In silico study on Arabidopsis BAG gene expression in response to environmental stresses

Ganesh M Nawkar,Punyakishore Maibam,Joung Hun Park,Sang Yeol Lee,Chang Ho Kang,Cha Young Kim,Su Gyeong Woo

doi:10.1007/s00709-016-0961-3

Abstract

BAG (Bcl-2 athanogene) family proteins are conserved in a wide range of eukaryotes, and they have been proposed to play a crucial role in plant programmed cell death (PCD). During the past decade, with the help of advanced bioinformatics tools, seven homologs of BAG genes have been identified in the Arabidopsis genome; these genes are involved in pathogen attack and abiotic stress conditions. In this study, gene expression of Arabidopsis BAG family members under environmental stresses was analyzed using the Botany Array Resource (BAR) expression browser tool and the in silico data were partially confirmed by qRT-PCR analysis for the selected stress- and hormone-treated conditions related to environmental stresses. Particularly, the induction of AtBAG6 gene in response to heat shock was confirmed by using GUS reporter lines. The loss of the AtBAG6 gene resulted into impairment in basal thermotolerance of plant and showed enhanced cell death in response to heat stress. To elucidate the regulatory mechanisms of BAG genes, we analyzed ∼1-kbp promoter regions for the presence of stress-responsive elements. Our transcription profiling finally revealed that the Arabidopsis BAG genes differentially respond to environmental stresses under the control of specifically organized upstream regulatory elements.

Highlights

All eukaryotic cells possess a genetically controlled selfdestruction mechanism known as programmed cell death (PCD), which is essential for normal development and stress response (Dickman and Fluhr 2013; Kimchi 2007; Lam 2004)
The expression level of AtBAG6 transcript was slightly increased by treatment with ACC, methyl jasmonate (MeJA), and abscisic acid (ABA), while it was slightly repressed by salicylic acid (SA)
The Bcl-2 athanogene (BAG) family is a multifunctional group of proteins that act as co-chaperones that regulate cell signaling, growth, and development and are involved in environmental stress responses (Doukhanina et al 2006; Kim et al 2011)

Summary

Introduction

All eukaryotic cells possess a genetically controlled selfdestruction mechanism known as programmed cell death (PCD), which is essential for normal development and stress response (Dickman and Fluhr 2013; Kimchi 2007; Lam 2004). PCD has been characterized in plants during normal growth and development, as well as in response to various types of stress, including abiotic stress conditions such as heat, cold, salt, and UV radiation and biotic stress conditions such as the hypersensitivity response (HR) to pathogens (Nawkar et al 2013; Williams and Dickman 2008). Like the mammalian BAG proteins, members of the Arabidopsis BAG family are characterized by the presence of a 110–130-amino acid-conserved C-terminal BAG domain (BD). Among the seven members of the Arabidopsis BAG gene family, AtBAG4, AtBAG6, and AtBAG7 have been studied in relation to the plant PCD in response to cold, heat, UV, pathogen attack, and the unfolded protein response (UPR) (Doukhanina et al 2006; Williams et al 2010). The refolding activities of Hsp and Hsc are of particular importance for cell survival; it is important to tightly regulate the levels of these proteins

Methods

Results

Conclusion