Expression analysis of and genes governing accumulation of provitamin-A, lysine and tryptophan during kernel development in biofortified sweet corn.

Traditional sweet corn possesses low levels of provitamin-A (proA), lysine and tryptophan. Mutant version of () gene affecting the accumulation of β-carotene (BC), β-cryptoxanthin (BCX) and proA, and () gene governing the enhancement of lysine and tryptophan were introgressed together into elite sweet corn inbreds through marker-assisted selection. Here, we analyzed the expression pattern of and genes among introgressed and traditional sweet corn inbreds at 20-, 24- and 28-days after pollination (DAP). The introgressed inbreds possessed two- to sevenfolds higher BC, BCX, proA, lysine and tryptophan compared to their original inbreds. However, all the nutrients attained the peak at 20-DAP (BC: 9.95 µg/g, BCX: 8.21 µg/g, proA: 14.05 µg/g, lysine: 0.301%, tryptophan: 0.074%), which gradually reduced through 24-DAP (BC: 8.24 µg/g, BCX: 7.53 µg/g, proA: 12.01 µg/g, lysine: 0.273%, tryptophan: 0.057%) and 28-DAP (BC: 5.84 µg/g, BCX: 5.82 µg/g, proA: 8.75 µg/g, lysine: 0.202%, tryptophan: 0.037%). Biofortified sweet corn inbreds possessed significantly lower expression levels of (4.1-fold) and (2.2-fold) compared to their wild type alleles in traditional sweet corn inbreds across DAPs. The expression of and increased from 20-DAP to attain the highest peak at 24-DAP, and further decreased by 28-DAP. The transcript levels of were negatively correlated with BC ( = - 0.83), BCX ( = - 0.79) and proA ( = - 0.83) across dates of harvest. Lysine ( = - 0.83) and tryptophan ( = - 0.73) were also inversely associated with transcript levels. This is the first report on expression of and genes during kernel development in biofortified sweet corn. This information holds immense promise in understanding the dynamics of gene-regulation during kernel development in sweet corn.