Characterization of differentially expressed stress-associated proteins in starch granule development under heat stress in wheat (<i>Triticum aestivum </i>L.)
126-138Abiotic stress
causes abrupt increase in the expression of stress-associated proteins, which
provide tolerance by modulating the defense mechanism of plants. Small heat
shock proteins (sHSPs) and anti-oxidant enzymes are important for environmental
stress tolerance of the plants. In this study, two full-length cDNAs encoding
small heat shock protein (sHSP) and superoxide dismutase (SOD), designated as TasHSP
and SODI were identified and characterized from C-306
(thermotolerant) and PBW343 (thermosusceptible) cultivars of wheat (Triticum
aestivum L.). An alpha crystalline domain was observed in TasHSP and
manganese/iron binding domain in case of SODI. Quantitative real-time
PCR showed very high transcript level of TasHSP and SOD in C-306
compared to PBW343 at different stages of growth and against differential heat
stress (HS). Under differential HS at milky-dough stage, the fold change in
transcript of both TasHSP and SOD was observed maximum in C-306,
compared to PBW343. Protein profiling and isoenzymes analysis showed the
expression of several heat-stable proteins and prominent isoenzymes of SOD in
C-306, compared to PBW343. Scanning electron microscopy (SEM) of starch
granules showed globular, well-shaped and more numbers of endospermic cells in
C-306, compared to defragmented, irregular shaped and shrunken granules in case
of PBW343 under HS treatment (42°C for 2 h). Diurnal change in soluble starch
synthase (SSS) activity showed an increase in the activity during afternoon
(35°C), compared to morning (29°C) and evening (32°C) in both the cultivars.
Under heat stress (42°C for 2 h), a drastic decrease in the SSS activity was
observed, due to the thermal denaturation of the enzyme. Thermotolerance
capacity analyzed using cell membrane stability (CMS) showed significantly
higher CMS in case of C-306, compared to PBW343 at different stages of growth.
Findings suggest that abundance of TasHSP and SODI during
milky-dough stage plays a very important role in starch granule biosynthesis.
The mechanism may be further exploited to develop tolerant wheat cultivar with
high quality seeds