Deletion-based reverse genetics in Medicago truncatula.

Area of Science:

• Plant genetics
• Molecular biology
• Genomics

Background:

• Reverse genetics aims to identify null mutations in targeted genes by screening large plant populations.
• Current methods like T-DNA, transposon mutagenesis, and TILLING (Targeting Induced Local Lesions IN Genomes) have limitations in efficiency and applicability across species.
• These methods are often dependent on efficient transformation and tissue culture or primarily identify point mutations, with only a small percentage being null mutations.

Purpose of the Study:

• To introduce an alternative reverse genetics strategy, Deletion TILLING (De-TILLING), for the efficient identification of knockout mutants.
• To demonstrate a method that relies on physically induced genomic deletions, independent of target size.
• To provide a strategy applicable to any plant species, overcoming limitations of current techniques.

Main Methods:

• De-TILLING employs fast neutron mutagenesis to induce genomic deletions.
• A sensitive polymerase chain reaction (PCR)-based detection method is utilized for mutant screening.
• A large population of 156,000 *Medicago truncatula* plants was structured into towers for efficient screening using dual screening and 3D pooling.

Main Results:

• The De-TILLING strategy allows screening of a single tower with only four PCR reactions.
• Mutants were detected at a rate of 29% across five targets per gene within the tested population.
• The method exclusively recovers knockout mutants, independent of target size.

Conclusions:

• De-TILLING is an efficient reverse genetics strategy that exclusively identifies knockout mutants.
• This method is independent of plant tissue culture and transformation efficiency, making it broadly applicable to diverse plant species.
• De-TILLING mutants are advantageous for crop improvement due to minimal background mutations and absence of exogenous DNA.