Phytic acid (myo-inositol-1, 2, 3, 4, 5, 6-hexakisphosphate or Ins P6) typically represents approximately 75% to 80% of maize (Zea mays) seed total P. Here we describe the origin, inheritance, and ...seed phenotype of two non-lethal maize low phytic acid mutants, lpa1-1 and lpa2-1. The loci map to two sites on chromosome 1S. Seed phytic acid P is reduced in these mutants by 50% to 66% but seed total P is unaltered. The decrease in phytic acid P in mature lpa1-1 seeds is accompanied by a corresponding increase in inorganic phosphate (Pi). In mature lpa2-1 seed it is accompanied by increases in Pi and at least three other myo-inositol (Ins) phosphates (and/or their respective enantiomers): D-Ins(1,2,4,5,6) P5; D-Ins (1,4,5,6) P4; and D-Ins(1,2,6) P3. In both cases the sum of seed Pi and Ins phosphates (including phytic acid) is constant and similar to that observed in normal seeds. In both mutants P chemistry appears to be perturbed throughout seed development. Homozygosity for either mutant results in a seed dry weight loss, ranging from 4% to 23%. These results indicate that phytic acid metabolism during seed development is not solely responsible for P homeostasis and indicate that the phytic acid concentration typical of a normal maize seed is not essential to seed function.
Phytic acid (myo-inositol hexakisphosphate), the major storage form of P in seeds, is believed to have a negative impact on nutritional quality. Since breeding for low phytic acid has been proposed ...for several cereals and legumes, it is important to predict the effects of selection against phytic acid on other major grain components. Experiments were conducted to determine the quantitative relationship between grain phytic acid P, total P, and protein in two winter wheat (Triticum aestivum L.) populations, each consisting of progeny of a double cross. Substantial variation in phytic acid P was observed, with the range in values equal to 30 and 48% of the respective population mean. Observed variation in phytic acid P was highly and positively correlated with variation in grain total P (r = 0.93 and 0.96 in Populations 1 and 2, respectively), and with variation in grain protein (r = 0.65 and 0.87, respectively). The close correlation of phytic acid P with both total P and protein indicates that selection against grain phytic acid would lead to undesirable reductions in both grain total P and protein
Phytic acid (
myo
-inositol-1, 2, 3, 4, 5, 6-hexa
kis
phosphate or Ins P
6
) typically represents approximately 75% to 80% of maize (
Zea mays
) seed total P. Here we describe the origin, ...inheritance, and seed phenotype of two non-lethal maize
low phytic acid
mutants,
lpa1-1
and
lpa2-1
. The loci map to two sites on chromosome 1S. Seed phytic acid P is reduced in these mutants by 50% to 66% but seed total P is unaltered. The decrease in phytic acid P in mature
lpa1-1
seeds is accompanied by a corresponding increase in inorganic phosphate (P
i
). In mature
lpa2-1
seed it is accompanied by increases in P
i
and at least three other
myo
-inositol (Ins) phosphates (and/or their respective enantiomers):
d
-Ins(1,2,4,5,6) P
5
;
d
-Ins (1,4,5,6) P
4
; and
d
-Ins(1,2,6) P
3
. In both cases the sum of seed P
i
and Ins phosphates (including phytic acid) is constant and similar to that observed in normal seeds. In both mutants P chemistry appears to be perturbed throughout seed development. Homozygosity for either mutant results in a seed dry weight loss, ranging from 4% to 23%. These results indicate that phytic acid metabolism during seed development is not solely responsible for P homeostasis and indicate that the phytic acid concentration typical of a normal maize seed is not essential to seed function.
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