Poster: Membrane transport
Abs #
186: Studies on source-sink translocation of ureides in French bean
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Presenter: |
Grennan, Aleel , aleelg@yahoo.com |
Authors | Pelissier, Helene C (A) Grennan, Aleel (A) Tegeder, Mechthild (A) | | Affiliations: |
(A): Washington State University
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Nodulated legumes receive their nitrogen via N-fixing rhizobia. In nodules of tropical legumes, like Phaseolus vulgaris (French bean) and Glycine max (soybean), the fixed nitrogen is reduced to the ureides allantoin and allantoic acid. These are then transported into the vascular system of the roots for long distance transport. Recently, an allantoin transporter (PvUPS1) was isolated from French bean (Pelissier et al., 2004) showing strong expression in nodules and roots. In roots, expression was dependent on nodulation and nitrogen source supplied. PvUPS1 transcripts were localized to the nodule endodermis and vasculature. Within the vascular bundle, strong transporter expression was detected in the vascular endodermis and phloem. These results suggest PvUPS1 is involved in directing allantoin to the vasculature for long-distance transport.
Proper partitioning of organic nitrogen from source to sink is essential for plant growth and development. To study allantoin translocation in bean plants, [14C]allantoin was fed to source leaves and the accumulation of label in sinks was analyzed. Whole plant autoradiography and HPLC analysis of label in the pods demonstrated that allantoin is translocated from source to sink. PvUPS1 is likely to play a role in this process since strong expression in source leaves, pods, seed coats and cotyledons was detected using Northern blot analysis. The cellular localization of PvUPS1 in these tissues was resolved by in situ RNA hybridization. In summary, RNA expression and localization studies, together with the feeding experiments strongly indicate that PvUPS1 plays an important role in supplying sink tissues with allantoin.
NRI Competitive Grants Program- USDA grant no. 2001–35318–10990.
Pélissier et al, (2004) Plant Physiol 134: 664-675
