Biochemical analysis and in silico modeling of AGPase in wheat (Triticum aestivum L.)
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Date
2015
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
CCSHAU
Abstract
ADP-glucose pyrophosphorylase (AGPase) play a key role in starch biosynthesis in higher plants and is
heterotetramer, consisting of two large subunits and two small subunits with different functions. Much of the ADPGlc required for starch synthesis in the plastids of cereal endosperm is synthesized in the cytosol and transported
across the plastid envelope. In the present investigation, AGPase activity and grain growth rate (GGR) were
determined in developing grains of four wheat cultivars viz. WH1105 and WH1124 (newly released high yielding)
WH542 (small grain) and HD2967 (bold grain) at 14, 21, 28, 35 and 42 days after anthesis (DAA). Data on yield
and yield attributes were recorded on maturity. In addition, homology modeling of the three-dimensional structure
of the LS and SS from wheat (Triticum aestivum L.) was carried out to obtain the best orientation of large and
small subunits of the enzyme. AGPase activity increased till 28
th
DAA in three wheat cultivars both in field and net
house except in WH542 where AGPase activity increased till 21
st
DAA and declined thereafter. At 28
th
DAA, the
highest AGPase activities of 340.1 nmoles min
-1
g
-1
fresh weight and 183.1 nmolesmin
-1
g
-1
fresh weights were
observed in WH1105 and HD2967 grown in the field and net house, respectively. GGR also had similar pattern as
AGPase activity. The maximum number of spikes per plant (10.2), spike length (10.3cm), grain weight per spike
(1.66g), thousand grain weight (41.2g) and yield (16.8g) were observed in WH1105 in field. Similar performance
for WH1105 was observed in net house although the number of spikes and yield by itself was less. Positive
correlation (r
2
= 0.79 at p= 0.05) was observed between AGPase activity at 28
th
day and yield in all the varieties.
For homology modeling, the SS (1YP2A) from the crystal structure of potato tuber was taken as the template for
both large and small subunits of wheat AGPase. The models were build using Modeller 9v7 and Swiss
Model Server. Based on Qmean Score, Z-score, Dfire–energy and Gromos the models build with Swiss
Model Server were further evaluated from SAVES Server that included PROCHECK, VERIFY3D and
ERRAT. Best 3D orientations of large and small subunits obtained by Swiss Model Server were
superimposed on the template 1YP2A using UCSF Chimera and RMSD of 0.190 A
°
and 0.695 A
°
, respectively
were observed.
Description
Keywords
Starch, AGPase, Homology modeling, Swiss model