This article is a Plant Cell Advance Online Publication. The date of its first appearance online is the official date of publication. The article has been
edited and the authors have corrected proofs, but minor changes could be made before the final version is published. Posting this version online
reduces the time to publication by several weeks.
COMMENTARY
Robust Self-Incompatibility in the Absence of a Functional ARC1
Gene in Arabidopsis thaliana
June B. Nasrallah1 and Mikhail E. Nasrallah
Department of Plant Biology, Cornell University, Ithaca, New York 14853
Self-incompatibility (SI) is the primary determinant of the outbreeding mode of sexual reproduction in the Brassicaceae. All
Arabidopsis thaliana accessions analyzed to date carry mutations that disrupt SI functions by inactivating the SI specificitydetermining S locus or SI modifier loci. S-locus genes isolated from self-incompatible close relatives of A. thaliana restore robust SI
in several accessions that harbor only S-locus mutations and confer transient SI in accessions that additionally harbor mutations at
modifier loci. Self-incompatible transgenic A. thaliana plants have proved to be valuable for analysis of the recognition and signaling
events that underlie SI in the Brassicaceae. Here, we review results demonstrating that S-locus genes are necessary and sufficient
for SI signaling and for restoration of a strong and developmentally stable SI phenotype in several accessions of A. thaliana. The data
indicate that introduction of a functional E3 ligase-encoding ARC1 gene, which is deleted in all accessions that have been analyzed
to date, is not required for SI signaling leading to inhibition of self pollen or for reversion of A. thaliana to its fully self-incompatible
ancestral state.
It is well established that specific pollen
recognition in the self-incompatibility (SI)
response of the Brassicaceae is determined
by allele-specific interactions that occur at
the stigma surface between two highly polymorphic proteins encoded in the S locus: the
S-locus receptor kinase SRK and its ligand,
the S-locus cysteine-rich protein SCR. Arabidopsis thaliana lacks a functional SI system
and harbors nonfunctional S-locus variants
that contain defective alleles of the SRK and/or
SCR genes (Kusaba et al., 2001; ShermanBroyles et al., 2007; Tang et al., 2007; Shimizu
et al., 2008; Boggs et al., 2009a; Tsuchimatsu
et al., 2010; Dwyer et al., 2013). Despite being
highly self-fertile, A. thaliana can be made to
express SI upon transformation with functional SRK-SCR gene pairs isolated from its
self-incompatible close relatives (Nasrallah
et al., 2002, 2004; Boggs et al., 2009a,
2009b). The first transfer of the SI trait into
A. thaliana was achieved using the SRKbSCRb gene pair isolated from the Sb locus
of Arabidopsis lyrata (Kusaba et al., 2001;
Nasrallah et al., 2002, 2004). Many of the
subsequent studies that have been performed in the transgenic A. thaliana SRKSCR system have used plants transformed
with p548, a plasmid that we constructed
by inserting the A. lyrata SRKb and SCRb
genes with their 5# and 3# regulatory se1Address correspondence to [email protected].
www.plantcell.org/cgi/doi/10.1105/tpc.114.129387
quences into the pBIN1 binary vector
(Nasrallah et al., 2004).
Indriolo et al. (2014) recently used the
p548 plasmid to generate SRKb-SCRb transformants and test the role of the ARM Repeat
Containing1 (ARC1) gene in SI. ARC1 was
originally identified as a Brassica napus
protein that interacts with the SRK kinase
domain in yeast (Gu et al., 1998), and it was
subsequently inferred to be required for SI
because downregulation of the ARC1 gene
in B. napus (Stone et al., 1999) and A. lyrata
(Indriolo et al., 2012), as well as overexpression of ARC1’s target, Exo70A1, in B. napus
(Samuel et al., 2009), caused partial breakdown of the SI response. However, the
involvement of the proposed SRK-ARC1Exo70A1 pathway in SI has been questioned because the ARC1 gene was found
to be deleted in all A. thaliana accessions
analyzed to date (Kitashiba et al., 2011;
Indriolo et al., 2012), including those in which
the SRKb-SCRb transgenes confer a strong
SI phenotype (Kitashiba et al., 2011). Additionally, overexpression of Exo70A1 did not
cause weakening of the SI response in
A. thaliana SRKb-SCRb plants (Kitashiba
et al., 2011).
