New Horizons in Insect Science Towards Sustainable Pest Management

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Diapause-Related Gene

Expression in Eggs of

Multivoltine Bombyx mori

L. Silkworm Races

Kangayam M. Ponnuvel, Sirigineedi Sasibhushan,

N. Murthy Geetha and CGP Rao

A. K. Chakravarthy (ed.), New Horizons in Insect Science: Towards Sustainable Pest Management,

DOI 10.1007/978-81-322-2089-3_18, © Springer India 2015

K. M. Ponnuvel () · S. Sasibhushan · N. M. Geetha ·
CGP. Rao
Seribiotech Research Laboratory, Carmelaram Post,
Kodathi Bangalore, Karnataka 560035, India
e-mail: [email protected]

Abstract

The diapause hormone has been identified as a major factor inducing dia-

pause in silkworm, Bombyx mori L. However, the molecular mechanism

controlling egg diapause in multivoltine silkworm remains unclear. In

this study, an attempt is made to decipher molecular events during em-

bryonic diapause in multivoltine silkworm. Using suppressive subtrac-

tive hybridization (SSH) 186 cDNA clones were isolated and sequenced

from both diapause and non-diapause eggs wherein 29 diapause-related

genes were identified and classified into six functional groups. The qPCR

analysis confirmed the expression of 11 of these genes, wherein, three

were upregulated during diapause and another seven during non-diapause,

while, one gene remained unchanged. The gene expression profiles of

diapause-induced and non-diapause eggs of multivoltine silkworm were

also investigated at 18 and 30 h after oviposition using oligonucleotide mi-

croarrays containing 24,924 probes. Data analysis revealed upregulation

of 638 genes and downregulation of 1136 genes at 18 h after oviposition.

Further at 18 and 30 h after oviposition, 115 genes were stably upregu-

lated, while 117 were stably downregulated. The annotated genes showing

fold change of one and above were classified into seven functional groups,

viz. immune, metabolism, stress, signal transduction, cell cycle, transcrip-

tion, and apoptosis. The overall genes expressed at 18 h was higher than

that at 30 h under both diapause and non-diapause conditions indicating

that crucial biological processes for initiation or termination of diapause

mechanism occur during 18 h time period.

Keywords

Bombyx mori · Diapause · Gene expression · Multivoltine