Transgenic expression of phytase in wheat endosperm increases bioavailability of iron and zinc in grains

Abstract

Phytate is a major constituent of wheat seeds and chelates metal ions, thus reducing their bioavailability and so the nutritional value of grains. Transgenic plants expressing heterologous phytase are expected to enhance degradation of phytic acid stored in seeds and are proposed to increase the in vitro bioavailability of mineral nutrients. Wheat transgenic plants expressing Aspergillus japonicus phytase gene (phyA) in wheat endosperm were developed till T generation. The transgenic lines exhibited 18-99 % increase in phytase activity and 12-76 % reduction of phytic acid content in seeds. The minimum phytic acid content was observed in chapatti (Asian bread) as compared to flour and dough. The transcript profiling of phyA mRNA indicated twofold to ninefold higher expression as compared to non transgenic controls. There was no significant difference in grain nutrient composition of transgenic and non-transgenic seeds. In vitro bioavailability assay for iron and zinc in dough and chapatti of transgenic lines revealed a significant increase in iron and zinc contents. The development of nutritionally enhanced cereals is a step forward to combat nutrition deficiency for iron and zinc in malnourished human population, especially women and children.

Solid-State Fermentation Reduces Phytic Acid Level, Improves the Profile of Myo-inositol Phosphates and Enhances the Availability of Selected Minerals in Flaxseed Oil Cake

“…This is consistent with earlier fi ndings of many researchers concerning the preparation of dephytinised wheat (31), rye-wheat bread (32) and bread with the addition of pseudocereal grains (33), where the treatment of samples with microbial phytases increased the bioavailability of minerals, especially Ca, Zn and Fe. Recent paper by Abid et al (34) demonstrates that transgenic expression of phytase in wheat endosperm increases Zn and Fe bioavailability, thus enhancing its nutritional value.…”

Introductory Chapter: Transgenics—Crops Tailored for Novel Traits

“…Addition of iron-containing compounds during the grinding of wheat, otherwise deficient in iron, protects the wheat-dependant populace from diseases caused by deficiency such as iron-deficiency anemias, etc. Iron fortification of wheat has been proven transgenically by expressing phytase gene (phyA) from Aspergillus japonicas [40].…”

“…In situ degradation of phytates in the seed endosperm is considered desirable in order to increase bioavailability of micronutrients [40].…”

Fungal Phytase Production in Different Hosts: A Brief Review

“…Other types of plants have also been addressed for the expression of heterologous phytase. Plants such as Triticum aestivum, Chlamydomonas reinhardtii, Mature maize, Brassica napus and Zea mays L were used to express A. japonicas phytases reported by Abid, et al (2017) and A. niger studied by Rao, et al (2016), Rao J, et al (2013), and Drakakaki, et al (2005) [33][34][35][36][37] respectively.…”