Mutant floury2 Expression Correlates With Increased Methionine in Developing Maize Kernels

Introgressed maize inbred lines carrying the recessive mutant floury2 gene exhibit significantly elevated transcript abundance and enhanced methionine accumulation during kernel development compared to wild-type counterparts. In a developmental evaluation tracking maize kernels across key reproductive intervals, researchers identified consistent positive associations between floury2 gene expression and the concentration of methionine in the kernel endosperm. The study systematically quantified both gene expression levels and amino acid contents across three distinct post-pollination growth stages, demonstrating that incorporating the mutant allele into elite inbred lines enhances methionine levels throughout kernel development.

This research addresses a major nutritional limitation in cereal grain production. Maize endosperm protein naturally lacks the essential sulphur-containing amino acid methionine. Currently, compensating for this amino acid deficiency requires the addition of synthetic methionine in animal feed, a practice that is recognized as both costly and unsustainable. Because the recessive floury2 (fl2) gene enhances methionine accumulation in maize endosperm proteins, evaluating its expression dynamics across kernel development provides vital biological insights for targeted crop improvement.

To evaluate these temporal dynamics, the experimental investigation examined fl2 gene expression at three specific developmental stages: 20, 30, and 40 days after pollination. The plant materials evaluated in the experiment comprised two wild-type inbred lines, PMI-PV5 and PMI-PV6, which carry the dominant Fl2 allele, alongside four marker-assisted backcross-derived introgressed inbred lines carrying the recessive mutant fl2 allele. By comparing these genetic backgrounds, the researchers isolated the developmental effects of the introgressed fl2 allele on transcript abundance and methionine accumulation.

Quantification of floury2 transcript abundance revealed substantial up-regulation in the introgressed inbreds relative to the wild-type controls across kernel development. Across all kernel growth stages, the introgressed inbreds exhibited an average 2.61-fold increase in fl2 transcript abundance over the wild-type inbreds. Relative expression peaked during earlier development, with introgressed lines showing an average 3.60-fold increase in fl2 transcript abundance over wild-type inbreds at 20 days after pollination, a 2.72-fold increase at 30 days after pollination, and a 1.51-fold increase by 40 days after pollination.

Biochemical analyses confirmed that elevated transcript abundance was accompanied by higher methionine accumulation in developing grain. Overall, introgressed inbreds accumulated higher methionine in kernels over the wild-type inbreds, averaging a 1.63-fold elevation across growth stages. At 20 days after pollination, fl2-based introgressed inbreds accumulated 0.452 percent methionine compared to 0.349 percent in wild-type inbreds. At 30 days after pollination, introgressed lines contained 0.404 percent methionine versus 0.235 percent in controls. By 40 days after pollination, introgressed kernels maintained 0.351 percent methionine, compared to 0.187 percent in wild-type inbreds.

Across both wild-type and introgressed inbreds, fl2 gene expression and methionine accumulation peaked early and declined as kernels matured. When evaluated across all lines, fl2 gene expression peaked at 20 days after pollination with a value of 1553.66 and a mean methionine content of 0.418 percent. Expression declined towards 30 days after pollination, dropping to 662.80 with a methionine content of 0.348 percent. By 40 days after pollination, expression further decreased to 304.65, while methionine concentration reached 0.296 percent, illustrating synchronized declines during later grain filling.

Statistical assessments revealed significant positive associations between fl2 gene expression and kernel methionine concentration at every developmental stage evaluated. At 20 days after pollination, fl2 gene expression and methionine concentration were strongly correlated, recording a correlation coefficient of r = 0.96 with a significance value of p < 0.001. A strong positive association persisted at 30 days after pollination, showing r = 0.84 with p < 0.001. At 40 days after pollination, the association remained statistically significant, exhibiting a correlation coefficient of r = 0.45 with p < 0.05.

Cross-stage evaluations demonstrated that early fl2 transcript abundance was strongly associated with subsequent kernel methionine content during later growth stages. Higher fl2 expression at 20 days after pollination was strongly associated with elevated methionine content at both 30 days after pollination (r = 0.96, p < 0.001) and 40 days after pollination (r = 0.97, p < 0.001). Demonstrating this positive association between fl2 expression and methionine accumulation during kernel development provides an essential foundation for breeding methionine-enriched maize to enhance nutritional security.

Subject of Research: Expression dynamics of the floury2 gene and methionine accumulation in developing maize kernels

Article Title: Untying the expression dynamics of mutant floury2 gene and methionine accumulation during kernel development in maize for nutritional security

Article References: Duo, H., Chhabra, R., Mishra, S. J., Sharma, G., Kumar, A., Zunjare, R. U., Muthusamy, V., & Hossain, F. (2026). Untying the expression dynamics of mutant floury2 gene and methionine accumulation during kernel development in maize for nutritional security. Molecular Biology Reports, 53(1), Article 1966. https://doi.org/10.1007/s11033-026-13035-8

Image Credits: AI Generated

DOI: 10.1007/s11033-026-13035-8

Keywords: maize, floury2 gene, fl2 mutant, methionine accumulation, kernel development, endosperm protein, amino acids, marker-assisted backcrossing, introgressed inbreds, wild-type maize, PMI-PV5, PMI-PV6, transcript abundance, days after pollination, nutritional security, animal feed, crop breeding