From the Department of Biology, University of York, P.O. Box 373, York YO10 5DD, United Kingdom
Received for publication, August 16, 2000, and in revised form, September 25, 2000
![]() |
ABSTRACT |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
A class of UDP-glycosyltransferases (UGTs)
defined by the presence of a C-terminal consensus sequence is found
throughout the plant and animal kingdoms. Whereas mammalian enzymes use
UDP-glucuronic acid, the plant enzymes typically use UDP-glucose in the
transfer reactions. A diverse array of aglycones can be glucosylated by these UGTs. In plants, the aglycones include plant hormones, secondary metabolites involved in stress and defense responses, and xenobiotics such as herbicides. Glycosylation is known to regulate many
properties of the aglycones such as their bioactivity, their
solubility, and their transport properties within the cell and
throughout the plant. As a means of providing a framework to start to
understand the substrate specificities and structure-function
relationships of plant UGTs, we have now applied a molecular
phylogenetic analysis to the multigene family of 99 UGT sequences in
Arabidopsis. We have determined the overall organization
and evolutionary relationships among individual members with a
surprisingly high degree of confidence. Through constructing a
composite phylogenetic tree that also includes all of the additional
plant UGTs with known catalytic activities, we can start to predict
both the evolutionary history and substrate specificities of new
sequences as they are identified. The tree already suggests that while
the activities of some subgroups of the UGT family are highly conserved
among different plant species, others subgroups shift substrate
specificity with relative ease.
Glycosyltransferases are found in all living organisms, catalyzing
the transfer of a glycosyl moiety from an activated donor to an
acceptor molecule, forming a glycosidic bond. These glycosyl transfer
reactions have been highlighted as the most important biotransformation
on earth, since in quantitative terms they account for the assembly and
degradation of the bulk of biomass (1).
A unique signature motif has been identified in the amino acid sequence
of many of these glycosyltransferases, leading to their classification
into a single UDP-glycosyltransferase
(UGT)1 superfamily (2).
Of these, the mammalian UGTs using UDP-glucuronic acid have attracted
considerable attention in pharmaceutical and clinical research due to
their central role in the metabolism and detoxification of foreign
chemicals such as carcinogens and hydrophobic drugs (3, 4).
Plant UGTs are involved in a parallel range of activities, the majority
of which use UDP-glucose in the transfer reaction. These reactions are
known to have a number of important consequences. First, compounds can
be activated or inactivated by their conjugation to glucose. For
example, glucose esters are high energy compounds that are known to act
as biosynthetic intermediates for further reactions involving the
aglycones (5). In contrast, many of the plant hormones are known to be
inactivated following glucosylation (6, 7). Second, glucosylation
alters the solubility of compounds by increasing their hydrophilic
properties and providing access to active membrane transport systems
that recognize the glucosides but not the aglycones (8).
As a consequence of these events, glucosylation plays a crucial role in
the maintenance of cellular homeostasis in plants through regulating
the level, activity, and location of key cellular metabolites. Despite
this general importance and the likely large number of these enzymes,
given the diversity of substrates, plant UGTs have not been studied
systematically. Rather, individual UGTs have been purified on the basis
of a particular catalytic activity (9-20). The disadvantage of this
approach is that the relationships of different UGTs cannot be defined
easily, and, in consequence, predictions of catalytic activities based
on structure-function relatedness cannot be made.
Genome sequencing programs offer a new route into understanding
multigene families both within a single species and across different
species. In this study, we have used the data available from the
Arabidopsis genome sequencing program to start to build a
foundation for understanding the UGT multigene family. This analysis
focuses on the phylogeny and evolution of UGTs and complements parallel
investigations into substrate specificity using recombinant proteins
corresponding to known UGT sequences (21, 22).
Data Base Searching and Sequence Analysis for Coding Regions and
Introns--
A UGT signature motif in a known tomato UGT (23) was used
in a BLAST search of the GenBankTM data base (available on
the World Wide Web). ORFs and intron positions of putative
Arabidopsis UGT sequences were first identified using Map
and Codepreference programs of Wisconsin Package version 10.0 (Genetic
Computing Group). Intron positions were decided by visual scanning of
likely exon boundaries for Arabidopsis intron splice site
consensus sequences (available on the World Wide Web) and by
analyses using the program NetGene2 (available on the World Wide
Web). In all cases, both methods found identical results. In all
12 cases where cDNAs were available, the predicted intron boundaries were confirmed by sequencing.
