Plant Molecular Biology 38: 663–669, 1998.
© 1998 Kluwer Academic Publishers. Printed in the Netherlands.
A monocot pollen-speciﬁc promoter contains separable pollen-speciﬁc and
Douglas A. Hamilton
, Yuka H. Schwarz and Joseph P. Mascarenhas
Department of Biological Sciences and Center for Molecular Genetics, University at Albany, State University
of New York, Albany, NY 12222, USA (
author for correspondence);
Present address: Department of Biology,
Hartwick College, Oneonta, NY 13820, USA
Received 8 October 1997; accepted in revised form 14 April 1998
Key words: maize, pollen, pollen-speciﬁc promoter, transgenic plants, Arabidopsis
The region of the promoter of the pollen-speciﬁc maize gene, ZM13, from −119 to −37 was analyzed by a linker-
scanning type of substitution mutagenesis and two areas were shown to be responsible for pollen expression: a
proximal region delineated by mutations from −84 to −53 that conferred pollen speciﬁcity, and an upstream
regiondelineated by a mutation from −107 to −102 (Q-element) that could increase the expression of the proximal
regionbut showedno ability to cause expression in pollen on its own.Replacementof both of these areas with other
sequences including the CaMV 35S promoter failed to replace activity.
Pollen-speciﬁc genes and pollen-expressed genes that
are active during variousstages of pollen development
and germination have been isolated by several labo-
ratories [see reviews 3, 15, 23, 24, 26, 27, 31, 34].
Analyses with various degrees of detail, have been
made with the promoters of several pollen-expressed
genes from dicotyledonous plants. In general, the
cis-active sequence elements responsible for tissue
speciﬁcity and temporal speciﬁcity of transcription
of pollen-expressed genes appear to reside in the 5
ﬂanking region relatively near to the start of transcrip-
tion [1, 8, 10, 12, 13, 16, 33, 35, 36, 39, 40, 41, 43].
The elements responsible for pollen expression are
not universally present in all pollen promoters, despite
the ability of most tested pollen promoters to function
correctly in heterologous transgenic plants. Thus it is
difﬁcult to make generalizations regarding the nature
of pollen promoter elements.
ZM13 is a pollen-speciﬁc gene that has been
shownto be highlyexpressedin maturingmaize pollen
[14, 18]. RNA blot analysis has shown that the ZM13
mRNA is initially transcribed after microspore mi-
tosis and increases in abundance until anthesis. The
function of the ZM13 protein is not yet known; the
anti-sense expression of the mRNA of a homolo-
gous gene (LAT52) from tomato has, however, been
shown to disrupt pollen function . We have used
a transient transformation system which assays for the
efﬁciency of pollen promoters by measuring the activ-
ity of the reporter gene, β-glucuronidase (GUS), after
ticle bombardment . Using this system, it was
found that a fragment consisting of ZM13 promoter
sequences extendingfrom −261 to +61 was sufﬁcient
to cause high levels of GUS expression in pollen .
Additionally, sequences from −101 to +61 could also
direct pollen expression, albeit at lower levels, while
virtually no expression was seen with a −54 promoter
fragment. Since the expression of the −101 fragment
was diminished but clearly not abolished, these data
were interpreted as indicating that a pollen-speciﬁcity
element(s) resided in the −101 to −54 region, while
a quantitative element(s) resided upstream of −101
. Pollen speciﬁcity of expression for the −261
and −101 promoter fragments was demonstrated by a
lack of expression of GUS activity in leaves and tissue
culture cells after microprojectile bombardment .