Weig, A R; Komor, E: An active sucrose carrier (SCR1) that is predominantly expressed in the seedling of Ricinus communis L., Journal of Plant Physiology, 147, 685-690 (1996)
During the germination of Ricinus communis seedlings sucrose is released from the endosperm and taken up by the cotyledons for their growth and for export to the rapidly growing hypocotyl and roots. Both the mesophyll cells and the phloem of castor bean possess active sucrose carriers. We isolated one of these carriers by heterologous screening with the spinach sucrose carrier cDNA for further investigation of sucrose transport at the cellular level. The deduced peptide sequence of this sucrose carrier (Scr1) has 12 putative membrane spanning domains and shares homology with other transporters of the major facilitator superfamily (MFS). When expressed in Saccharomyces cerevisiae, Scr1 shows active sucrose transport that can be inhibited by PCMBS or CCCP. According to the pH-dependence the carrier seems related to SUC2 of Arabidopsis and Plantago, which are phloem-specific in these plants. It also shows a relatively high specificity for sucrose, compared with maltose or raffinose. Scr1 is expressed in equal amounts in all organs of a 6-day-old castor bean seedling and to a lesser extent in green sink and source leaves.

last modified 2004-04-13