Plant Molecular Biology 35: 367–375, 1997.
1997 Kluwer Academic Publishers. Printed in Belgium.
zrp2: a novel maize gene whose mRNA accumulates in the root cortex and
Bruce M. Held
, Isaac John
, Huiquing Wang
, Lathika Moragoda, T. Shamala Tirimanne
Eve Syrkin Wurtele and James T. Colbert
Department of Botany, Bessey Hall, Iowa State University, Ames, IA 50011, USA (
author for correspondence);
Stine Biotechnology, ISU Research Park, Suite 611, Ames, IA 50010, USA;
Biology, University of Michigan, Ann Arbor, MI 48109, USA;
SUGEN, Redwood City, CA 94305, USA;
Department of Botany, University of Colombo, Colombo, Sri Lanka
Received 18 December 1996; accepted in revised form 5 June 1997
Key words: cortex, gene expression, in situ hybridization, organ-preferential, root, Zea mays
A near full-length cDNA clone (pZRP2) was isolated from a cDNA library constructed from maize root mRNAs.
The predicted polypeptide has a calculated molecular mass of 66 975 Da, is largely hydrophilic, and contains 26
repeats of a motif the consensus sequence of which is RKATTSYG[S][D/E][D/E][D/E][D/E][P]. The function of
the putative protein remains to be elucidated. The ZRP2 mRNA accumulates to the highest levels in young roots,
and is also present in mature roots and stems of maize. Further analysis of young roots indicates that the lowest
level of ZRP2 mRNA is near the root tip, with relatively high levels throughout the remainder of the root. In situ
hybridization reveals that ZRP2 mRNA accumulates predominantely in the cortical parenchyma cells of the root.
In vitro nuclear run-on transcription experiments indicate a dramatically higher level of zrp2 gene transcription in
3-day old roots than in 5-day old leaves. A zrp2 genomic clone, which includes the transcribed region and 4.7 kb
of upstream sequence, was isolated and characterized.
Root function is integratedwith shoot function through
transport and storage of water and nutrients needed
for growth, as well as through translocation of signal-
ing molecules affecting growth and development. One
approach that has provided insight into the molecu-
lar basis of root development and function has been
the identiﬁcation of mutants in root development [1,
33, 38, 39]. The genetic approach is a powerful
means to identify genes whose expression effects eas-
ily observed phenotypes, such as the production and
morphology of root hairs. Another approach that has
been employed to increase understandingof root devel-
opment and functionis the isolation of genes expressed
in a root-speciﬁc or root-preferential manner [4, 7, 8,
The nucleotidesequence data reported will appear in the EMBL,
GenBank and DDBJ Nucleotide Sequence Databases under the
accession numbers U38790 (genomic) and U38791 (cDNA).
9, 11, 13, 20, 23, 29, 34, 35, 46, 49, 50, 51]. This
approach rests upon the assumption that expression of
a gene in speciﬁc organsor tissues reveals an important
role for that gene product in those organs or tissues.
Here we report on the isolation of a maize cDNA
clone whose corresponding mRNA accumulates to
high levels in both the roots and mature stems of the
maize plant. The deduced ZRP2 polypeptide is pre-
dominantly composed of an unusual repeated motif
and shares no extensive sequence similarity with any
known protein. The ZRP2 mRNA was transcribed at a
much higher rate in young roots than in young leaves.
A genomic clone was isolated that includes the entire
transcribed region of the zrp2 gene, as well as 4.7 kb
of the 5
Gr.: 201001110, PIPS Nr. 142986 BIO2KAP
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