title: Low levels of ribosomal RNA partly account for the very  high photosynthetic phosphorus-use efficiency of  Proteaceae species.
abstract: Proteaceae species in south-western Australia occur on phosphorus- (P) impoverished soils. Their leaves contain very low P levels, but have relatively high rates of photosynthesis. We measured ribosomal RNA (rRNA) abundance, soluble protein, activities of several enzymes and glucose 6-phosphate (Glc6P) levels in expanding and mature leaves of six Proteaceae species in their natural habitat. The results were compared with those for Arabidopsis thaliana. Compared with A. thaliana, immature leaves of Proteaceae species contained very low levels of rRNA, especially plastidic rRNA. Proteaceae species showed slow development of the photosynthetic apparatus (‘delayed greening’), with young leaves having very low levels of chlorophyll and Calvin-Benson cycle enzymes. In mature leaves, soluble protein and Calvin-Benson cycle enzyme activities were low, but Glc6P levels were similar to those in A. thaliana. We propose that low ribosome abundance contributes to the high P efficiency of these Proteaceae species in three ways: (1) less P is invested in ribosomes; (2) the rate of growth and, hence, demand for P is low; and (3) the especially low plastidic ribosome abundance in young leaves delays formation of the photosynthetic machinery, spreading investment of P in rRNA. Although Calvin-Benson cycle enzyme activities are low, Glc6P levels are maintained, allowing their effective use.
authors.forename: Ronan
authors.initials: R
authors.lastname: Sulpice
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Ishihara
authors.forename: Armin
authors.initials: A
authors.lastname: Schlereth
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Cawthray
authors.forename: Beatrice
authors.initials: B
authors.lastname: Encke
authors.forename: Patrick
authors.initials: P
authors.lastname: Giavalisco
authors.forename: Alexander
authors.initials: A
authors.lastname: Ivakov
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Arrivault
authors.forename: Ricarda
authors.initials: R
authors.lastname: Jost
authors.forename: Nicole
authors.initials: N
authors.lastname: Krohn
authors.forename: John
authors.initials: J
authors.lastname: Kuo
authors.forename: Etienne
authors.initials: E
authors.lastname: Laliberté
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Pearse
authors.forename: John A
authors.initials: JA
authors.lastname: Raven
authors.forename: Wolf-Rüdiger
authors.initials: WR
authors.lastname: Scheible
authors.forename: François
authors.initials: F
authors.lastname: Teste
authors.forename: Erik J
authors.initials: EJ
authors.lastname: Veneklaas
authors.forename: Mark
authors.initials: M
authors.lastname: Stitt
authors.forename: Hans
authors.initials: H
authors.lastname: Lambers
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D002734:Chlorophyll / Q000378:metabolism; D019298:Glucose-6-Phosphate / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism*; D010788:Photosynthesis; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D010940:Plant Proteins / Q000378:metabolism; D039105:Proteaceae / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018749:RNA, Plant / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000378:metabolism*; D012269:Ribosomal Proteins / Q000378:metabolism; D013213:Starch / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D018749:RNA, Plant; D012335:RNA, Ribosomal; D012269:Ribosomal Proteins; D002734:Chlorophyll; D010758:Phosphorus; D019298:Glucose-6-Phosphate; D013213:Starch