Identification of Pseudogenes--
Sequence alignment indicated
eight pseudogenes. Of these, five (71B4, 72D2,
89A1, 76E10, and
84B3)2 were found
to contain a single nucleotide substitution, insertion, or
deletion, therefore causing interruption of ORFs. The single base
changes for 71B4, 72D2, and 84B3 were
confirmed by sequencing of the cloned PCR amplification products from
genomic DNA using Pfu DNA polymerase. 76E8 had
two single nucleotide nonsense substitutions. 71B3 contained
a 40-base pair deletion causing a frameshift and in-frame stop codon;
90A3 contained multiple nonsense substitutions, insertions,
and deletions throughout.
PCR Amplification, Cloning, and Sequencing--
DNA sequences
were amplified from the genomic DNA of Arabidopsis thaliana
Columbia by PCR, using Pfu DNA polymerase (Stratagene) and
gene-specific oligomers. PCR products were subcloned into restriction
sites on the multiple cloning site of pBluescriptII (24). Nucleotide
substitutions and insertion/deletions in the pseudogenes were confirmed
by sequencing using the appropriate oligomers. Intron positions in
73B1, 73B2, 74D1, 74E2,
74F2, 76C5, 76E3, 78D1,
87A2, and 88A1 were also confirmed by sequencing
their corresponding expressed sequence tags obtained from the
Arabidopsis Biological Resource Center.
Sequence Alignment and Phylogenetic Analysis--
The amino acid
sequences of the ORFs were initially aligned using the program ClustalX
version 1.8 with default gap penalties (25). These alignments were then
reconciled and further adjusted by eye to minimize insertion/deletion
events. The conserved motifs were defined as alignable regions among
all sequences. Smaller groups of more closely related sequences were
then aligned separately by the same methods. Only regions of
unambiguous alignments were used in the subsequent phylogenetic analyses.
Trees were constructed initially from amino acid sequences of nine
conserved motifs present and alignable in all sequences, giving a total
of 290-300 amino acid positions for all sequences. Distance analyses
used the program Protdist of Phylip 3.5c with a PAM250 substitution
matrix and trees calculated by neighbor-joining algorithms. Distance
bootstrap analyses consisted of 1000 replicates using the same
protocol. Parsimony analyses utilized PAUP* 4.0b2a. Shortest tree
searches consisted of 1000-10,000 replicates of random sequence
addition with tree bisection-reconnection branch swapping. Bootstrap
analyses used 1000 replicates of a single round of random addition each.
Strongly supported subgroups (bootstrap percentage >90%) were then
analyzed further to refine all of the subtrees. Analysis of 105 UGTs,
including Arabidopsis and other plant species, used only the
distance method.
The UGT Family of Arabidopsis Is Large and Diverse--
A
signature sequence involved in the binding of the UDP moiety of the
nucleotide sugar has been identified as a characteristic of UGT
sequences from a range of prokaryotic and eukaryotic organisms (2, 26,
27). To gain insight into the size of the UGT family in the model plant
Arabidopsis thaliana, a 44-amino acid sequence corresponding
to this signature motif in a known UGT from tomato (23, 28) was used to
screen the GenBankTM data base. To our surprise, 99 sequences containing the signature motif were identified. Since to date
(March 1, 2000), 86.5% of the Arabidopsis genome is
sequenced and publicly available, our data estimate that the total
genome will contain ~120 UGTs. This indicates that
UGTs constitute one of the largest multigene families in
Arabidopsis.
Each of the putative UGT genes identified in this study has been newly
classified using the standardized system recommended by the UGT
Nomenclature Committee (2) (Table S1). Of the 99 UGT sequences
identified, eight were found to be pseudogenes on the basis of
interruptions to ORFs (71B3P, 71B4P,
72D2P, 76E8P, 76E10P,
84B3P, 89A1P, and 90A3P); three were
only partial (76B1, 76C2, and 85A3).
Detailed sequence analyses indicated 19 errors to current data base
annotation (Table S2). This left 88 unique, complete genes, which were
then subjected to further analysis. The deduced amino acid sequences of
the putative UGTs ranged from 442 amino acids
(79B7 and 79B8) to 507 amino acids
(73D1).
While all of the UGT sequences identified contain the signature motif,
the overall sequence similarity varies substantially between individual
pairs of sequences, from 95% to lower than 30% identity. Despite this
diversity, a total of nine conserved motifs are clearly present.
Conserved motif 5 separates all of the UGTs into N-terminal and
C-terminal regions. The N-terminal region is more highly variable than
the C-terminal region. This observation supports the suggestion that
the N-terminal region is likely to be involved in the recognition and
binding of the highly diverse aglycone substrates, whereas the
C-terminal region, including the signature sequence in motif 7, is
involved in binding the nucleotide sugar substrates. The complete
alignment of these unique sequences is provided in Fig. S1.
