Creation of aromatic maize by CRISPR/Cas.

Area of Science:

• Plant genetics and breeding
• Food science and technology
• Biotechnology

Background:

• Aroma is a key trait in rice breeding, with compounds like 2-acetyl-1-pyrroline (2AP) contributing to desirable scents.
• Fragrant germplasm is found in various plant species, often linked to reduced activity of the BETAINE ALDEHYDE DEHYDROGENASE 2 (BADH2) enzyme.
• Maize (Zea mays) currently lacks described natural aromatic germplasm, presenting an opportunity for genetic improvement.

Purpose of the Study:

• To investigate the role of maize BADH2 homologs (ZmBADH2a and ZmBADH2b) in 2AP biosynthesis.
• To develop aromatic maize through targeted gene editing.
• To establish a foundation for breeding aromatic maize varieties.

Main Methods:

• Characterization of two maize BADH2 homologs, ZmBADH2a and ZmBADH2b.
• Generation of single (zmbadh2a, zmbadh2b) and double (zmbadh2a-zmbadh2b) mutants using CRISPR/Cas gene editing in four inbred lines.
• Sensory evaluation for popcorn-like scent and quantification of 2AP levels in mutant and wild-type seeds.

Main Results:

• A noticeable popcorn-like scent was exclusively detected in the seeds of the zmbadh2a-zmbadh2b double mutant.
• 2-acetyl-1-pyrroline (2AP) was detected only in the double mutant seeds, with accumulation ranging from 0.028 to 0.723 mg/kg.
• Single mutants and wild-type maize did not exhibit the aromatic scent or significant 2AP accumulation.

Conclusions:

• ZmBADH2a and ZmBADH2b redundantly function in the biosynthesis pathway of 2AP in maize.
• Simultaneous genome editing of both ZmBADH2 genes successfully created the world's first aromatic maize.
• This research opens avenues for developing novel aromatic maize cultivars with enhanced market value.