Secondary metabolites donors

Any chemical produced by a plant (donor) that stimulates or inhibits the growth of a neighbour (receiver or receptor) is broadly termed an allelochemical. Typically, allelochemicals are secondary metabolites (Whittaker and Feeney 1971 Rice, 1984 Rizvi et al., 1992), produced as by-products of the acetate and shikimic acid pathways. They may also form as degradation products from the action of microbial enzymes... 

In comparison with mammals, plants contain considerably more GTs because, in addition to the reactions carried out by mammalian GTs, they are required to convert the products of photosynthesis into diverse cell carbohydrates. For example, these GTs synthesize cell wall polysaccharides as well as secondary metabolites and xenobiotics. Plant GTs differ from mammalian GTs even more by their diversity of nucleotide donors. They use not only eight of the nine mammalian nucleotide donors, but numerous others such as UDP-L-rhamnose, GDP-L-glucose, GDP-L-galactose, UDP-L-arabinose, UDP-D-galacturonic acid, UDP-D-apiose, and so on. (29). 

Typical organic precursors for COS, CS2 and the methylated sulfur gases include methionine and cysteine from proteins and isothiocyanates and thiocyanates from plant secondary metabolites. Methanethiol and DMS are also formed in anoxic freshwater sediments from reactions based on H2S and various methyl donors, for example, methoxylated aromatic acids, such as syringic acid from lignins. The rates of DMS emission per unit area are similar for both the oceans and Sphagnum-AommattA wetlands. Only the area of this peat land limited the relative importance of the latter source. 

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