Effects of stereoisomers of proline-deoxymugineic acid on iron uptake in Poaceae plants

All stereoisomers of proline-deoxymugineic acid, a low-cost and stable analog of phytosiderophore deoxymugineic acid, were synthesized and evaluated for their iron transport activity and growth effect in rice. In addition, the stabilities of their iron complexes were analysed by Electrospray ionization mass spectrometry (ESI-MS). All stereoisomers showed the iron transport activity in Sf9 cell assay, and a yeast assay also suggested the presence of iron transport activity in all but the DDL and LDD analogs. Rice grew better in alkaline soil by applications of stereoisomers of PDMA, and the natural LLL (PDMA) and unnatural LLD analogs in particular showed significant growth-promoting effects. The diastereomeric mixure at the 3’’ position was found to be promising as a fertilizer, as was the single isomer of LLL (PDMA). Mass spectrometry suggested that the LLD analog forms a stable iron complex, and the stability of iron complexes was correlated with rice growth activity.