THE PLANT CELL, Vol 8, Issue 8 1261-1275, Copyright © 1996 by American Society of Plant Biologists
A Pollen-, Ovule-, and Early Embryo-Specific Poly(A) Binding Protein from Arabidopsis Complements Essential Functions in Yeast
D. A. Belostotsky and R. B. Meagher
Department of Genetics, University of Georgia, Athens, Georgia 30602-7223
Poly(A) tails of eukaryotic mRNAs serve as targets for regulatory proteins
affecting mRNA stability and translation. Differential mRNA polyadenylation
and deadenylation during gametogenesis and early development are now widely
recognized as mechanisms of translational regulation in animals, but they
have not been observed in plants. Here, we report that the expression of
the PAB5 gene encoding one of the poly(A) binding proteins (PABPs) in
Arabidopsis is restricted to pollen and ovule development and early
embryogenesis. Furthermore, PAB5 is capable of rescuing a PABP-deficient
yeast strain by partially restoring both poly(A) shortening and
translational initiation functions of PABP. However, PAB5 did not restore
the linkage of deadenylation and decapping, thus demonstrating that this
function of PABP is not essential for viability. Also, like endogenous
PABP, PAB5 expressed in yeast demonstrated genetic interaction with a
recently characterized yeast protein SIS1, which is also involved in
translational initiation. We propose that PAB5 encodes a
post-transcriptional regulatory factor acting through molecular mechanisms
similar to those reported for yeast PABP. This factor may have evolved
further to post-transcriptionally regulate plant sexual reproduction and
early development.
