The RNA Editing Factor SlORRM4 Is Required for Normal Fruit Ripening in Tomato

Area of Science:

• Plant molecular biology
• Posttranscriptional gene regulation
• Fruit development and ripening

Background:

• RNA editing is a key posttranscriptional mechanism influencing gene expression in plants.
• Research on cytidine-to-uridine RNA editing has primarily focused on model plants like maize, rice, and Arabidopsis.
• The role and regulation of RNA editing in crucial agronomic processes, such as fruit ripening, remain underexplored.

Purpose of the Study:

• To investigate the role of RNA editing factors in tomato (Solanum lycopersicum) fruit ripening.
• To identify specific RNA editing factors involved in regulating tomato fruit development.
• To elucidate the molecular mechanisms by which RNA editing influences fruit ripening and mitochondrial function.

Main Methods:

• Analysis of expression profiles for 33 RNA editing factors in tomato.
• Identification of 11 putative fruit ripening-related RNA editing factors.
• Virus-induced gene silencing (VIGS) to assess the function of SlORRM4.
• CRISPR/CRISPR-associated protein 9 (CRISPR/Cas9) genome editing to create SlORRM4 knockout mutants.
• Measurement of respiratory rate and ethylene production.
• Gene expression analysis of ripening and mitochondrial function-related genes.
• Assessment of mitochondrial transcript editing levels.

Main Results:

• SlORRM4 was identified as a key factor affecting tomato fruit ripening.
• Knockout of SlORRM4 using CRISPR/Cas9 significantly delayed fruit ripening, characterized by reduced respiration and ethylene production.
• SlORRM4 knockout led to significant alterations in the expression of genes related to fruit ripening and mitochondrial function.
• Loss of SlORRM4 function resulted in reduced RNA editing efficiency in mitochondrial transcripts, impacting the expression of essential subunits for mitochondrial complex assembly (e.g., Nad3, Cytc1, COX II).

Conclusions:

• SlORRM4 plays a significant role in RNA editing of mitochondrial transcripts during tomato fruit ripening.
• This RNA editing activity is essential for regulating mitochondrial function and key ripening processes.
• SlORRM4 is a critical regulator linking RNA editing, mitochondrial activity, and fruit development in tomato.