All of the UGTs identified as transferring glucuronic acid to
hydrophobic substrates in mammalian cells are membrane-bound enzymes
(29) localized in the endoplasmic reticulum with their catalytic sites
facing the lumen. Two functional motifs in mammalian UGTs are thought
to be important to the topology of proteins within the cell. First, a
distinct hydrophobic C-terminal halt sequence anchors the enzymes to
the membrane region (30-34). Second, the mammalian UGTs also contain
the N-terminal signal sequence cleaved on cotranslational segregation
into the endoplasmic reticulum (29, 35). However, neither motif was
identified in our analyses of Arabidopsis UGTs using
programs TopPred2 (available on the World Wide Web), SignalP (available
on the World Wide Web), and Psort (available on the World Wide
Web) (data not shown), supporting the general assumption that
the plant UGTs are cytoplasmic enzymes.
Phylogeny of the UGT Superfamily--
An alignment of nine
conserved motifs, encompassing ~60% of the total deduced protein
sequence of all Arabidopsis UGTs, were analyzed by neighbor
joining and parsimony with statistical confidence measured by bootstrap
analysis. Both sets of analyses define 12 major groups, each with a
bootstrap support greater than 90% in distance analysis (Fig.
1).
Relationships of some individual UGTs in well supported subgroups could
not be strongly resolved due to the very high similarity among closely
related sequences in the nine conserved motifs (Fig. 1A).
These subgroups were analyzed to better resolve fine level relationships using larger data sets with additional alignable residues
(Fig. 1B).
The 12 well defined major groups of UGTs suggest that there were at one
time 12 ancestral genes. However, the branching order among these 12 ancestral genes is not clearly resolved by these analyses. One possible
source of artifact is the presence of two sequences (83A1 and 78D1)
with long unique terminal branches, suggesting accelerated evolutionary
rates. Such long branches tend to distort phylogenetic analyses by
reducing apparent bootstrap support for nearby clades (36). Therefore,
we reanalyzed the data with these two sequences removed. These analyses
give strong statistical confidence that five of the ancestral genes,
corresponding to groups G, H, J, K, and L, are likely to share a more
recent common origin (Fig. 1A, 84/70% bootstrap). Within
these groups, G and H are more likely to be closely related (Fig.
1A, 78/57% bootstrap).
The phylogenetic tree described in this study has not been rooted (Fig.
1). Several UGT sequences of mammalian and bacterial origin were used
as outgroups in an attempt to define the earliest branch in the
Arabidopsis UGT tree. However, no single branch was
consistently or strongly identified (data not shown). This is most
probably due to the remoteness of the outgroups used and the fact that
only motif 7 is clearly alignable among all these sequences, so only
~60 amino acid positions could be used for the analyses (data not shown).
Chromosomal Organization of UGT Genes--
When the nearest
recombinant inbred markers of the bacterial artificial
chromosome clones (Table S1) were used as indications of their
chromosomal positions, the UGT genes were found to be scattered
throughout the chromosomes of the Arabidopsis genome, which
is similar to the Arabidopsis R2R3-MYB gene family (37). Another distinctive feature of the Arabidopsis UGT gene
family is the clustering of sequences into groups with sizes ranging from two to seven genes per group (Fig.
2). The genes in any particular cluster
often show a high degree of sequence similarity among themselves, also reflecting their
closeness in the terminal subgroups of the phylogenetic tree (Fig.
1).
The presence of clusters of UGT sequences on individual chromosomes
implies that they have evolved from gene duplications of more recent
unequal recombination events. There are also clear examples of
transpositional gene duplications in the UGT family. For
example, in the 73B subfamily, a gene cluster comprising
73B1-73B3 is located on chromosome IV with a second cluster
comprising 73B4 and 73B5 on chromosome II.
Therefore, it is likely that ancestors of these genes were the result
of a transpositional gene duplication event. Such features can also be
found in the Arabidopsis multigene family encoding the
detoxifying enzymes, glutathione S-transferases (38).
Intron Gain and Loss in the UGT Multigene Family--
Our study
revealed that 37 in 88 UGT genes contained introns, with all but three
of these genes containing only a single intron (Figs. 1 and 3).
Comparing intron positions with sequence relationships predicted by
phylogenetic analysis (Fig. 1), a minimum of nine independent intron
insertion events appear to have happened in the course of
UGT evolution. The most widespread, and therefore probably
the oldest intron, is intron 2, which is found in all of the 23 UGT
sequences in groups F-K (Fig. 1). All other introns are found only
within a single restricted subgroup of closely related sequences or in
only a single gene. This suggests a general pattern of intron gain
during evolution of the UGT gene family.
