Identification and Functional Characterization of the BAG Protein Family in Arabidopsis thaliana

Elena V Doukhanina,Shaorong Chen,Esther Van Der Zalm,Adam Godzik,John Reed,Martin B Dickman

doi:10.1074/jbc.m511794200

Abstract

The genes that control mammalian programmed cell death are conserved across wide evolutionary distances. Although plant cells can undergo apoptosis-like cell death, plant homologs of mammalian regulators of apoptosis have, in general, not been found. This is in part due to the lack of primary sequence conservation between animal and putative plant regulators of apoptosis. Thus, alternative approaches beyond sequence similarities are required to find functional plant homologs of apoptosis regulators. Here, we present the results of using advanced bioinformatic tools to uncover the Arabidopsis family of BAG proteins. The mammalian BAG (Bcl-2-associated athanogene) proteins are a family of chaperone regulators that modulate a number of diverse processes ranging from proliferation to growth arrest and cell death. Such proteins are distinguished by a conserved BAG domain that directly interacts with Hsp70 and Hsc70 proteins to regulate their activity. Our searches of the Arabidopsis thaliana genome sequence revealed seven homologs of the BAG protein family. We further show that plant BAG family members are also multifunctional and remarkably similar to their animal counterparts, as they regulate apoptosis-like processes ranging from pathogen attack to abiotic stress and development.

Highlights

The identification of homologs of animal cell death regulators is of considerable interest
We further show that plant BAG family members are multifunctional and regulate processes from pathogen attack to abiotic stress and development
Identification of the Arabidopsis bag Gene Family—Low sequence identities (13–25%) and similarities (32– 46%) between the BAG domain (BD) of Arabidopsis and animal BAG proteins explain the inability of BLAST searches to find animal BAG homologs in the Arabidopsis genome

Summary

Introduction

The identification of homologs of animal cell death regulators is of considerable interest. To induce cell death by cold treatment, wild-type and low atbag4-expressing tobacco plants were stressed at Ϫ20 °C for 10 min. We found that the Hsc70-binding surfaces (␣2 and ␣3 helices) of the BDs from AtBAG4 and human BAG4 are very similar in charge distribution (Fig. 2E).

Results

Conclusion