Indriolo et al. (2014) reported on their
characterization of the SI response in plants
of the Sha and Columbia-0 (Col-0) accessions, which they either transformed with
the p548 plasmid alone or cotransformed
with p548 and a plasmid containing an
ARC1 gene isolated from A. lyrata or B. napus.
They concluded that, along with SRK and
SCR, “ARC1 is the third component that is
required to return A. thaliana to its ancestral
self-incompatibility state.” However, this
conclusion is inconsistent with results of
previous studies of SI in transgenic A. thaliana
SRK-SCR transformants, which have shown
that several A. thaliana accessions are rendered fully self-incompatible by transformation with the p548 plasmid without the
addition of a functional ARC1 gene. Contrary to Indriolo et al.’s assertion that in
previous studies of A. thaliana SRK-SCR
transformants, “the self-pollen rejection response was incomplete,” we reported that
among 11 A. thaliana accessions tested by
transformation with the p548 plasmid, five
accessions (C24, Cvi-0, Hodja, Kas-2, and
Sha) were converted to full SI by expression
of the SRKb and SCRb genes alone (Nasrallah
et al., 2004; Boggs et al., 2009a). Importantly,
the SI phenotype of these self-incompatible
SRKb-SCRb transformants faithfully recapitulates the SI phenotype of naturally selfincompatible Brassicaceae with respect to
the four defining features of SI in this family:
(1) site of pollen inhibition at the stigma
surface, (2) intensity of the response, (3) developmental regulation over the course of
stigma maturation, and (4) heritability. These
features suggest that the inhibition of self
pollen in self-incompatible A. thaliana SRKSCR transformants is achieved via the same
The Plant Cell Preview, www.aspb.org ã 2014 American Society of Plant Biologists. All rights reserved.
1 of 4
2 of 4
The Plant Cell
COMMENTARY
signaling pathway as that utilized by other
self-incompatible Brassicaceae species.
ROBUST SI IN SRKb-SCRb
TRANSFORMANTS OF THE Sha
ACCESSION IN THE ABSENCE OF
FUNCTIONAL ARC1
In the particular case of the Sha accession,
Boggs et al. (2009a) reported that 80%
(8 of 10) of the independent primary SRKbSCRb transformants analyzed expressed
an intense SI phenotype, which was faithfully
transmitted over ten generations. Accordingly, instead of the thousands of seeds
produced by untransformed Sha plants,
Sha[SRKb-SCRb] transformants were found
to produce on average 219 6 25 seeds over
their lifetime (i.e., ;1 seed per silique on
average, with the majority of siliques containing no seed). While somewhat higher
than the amount of seed produced by SRKbSCRb transformants of the C24 and Cvi-0
accessions, which set only ;50 to 60
seeds (or ;0.25 to 0.3 seeds per silique on
average) over their lifetime (Boggs et al.,
2009a), the low amount of seed produced
by Sha[SRKb-SCRb] plants still underscores the stability of the SI phenotype
throughout the life of these plants. Moreover, as for SRKb-SCRb transformants of
the C24, Cvi-0, Hodja, and Kas-2 accessions, the strength and developmental
stability of SI in Sha[SRKb-SCRb] transformants is demonstrated by the observation that manual self-pollination of stigmas
from stage 13 floral buds and older flowers
results in severe inhibition of pollen grains
at the stigma surface (typically 0 to 5 pollen
tubes per stigma) (Boggs et al., 2009a;
Figures 1 and 2) and the production of
siliques containing no seed or very few
seeds (e.g., 0, 1.7, and 2.3 seeds per silique
on average produced by 20 manual selfpollinations in each of three independent
lines). These seed values are equivalent
to those observed in the strongest selfincompatible SRKb-SCRb1ARC1 Sha plants
reported by Indriolo et al. (2014), in which
manual self-pollination produced an average
of 0.7, 1.2, 1.3, and 3.5 seeds per silique.
Most importantly, the small amount of seed
produced by the Sha[SRKb-SCRb] plants
Figure 1. Intense SI Exhibited by Sha[SRKb-SCRb] Transformants in the Absence of a Functional
ARC1 Gene.
