; P deficiency; Plant growth; Plant nutrition; Relative abundance; Rhizosphere; Rhizosphere microorganisms; Root development; Roots; Shoots; Soil fertility; White lupin
• ISSN: 0038-0768; 1747-0765
• DOI: 10.1080/00380768.2018.1536847

We studied microbe-plant interactions of white lupin, a cluster root-forming plant, under low P and N conditions to examine increased nutrient acquisition by plants either by a shift to a more specialized microbial community or changes in microbial enzyme production. White lupin plants were grown in rhizoboxes filled with either P- or N-deficient soil; fertilized soil was used as control. After cultivation of plants in a glasshouse for 41 d, plant growth (shoot and roots) and P and N accumulation in shoots were measured. Microbial functions were analyzed by P- and N-cycling enzymes. The microbial community structure was estimated by fingerprinting (denaturing gradient gel electrophoresis) and sequencing techniques. P deficiency induced the released citrate and acid phosphomonoesterases from cluster roots and stimulated the production of microbe-derived alkaline phosphomonoesterase in the rhizosphere. P deficiency decreased microbial diversity in the cluster root rhizosphere. Increased relative abundance of Burkholderiales in the rhizosphere of P deficient plants might be responsible for the degradation of different organic P fractions such as phytates. N deficiency induced an increase of the number of nodules and P concentration in shoot as well as roots of white lupin. We clarified that high release of citrate from cluster roots might be the preferred mechanisms to meet the P demand of nodulated plants under N deficiency. In addition, the high abundance of Rhizobiales and Rhodospirillales in the rhizosphere of cluster roots showed that the importance of N-fixing microorganisms under N deficiency. The contribution of rhizosphere microorganisms due to similar activities of N-cycling enzymes under the two different N treatments is less important for N nutrition of plants. Further understanding of the regulation of cluster roots under N-deficiency will provide new information on the interactions between P and N nutrition.