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Title: Differential gene expression during early embryonic development in diapause and non-diapause eggs of multivoltine silkworm <i style="">Bombyx mori</i>
Authors: Ponnuvel, Kangayam M
Murthy, Geetha N
Awasthi, Arvind K
Rao, Guruprasad
Vijayaprakash, Nanjappa B
Keywords: <i style="">Bombyx mori</i>
Differential gene expression
Issue Date: Nov-2010
Publisher: NISCAIR-CSIR, India
Abstract: Quantification of the differential expression of metabolic enzyme and heat-shock protein genes (<i style="">Hsp</i>) during early embryogenesis in diapause and non-diapause eggs of the silkworm <i style="">B. mori</i> was carried out by semi-quantitative RT-PCR. Data analysis revealed that, the <i style="">phosphofructokinase (PFK)</i> expression started at a higher level in the early stage (6 h after oviposition) in non-diapause eggs, while in diapause induced eggs, it started at a lower level. However, the <i style="">PFK</i> gene expression in diapause eggs was comparatively higher than in non-diapause eggs. <i style="">PFK</i> facilitates use of carbohydrate reserves. The lower level of <i style="">PFK</i> gene expression in the early stage of diapause induced eggs but comparatively higher level of expression than in non-diapause eggs is due to enzyme inactivation via protein phosphorylation during early embryogenesis followed by de-phosphorylation in later stage. The <i style="">sorbitol dehydrogenase-2 (SDH-2)</i> gene was down regulated in diapause induced eggs up to 24 h and its expression levels in diapause induced eggs coincided with that of <i style="">PFK</i> gene at 48h in non-diapause eggs. During carbohydrate metabolism, there is an initial temporary accumulation of sorbitol which acts as protectant. The down regulation of <i style="">SDH-2 </i>gene<i style=""> </i>during the first 24 hours in diapause induced eggs was due to the requirement of sorbitol as protectant. However, since the diapause process culminates by 48 h, the <i style="">SDH-2 </i>gene expression increased and coincided with that of <i style="">PFK</i> gene expression. The <i style="">trehalase</i> (<i style="">Tre</i>) gene expression was at a lower level in diapause induced eggs compared to non-diapausing eggs. The induction of <i style="">Tre</i> activity is to regulate uptake and use of sugar by the tissues. The non-diapause eggs revealed maximum expression of <i style="">GPase</i> gene with major fluctuations as well as an overall higher expression compared to diapause induced eggs. The diapause process requires less energy source which reflects lower activity of the gene. Heat shock protein (<i>Hsp</i>)genes (<i style="">Hsp20.4, 40, 70</i>, and <i style="">90</i>) revealed differential levels of expression in both the eggs at all stages of embryonic development. The present study thus provides an overview of the differential expression levels of metabolic enzyme and <i style="">Hsp</i> genes in non-diapause and diapause induced eggs of multivoltine silkworm <i style="">B. mori</i> within 48 h after oviposition, confirming the major role of in early embryogenesis.
Description: 1143-1151
ISSN: 0975-1009 (Online); 0019-5189 (Print)
Appears in Collections:IJEB Vol.48(11) [November 2010]

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