AN ARABIDOPSIS-THALIANA CDNA COMPLEMENTING A HAMSTER APOPTOSIS SUPPRESSOR MUTANT

Programmed cell death or apoptosis is a process in which unwanted cell s are eliminated during growth and development. In mammals, several ge nes have been identified whose products are necessary to prevent entry into the apoptotic process. We have isolated a clone from an Arabidop sis thaliana cDNA library whose predicted translation product shows hi ghly significant similarity to the mammalian defender against apoptoti c death 1 (DAD1) protein. Transformation of the mutant hamster tsBN7 c ells, which undergo apoptosis at restrictive temperature, demonstrates that the plant protein is as efficient as human DAD1 in rescuing thes e hamster cells from apoptosis. In contrast to mammals, Southern hybri disation and genomic data indicate that there are probably two genes i n Arabidopsis thaliana. Northern blot analysis shows that AtDAD transc ripts are present in all tissues examined, although the abundance of t he transcripts is reduced in siliques during the maturation and desicc ation phase of the seed. This is the first experimental proof that a h omologue of an animal gene involved in apoptosis exists in plants and the first demonstration of complementation of a vertebrate mutant by a plant cDNA. Our results suggest that this process of suppression of a poptosis has been conserved in animals and plants.