The roles of epigenetic modifications in the regulation of auxin biosynthesis

4-Allylanisole Promotes the Root Growth of Arabidopsis thaliana by Inhibiting AtHDA9 Activity

This study elucidates the epigenetic mechanism through which 4-allylanisole, a key monoterpene in Foeniculum vulgare essential oils, regulates plant growth. Integrated RNA-Seq and ChIP-Seq analyses revealed 4-allylanisole enhances histone H3K9 acetylation (H3K9ac) at promoters of growth-related genes in Arabidopsis thaliana, concomitant with improved root development and biomass accumulation. Biochemical assays identified AtHDA9 histone deacetylase as the molecular target, showing 4-allylanisole directly inhibits its enzymatic activity through stable interactions with catalytic residues (Asp95, Phe202, Leu268, His174) confirmed by molecular docking and dynamics simulations. The suppressed deacetylation elevated endogenous indole-3-acetic acid (IAA) levels and amplified auxin signaling transduction. These findings establish a dual mechanism whereby 4-allylanisole epigenetically activates growth-related gene expression through H3K9ac accumulation while coordinately enhancing IAA biosynthesis and signaling. This work provides the first evidence of plant-derived volatile compounds regulating growth through histone modification-auxin crosstalk, proposing novel strategies for developing eco-friendly plant growth regulators.

Epigenetics and plant hormone dynamics: a functional and methodological perspective

Plant hormones, pivotal regulators of plant growth, development, and response to environmental cues, have recently emerged as central modulators of epigenetic processes governing gene expression and phenotypic plasticity. This review addresses the complex interplay between plant hormones and epigenetic mechanisms, highlighting the diverse methodologies that have been harnessed to decipher these intricate relationships. We present a comprehensive overview to understand how phytohormones orchestrate epigenetic modifications, shaping plant adaptation and survival strategies. Conversely, we explore how epigenetic regulators ensure hormonal balance and regulate the signalling pathways of key plant hormones. Furthermore, our investigation includes a search for novel genes that are regulated by plant hormones under the control of epigenetic processes. Our review offers a contemporary overview of the epigenetic-plant hormone crosstalk, emphasizing its significance in plant growth, development, and potential agronomical applications.

Precise Regulation of the TAA1/TAR-YUCCA Auxin Biosynthesis Pathway in Plants

The indole-3-pyruvic acid (IPA) pathway is the main auxin biosynthesis pathway in the plant kingdom. Local control of auxin biosynthesis through this pathway regulates plant growth and development and the responses to biotic and abiotic stresses. During the past decades, genetic, physiological, biochemical, and molecular studies have greatly advanced our understanding of tryptophan-dependent auxin biosynthesis. The IPA pathway includes two steps: Trp is converted to IPA by TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS/TRYPTOPHAN AMINOTRANSFERASE RELATED PROTEINs (TAA1/TARs), and then IPA is converted to IAA by the flavin monooxygenases (YUCCAs). The IPA pathway is regulated at multiple levels, including transcriptional and post-transcriptional regulation, protein modification, and feedback regulation, resulting in changes in gene transcription, enzyme activity and protein localization. Ongoing research indicates that tissue-specific DNA methylation and miRNA-directed regulation of transcription factors may also play key roles in the precise regulation of IPA-dependent auxin biosynthesis in plants. This review will mainly summarize the regulatory mechanisms of the IPA pathway and address the many unresolved questions regarding this auxin biosynthesis pathway in plants.