Alanine aminotransferase contributes to hypoxia sensitivity and dormancy in barley seeds

Seed dormancy is regulated by a combination of developmental and environmental cues to ensure seedling survival in a changing environment. In barley (Hordeum vulgare L.), the SD1 and SD2 (where SD is standard deviation) loci regulate dormancy and pre-harvest sprouting (PHS), though their role in physiological development remains unclear. Malting barley production in Eastern Canada is currently limited due to the high potential for PHS in the region. To understand what genetic loci might be influencing dormancy in Eastern Canadian barley, we evaluated the LegCi biparental population, which was derived from the Léger variety. A quantitative trait loci close to the SD1 on chromosome 5 locus was identified as regulating germination in LegCi, suggesting that the alanine aminotransferase gene (AlaAT1), which underlies dormancy regulation at SD1, influences dormancy in LegCi. Alanine aminotransferases influence energy production in the cell, particularly during nitrogen limitation or oxygen deprivation. LegCi genotypes segregating for dormancy at the SD1 allele showed no differences in abscisic acid or GA-dependent gene expression during grain fill but varied for hypoxia-induced gene expression. Hypoxia suppressed germination in all genotypes but had a significantly higher impact on genotypes with the dormant AlaAT1 relative to genotypes with the non-dormant AlaAT1. This trend was not dependent on the presence of the hull, suggesting that signaling or metabolism inside the germinating seed is influencing hypoxia sensitivity. This work suggests that the non-dormant allele of SD1 is associated with reduced hypoxia stress sensitivity to promote germination. Further work is needed to determine if this trend extends to other barley genotypes.