The figure shows typical pollination results obtained by manual self-pollination of open flower stigmas
in transgenic self-incompatible Sha[SRKb-SCRb] plants. A T12 plant homozygous for a single integration
of the SRKb-SCRb transgenes was used for self-pollination (left) and for cross-pollination with pollen
from an untransformed plant (right). Note the severe inhibition of pollen at the surface of the selfpollinated stigma and the profuse pollen tube growth on the cross-pollinated stigma. The images were
generated by UV fluorescence microscopy observation of stigmas that were stained with aniline blue
two hours after manual self-pollination as previously described (Nasrallah et al., 2004). Bars ¼ 10 mm.
reported by Boggs et al. (2009a) and their
progenies is equivalent to the amount of seed
produced by naturally self-incompatible
Brassicaceae. As is the case with other
biological phenomena, SI is not an absolute
response and a few pollen grains can occasionally escape inhibition on some stigmas
of the most highly self-incompatible plants.
Thus, in self-incompatible A. lyrata, Arabidopsis halleri, and Arabis alpina plants collected from the wild, ;10 to 15% of manual
self-pollinations result in the production of
siliques containing seed (Mable et al., 2005;
Bechsgaard et al., 2006; Tedder et al., 2011).
Figure 2. Developmentally Stable SI in Sha[SRKb-SCRb] Transformants and Transient SI in Col-0
[SRKb-SCRb] Transformants Lacking a Functional ARC1 Gene.
The graph shows the developmental regulation of SI in the stigmas of Sha[SRKb-SCRb] and Col-0[SRKbSCRb] plants carrying a single integration of the SRKb-SCRb transgenes. Manual pollinations were performed
on the stigmas of floral buds and flowers at stage 12, stage 13, early stage 14 (14E), and late stage 14 (14L)
of development. Representative images of Col-0 floral buds and flowers at these developmental stages are
shown below the graph. The results of replicate pollinations are expressed as the mean number (6SE) of
pollen tubes that form upon manual self-pollination of stigmas (filled columns) or manual cross-pollination
with pollen from untransformed plants (adjoining white columns). For Sha[SRKb-SCRb] (T2 generation,
homozygous for the transgenes), each column represents the results of 16 replicate pollinations. The
Col-0[SRKb-SCRb] pollination data were previously reported by Nasrallah et al. (2002).
October 2014
3 of 4
COMMENTARY
In Brassica oleracea, instead of 20 to 25
seeds per pod produced in compatible
pollinations, manual self-pollination of selfincompatible stigmas produces, on average, 0.15 to 0.25 seeds per pod (Nasrallah
and Wallace, 1968; Nakanishi and Hinata,
1975) or as much as one to two seeds per
pod (Thompson and Taylor, 1971).
It is puzzling that none of the Sha[SRKbSCRb] plants generated by Indriolo et al.
exhibited as strong an SI phenotype as that
observed in the Sha[SRKb-SCRb] transformants reported by Boggs et al. (2009a).
Among 17 transformants that they analyzed
by manual self-pollination of open flower
stigmas, none exhibited strong SI (defined
by the growth of ,10 pollen tubes per
stigma) and three exhibited only a moderate
level of SI. The level of SRK transcripts and
protein that accumulate in stigma epidermal
cells is the primary determinant of the strength
of the SI response and its stability over the
course of stigma development in A. thaliana
SRK-SCR transformants, as in naturally selfincompatible members of the Brassicaceae.
Therefore, it is possible that the Indriolo et al.
transformants might have had relatively low
expression levels of the SRKb transgene.
ROBUST SI SIGNALING IN SRKb-SCRb
TRANSFORMANTS OF THE COL-0
ACCESSION IN THE ABSENCE OF
FUNCTIONAL ARC1
We previously reported that SRKb-SCRb
transformants of the Col-0 accession produce amounts of seed equivalent to those
produced by untransformed plants (Nasrallah
et al., 2002, 2004; Tantikanjana et al., 2009;
Tantikanjana and Nasrallah, 2012), and this
phenotype was observed in the Indriolo et al.
(2014) study. However, this high seed set is
not due to the inability of Col-0[SRKb-SCRb]
plants to effect SI signaling, as implied by
Indriolo et al.’s description of these plants
as “remaining self-compatible.” Rather, as
previously reported (Nasrallah et al., 2002;
Tantikanjana et al., 2009; Tantikanjana and
Nasrallah, 2012) and shown in Figure 2,
Col-0[SRKb-SCRb] plants (unlike untransformed Col-0 plants) express an intense SI
response in the stigmas of mature floral buds
(stage 13) and young flowers (early stage 14),
and the high number of seeds produced by
these plants is due to subsequent weakening of SI at later stages of flower development. This transient SI phenotype,
which is often observed in natural and
cultivated populations of various species,
was also observed in SRKb-SCRb transformants of the RLD and Ws-0 accessions
(Nasrallah et al., 2004; Liu et al., 2007) and
independently by Tsuchimatsu et al. (2010)
in plants of the Wei accession that were
transformed with another S-locus transgene.
