MYB80, a regulator of tapetal and pollen development,
is functionally conserved in crops
Huy A. Phan
Song F. Li
Roger W. Parish
Received: 1 September 2011 / Accepted: 9 November 2011 / Published online: 16 November 2011
Ó Springer Science+Business Media B.V. 2011
Abstract The Arabidopsis AtMYB80 transcription factor
(formerly AtMYB103) regulate genes essential for tapetal
and pollen development. One of these genes, coding for an
aspartic protease (UNDEAD), may control the timing of
tapetal programmed cell death (PCD). In crop plants such as
rice and wheat, abiotic stresses lead to abnormal tapetal
development resulting in delayed PCD. Manipulation of
AtMYB80 function has been used to develop a reversible
male sterility system applicable to hybrid crop production.
MYB80 homologs were cloned from wheat, rice, canola and
cotton. The promoters of the homologs drove temporal and
spatial expression patterns of the GUS reporter gene in the
tapetum and microspores of Arabidopsis anthers identical to
the AtMYB80 promoter. A short region is conserved in all
ﬁve MYB80 promoters. The MYB80 homolog genes, driven
by the AtMYB80 or their respective promoters, rescued the
atmyb80 mutant, completely restoring male fertility. The
canola MYB80 was fused to the EAR (ERF-associated
amphiphilic repression) repressor and canola plants trans-
genic for the construct exhibited premature tapetal degra-
dation and subsequent pollen abortion. The ﬁve MYB80
homologs all shared a 44 amino acid sequence immediately
adjacent to the R2R3 domain which appears to be necessary
for MYB80 function.
Keywords MYB80/MYB103 Á Tapetal PCD Á Pollen
development in rice/wheat/canola Á Anther development
AtMYB80 (formerly AtMYB103) is an Arabidopsis pro-
tein expressed in the developing tapetum and microspores
(Li et al. 1999, 2007; Higginson et al. 2003). Expression is
prominent at stage 7 of anther development when meiosis
is complete and tetrads are formed. Expression continues
until stage 10 when tapetum degeneration is initiated.
Functional disruption of AtMYB80 results in male sterility
(Higginson et al. 2003; Li et al. 2007; Zhang et al. 2007).
When AtMYB80 function was restored in the atmyb80
mutant, the expression levels of 79 genes were changed
(Phan et al. 2011). At least three of these genes are directly
regulated by AtMYB80, one of which encodes an A1
aspartic protease (UNDEAD) that is postulated to hydro-
lyze apoptosis-inducing proteins in the tapetal mitochon-
dria. The AtMYB80/UNDEAD system may regulate the
timing of tapetal programmed cell death (PCD).
The timing of PCD is critical for viable pollen produc-
tion and inhibiting PCD results in tapetal vacuolization and
hypertrophy (Kawanabe et al. 2006; Parish and Li 2010).
Inhibiting the Arabidopsis genes encoding the transcription
factors DISFUNCTIONAL TAPETUM1 (Zhang et al.
2006), MYB33/MYB65 (Millar and Gubler 2005), TAP-
ETAL DEVELOPMENT AND FUNCTION1 (Zhu et al.
2008) and ABORTED MICROSPORES (Sorensen et al.
2003; Xu et al. 2010), whose expression commences prior
to the anther development stage 7 (i.e. prior to AtMYB80),
results in strong vacuolization and hypertrophy of tapetal
cells (Parish and Li 2010). Inhibiting AtMYB80 function
causes premature tapetal cell death (Higginson et al. 2003;
Li et al. 2007; Zhang et al. 2007
), apparently because the
UNDEAD gene is not activated (Phan et al. 2011).
A system involving manipulation of AtMYB80 function
has been developed for the production of F1 hybrid seeds
Electronic supplementary material The online version of this
article (doi:10.1007/s11103-011-9855-0) contains supplementary
material, which is available to authorized users.
H. A. Phan Á S. F. Li Á R. W. Parish (&)
Botany Department, La Trobe University,
Melbourne 3086, Australia
Plant Mol Biol (2012) 78:171–183