ABA and Ethylene Mediates Tomato Root Development Modulation During Endophytic Fungal Interaction

Area of Science:

• Plant-microbe interactions
• Plant hormone signaling
• Endophytic fungi

Background:

• Early plant-microbe interactions are crucial for establishing beneficial symbioses.
• Endophytic fungi can influence plant development and physiology.
• Abscisic acid (ABA) and ethylene (ET) are key plant hormones regulating growth and stress responses.

Purpose of the Study:

• To investigate how Fusarium solani (FsK) modulates tomato (Solanum lycopersicum) development and hormone pathways during early in vitro co-cultivation.
• To analyze transcriptional changes in ABA and ET pathways in tomato roots and leaves.
• To examine the expression of fungal ET-biosynthesis genes during interaction.

Main Methods:

• In vitro co-cultivation of tomato seedlings with Fusarium solani (FsK).
• Sampling at three early interaction stages: pre-contact (T1), initial contact (T2), and 3 days post-contact (T3).
• Quantification of root traits, root and leaf transcripts for ABA and ET pathways, and fungal ET-biosynthesis genes.

Main Results:

• FsK significantly altered root system architecture, increasing root area, lateral root number, root-hair length, and fresh biomass.
• In leaves, FsK modulated ABA pathway genes, indicating reduced de novo synthesis and enhanced deconjugation of stored ABA.
• ET biosynthesis in leaves was curtailed via down-regulation of ACC oxidase, with isoform-specific changes in ACC synthase; fungal ET-biosynthesis genes showed staged activation.

Conclusions:

• Fusarium solani (FsK) promotes tomato root development through coordinated transcriptional control of plant hormone pathways (ABA and ET).
• The observed hormonal shifts and enhanced root growth suggest FsK's potential as a biostimulant.
• This study reveals a complex interplay between fungal and plant hormone signaling during early symbiotic interactions.