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Expression of heat shock protein 70a mRNA in Bombyx mori diapause eggs
Yoriko Moribe1, Keigo Oka, Teruyuki Niimi
1Sericulture & Entomoresources, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, Japan.
Abstract:
In an effort to understand whether heat shock protein 70 (Hsp70) participates in the environmental 5 degrees C signal reception/transduction toward breaking embryonic diapause of the silkworm Bombyx mori, we isolated a cDNA for Hsp70a and examined the expression of Hsp70a mRNA in B. mori diapause and nondiapause eggs by quantitative real-time PCR. Hsp70a mRNA gradually increased in diapause eggs continuously kept at 25 degrees C after oviposition to maintain diapause. When diapause eggs were exposed to the diapause-terminating condition of 5 degrees C beginning at 2 days post-oviposition, Hsp70a mRNA increased beginning at 5 days post-cold treatment. Even in nondiapause eggs, Hsp70a mRNA increased slightly with exposure to 5 degrees C. These results suggest that Hsp70a is involved in reception/transduction of the diapause-terminating (5 degrees C) signal via gene activation. The expression patterns of Hsp70a mRNA are discussed in relation to those of the cold-response gene Samui.
Insights
Heat shock protein 70 (Hsp70) gene activation is crucial for silkworm embryonic diapause termination. Hsp70a mRNA levels increase upon exposure to the cold signal, indicating its role in environmental cue reception.
Area of Science:
- Entomology
- Molecular Biology
- Developmental Biology
Background:
- Embryonic diapause is a crucial developmental arrest in insects like Bombyx mori.
- Understanding the molecular mechanisms of diapause termination is vital for insect pest control and agricultural applications.
Purpose of the Study:
- To investigate the role of heat shock protein 70 (Hsp70) in the reception and transduction of the cold (5°C) signal that breaks embryonic diapause in Bombyx mori.
- To analyze the expression patterns of Hsp70a mRNA in response to diapause-maintaining and diapause-terminating conditions.
Main Methods:
- Isolation of heat shock protein 70a (Hsp70a) cDNA from Bombyx mori.
- Quantitative real-time PCR (qPCR) to measure Hsp70a mRNA expression levels.
- Analysis of Hsp70a mRNA expression in both diapause and non-diapause Bombyx mori eggs under different temperature conditions (25°C and 5°C).
Main Results:
- Hsp70a mRNA levels gradually increased in diapause eggs maintained at 25°C, suggesting a role in maintaining diapause.
- Upon exposure to the diapause-terminating 5°C condition, Hsp70a mRNA levels increased significantly starting 5 days post-cold treatment.
- A slight increase in Hsp70a mRNA was also observed in non-diapause eggs when exposed to 5°C.
Conclusions:
- Heat shock protein 70a (Hsp70a) is implicated in the reception and signal transduction of the cold (5°C) environmental cue that terminates embryonic diapause in Bombyx mori.
- The observed gene activation of Hsp70a suggests its involvement in the molecular pathway triggered by cold exposure to break diapause.
- Expression patterns of Hsp70a mRNA provide insights into the interplay between cold-response genes and diapause termination mechanisms.
