Insight in phytohormone-induced gene regulatory networks reveals unknown defence controllers

In nature, plants are subject to attack by a broad range of harmful pathogens and pests. To survive, plants have evolved sophisticated immune signalling networks that enable them to mount an effective defence response upon recognition of invaders. Plant hormones, especially salicylic acid (SA) and jasmonic acid (JA), emerged as core players in the orchestration of the signalling networks that underlie activation of plant defence responses. The SA and JA pathways cross-communicate, providing plants with a highly flexible regulatory capacity to finely tune their defence responses against the attacker at hand. On top of that, other hormones like abscisic acid (ABA) and ethylene (ET) can modulate the SA- and JA-induced gene regulatory networks. Moreover, a previous encounter with an attacker or with a beneficial microbe can prime plants to activate a faster and stronger SA- or JA-dependent defence response. We take a systems approach to advance our understanding of the different modes of regulation of SA- and JA-induced defence responses. We performed high-resolution RNA-Seq time series of SA-, JA-, and ABA-treated Arabidopsis to build dynamic gene regulatory network models. This allowed us to uncover novel regulators of the individual hormone-induced responses. We are also working on identifying regulators of hormone signal integration and of defence priming. The significance of these novel regulatory components is validated by molecular and genetic analyses and by bioassays using pathogens and insects. Understanding how plants shape their hormone-induced pathways to effectively defend themselves against different harmful organisms will identify strategies for breeding agricultural crops with a cost-efficient resistance to improve yield and reduce the need for pesticides.

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