JXB Advance Access originally published online on February 9, 2009
Journal of Experimental Botany 2009 60(3):967-978; doi:10.1093/jxb/ern345
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RESEARCH PAPER |
Phytic acid prevents oxidative stress in seeds: evidence from a maize (Zea mays L.) low phytic acid mutant
1Dipartimento di Genetica e Microbiologia, Università degli Studi di Pavia, Via Ferrata 1, I-27100 Pavia, Italy
2Dipartimento di Biologia, Università degli Studi di Pisa, Via L. Ghini 5, I-56126 Pisa, Italy
3Istituto per i Processi Chimico-Fisici, CNR, Via G. Moruzzi 1, I-56124 Pisa, Italy
4Dipartimento di Produzione Vegetale, Università degli Studi di Milano, Via Celoria 2, I-20133 Milano, Italy
* To whom correspondence should be addressed: E-mail: nielsen{at}ipvgen.unipv.it
A maize mutant defective in the synthesis of phytic acid during seed maturation was used as a tool to study the consequences of the lack of this important reserve substance on seed survival. Data on germinability, free iron level, free radical relative abundance, protein carbonylation level, damage to DNA, degree of lipid peroxidation, 
- and 
-tocopherol amount and antioxidant capacity were recorded on seeds of maize B73 and of an isogenic low phytic acid mutant (lpa1-241), either unaged or incubated for 7 d in accelerated ageing conditions (46 °C and 100% relative humidity). The lpa1-241 mutant, compared to wild type (wt), showed a lower germination capacity, which decreased further after accelerated ageing. Whole lpa1-241 mutant kernels contained about 50% more free or weakly bound iron than wt ones and showed a higher content of free radicals, mainly concentrated in embryos; in addition, upon accelerated ageing, lpa1-241 seed proteins were more carbonylated and DNA was more damaged, whereas lipids did not appear to be more peroxidated, but the -tocopherol content was decreased by about 50%. These findings can be interpreted in terms of previously reported but never proven antioxidant activity of phytic acid through iron complexation. Therefore, a novel role in plant seed physiology can be assigned to phytic acid, that is, protection against oxidative stress during the seed's life span. As in maize kernels the greater part of phytic acid (and thus of metal ions) is concentrated in the embryo, its antioxidant action may be of particular relevance in this crop.
Key words: Antioxidant, low phytic acid mutant, oxidative stress, seed
Received 8 September 2008; Revised 2 December 2008 Accepted 5 December 2008