Apple Ripening Is Controlled by a NAC Transcription Factor

Area of Science:

• Plant genetics
• Fruit ripening biology
• Agricultural science

Background:

• Fruit softening during ripening affects texture and postharvest shelf life, making it a key trait for crop improvement.
• Previous genome-wide association studies (GWAS) identified a major locus influencing apple harvest date and firmness.

Purpose of the Study:

• To investigate the role of the NAC18.1 gene in determining apple fruit firmness and postharvest storage quality.
• To validate and expand upon previous GWAS findings linking NAC18.1 to fruit texture traits.

Main Methods:

• Phenotypic and genotypic data from approximately 800 apple accessions were analyzed.
• Genetic markers within NAC18.1 were compared to those of other firmness-related genes (ACS1, ACO1, PG1).
• NAC18.1 was sequenced across 18 accessions, and its function was assessed by introducing haplotypes into tomato nor mutants.

Main Results:

• A genetic marker within NAC18.1 was the strongest predictor of both harvest firmness and firmness after cold storage.
• Sequencing revealed two major NAC18.1 haplotypes with numerous single nucleotide polymorphisms (SNPs) and insertions/deletions (indels).
• Both NAC18.1 haplotypes successfully complemented the ripening deficiency in tomato nor mutants, indicating functional conservation.

Conclusions:

• Polymorphisms in the apple NAC18.1 gene are strongly associated with variations in fruit firmness.
• NAC18.1 plays a role in a conserved fruit ripening program, offering a target for breeding improved apple varieties.
• Understanding NAC18.1 variation can lead to enhanced apple texture and extended postharvest stability.