Molecular characterization of Eleusine coracana (L.) Gaertn. genotypes for variability in zinc content and development of transgenics with high grain zinc
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Date
2009-10-19
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University of Agricultural Sciences GKVK, Bangalore
Abstract
Zinc deficiency ranks fifth among the most important health risk factors throughout the world. Zn
plays a crucial role in structure and function of various proteins, including enzymes, transcription
factors, hormonal receptor sites and biological membranes of all organisms. Because Zn plays
multiple roles in plant biochemical and physiological processes, even slight deficiencies will cause
a decrease in growth, yield and zinc content of edible parts. Therefore, it is necessary to understand
the physiological and molecular details of how plants take up, translocate and store zinc. The
inadequate amount of Zn in plants has lead to serious health concern to humans. In this regard any
approach to improve the Zn content in edible parts is a need of hour. Biofortification, a new
approach that relies on conventional plant breeding and modern biotechnology to increase the
micronutrient density of staple crops. In the present study we assessed the grain Zn content in
different finger millet genotypes and studied the distribution of Zn in different plant tissues and
analysed the expression of Zn transporter genes in contrasting genotypes of finger millet grown in
presence of various levels of Zn.
The results revealed that the contrasting genotypes exhibit differential response in Zn uptake and
translocation to shoots from roots subjected to external Zn application. Similarly ZIP family
transporters of Zn are differentially expressed in leaves and roots of finger millet under different
level of Zn treatments, however, ZIP1 transcript level is high under Zn deficient conditions. The
role of AtZIP3 transporter gene was studied in Arabidopsis mutants and showed decreased Zn
content in roots suggesting the AtZIP3 was involved in uptake rather than translocation to shoots.
Transgenic plants of tobacco and finger millet expressing OsZIP1 were also developed. The
transgenic finger millet plants showed better assimilation and gas exchange parameters than wild
type plants. Transgenic expressing OsZIP1 under the control of endosperm specific promoter
(Bx17) showed higher levels of zinc in grains compared to OsZIP1 plants under constitutive
(CaMV35S) promoter, therefore tissue specific expression is a promising approach.
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