title: Rice SPX1 and SPX2 inhibit phosphate starvation responses through interacting with PHR2 in a phosphate-dependent manner.
abstract: In plants, sensing the levels of external and internal nutrients is essential for reprogramming the transcriptome and adapting to the fluctuating environment. Phosphate (Pi) is a key plant nutrient, and a large proportion of Pi starvation-responsive genes are under the control of Phosphate Starvation Response Regulator 1 (PHR1) in Arabidopsis (AtPHR1) and its homologs, such as Oryza sativa (Os)PHR2 in rice. AtPHR1 and OsPHR2 expression is not very responsive to Pi starvation, raising the question as to how plants sense changes in cellular Pi levels to activate the central regulator. SPX [named after SYG1 (suppressor of yeast gpa1), Pho81 (CDK inhibitor in yeast PHO pathway), and XPR1 (xenotropic and polytropic retrovirus receptor)] proteins that harbor only the SPX domain are reported to be involved in the negative regulation of Pi starvation responses. Here, we show that the nuclear localized SPX proteins SPX1 and SPX2 are Pi-dependent inhibitors of the activity of OsPHR2 in rice. Indeed, SPX1 and SPX2 proteins interact with PHR2 through their SPX domain, inhibiting its binding to P1BS (the PHR1-binding sequence: GNATATNC). In vivo data, as well as results from in vitro experiments using purified SPX1, SPX2, and OsPHR2 proteins, showed that SPX1 and SPX2 inhibition of OsPHR2 activity is Pi-dependent. These data provide evidence to support the involvement of SPX1 and SPX2 in the Pi-sensing mechanism in plants.
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China mcz@zju.edu.cn.
authors.forename: Zhiye
authors.initials: Z
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Wenyuan
authors.initials: W
authors.lastname: Ruan
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Shi
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Xiang
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Changying
authors.initials: C
authors.lastname: Li
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Zhongchang
authors.initials: Z
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Yu
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Huixia
authors.initials: H
authors.lastname: Shou
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Mo
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China mcz@zju.edu.cn.
authors.forename: Chuanzao
authors.initials: C
authors.lastname: Mao
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Wu
mesh_terms: D020816:Amino Acid Motifs; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D008954:Models, Biological; D012275:Oryza / Q000187:drug effects / Q000378:metabolism*; D010710:Phosphates / Q000172:deficiency* / Q000494:pharmacology; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D015398:Signal Transduction / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D010710:Phosphates; D010940:Plant Proteins
keywords: PHR2; Pi signaling; Pi-dependent inhibition; SPX-domain protein