title: Nitric oxide is the shared signalling molecule in phosphorus- and iron-deficiency-induced formation of cluster roots in white lupin (Lupinus albus).
abstract: OBJECTIVE
  Formation of cluster roots is one of the most specific root adaptations to nutrient deficiency. In white lupin (Lupinus albus), cluster roots can be induced by phosphorus (P) or iron (Fe) deficiency. The aim of the present work was to investigate the potential shared signalling pathway in P- and Fe-deficiency-induced cluster root formation.
  
  
  METHODS
  Measurements were made of the internal concentration of nutrients, levels of nitric oxide (NO), citrate exudation and expression of some specific genes under four P × Fe combinations, namely (1) 50 µm P and 10 µm Fe (+P + Fe); (2) 0 P and 10 µm Fe (-P + Fe); (3) 50 µm P and 0 Fe (+P-Fe); and (4) 0 P and 0 Fe (-P-Fe), and these were examined in relation to the formation of cluster roots.
  
  
  RESULTS
  The deficiency of P, Fe or both increased the cluster root number and cluster zones. It also enhanced NO accumulation in pericycle cells and rootlet primordia at various stages of cluster root development. The formation of cluster roots and rootlet primordia, together with the expression of LaSCR1 and LaSCR2 which is crucial in cluster root formation, were induced by the exogenous NO donor S-nitrosoglutathione (GSNO) under the +P + Fe condition, but were inhibited by the NO-specific endogenous scavenger 2-(4-carboxyphenyl)-4, 4, 5, 5-tetramethylimidazoline-1-oxyl- 3-oxide (cPTIO) under -P + Fe, +P-Fe and -P-Fe conditions. However, cluster roots induced by an exogenous supply of the NO donor did not secrete citrate, unlike those formed under -P or -Fe conditions.
  
  
  CONCLUSIONS
  NO plays an important role in the shared signalling pathway of the P- and Fe-deficiency-induced formation of cluster roots in white lupin.
authors.affiliation: College of Life Sciences, Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education, Zhejiang University, Hangzhou 310058, China.
authors.forename: Zhi Bin
authors.initials: ZB
authors.lastname: Meng
authors.forename: Li Qian
authors.initials: LQ
authors.lastname: Chen
authors.forename: Dong
authors.initials: D
authors.lastname: Suo
authors.forename: Gui Xin
authors.initials: GX
authors.lastname: Li
authors.forename: Cai Xian
authors.initials: CX
authors.lastname: Tang
authors.forename: Shao Jian
authors.initials: SJ
authors.lastname: Zheng
mesh_terms: D000222:Adaptation, Physiological; D000090463:Iron Deficiencies; D031297:Lupinus / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism*; D010758:Phosphorus / Q000172:deficiency*; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D010758:Phosphorus; D009569:Nitric Oxide