Transcriptomic Analysis Reveals the Key Role of Histone Deacetylation-mediated Phytohormones Interaction in Fiber Initiation of Cotton

Abstract Background: Histone deacetylation is one of the most important epigenetic modifications and plays diverse roles in plant development. However, the detailed functions and mechanisms of histone deacetylation in fiber development of cotton are still unclear. HDAC inhibitors (HDACi) have been used commonly to study the molecular mechanism underlying histone deacetylation or to facilitate disease therapy in humans through hindering the histone deacetylase catalytic activity. Trichostatin A (TSA) - the most widely used HDACi has been used to determine the role of histone deacetylation on different developmental stages of plants. Results: Here, exogenous TSA was applied in the fiber initiation and elongation in vitro, and the results demonstrated the crucial role of histone deacetylation in fiber initiation regulation. Therefore, we made a transcriptomic analysis to reveal the underlying mechanisms. Through RNA-Seq analysis, the differentially expressed genes were mostly enriched in plant hormone signal transduction,phenylpropanoid biosynthesis, photosynthesis, and carbon metabolism pathways, suggesting the potential role of phytohormone, phenylpropanoid metabolism, and energy metabolism downstream of histone deacetylation in fiber initiation. The phytohormone signal transduction pathways harbor the most differentially expressed genes. Deeper studies showed that some genes promoting auxin, Gibberellic Acid (GA), and Salicylic Acid (SA) signaling were down-regulated, while some genes facilitating Abscisic Acid (ABA) and inhibiting Jasmonic Acid (JA) singling were up-regulated after the TSA treatments. Conclusions: Collectively, we established a model, in which histone deacetylation can regulate some key genes involved in different phytohormone pathways, consequently, promoting the auxin, GA, JA and SA signaling, whereas, repressing the ABA signaling to improve the fiber cell initiation; besides that the genes associated with energy metabolism, phenylpropanoid, and glutathione metabolism were also involved in. The above results provided novel clues to illuminate the underlying mechanisms of epigenetic modifications as well as interactions of different phytohormones in fiber cell differentiation, which is also very valuable for molecular breeding of higher quality cotton.