. 2006 Jul;98(1):1–8. doi: 10.1093/aob/mcl099

Table 2.

Properties of Arabidopsis oligopeptide transporters (OPTs)

	Substrates transported				Expression patterns
Transporter	Tetrapeptides	Pentapeptides	Glutathione	Metal ions	Flower	Stems/leaves	Roots	Pollen	Seeds/funiculi
AtOPT1	×	✓			✓	✓	✓	✓	✓
					high	moderate	low
AtOPT2	×	×		Cu²⁺, Zn²⁺?	✓	✓	✓
					moderate	moderate	moderate
AtOPT3	×	×		Cu²⁺, Mn²⁺, Fe²⁺	✓	✓	✓	✓	✓
					high	leaf, high;	high
						stem, moderate
AtOPT4	✓	✓	×		✓	✓	✓		✓
					moderate	moderate	moderate
AtOPT5	×	✓			✓	✓	✓
					high	low	low
AtOPT6	×	✓	✓?	Cd²⁺	✓	✓	✓		✓
			Also Cd²⁺–GSH	Cd²⁺	high	low	high
AtOPT7	×	✓	Cd²⁺–GSH		✓	✓	✓		✓
					high	low	high
AtOPT8					✓			✓	✓
					low

AtOPTs able to transport a given substrate when produced in yeast or Xenopus oocytes are indicated by (✓). Substrates that do not appear to be transported by a given AtOPT are indicated by (×). The absence of any symbol in a ‘substrate transported’ column indicates that the substrate was not tested with that specific AtOPT. Note that only a limited number of peptides have been tested as potential substrates of the AtOPTs when these transporters have been produced in heterologous systems and so probably do not represent the range of substrates found in planta. AtOPTs expressed as transcripts in a specific tissue are indicated by (✓). The absence of any symbol in a box under ‘expression patterns’ indicates that expression of that specific AtOPT in that tissue was either very low or undetectable by use of either quantitative PCR analysis or expression of OPT promoter–GUS fusions in transformed plants. The relative levels of AtOPT expression indicated as high, moderate or low are those determined from quantitative PCR analysis (Koh et al., 2002).