IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

17 th International Congress on Nitrogen Fixation
Fremantle, Western Australia
27 November – 1 December 2011
Title Study on soybean nodule symbiosome membrane localised transporters
Authors Chen C., Loughlin P., Day D., Smith P.
Poster Board Number 32
In nodules, the symbiosome membrane (SM) shares properties of both the plasma membrane and vacuolar
membrane, however the unique nature of the SM suggests specific mechanism(s) for targeting proteins is
essential. Recent work has indentified the first 24 amino acids from the N-terminus of a Medicago symbiosome
protein as an address label (signal peptide) for its targeting (Hohjnec et al., 2009), however this signal peptide is
not present on many known SM proteins. We are focusing on clarifying the targeting mechanism of soybean
nodule SM-localised GmZIP1 (zinc transporter) and GmYSL1 (iron transporter). In silico analysis predicts the first
28 amino acids of GmZIP1 may be a signal peptide. Full length GmZIP1 with GFP fused internally, immediately
after the last predicted transmembrane domain is targeted to the SM. Deletion of the predicted signal peptide
appears to disrupt the expression and/or localization of the fusion protein. GmYSL1 is not predicted to have an
N-terminal signal peptide and N-terminal fusion of GFP does not disrupt its SM localisation. We are currently
examining the localisation of a C-terminally truncated GmYSL1 construct to determine whether this is important
for SM targeting. Furthermore we have characterised 4 novel soybean promoters that can drive high and specific
expression in soybean nodule infected cells. Role of other soybean ZIP homologues are being characterised
through expression, function and localisation studies to elucidate the zinc transporter family.
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