A single clear case of recent intron loss is seen in the subfamily of
closely related genes 73B1-73B5 in group D. Four of these
genes contain intron 7, yet in the closely related pair of sequences
73B2 and 73B3 (85% sequence identity), only
73B2 contains the intron. This implies that an intron loss
event has occurred along the line leading to 73B3, after the
gene duplication event that gave rise to 73B2 and
73B3. Similarly, the absence of intron 2 in group L may also
have arisen from an intron loss that occurred in the duplication event
separating group L from groups I, J, and K. However, the relationship
between group L and groups F-K is not resolved; therefore, this intron
loss event is uncertain.
Thus, analysis of the evolution of the UGT multigene family provides
evidence for both intron gain and intron loss and is thereby strongly
consistent with the "intron-late" theory of intron evolution
(39-42).
Structure-Function Relatedness of the UGT Family--
Numerous
sequences containing the UGT signature motif have been identified from
a wide range of plant species. Of these, 14 of the corresponding gene
products have been characterized biochemically (Table
I) (9-20, 43), and the functions of
three additional proteins have been defined conclusively by genetic
analysis (44-47). Therefore, we aligned these 17 additional sequences
with 88 Arabidopsis sequences and constructed the
phylogenetic trees. The trees were based on the nine conserved motifs
by superimposing the predicted position of these 17 new sequences onto
the tree in Fig. 1 based on the results of the 105 sequence analyses
(Fig. 4). The results reveal a number of
interesting relationships.
The composite tree (Fig. 4) suggests the possible presence of an
additional ancient UGT family distinct from the 12 groups we have so
far identified in Arabidopsis (Fig. 1). This additional group includes two sequences encoding enzymes that glycosylate the
plant hormone, zeatin (19, 20). While one of these UGTs uses
UDP-glucose as the sugar donor, the other with identical aglycone
specificity uses UDP-xylose. The two sequences are 87% identical,
implying that they have arisen from a common ancestor with one of the
pair subsequently shifting its substrate specificity.
The remaining 15 UGT genes from plant species other than
Arabidopsis all cluster within the 12 groups identified by
this study (Fig. 4). Interestingly, three of these UGTs
clustered in group F are known to be involved in the
3-O-glucosylation of anthocyanidins, implying that the
Arabidopsis 78D1 gene products may have a related specificity. Since this cluster contains sequences from maize, gentian,
and grapevine (12, 10, 45), the biochemical function of the product
from the common ancestral gene may have evolved prior to the division
of monocots and dicots. Although a fourth UGT, from petunia, is also
present in the lower branches of the same cluster, the enzyme is known
not to glycosylate anthocyanidins (16).
The 3-O-glucosides of anthocyanidins can be further modified
either by the addition of rhamnose to the glucose moiety or by glucosylation of other hydroxyl groups. The petunia UGTs transferring rhamnose to the glucose ring of anthocyanins (46, 47) are located in
group A of the composite phylogenetic tree (Fig. 4), whereas an example
of a UGT from perilla (15) transferring glucose to the 5-O
position is in group L. This suggests that the enzymes involved in
these further modifications of anthocyanins have evolved independently.
Similarly, while the biosynthesis of glucosinolates and cyanogenic
glucosides share common intermediates in the form of oximes and also
share the involvement of UGTs (17, 43, 48, 49), there is no close
evolutionary relationship between these UGTs. The enzyme involved in
glucosinolate formation (43) is found within group L, whereas that
involved in cyanogenic glucoside formation (17) is found within Group G.
In parallel studies to this phylogenetic analysis, we have screened
representatives from each of the major groups of the
Arabidopsis multigene family for their ability to
glucosylate cinnamic acids. The results have shown that within 36 family members that have been analyzed, the ability to form glucose
esters only resides within group L (21). This group contains the maize
iaglu gene product (9) and the equivalent enzyme of
Arabidopsis, 84B1, that forms the glucose ester of
indole-3-acetic acid (22). Group L also contains the recently described
tobacco gene product forming the glucose ester of benzoic acid and
salicylic acid (18). These data suggest that the formation of glucose
esters may have evolved from a deep ancestral branch recognizing
carboxyl groups of the aglycones. From data currently available,
biochemical analyses indicate that two UGTs from petunia and
Brassica napus (15, 43) that are also located within group L
form glucosides. However, phylogenetic analysis of their sequences
shows that they are of relatively recent origin compared with the UGTs
involved in glucose ester formation. This is further supported by the
comparatively recent evolution of the glucosinolate synthesis pathway,
which is restricted only to plants in some families in the order of Capparalle (49).
