Transcriptome analysis for zinc and iron homeostasis and carbohydrate metabolism in rice (Oryza sativa L.)
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Date
2017
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CCSHAU
Abstract
Biochemical and molecular changes in root and shoot tissues of four rice varieties (HKR47, PUSA1121, HBC19
and PAU201) were studied in response to varied iron and zinc concentrations (T1 = 0.1 mM Fe(II)-EDTA+ 0.06
mM ZnSO4.7H2O, T2 = 0.1 mM Fe(II)-EDTA+ 0.12 mM ZnSO4.7H2O, T3 = 0.1 mM Fe(II)-EDTA+ 0.48 mM
ZnSO4.7H2O, T4 = 0.5 mM Fe(II)-EDTA+ 0.06 mM ZnSO4.7H2O, T5 = 0.5 mM Fe(II)-EDTA+ 0.12 mM
ZnSO4.7H2O, T6 = 0.5 mM Fe(II)-EDTA+ 0.48 mM ZnSO4.7H2O and T7 = 0.05 mM Fe(II)-EDTA+ 0.48 mM
ZnSO4.7H2O) at vegetative and reproductive stages. Fe content in roots, shoots and grains was maximum at T4
treatment while contrarily Zn content was highest at T7 treatment in all the four varieties. Highest iron and zinc
in dehusked grains was recorded in HBC19 at all the treatments. The maximum specific enzymes’ activity of
glycolytic pathway (Hexokinase, phosphofructokinase, fructose-1,6 bisphosphate aldolase, pyruvate kinase),
Hexose monophosphate pathway (Glucose 6 phosphate dehydrogenase and 6-phosphate gluconate
dehydrogenase) and tricarboxylic acid cycle (isocitrate dehydrogenase and malate dehydrogenase) was
observed at T7 while at T4 treatment activity of these enzymes reduced the most. Reducing sugar and total
soluble sugar content increased at T1, T4, T5 and T6 treatments as compared to control (T2); maximum increase
being at T4. Expression of genes involved in iron and zinc homeostasis [Nicotinamine synthase 1 (OsNAS1),
Nicotinamine synthase 2 (OsNAS2), Nicotinamine synthase 3 (OsNAS3), Iron-regulated transporter 1 (OsIRT1)
and Yellow stripe like 2 (OsYSL2), zinc-regulated transporter (ZRT), iron-regulated transporter (IRT)-like
protein 1 (OsZIP1), OsZIP3,OsZIP4 and OsZIP8] were analyzed at T2, T4 and T7 treatments at vegetative stage;
reduced expression of OsNAS1,OsNAS2, OsIRT1and OsYSL2 was observed at T4 treatment in all the four
varieties as compared to the control (T2) in both the tissues. Conversely, these genes had enhanced expressions
at T7 treatment. OsNAS3, OsZIP1, OsZIP3, OsZIP4 and OsZIP8 genes contrarily showed enhancement in
relative expressions at T4 treatment and reduction at T7 treatment as compared to control (T2). Differential gene
expression under low iron or low zinc conditions suggests that poor uptake of zinc and iron via roots and further
translocation to shoots may not be the reason for low iron and zinc in grains. All the four rice varieties had
better growth, grain yield and yield attributes at T7 (low iron and high zinc) treatment as compared to control
(T2). Higher activities of carbohydrate metabolism’s enzymes, plant growth and productivity under high zinc
environment clearly indicate the importance of Zn for plants.
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