Understanding the Impact of Low Temperatures in Maize Seed Germination

Maize (Zea mays) is one of the most widely cultivated crops worldwide; however, it is also considered as a chilling sensitive plant. Plants subjected to suboptimal temperatures suffer changes in numerous chemicals, metabolic and physiological responses. Thus, chilling results in decreased field productivity and quality and causes significant crop losses. Low temperatures are an important limiting factor that affects every plant developmental stage, especially germination. Germination is one of the most important plant phases, which has a huge impact on its future performance. Chilling temperatures cause modifications in the seed membrane structure and fluidity originating in the solid-gel phase. The lipids, which constitute this solid-gel phase, are more tightly packed, creating a more rigid and less fluid membrane, which obstructs water uptake and germination. The aim of this project is to study the role of desaturase enzymes during seed germination in two different maize cultivars (American cultivar, W2080 and European cultivar, Oxxgoode). Fatty Acid Desaturases (FAD) are enzymes responsible for regulating seed membrane fluidity by inserting double bonds in the fatty acid chain of the membrane bilayer. A total of 30 fatty acid desaturase genes have been identified in maize, which are distributed on the maize chromosomes. Based on the phylogenetic analysis, desaturase genes are classified in five different subgroups, regarding their mode of action and gene structures. Expression analysis reveals that FAB2.3, FAB2.8, DES, FAD2.1, FAD6, FAB2.11, FAD7, SLD3 and FAD7 genes play an important role during seed germination in both cultivars. However, under chilling conditions the gene upregulation varies; the American cultivar, W2080, shows a significantly higher level of gene expression of FAD2.1, SLD3, FAB2.4 and FAB2.8 genes while FAD2.1 and FAD2.2 desaturase genes are upregulated in the European cultivar, Oxxgoode. In conclusion, FAD genes play an important role in chilling stress response during maize seed germination.