Genetic variant in corn may reduce seed losses.

A natural mutation in the DNA that regulates the ZmPIMT1 gene increases the aging tolerance of corn seeds. The discovery, made by researchers from the United States and China, could help producers and companies reduce germination losses in stored seeds.

The ZmPIMT1 gene controls the production of an enzyme that repairs damaged proteins within the seed. This enzyme acts on the PABP2 protein, which is essential for the seed to produce new proteins when germination begins. When there is more active ZmPIMT1, PABP2 functions better, and the seed is more resistant to stress caused by time or adverse storage conditions.

Two versions

Scientists have identified two versions of the promoter region of the ZmPIMT1 gene. This region acts as a "switch" that turns the gene on. The variant called Hap C7-2, found in the Chang7-2 lineage, activates the gene more strongly. The Hap Z58 version, present in the Zheng58 lineage, has a 2.316 base pair insertion in the DNA that reduces the gene's activity.

Seeds with the Hap C7-2 variant showed higher germination rates after accelerated aging tests. In a population of recombinant lines derived from the Zhengdan 958 hybrid, 81% of seeds with the Hap Z58 haplotype germinated below 30%, compared to 53% in lines with Hap C7-2. Furthermore, 20% of the lines with Hap C7-2 exceeded 60% germination, while only 6,25% of the Hap Z58 lines reached that level.

Experiments with genetically modified plants reinforced the data. Corn lines with overexpression of the ZmPIMT1 gene produced seeds with greater vigor after accelerated aging. The same occurred with model plants of the species. Arabidopsis thalianaOn the other hand, plants with the ZmPIMT1 gene silenced had reduced germination.

The activity of the ZmPIMT1 enzyme was confirmed by molecular interaction assays with PABP2, both from corn and from ArabidopsisThe enzyme restores the structure of the damaged protein, maintaining its ability to bind to messenger RNA, which is crucial for the synthesis of new proteins during germination.

Breeding programs

The discovery provides a useful genetic marker for breeding programs. With it, it is possible to select lines that are more resistant to seed aging. This can reduce losses during storage, improve the reliability of seed lots, and benefit farmers by reducing the need for replanting.

Bruce Downie, a professor at the University of Kentucky and co-author of the study, highlights the relevance of the work for agriculture. "Modern life depends on seeds. If they fail, the losses affect producers, companies, and consumers," he stated.

The study also indicated that this genetic variation arose naturally and did not undergo selection during the domestication of maize. This suggests that it may have been overlooked by breeders in the past, despite its agronomic benefits.

Further information can be found at doi.org/10.1093/plcell/koaf217