title: SIZ1 regulation of phosphate starvation-induced root architecture remodeling involves the control of auxin accumulation.
abstract: Phosphate (Pi) limitation causes plants to modulate the architecture of their root systems to facilitate the acquisition of Pi. Previously, we reported that the Arabidopsis (Arabidopsis thaliana) SUMO E3 ligase SIZ1 regulates root architecture remodeling in response to Pi limitation; namely, the siz1 mutations cause the inhibition of primary root (PR) elongation and the promotion of lateral root (LR) formation. Here, we present evidence that SIZ1 is involved in the negative regulation of auxin patterning to modulate root system architecture in response to Pi starvation. The siz1 mutations caused greater PR growth inhibition and LR development of seedlings in response to Pi limitation. Similar root phenotypes occurred if Pi-deficient wild-type seedlings were supplemented with auxin. N-1-Naphthylphthalamic acid, an inhibitor of auxin efflux activity, reduced the Pi starvation-induced LR root formation of siz1 seedlings to a level equivalent to that seen in the wild type. Monitoring of the auxin-responsive reporter DR5::uidA indicated that auxin accumulates in PR tips at early stages of the Pi starvation response. Subsequently, DR5::uidA expression was observed in the LR primordia, which was associated with LR elongation. The time-sequential patterning of DR5::uidA expression occurred earlier in the roots of siz1 as compared with the wild type. In addition, microarray analysis revealed that several other auxin-responsive genes, including genes involved in cell wall loosening and biosynthesis, were up-regulated in siz1 relative to wild-type seedlings in response to Pi starvation. Together, these results suggest that SIZ1 negatively regulates Pi starvation-induced root architecture remodeling through the control of auxin patterning.
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba 305-8572, Japan. kmiura@gene.tsukuba.ac.jp
authors.forename: Kenji
authors.initials: K
authors.lastname: Miura
authors.forename: Jiyoung
authors.initials: J
authors.lastname: Lee
authors.forename: Qingqiu
authors.initials: Q
authors.lastname: Gong
authors.forename: Shisong
authors.initials: S
authors.lastname: Ma
authors.forename: Jing Bo
authors.initials: JB
authors.lastname: Jin
authors.forename: Chan Yul
authors.initials: CY
authors.lastname: Yoo
authors.forename: Tomoko
authors.initials: T
authors.lastname: Miura
authors.forename: Aiko
authors.initials: A
authors.lastname: Sato
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Bohnert
authors.forename: Paul M
authors.initials: PM
authors.lastname: Hasegawa
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D008025:Ligases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D010710:Phosphates / Q000172:deficiency / Q000378:metabolism*; D010797:Phthalimides / Q000494:pharmacology; D010937:Plant Growth Regulators / Q000378:metabolism; D018517:Plant Roots / Q000201:enzymology / Q000254:growth & development*; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D036226:Seedlings / Q000254:growth & development
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D010710:Phosphates; D010797:Phthalimides; D010937:Plant Growth Regulators; D018749:RNA, Plant; C002687:alpha-naphthylphthalamic acid; D008025:Ligases; C502552:SIZ1 protein, Arabidopsis