Developmental stage-specific expression of the phytase1 gene and its association with phytase activity in maize...

Phytic acid in grains chelates essential minerals, thereby reducing the bioavailability of phosphorus and micronutrients in maize-based food and feed. Understanding the temporal expression pattern of the phytase1 gene, which regulates phytase activity, holds immense potential for maize biofortification efforts.

The expression of the phytase1 gene and its impact on phytase activity were explored at different grain developmental stages using maize inbreds with contrasting activity. The phytase1 expression pattern was analyzed using quantitative RT-PCR with adh1 as a reference gene. Combined ANOVA revealed significant variation (p < 0.01) due to inbreds (G) and developmental stages (DAP). High phytase genotypes, PMI-Q1 (1302.0 U kg^- 1), PMI-PV7 (1345.0 U kg^- 1), and PMI-PV8 (1413.3 U kg^- 1) showed higher expression of the phytase1 gene transcript levels of 0.114, 0.109, and 0.104, respectively. PMI-PV2 (586.4 U kg^- 1), PMI-PV4 (688.3 U kg^- 1), and PMI-PV5 (650.8 U kg^- 1) with the lower phytase activity had lower expression of phytase1 transcript levels of 0.040, 0.031, and 0.036, respectively. Furthermore, the correlation between phytase activity and relative expression pattern at different developmental stages was positive (p < 0.01; r = 0.79, 0.86, and 0.89 at 15, 30, and 45 DAP, respectively). Notably highest phytase activity was found at 15 DAP (1127.7 U kg^- 1) and declined progressively towards 45 DAP (895.4 U kg^- 1) across genotypes, with a corresponding reduction in phytase1 gene expression.

Validating the high phytase genotypes through gene expression profiling offers promising donors for maize molecular breeding to transfer high phytase activity into elite genotypes.