Revealing the Core Transcriptome Modulating Plant Growth Phase in Arabidopsis thaliana by RNA Sequencing and Coexpression Analysis of the fhy3 far1 Mutant

Plants must continually calibrate their growth in response to the environment throughout their whole life cycle. Revealing the regularity of plant early growth and development is of great significance to plant genetic modification. It was previously demonstrated that loss of two key light signaling transcription factors, FHY3 and FAR1, can cause a stunted stature in the plant adult stage, and numerous defense response genes can be continuously activated. In this study, we performed a time-course transcriptome analysis of the early 4 weeks of leaf samples from wild plants and their fhy3 and far1 transcription factors. By comparative transcriptome analysis, we found that during the early 4 weeks of plant growth, plants primarily promoted morphogenesis by organizing their microtubules in the second week. In the third week, plants began to trigger largescale defense responses to resist various external stresses. In the fourth week, increased photosynthetic efficiency promoted rapid biomass accumulation. Weighted gene coexpression network analysis of FHY3 and FAR1 revealed that the two light signaling transcription factors may be originally involved in the regulation of genes during embryonic development, and in the later growth stage, they might regulate gene expression of some defense-related genes to balance plant growth and immunity. Remarkably, our yeast two-hybrid and bimolecular fluorescence complementation experiments showed that FAR1 interacts with the immune signaling factor EDS1. Taken together, this study demonstrates the major biological processes occurring during the early 4 weeks of plant growth. The light signaling transcription factors, FHY3 and FAR1, may integrate light signals with immune signals to widely regulate plant growth by directly interacting with EDS1.