It should also be noted that the transient
SI phenotype of Col-0[SRKb-SCRb] plants,
which is caused by modifier loci harbored
in the Col-0 genome (Boggs et al., 2009a),
has been converted to full SI in the absence
of functional ARC1: Loss-of-function mutations in the RDR6 gene (Tantikanjana et al.,
2009) and overexpression of the auxin
response factor ARF3 both resulted in expression of a strong self-pollen rejection
phenotype that persisted into late stages of
flower development, causing lack of seed
set (Tantikanjana and Nasrallah, 2012).
A STANDARDIZED STRATEGY FOR
FUNCTIONAL STUDIES OF SI IN
TRANSGENIC A. THALIANA
The results reviewed here indicate that all
factors required for self-pollen rejection have
been retained in several A. thaliana accessions
and that a functional ARC1 gene is not
required for SRK-mediated signaling or for
conversion of these accessions to full SI. The
contradictory results reported for A. thaliana
SRKb-SCRb transformants in previous studies and by Indriolo et al. (2014) cannot be
easily reconciled. However, we note that
proper interpretation of pollination phenotypes
in the A. thaliana SRK-SCR system requires
consideration of the following issues.
(1) The major source of phenotypic variability among independent SRK-SCR transformants is differential SRK expression levels
that inevitably result from different sites of
transgene integration. Consequently, careful
comparison of SRK transcript levels in independent SRK-SCR transformants is critical.
In view of the well-documented developmental regulation of SI and of SRK transcript
levels in stigmas, accurate quantification of
these transcripts requires the use of stigmas
or pistils harvested from floral buds or
flowers at the same stage of development
rather than from a mixture of buds or flowers
at different stages of development, as may
have been done by Indriolo et al. (2014).
Indeed, the levels of SRK transcripts will be
overestimated in samples containing an excess of stigmas from stage 13 or stage 14
buds and underestimated in samples containing an excess of stigmas from immature
buds or older flowers.
(2) In view of the variable levels of transgene expression in independent transformants, it is imperative that experiments aimed
at testing the role of a gene of interest in SI
use a true-breeding SRK-SCR transgenic
line having a well-defined, stable, and heritable SI phenotype and ideally harboring a
single integration of the SRK-SCR transgenes (to minimize the possibility of transgene silencing in subsequent generations
and to facilitate progeny analysis). This homozygous SRK-SCR line would then be transformed with a construct designed to test the
role of a gene of interest (GOI), either by root
transformation in cases where the SRK-SCR
line is fully self-incompatible and sets little or
no seed, or by floral dipping in cases where
the SRK-SCR line expresses transient SI.
This strategy leads to unambiguous evaluation of the role of the GOI in SI because it
allows direct comparison of plants having
or lacking the GOI construct in the same
genetic background (i.e., in plants having
the same integration site and expression
levels of the SRK and SCR transgenes) as
well as a straightforward determination of
whether a pollination phenotype cosegregates with the GOI transgene in subsequent
generations. By contrast, a strategy of cotransformation with the SRK-SCR genes and
the GOI construct, as used by Indriolo et al.
(2014) for testing the role of ARC1, will
inevitably produce transformants having a
range of expression levels, not only of the
GOI transgene, but also of SRK and SCR,
thus complicating interpretation of observed
phenotypes. This issue is compounded in
transgenic progenies due to the segregation
of plants that are homozygous or hemizygous
for the SRK-SCR and/or GOI transgene
integrations and is even more problematic
when the primary transformants contain more
than one integration of the transgenes.
4 of 4
The Plant Cell
COMMENTARY
To avoid the pitfalls associated with variable
SRK expression in independent A. thaliana
SRK-SCR transformants and to facilitate
comparison of results obtained in different
laboratories, we suggest the adoption of
a standardized strategy for functional studies of SI based on three elements: (1) the
use of well-defined true-breeding SRK-SCR
lines; (2) analysis of SRK transcript levels in
carefully staged stigmas; and (3) evaluation
of SI phenotypes by microscopic examination of pollen tube growth in manually selfpollinated stigmas over the course of their
development, which allows detection of transient SI phenotypes. The microscopic pollination assay is preferred over the seed counting
method because it is a rapid assay that
samples large numbers of pollen grains
(;1000 pollen grains may be sampled by
microscopy observation of just 10 selfpollinated stigmas). By contrast, the seed
count method can produce ambiguous results, as previously noted in naturally selfincompatible Brassicaceae (Sampson, 1964),
because it reports only on the fate of the few
pollen grains that produce seed and because
factors other than pollen inhibition at the
stigma surface can affect seed production.
