Sequence Variation And Expression Analyses Of Seed Dormancy-and Germination-associated Genes In Rice Cultivars

Seed dormancy has been defined as a temporary failure of a viable seed to germinate in conditions that favor germination when the restrictive state has come to an end. Abscisic acid (ABA) and Gibberellic acid (GA) play key roles in the regulation of seed dormancy and germination. Not only is the dormancy status influenced by the seed maturation environment, it is also continuously changing with time following shedding in a manner determined by the ambient environment. As dormancy is present throughout the higher plants in all major climatic regions, adaptation has resulted in divergent responses to the environment. Through this adaptation, germination is timed to avoid unfavourable weather for subsequent plant establishment and reproductive growth.First, when examining germination of different rice cultivars, we found that their germination timing and dormancy status are rather distinct, coupled with different GA/ABA ratio. Second, we studied genomic sequences of ABA and GA dormancy-and germination-associated genes in rice and discovered single nucleotide polymorphisms (SNPs) and insertions/deletions (Indels) in both coding and regulatory sequences. We aligned all these variations to the genome assemblies of9311and PA64s and demonstrated their relevance to seed dormancy both quantitatively and qualitatively based on gene expression data. Third, we surveyed and compared differentially-expressed genes in dry seeds between9311and PA64s to show that these differentially-expressed genes may play roles in seed dormancy and germination.