Estimation of the Circadian Phase by Oscillatory Analysis of the Transcriptome in Plants

The phase of the circadian clock (body time) is related to various aspects of physiology and metabolism in plants. Therefore, it is important to evaluate body time to control plant quality and growth. The molecular timetable method, a statistical analysis of the transcriptome, is useful for plant body time estimation. However, it is necessary to verify some assumptions in this method for high resolution estimation in plants under various conditions. To investigate whether the assumptions are valid, we analyzed the period length and expression pattern of genes. We used Arabidopsis thaliana as a model plant, and both lettuce and tomato as model crops. A. thaliana and lettuce were cultivated under conditions of constant light in a closed plant factory, and tomato was cultivated in a sunlight-type plant factory. We found that estimation of the period length of the plant circadian rhythm was possible and that the gene expression pattern correlates well with test-fit cosine curves. Thus, we successfully demonstrated high-resolution estimation of body time in plants using a molecular timetable method.