ACKNOWLEDGMENTS
Work in the Nasrallah laboratory is supported by
National Science Foundation Grant IOS-1146725.
The funders had no role in study design, data
collection and analysis, decision to publish, or
preparation of the article.
AUTHOR CONTRIBUTIONS
J.B.N. and M.E.N. wrote the commentary.
Received July 2, 2014; revised August 7, 2014;
accepted October 2, 2014; published October
21, 2014.
REFERENCES
Bechsgaard, J.S., Castric, V., Charlesworth, D.,
Vekemans, X., and Schierup, M.H. (2006). The
transition to self-compatibility in Arabidopsis
thaliana and evolution within S-haplotypes over
10 Myr. Mol. Biol. Evol. 23: 1741–1750.
Boggs, N.A., Nasrallah, J.B., and Nasrallah,
M.E. (2009a). Independent S-locus mutations
caused self-fertility in Arabidopsis thaliana. PLoS
Genet. 5: e1000426.
Boggs, N.A., Dwyer, K.G., Shah, P., McCulloch,
A.A., Bechsgaard, J., Schierup, M.H.,
Nasrallah, M.E., and Nasrallah, J.B. (2009b).
Expression of distinct self-incompatibility specificities in Arabidopsis thaliana. Genetics 182:
1313–1321.
Dwyer, K.G., Berger, M.T., Ahmed, R., Hritzo,
M.K., McCulloch, A.A., Price, M.J., Serniak,
N.J., Walsh, L.T., Nasrallah, J.B., and
Nasrallah, M.E. (2013). Molecular characterization and evolution of self-incompatibility
genes in Arabidopsis thaliana: the case of the
Sc haplotype. Genetics 193: 985–994.
Gu, T., Mazzurco, M., Sulaman, W., Matias,
D.D., and Goring, D.R. (1998). Binding of an
arm repeat protein to the kinase domain of the
S-locus receptor kinase. Proc. Natl. Acad. Sci.
USA 95: 382–387.
Indriolo, E., Safavian, D., and Goring, D.R.
(2014). The ARC1 E3 ligase promotes two
different self-pollen avoidance traits in Arabidopsis. Plant Cell 26: 1525–1543.
Indriolo, E., Tharmapalan, P., Wright, S.I., and
Goring, D.R. (2012). The ARC1 E3 ligase gene
is frequently deleted in self-compatible Brassicaceae species and has a conserved role in
Arabidopsis lyrata self-pollen rejection. Plant
Cell 24: 4607–4620.
Kitashiba, H., Liu, P., Nishio, T., Nasrallah,
J.B., and Nasrallah, M.E. (2011). Functional
test of Brassica self-incompatibility modifiers
in Arabidopsis thaliana. Proc. Natl. Acad. Sci.
USA 108: 18173–18178.
Kusaba, M., Dwyer, K., Hendershot, J.,
Vrebalov, J., Nasrallah, J.B., and Nasrallah,
M.E. (2001). Self-incompatibility in the genus
Arabidopsis: characterization of the S locus in
the outcrossing A. lyrata and its autogamous
relative A. thaliana. Plant Cell 13: 627–643.
Liu, P., Sherman-Broyles, S., Nasrallah, M.E.,
and Nasrallah, J.B. (2007). A cryptic modifier
causing transient self-incompatibility in Arabidopsis thaliana. Curr. Biol. 17: 734–740.
Mable, B.K., Robertson, A.V., Dart, S., Di
Berardo, C., and Witham, L. (2005). Breakdown of self-incompatibility in the perennial
Arabidopsis lyrata (Brassicaceae) and its genetic consequences. Evolution 59: 1437–1448.
Nakanishi, T., and Hinata, K. (1975). Self-seed
production by CO 2 gas treatment in selfincompatible cabbage. Euphytica 24: 117–118.
Nasrallah, M.E., Liu, P., and Nasrallah, J.B.
