Disease relevance of IRT1

• Although IRT1 and IRT2 are thought to perform redundant functions as root-specific metal transporters, insertional inactivation of the IRT1 gene alone results in typical symptoms of iron deficiency causing severe leaf chlorosis and lethality in soil [1].

High impact information on IRT1

• In this study, we identify and characterize LIT1, a novel L. amazonensis membrane protein with extensive similarity to IRT1, a ZIP family ferrous iron transporter from Arabidopsis thaliana [2].
• We demonstrate that FIT1 regulates FRO2 at the level of mRNA accumulation and IRT1 at the level of protein accumulation [3].
• IRT1-green fluorescent protein fusion, transiently expressed in culture cells, localized to the plasma membrane [4].
• Under these conditions, plants that overexpressed IRT1 accumulated higher levels of cadmium and zinc than wild-type plants, indicating that IRT1 is responsible for the uptake of these metals and that IRT1 protein levels are indeed increased in these plants [5].
• Two other mutations, replacing the aspartic acid residues at either positions 100 or 136 with alanine, also increase IRT1 metal selectivity by eliminating transport of both iron and manganese [6].

Biological context of IRT1

• By heterologous expression in yeast, we show here that the replacement of a glutamic acid residue at position 103 in wild-type IRT1 with alanine increases the substrate specificity of the transporter by selectively eliminating its ability to transport zinc [6].
• Regulation of the root high-affinity iron uptake system by whole-plant signals was investigated at the molecular level in Arabidopsis, through monitoring FRO2 and IRT1 gene expression [7].
• The metal ion transporter IRT1 is necessary for iron homeostasis and efficient photosynthesis in Arabidopsis thaliana [8].
• These data support the conclusion that IRT1 is an essential metal transporter required for proper development and regulation of iron and zinc homeostasis in Arabidopsis [1].
• Knock-out of Arabidopsis metal transporter gene IRT1 results in iron deficiency accompanied by cell differentiation defects [1].

Anatomical context of IRT1

• Additionally, frd4 chloroplasts are smaller in size and possess dramatically fewer thylakoid membranes and grana stacks when compared with wild-type chloroplasts. frd4 mutant plants express both FRO2 and IRT1 mRNA normally in their roots under iron deficiency, arguing against any defects in systemic iron-deficiency signaling [9].
• To account for the results presented, we propose that AtNRAMP3 influences metal accumulation and IRT1 and FRO2 gene expression by mobilizing vacuolar metal pools to the cytosol [10].

Associations of IRT1 with chemical compounds

• Yeast expressing IRT1 possess a novel Fe(II) uptake activity that is strongly inhibited by Cd [11].
• The current studies demonstrated that IRT1, when expressed in yeast, can transport manganese as well [12].
• This manganese uptake activity was inhibited by cadmium, iron(II) and zinc, suggesting that IRT1 can transport these metals [12].
• To provide a chemical basis for this role, we prepared and studied a peptide corresponding to this sequence from the first iron-regulated transporter (IRT1) of Arabidopsis thaliana, which transports Fe(2+) as well as Mn(2+), Co(2+), Zn(2+), and Cd(2+) [13].
• This paper is a study of the effects of ethylene inhibitors and precursors on the expression of the genes encoding the ferric reductases and iron transporters of Arabidopsis thaliana (FRO2 and IRT1) and Lycopersicon esculentum (=Solanum lycopersicum) (FRO1 and IRT1) plants [14].

Other interactions of IRT1

• Here we report the cloning and characterization of the IRT2 cDNA, a member of the ZIP family of metal transporters, highly similar to IRT1 at the amino-acid level [15].

Analytical, diagnostic and therapeutic context of IRT1

• We also show, through promoter::beta-glucuronidase analysis and in situ hybridization, that IRT1 is expressed in the external cell layers of the root, specifically in response to iron starvation [4].
• Data base comparisons and Southern blot analysis indicated that IRT1 is a member of a gene family in Arabidopsis [11].

References