Role of BmDredd during Apoptosis of Silk Gland in Silkworm, Bombyx mori.

Rui-Ting Chen,Zhen Liu,Deng-Pan Zhang,Peng Jiao,Yun-Gen Miao,Yan Lu,Hu-Hu Xin,Erjun Ling

doi:10.1371/journal.pone.0169404

Abstract

Silk glands (SGs) undergo massive apoptosis driven degeneration during the larval-pupal transformation. To better understand this event on molecular level, we investigated the expression of apoptosis-related genes across the developmental transition period that spans day 4 in the fifth instar Bombyx mori larvae to day 2 pupae. Increases in the expression of BmDredd (an initiator caspase homolog) closely followed the highest BmEcR expression and resembled the expression trend of BmIcE. Simultaneously, we found that BmDredd expression was significantly higher in SG compared to other tissues at 18 h post-spinning, but reduced following injection of the apoptosis inhibitor (Z-DEVD-fmk). Furthermore, BmDredd expression correlated with changes of caspase3-like activities in SG and RNAi-mediated knockdown of BmDredd delayed SG apoptosis. Moreover, caspase3-like activity was increased in SG by overexpression of BmDredd. Taken together, the results suggest that BmDredd plays a critical role in SG apoptosis.

Highlights

Programmed cell death (PCD) is a vital biological event accompanied by characteristic events including chromatin condensation, DNA fragmentation, vacuolization, and apoptotic body formation [1]
In the posterior silk gland (PSG), BmEcR, BmIcE and Bombyx mori death related ced-3/Nedd2-like protein (BmDredd) were elevated during the larval to pupal metamorphosis stage, which is the period when SG apoptosis begins
We investigated their expression profile in SG and found that BmDredd, BmEcR and BmIce transcription levels significantly increased in the middle silk gland (MSG) and PSG during the larval-pupal transition (Fig 1A)

Summary

Introduction

Programmed cell death (PCD) is a vital biological event accompanied by characteristic events including chromatin condensation, DNA fragmentation, vacuolization, and apoptotic body formation [1]. Silkworm Bombyx mori is an important economic insect and model organism which has been used effectively in various biological researches [8]. The SG degenerates rapidly after the spinning stage in response to endocrine hormones (including juvenile hormone and ecdysone) [4, 11, 12]. This process includes 5 characteristics (nuclear condensation, DNA fragmentation, nuclear fragmentation, cells chrinkage and apoptotic body formation) and involves in PCD

Methods

Results

Conclusion