(2002). Generation of self-incompatible Arabidopsis thaliana by transfer of two S locus genes
from A. lyrata. Science 297: 247–249.
Nasrallah, M.E., Liu, P., Sherman-Broyles, S.,
Boggs, N.A., and Nasrallah, J.B. (2004).
Natural variation in expression of self-incompatibility in Arabidopsis thaliana: implications
for the evolution of selfing. Proc. Natl. Acad.
Sci. USA 101: 16070–16074.
Nasrallah, M.E., and Wallace, D.H. (1968). The
influence of modifer genes on the intensity and
stability of self-incompatibility in cabbage. Euphytica 17: 495–503.
Sampson, D.R. (1964). A one-locus selfincompatibility system in Raphanus raphanistrum.
Can. J. Genet. Cytol. 6: 435–445.
Samuel, M.A., Chong, Y.T., Haasen, K.E.,
Aldea-Brydges, M.G., Stone, S.L., and
Goring, D.R. (2009). Cellular pathways regulating
responses to compatible and self-incompatible
pollen in Brassica and Arabidopsis stigmas intersect at Exo70A1, a putative component of the
exocyst complex. Plant Cell 21: 2655–2671.
Sherman-Broyles, S., Boggs, N., Farkas, A.,
Liu, P., Vrebalov, J., Nasrallah, M.E., and
Nasrallah, J.B. (2007). S locus genes and the
evolution of self-fertility in Arabidopsis thaliana. Plant Cell 19: 94–106.
Shimizu, K.K., Shimizu-Inatsugi, R., Tsuchimatsu,
T., and Purugganan, M.D. (2008). Independent
origins of self-compatibility in Arabidopsis thaliana.
Mol. Ecol. 17: 704–714.
Stone, S.L., Arnoldo, M., and Goring, D.R.
(1999). A breakdown of Brassica self-incompatibility in ARC1 antisense transgenic plants.
Science 286: 1729–1731.
Tang, C., Toomajian, C., Sherman-Broyles, S.,
Plagnol, V., Guo, Y.L., Hu, T.T., Clark, R.M.,
Nasrallah, J.B., Weigel, D., and Nordborg,
M. (2007). The evolution of selfing in Arabidopsis thaliana. Science 317: 1070–1072.
Tantikanjana, T., Rizvi, N., Nasrallah, M.E.,
and Nasrallah, J.B. (2009). A dual role for the
S-locus receptor kinase in self-incompatibility
and pistil development revealed by an Arabidopsis rdr6 mutation. Plant Cell 21: 2642–2654.
Tantikanjana, T., and Nasrallah, J.B. (2012). Noncell-autonomous regulation of crucifer selfincompatibility by Auxin Response Factor ARF3.
Proc. Natl. Acad. Sci. USA 109: 19468–19473.
Tedder, A., Ansell, S.W., Lao, X., Vogel, J.C.,
and Mable, B.K. (2011). Sporophytic selfincompatibility genes and mating system variation
in Arabis alpina. Ann. Bot. (Lond.) 108: 699–713.
Thompson, K.F., and Taylor, J.P. (1971). Selfcompatibility in kale. Heredity 27: 459–471.
Tsuchimatsu, T., Suwabe, K., Shimizu-Inatsugi,
R., Isokawa, S., Pavlidis, P., Städler, T., Suzuki,
G., Takayama, S., Watanabe, M., and Shimizu,
K.K. (2010). Evolution of self-compatibility in
Arabidopsis by a mutation in the male specificity
gene. Nature 464: 1342–1346.
Robust Self-Incompatibility in the Absence of a Functional ARC1 Gene in Arabidopsis thaliana
June B. Nasrallah and Mikhail E. Nasrallah
Plant Cell; originally published online October 21, 2014;
DOI 10.1105/tpc.114.129387
This information is current as of June 17, 2017
Permissions
https://www.copyright.com/ccc/openurl.do?sid=pd_hw1532298X&issn=1532298X&WT.mc_id=pd_hw1532298X
eTOCs
Sign up for eTOCs at:
http://www.plantcell.org/cgi/alerts/ctmain
CiteTrack Alerts
Sign up for CiteTrack Alerts at:
http://www.plantcell.org/cgi/alerts/ctmain
Subscription Information
Subscription Information for The Plant Cell and Plant Physiology is available at:
http://www.aspb.org/publications/subscriptions.cfm
© American Society of Plant Biologists
ADVANCING THE SCIENCE OF PLANT BIOLOGY