Autoactive MtDMI1 Reprogrammes Immunity and Development in Tomato via Ethylene Signalling.

Area of Science:

• Plant molecular biology
• Crop science
• Plant pathology

Background:

• The Common Symbiosis Signalling Pathway (CSSP) is crucial for plant-microbe interactions but underexplored for crop improvement.
• Gain-of-function mutants offer opportunities to dissect and manipulate signalling pathways.

Purpose of the Study:

• To investigate the effect of heterologously expressing the gain-of-function mutant SPD1 (MtDMI1^S760N) in tomato (Solanum lycopersicum).
• To assess SPD1's impact on plant immunity, development, and underlying molecular mechanisms.

Main Methods:

• Heterologous expression of SPD1 in tomato (cv. Micro-Tom).
• Phenotypic analysis of plant growth, development, and disease resistance.
• Transcriptome analysis to identify molecular pathways affected by SPD1.
• Ethylene inhibition assays using AVG.

Main Results:

• Constitutive activation of ethylene biosynthesis and broad-spectrum resistance against fungal, bacterial, and vascular pathogens.
• SPD1 accelerated seed germination, flowering, and fruit ripening, while reducing root growth and mycorrhizal colonization.
• Transcriptome data revealed constitutive activation of ethylene biosynthesis, immune markers, ROS, and MAPK pathways.
• Ethylene inhibition reversed SPD1-mediated immune activation and root defects.

Conclusions:

• Heterologous expression of an autoactive legume symbiotic component (SPD1) can reprogram defense and development in a non-legume (tomato) via ethylene signaling.
• SPD1 holds promise as a tool for breeding crops with enhanced early maturation and disease resistance.