Asparagine synthetase genes (<em>AsnS1</em> and <em>AsnS2</em>) in durum wheat: structural analysis and expression under nitrogen stress

International audience

英语. Wheat is one of the most widely grown cereal crops based on the amount of calories it provides in the human diet. Durum wheat (<em>Triticum turgidum</em> ssp.<em> durum</em>) is largely used for production of pasta and other products. In order to use genetic knowledge to improve the understanding of N-use efficiency, we carried out, for the first time in durum wheat, the isolation and the characterization of four members of the asparagine synthetase (<em>AsnS</em>) gene family. Phylogenetic inference clustered the <em>Ttu-AsnS1</em> (1.1 and 1.2) and <em>Ttu-AsnS2</em> (2.1 and 2.2) genes in <em>AsnS</em> gene class I, which is present in monocots and dicots. Class I genes underwent a subsequent duplication leading to the formation of two subgroups. Plants of Svevo cultivar were grown under N-stress conditions and expression of the four <em>AsnS</em> genes was investigated at three developmental stages (seedling, booting, and late milk development), crucial for N absorption, assimilation and remobilization. <em>AsnS1</em> genes were down-regulated in N-stressed roots, stems and leaves during seedling growth and booting, but seemed to play a role in N remobilization in flag leaves during grain filling. <em>AsnS2</em> genes were scarcely expressed in roots, stems, and leaves. In N-stressed spikes there was no differential expression in any of the genes. The genes were mapped in silico using a durum wheat SNP map, assigning <em>Ttu-AsnS1</em> genes to chromosome 5 and <em>Ttu-AsnS2</em> to chromosome 3. These findings provide a better understanding of the role of ASN genes in response to N stress in durum wheat.