Characterization of BiP Genes from Pepper (Capsicum annuum L.) and the Role of CaBiP1 in Response to Endoplasmic Reticulum and Multiple Abiotic Stresses.

Hu Wang,Minghui Lu,Huanhuan Niu,Yufei Zhai

doi:10.3389/fpls.2017.01122

Hu Wang, Minghui Lu + Show 2 more

Open Access

https://doi.org/10.3389/fpls.2017.01122

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Abstract

Adverse environmental conditions have a detrimental impact on crop growth and development, and cause protein denaturation or misfolding. The binding protein (BiP) plays an important protective role by alleviating endoplasmic reticulum (ER) stress induced by misfolded proteins. In this study, we characterized three BiP genes (CaBiP1, CaBiP2, and CaBiP3) in pepper, an economically important vegetable and spice species. The role of CaBiP1 in plant tolerance to ER stress and adverse environmental conditions (including heat, salinity, osmotic and drought stress) were investigated. All the expected functional and signaling domains were detected in three BiP proteins, but the motifs and exon-intron distribution differed slightly in CaBiP3. CaBiP1 and CaBiP2 were constitutively expressed in all the tested tissues under both normal and stressed conditions, whereas CaBiP3 was mainly expressed following stress. Silencing of CaBiP1 reduced pepper tolerance to ER stress and various environment stresses, and was accompanied by increased H2O2 accumulation, MDA content, relative electric leakage (REL), water loss rate, and a reduction in soluble protein content and relative water content (RWC) in the leaves. Conversely, overexpression of CaBiP1 in Arabidopsis enhanced tolerance to ER stress and multiple environment stresses, as demonstrated by an increase in germination rate, root length, survival rate, RWC, the unfolded protein response (UPR) pathway, and a decrease in water loss rate. Our results suggest that CaBiP1 may contribute to plant tolerance to abiotic stresses by reducing ROS accumulation, increasing the water-retention ability, and stimulating UPR pathways and expression of stress-related genes.

Highlights

IntroductionExtreme weather events, especially high temperatures and droughts in arid and semiarid areas, pose an increasing threat to crop productivity
With advancing global warming, extreme weather events, especially high temperatures and droughts in arid and semiarid areas, pose an increasing threat to crop productivity
The phylogenetic tree of binding proteins (BiP) proteins from pepper, Arabidopsis and rice showed that CaHsp70-8 and CaHsp70-7 share a close evolutionary relationship with AtBiP1 and AtBiP2, respectively, while CaHsp70-10 is more closely related to AtBiP3 and OsBiP2 (Figure 1)

Summary

Introduction

Extreme weather events, especially high temperatures and droughts in arid and semiarid areas, pose an increasing threat to crop productivity. To develop crop varieties that better tolerate these adverse conditions, a greater understanding of the mechanisms involved in environment stresses is crucial (Thiry et al, 2016). The growth and development of plants requires proteins to function in a normal manner, but the elaborate folding of proteins is disturbed by adverse environmental conditions, whereas it is well known that the accumulation of misfolded proteins is harmful to plant health (Howell, 2013). When misfolded proteins accumulate in the ER, the balance between folding pressure and folding capacity is broken, resulting ER stress (Wan and Jiang, 2016). Plants have developed a comprehensive mechanism to mitigate ER stress induced by adverse environmental conditions. One important strategy is up-regulating the transcription of ER chaperones to enhance the capacity of the protein folding machinery (Fanata et al, 2013)

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