New regulatory modules controlling growth and defense response in plants
As sessile organisms, plants' survival depends on their rapid adaptation to changes in their surroundings. When confronted with pathogens, plants must allocate their energy and resources toward defense responses, often at the expense of growth. Hormone cross-talk has emerged as an important player in regulating and balancing the growth and defense responses.
In Arabidopsis, the growth regulatory module SHR-SCR-BIRDs controls asymmetric cell division and cell fate determination by forming a cell-type specific protein complex to regulate target genes. Here, we show that this regulatory network coordinates plant defense against pathogens. We found that SHR-SCR-BIRDs proteins modulate the interplay between Jasmonates (JA) and Salicylates (SA). The growth regulatory network components interact with key repressors of Jasmonate, signaling the JAZ proteins and forming nuclear condensates while regulating the expression of JA and SA defense genes. Mutations of the BIRD proteins improved resistance to the pathogenic fungi Botrytis cinerea in Arabidopsis and tomato leaves without impeding growth. We also describe how the transcriptional regulator EMB1579 modulates the activity of SHR-SCR-BIRDs through Liquid-Liquid Phase Separation.
Our findings reveal the role of the growth regulatory network in finetuning growth and defense in plants and highlight the importance of LLPS in regulating this process.