Os05g0557700

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Annotated Information

Function

Although phosphate (Pi) starvation signaling is well studied in Arabidopsis (Arabidopsis thaliana), it is still largely unknown in rice (Oryza sativa). In this work, a rice leaf tip necrosis1 (ltn1) mutant was identified and characterized. Map-based cloning identified LTN1 as LOC_Os05g48390, the putative ortholog of Arabidopsis PHO2, which plays important roles in Pi starvation signaling.Analysis of transgenic plants harboring a LTN1 promoter::β-glucuronidase construct revealed that LTN1 was preferentially expressed in vascular tissues. The ltn1 mutant exhibited increased Pi uptake and translocation, which led to Pi overaccumulation in shoots. In association with enhanced Pi uptake and transport, some Pi transporters were up-regulated in the ltn1 mutant in the presence of sufficient Pi.

Expression

LTN1, Encoding a Protein Containing a Ubiquitin-Conjugating Domain, Is Responsible for Pi Overaccumulation in the ltn1 Mutant

The ltn1 Mutant Exhibits Increased Uptake and Translocation of Pi and Impaired Pi Remobilization.

LTN1 Is Involved in Regulating Acid Phosphatase and RNase Activities

A Mutation in LTN1 Results in Overaccumulation of Pi in Shoots

LTN1 Regulates Pi Uptake and Transport by Controlling Expression of PHT Genes

LTN1 Is Involved in Root Architecture Alteration under Pi Starvation

LTN1 Is Crucial in Regulating Multiple Pi Starvation Responses in Rice Roots

Evolution

Plants require large amounts of phosphate (Pi) to maintain growth and development .To cope with Pi starvation, plants have evolved multiple strategies to increase Pi availability.The Pi starvation signaling and regulatory system has been well studied in Arabidopsis (Arabidopsis thaliana; Bari et al., 2006; Schachtman and Shin, 2007), demonstrating that PHR1, SIZ1, PHOSPHATE-RESPONSIVE2 (PHO2), and miR399 are major players. PHR1, a MYB transcription factor, is a key regulator of Pi starvation signaling. PHR1 overexpression in Arabidopsis led to excessive Pi accumulation in shoots and activation of Pi starvation-induced gene expression (Rubio et al., 2001; Nilsson et al., 2007). SIZ1 is a small plant ubiquitin-like modifier (SUMO) E3 ligase that controls PHR1 sumoylation (Miura et al., 2005). miR399, the target gene of PHR1, is specifically induced by Pi starvation (Fujii et al., 2005) and can negatively regulate PHO2 expression through mRNA degradation (Chiou et al., 2006). Both miR399 overexpression and mutations in PHO2 resulted in overaccumulation of Pi in Arabidopsis shoots (Fujii et al., 2005; Chiou et al., 2006). Expression of several Pi starvation-induced genes such as Pht1;8, Pht1;9, AtIPS1, and AT4 was increased in pho2 mutants even under Pi-sufficient conditions, suggesting that PHO2 is involved in the regulation of Pi starvation responses (Bari et al., 2006).

Labs working on this gene

1.State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing)

2.Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China (B.H., C.Z., F.L., J.T., Y.W., A.L., L.L., R.C., C.C.);

3.Graduate School of the Chinese Academy of Sciences, Beijing 100049, China (B.H., A.L., L.L., R.C.)

References

1.Abel S, Ticconi CA, Delatorre CA. (2002) Phosphate sensing in higher plants. Physiol Plant 115: 1–8 [PubMed]

2.Ai P, Sun S, Zhao J, Fan X, Xin W, Guo Q, Yu L, Shen Q, Wu P, Miller AJ, et al. (2009) Two rice phosphate transporters, OsPht1;2 and OsPht1;6, have different functions and kinetic properties in uptake and translocation. Plant J 57: 798–809 [PubMed]

3.Chiou TJ, Aung K, Lin SI, Wu CC, Chiang SF, Su CL. (2006) Regulation of phosphate homeostasis by microRNA in Arabidopsis. Plant Cell 18: 412–421 [PMC free article] [PubMed]

4.Delhaize E, Randall PJ. (1995) Characterization of a phosphate-accumulator mutant of Arabidopsis thaliana. Plant Physiol 107: 207–213 [PMC free article] [PubMed]

5. Bin Hu;Chenguang Zhu;Feng Li;Jiuyou Tang;Yiqin Wang;Aihong Lin;Linchuan Liu;Ronghui Che;Chengcai Chu