Natural Occurrence and Biosynthesis

Although Se is not known to be required for the growth of plants, most assimilate it when grown on seleniferous soils, or in Se-containing 

1 Biosynthesis of selenomethionine adapted from Marschner (1995) Schrauzer (2000). 

The ability of plants to degrade SeMet to the DMSe is strongly species-dependent and represents a detoxification mechanism. However, Se volatilization may also result in losses of Se from food crops, aggravating Se deficiency in low-Se regions. Rice, broccoli and cabbage volatilized at the highest rates (200-350 pig Se/m2 leaf area per day) and sugar beet, bean, lettuce and onion volatilized at lowest rates (Terry et al., 1992). 

Marine algae also convert Se predominantly into SeMet (Bottino et al, 1984), Se uptake is dependent on the Se/S ratio in the medium and on the chemical form supplied. Chlorella vulgaris and Chaetoceros calcitrans, for example, take up Se(IV) preferentially over Se(VI). Some of the organoselenium compounds produced by these algae are not incorporated into cellular proteins but are extruded into the culture medium (Hu et al, 1997). Chlorella also takes up SeMet and its incorporation is antagonized by Met (Shrift, 1954a,b). 

2 Production of dimethylselenide (DMSe) from SeMet in plants via dimethylse-lenoniopropionate (DMSeP), adapted after Terry et al. (2000). 

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Coscia CJ, Guamaccia R (1968) Natural occurrence and biosynthesis of a eyelopentanoid monoterpene carboxylic acid. Chem Crunmrm 138-140... 

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