Distinct Expression and Function of Three Ammonium Transporter Genes (OsAMT1;1 – 1;3) in Rice

Abstract

;To study the regulation of ammonium uptake into rice roots, three ammonium transporter genes (OsAMT1;1, 1;2 and 1;3; Oryza sativa ammonium transporter) were isolated and examined. OsAMT1s belong to AMT1 family, containing 11 putative transmembrane-spanning domains. Southern blot analysis and screening of the rice genome database confirmed that with OsAMT1;1-1;3 the complete AMT1 family of rice had been isolated. Heterologous expression of OsAMT1s in the yeast Saccharomyces cerevisiae mutant 31019b showed that all three OsAMT1s exhibit ammonium transport activity. Northern blot analysis showed a distinct expression pattern for the three genes; more constitutive expression in shoots and roots for OsAMT1;1, root-specific and ammonium-inducible expression for OsAMT1;2, and root-specific and nitrogen-derepressible expression for OsAMT1;3. In situ mRNA detection revealed that OsAMT1; 2 is expressed in the central cylinder and cell surface of root tips. This gene expression analysis revealed a distinct nitrogen-dependent regulation for AMTs in rice, differing from that in tomato or Arabidopsis.

Ammonium transport and CitAMT1 expression are regulated by N in Citrus plants

“…5b), suggesting a speciWc signalling role for NH 4 + (or a product of its metabolism). Transcriptional repression of individual AMT genes by N status of the plant has been widely documented in many species (Gazzarrini et al 1999;Rawat et al 1999;von Wirén et al 2000b;Gansel et al 2001;Glass et al 2002;Sonoda et al 2003;Loqué and von Wirén 2004) (Sonoda et al 2003). The nature of the inducing signal is nevertheless unclear since stimulation of OsAMT1.1 and 1.2 expression can be obtained with glutamine as well (Sonoda et al 2003), while LeAMT1.2 is also responsive to NO 3 ¡ , which is not the case for CitAMT1.…”

“…However, several of these genes are also expressed in the aerial parts of the plant, such as AtAMT1.1 in Arabidopsis (Ninnemann et al 1994;Gazzarrini et al 1999;Kaiser et al 2002), LeAMT1.2 and 1.3 in tomato (von Wirén et al 2000), and OsAMT1.1 in rice (Sonoda et al 2003) and PtrAMT1.5; 1.6; 2.1; 2.2 and 3.1 in P. trichonocarpa (Couturier et al 2007). A possible role for AMT transporters in leaves is to prevent loss of 592 593 594NH 4 + from cells during photorespiration (Mayer and Ludewig 2006), a function that can also be fulWlled by CitAMT1 in Citrus.…”

Cell-Type Specificity of the Expression of Os BOR1, a Rice Efflux Boron Transporter Gene, Is Regulated in Response to Boron Availability for Efficient Boron Uptake and Xylem Loading

“…This represents a major difference between Os BOR1 and At BOR1. There are several reports of nutrient transporter genes that are induced by the nutrient conditions, including the rice genes AMT1;2 (Sonoda et al, 2003) and IRT1 (Ishimaru et al, 2006) and the Arabidopsis genes YSL2 (Schaaf et al, 2005) and the AMTs (for review, see Loque and von Wiré n, 2004), but in these cases, no changes in cell-type specific patterns of expression were reported.…”

Regulatory role of indeterminate domain 10 (IDD10) in ammonium-dependent gene expression in rice roots

“…3 The expression of ammonium transporters (AMTs) and assimilation genes (GS, NADH-GOGAT, GDH) is highly sensitive to exogenous ammonium. [4][5][6] The expression levels of AMT1;2 (ammonium transporter 1;2) and GDH2 (glutamate dehydrogenase 2) in the roots of idd10 mutants and IDD10 overexpressors were suppressed and enhanced, respectively. IDD10 regulation of the expression of AMT1;2 and GDH2 was demonstrated by molecular analysis.…”