Expression Dynamics of lpa1 Gene and Accumulation Pattern of Phytate in Maize Genotypes Possessing opaque2 and crtRB1 Genes at Different Stages of Kernel Development.

Phytic acid (PA) acts as a storehouse for the majority of the mineral phosphorous (P) in maize; ~80% of the total P stored as phytate P is not available to monogastric animals and thereby causes eutrophication. In addition, phytic acid chelates positively charged minerals making them unavailable in the diet. The mutant lpa1-1 allele reduces PA more than the wild-type LPA1 allele. Further, mutant gene opaque2 ( o2 ) enhances lysine and tryptophan and crtRB1 enhances provitamin-A (proA) more than wild-type O2 and CRTRB1 alleles, respectively. So far, the expression pattern of the mutant lpa1-1 allele has not been analysed in maize genotypes rich in lysine, tryptophan and proA. Here, we analysed the expression pattern of wild and mutant alleles of LPA1 , O2 and CRTRB1 genes in inbreds with (i) mutant lpa1 - 1 , o2 and crtRB1 alleles, (ii) wild-type LPA1 allele and mutant o2 and crtRB1 alleles and (iii) wild-type LPA1 , O2 and CRTRB1 alleles at 15, 30 and 45 days after pollination (DAP). The average reduction of PA/total phosphorous (TP) in lpa1-1 mutant inbreds was 29.30% over wild-type LPA1 allele. The o2 and crtRB1 -based inbreds possessed ~two-fold higher amounts of lysine and tryptophan, and four-fold higher amounts of proA compared to wild-type alleles. The transcript levels of lpa1-1 , o2 and crtRB1 genes in lpa1-1 -based inbreds were significantly lower than their wild-type versions across kernel development. The lpa1-1 , o2 and crtRB1 genes reached their highest peak at 15 DAP. The correlation of transcript levels of lpa1-1 was positive for PA/TP (r = 0.980), whereas it was negative with inorganic phosphorous (iP) (r = -0.950). The o2 and crtRB1 transcripts showed negative correlations with lysine (r = -0.887) and tryptophan (r = -0.893), and proA (r = -0.940), respectively. This is the first comprehensive study on lpa1-1 expression in the maize inbreds during different kernel development stages. The information generated here offers great potential for comprehending the dynamics of phytic acid regulation in maize.