Mutants of Arabidopsis defective in a sequence-specific mRNA degradation pathway

Mutants of Arabidopsis defective in a sequence-specific mRNA degradation pathway

^*Department of Energy Plant Research Laboratory, ^§Program in Cellular and Molecular Biology, and ^¶Department of Biochemistry, Michigan State University, Plant Biology Building, East Lansing, MI 48824-1312

Edited by Brian A. Larkins, University of Arizona, Tucson, AZ, and approved September 22, 2000 (received for review July 26, 2000)

Abstract

One of the ways a cell can rapidly and tightly regulate gene expression is to target specific mRNAs for rapid decay. A number of mRNA instability sequences that mediate rapid mRNA decay have been identified, particularly from multicellular eukaryotes, but pinpointing the cellular components that play critical roles in sequence-specific decay in vivo has been more difficult. In contrast, general pathways of mRNA degradation in yeast have been well established through the analysis of mutants affecting the general mRNA decay machinery. Strategies to isolate mutants in sequence-specific mRNA decay pathways, although extremely limited so far, have the potential to be just as powerful. In the study reported here, a selection in transgenic plants allowed the isolation of rare mutants of Arabidopsis thaliana that elevate the abundance of mRNAs that contain the plant mRNA instability sequence called DST (downstream element). This instability sequence is highly conserved in unstable small auxin up RNA (SAUR) transcripts. Genetic analysis of two dst mutants isolated via this selection showed that they are incompletely dominant and represent two independent loci. In addition to affecting DST-containing transgene mRNAs, mutations at both loci increased the abundance of the endogenous DST-containing SAUR-AC1 mRNA, but not controls lacking DST sequences. That these phenotypes are caused by deficiencies in DST-mediated mRNA decay was supported by mRNA stability measurements in transgenic plants. Isolation of the dst mutants provides a means to study sequence-specific mRNA degradation in vivo and establishes a method to isolate similar mutants from other organisms.

Footnotes

↵ † Present address: University of Chicago, Department of Molecular Genetics and Cell Biology, 1103 East 57th Street, EBC 304, Chicago, IL 60637.
↵ ‡ Present address: Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia, Camino de Vera 14, 46022 Valencia. Spain.
↵ ‖ To whom reprint requests should be addressed. E-mail: green{at}msu.edu.
This paper was submitted directly (Track II) to the PNAS office.
Article published online before print: Proc. Natl. Acad. Sci. USA, 10.1073/pnas.240354097.
Article and publication date are at www.pnas.org/cgi/doi/10.1073/pnas.240354097
Abbreviations:

DST,

downstream element;

dst,

mutant defective in DST-mediated mRNA degradation;

ARE,

AU-rich element;

UTR,

untranslated region;

SAUR,

small auxin up RNA;

EMS,

ethyl methanesulfonate;

HPH,

hygromycin phosphotransferase;

GUS,

β-glucuronidase;

WT,

wild type;

T-DNA,

transfer DNA