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Nitrification is a key process of the nitrogen (N) cycle in soil with major environmental implications. The recent discovery of ammonia-oxidizing archaea (AOA) questions the traditional assumption of the dominant role of ammoniaoxidizing bacteria (AOB) in nitrification. We investigated AOB and AOA growth and nitrification rate in two different layers of three grassland soils treated with animal urine substrate and a nitrification inhibitor [dicyandiamide (DCD)]. We show that AOB were more abundant in the topsoils than in the subsoils, whereas AOA were more abundant in one of the subsoils. AOB grew substantially when supplied with a high dose of urine substrate, whereas AOA only grew in the Controls without the urine-N substrate. AOB growth and the amoA gene transcription activity were significantly inhibited by DCD. Nitrification rates were much higher in the topsoils than in the subsoils and were significantly related to AOB abundance, but not to AOA abundance. These results suggest that AOB and AOA prefer different soil N conditions to grow: AOB under high ammonia (NH 3 ) substrate and AOA under low NH 3 substrate conditions.

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Lipoxygenases (LOXs) are a group of non-haem iron-containing dioxygenases that catalyse oxygenation of polyunsaturated fatty acids (PUFAs) and lipids, and initiate the formation of biologically active compounds known as oxylipins. Several plant oxylipins comprise important flavours and aromas in food and beverages. Analysis of the grape (Vitis vinifera L.) genome revealed that the grape LOX family consists of 18 individual members. Phylogenetic analysis places all except one of the identified grape LOXs into either a type II 13-LOX cluster or the type I 9-LOX cluster. Four LOX genes (VvLOXA, VvLOXO, VvLOXC, VvLOXD), representative of the major LOX groupings observed in the phylogenetic analyses, were selected for analysis of patterns of transcript abundance in berry tissues. VvLOXA and VvLOXO represent putative 13-LOXs, while VvLOXC represents a putative 9-LOX. VvLOXD represents a unique LOX that differs significantly from other characterised plant LOXs. All four LOXs exhibited a complex pattern of gene expression. Across all developmental stages, VvLOXA was the most abundant LOX and was expressed predominantly in berry skins. The expression pattern of VvLOXC and -D are more evenly distributed between seeds, pulp and skin, while VvLOXO is mostly expressed in the seed. Mechanical wounding and infection of berries with Botrytis cinerea Pers.: Fr resulted in rapid accumulation of VvLOXC and -O transcripts. VvLOXA expression decreased in diseased berries. Biochemical analysis of VvLOXA and -O recombinant proteins confirmed that these LOX genes encode functional 13-LOXs that exhibit different pH and temperature optima. Both enzymes showed activity with linoleic, linolenic and arachidonic acids.