Genome-Wide Analysis Revealed the Complex Regulatory Network of Brassinosteroid Effects in Photomorphogenesis

Light and brassinosteroids (BRs) have been proved to be crucial in regulating plant growth and development, however, the mechanism of how they synergistically function is still largely unknown. To explore the underlying mechanisms in photomorphogenesis, genome-wide analyses were carried out through examining the gene expressions of the dark-grown WT or BR biosynthesis-defective mutant det2 seedlings in presence of light stimuli, or exogenous Brassinolide (BL). Results showed that BR deficiency stimulates, while BL treatment suppresses, the expressions of light responsive genes and photomorphogenesis, revealing the negative effects of BR in photomorphogenesis. This is consistent with that genes involved in cell wall modification and cellular metabolism were specifically modulated by BL during dark-light transition, and altered expressions of genes related to energy utilization. Further analysis revealed that hormone biosynthesis and signaling related genes, especially those of auxin, were altered under BL treatment or light stimuli, indicating that BR may modulate photomorphogenesis through synergetic regulation with other hormones. Additionally, suppressed ubiquitin-cycle pathway during light-dark transition hinted the presence of a complicated network among light, hormone and protein degradation. The study provides the direct evidence of BR effects in photomorphogenesis and identified the genes involved in BR and light signaling pathway, which will help to elucidate the molecular mechanism of plant photomorphogenesis.

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Song LI, Zhou XY, Li LI, Xue LJ, Yang XI, Xue HW