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Leaders gathered at the US National Institutes of Health in November 2014 to discuss recent advances and emerging research areas in aspects of maternal-fetal immunity that may affect fetal development and pregnancy success.

We recently isolated the AtBI-1 (Arabidopsis Bax Inhibitor-1) gene, the expression of which suppressed Bax-induced cell death in yeast. To determine whether the same is true in the plant system, transgenic Arabidopsis plants overexpressing Bax protein under a dexamethasone (DEX)-inducible promoter were generated. On DEX treatment, such transgenic plants exhibited marked cell death at the whole-plant level, cell shrinkage, membranous destruction, and other apoptotic phenotypes. Transgenic Bax plants were retransformed with a vector containing the AtBI-1 gene (tagged with green fluorescent protein) under the control of the cauliflower mosaic virus 35S promoter. Plants expressing both Bax and AtBI-1 were able to maintain growth on DEX-treatment by sustaining intracellular integrity. Thus, we present here direct genetic evidence that the plant antiapoptotic protein AtBI-1 is biologically active in suppressing the mammalian Bax action in planta.A lthough relatively little is known about the mechanistic details of cell death in plants, some aspects of the molecular machinery are conserved between plants and animals (1). It has been demonstrated that overexpression of Bax, which encodes a mammalian proapoptotic protein, is lethal in the budding yeast Saccharomyces cerevisiae (2-5), even though yeasts have neither Bcl-2-related proteins nor caspases. Lacomme and Santa Cruz (6) demonstrated that expression of Bax by using a tobacco mosaic virus (TMV) vector triggered cell death in tobacco leaf cells, which closely resembled the hypersensitive response (HR) induced by TMV in tobacco plants carrying the N gene. Conversely, overexpression of human Bcl-X L in transgenic tobacco suppressed HR and conferred stress tolerance (7). It was also reported that caspase-specific peptide inhibitors could abolish bacteria-induced plant programmed cell death (8). These observations clearly suggest some common features of animal and plant cell death processes.Xu and Reed (9) transformed yeast cells containing a galactose-inducible Bax plasmid by using a human cDNA library (in which cDNAs were fused to a constitutively active yeast promoter) and isolated cDNAs that prevented Bax-induced lethality in response to galactose. This resulted in the identification of a gene, termed BI-1 (Bax Inhibitor-1), which is identical to a previously isolated human gene of unknown function called TEGT (testis enhanced gene transcript; refs. 10 and 11). We have previously cloned plant BI-1 cDNAs (Arabidopsis AtBI-1, and rice OsBI-1) (12). Interestingly, Sanchez et al. (13) reported that AtBI-1, the same gene isolated by our group, was obtained by differential screening of genes from plants challenged with the phytopathogen Pseudomonas syringae. Expression of AtBI-1 was rapidly up-regulated in plants during wounding or pathogen challenge. Furthermore, accumulation of the AtBI-1 transcript is significantly delayed in coi1 plants, indicating that reduced AtBI-1 mRNA levels may contribute to the enhanced susceptibility exhibited by coi1 plants to infection by v...