MATRILINEAL, a sperm-specific phospholipase, triggers maize haploid induction

Area of Science:

• Plant genetics
• Reproductive biology
• Crop science

Background:

• Sexual reproduction in plants relies on double fertilization.
• Doubled haploid production accelerates plant breeding by fixing genomes but often requires costly tissue culture.
• Existing in vivo doubled haploid systems in maize are limited and their mechanisms are unclear.

Purpose of the Study:

• To elucidate the genetic basis of haploid induction in maize.
• To identify the molecular mechanism underlying haploid induction.
• To explore the potential for developing novel in vivo haploid induction systems.

Main Methods:

• Fine mapping and genome sequencing of maize.
• Genetic complementation and gene editing.
• Pollen RNA-sequence profiling and protein localization studies.

Main Results:

• A frame-shift mutation in the pollen-specific phospholipase gene MATRILINEAL (MTL) was identified as the trigger for haploid induction.
• Novel edits in MTL resulted in a 6.7% haploid induction rate.
• Wild-type MTL protein localizes to sperm cytoplasm, and specific pollen genes are overexpressed during induction.

Conclusions:

• The MATRILINEAL (MTL) gene is crucial for haploid induction in maize.
• Understanding MTL's role opens avenues for developing efficient in vivo doubled haploid systems.
• This discovery has the potential to accelerate breeding programs in maize and other cereal crops.