Growth vs Defense: Unraveling the Molecular Players in Tomato Trade-Off Mechanisms

• Grant number: 25/08851-7
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• Start date: September 01, 2025
• End date: August 31, 2026
• Field of knowledge: Biological Sciences - Botany - Pant Physiology
• Principal Investigator: Maria Magdalena Rossi
• Grantee: Juliene dos Reis Moreira
• Supervisor: Andreas Hiltbrunner
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: University of Freiburg, Germany
• Associated to the scholarship: 24/12977-3 - Assessing the role of SlBBXs in shade avoidance and biotic stress, BP.PD

Abstract

Coping with biotic and abiotic stresses are the greatest challenges for plants in the current context of climate changes, directly affecting their growth, development and productivity. Plant responses to these stresses are mediated by a complex signaling network involving hormones and regulatory proteins. Among them, BBX transcription factors play key roles by integrating signals related to both growth and defense. Under stress, plants face a trade-off between growth and defense, prioritizing one pathway over the other. Although some molecular players in this crosstalk have been identified, the role of BBX proteins in this balance remains poorly understood. Using tomato as a model, our group has identified specific SlBBX proteins as key candidates in this regulatory interface. Previous findings revealed that SlBBX20 acts as a positive regulator of light signaling and defense response; as Slbbx20 mutants are light-hyposensitive and more susceptible to Botrytis cinerea infection. In contrast, SlBBX28 functions as a negative regulator of light signaling and defense response; since SlBBX28-RNAi plants showed light-hypersensitive and increased resistance to B. cinerea. Additionally, SlBBX20 is strongly induced by wounding, while SlBBX28 shows minimal response. Consistent with their roles in JA-mediated defense, the JA response master regulator SlMYC2 and its downstream targets are significantly impaired in the susceptible Slbbx20 mutant, whereas their expression is enhanced in the SlBBX28-RNAi genotype. Finally, both SlBBX proteins form heterodimers with key regulators of light and defense pathways. Based on this set of evidence, this work hypothesizes that SlBBX20 and SlBBX28 function as antagonistic regulators of the growth-defense trade-off via distinct molecular mechanisms. In this sense, this project aims to elucidate how these two SlBBX proteins mediate growth and defense responses under shading and simulated herbivory, respectively, deepening our understanding of how plants balance the response to multiple environmental stimuli simultaneously.