In conclusion, this study indicates that in the Arabidopsis
genome, the number of sequences containing the signature characteristic of UGTs is extremely high. The phylogenetic analysis, defining 12 distinct evolutionary groups, provides a useful new foundation for
understanding the structure-function relatedness of the UGT family
members and a new framework for exploring and modifying their substrate specificities.
INTRODUCTION
TOP
ABSTRACT
INTRODUCTION
EXPERIMENTAL PROCEDURES
RESULTS AND DISCUSSION
REFERENCES
EXPERIMENTAL PROCEDURES
TOP
ABSTRACT
INTRODUCTION
EXPERIMENTAL PROCEDURES
RESULTS AND DISCUSSION
REFERENCES
RESULTS AND DISCUSSION
TOP
ABSTRACT
INTRODUCTION
EXPERIMENTAL PROCEDURES
RESULTS AND DISCUSSION
REFERENCES
View larger version (32K):
[in a new window]
Fig. 1.
Phylogenetic analysis of the
Arabidopsis UGT superfamily shows 12 distinct
groups. A, the tree shown was derived by
neighbor-joining distance analysis of nine conservative motifs
described in Fig. S1. Bootstrap values over 50% are indicated
above the nodes, with the number on the
left for the neighbor joining and right for
parsimony. Bootstrap values in brackets were derived by
analysis excluding the two long-branch sequences 78D1 and 83A1.
Triangles indicate subtrees that were subjected to further
refinement. The lengths of triangles are drawn
roughly proportional to the overall branch length of the whole group.
B, relationships among sequences within triangles
were further refined using additional amino acid positions shared
within each group. Hypothetical intron gains and losses are indicated
by diamonds followed by intron number (see Fig. 3).
Postulated intron gains are indicated by filled
diamonds, intron losses by unfilled
diamonds, and the questionable intron loss by
striped diamonds.
View larger version (21K):
[in a new window]
Fig. 2.
Deduced chromosomal positions of
Arabidopsis UGT genes. The positions are given
according to the nearest recombinant inbred markers. Genetic
distances in centimorgans (cM) are according to the Lister
and Dean recombinant inbred map.
View larger version (88K):
[in a new window]
Fig. 3.
Distribution of introns among 37 UGT genes of
Arabidopsis. The introns are mapped and numbered
to the alignment of their amino acid sequences. The nine conserved
motifs are shown as shadow rectangles and aligned. Rectangles with
broken lines represent regions with a variable number of amino acid
residues. Inverted triangles indicate positions of introns that are
found or predicted in the corresponding genes. Phase 0 introns are
indicated by open inverted triangles; phase 1 introns by solid inverted
triangles and phase 2 introns by shaded inverted triangles.
Substrate specificity of UGT enzymes from other plant species
View larger version (25K):
[in a new window]
Fig. 4.
A composite tree of plant UGT sequences
indicates the evolutionary relationships. Branch positions of 17 additional UGTs from plant species other than Arabidopsis
were determined by neighbor-joining analysis of nine conserved
motifs together with all 88 Arabidopsis UGT sequences. The
relative positions of these 17 sequences (Table I) were then
superimposed onto the tree shown in Fig. 1 as indicated by broken
lines. Major groups identified in Fig. 1 are indicated in
brackets.
![]() |
ACKNOWLEDGEMENTS |
---|
We thank the Arabidopsis Biological Resource Center for providing all expressed sequence tag clones. We also thank Dr. Joe Ross for critical reading of the manuscript and helpful discussions.
![]() |
Note Added in Proof |
---|
An additional 18 complete UGT sequences have been identified in Arabidopsis genome data base subsequent to the submission of this manuscript. These do not change the composition of the groups defined in this manuscript, and they add an additional two groups to the tree.
![]() |
FOOTNOTES |
---|
* Financial support of this work was provided by Biotechnology and Biological Sciences Research Council grant 87/97 8855 to D. J. B.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The on-line version of this article (available at
http://www.jbc.org) contains supplementary material including
additional details of the Arabidopsis UGTs analyzed in this
study (Table S1), corrections to the data base annotations of UGT
sequences (Table S2), and the complete amino acid sequence alignment of 88 Arabidopsis UGTs (Fig. S1).
To whom correspondence should be addressed. Tel.: 44-1904-434334;
Fax: 44-1904-434336; E-mail: djb32@york.ac.uk.
Published, JBC Papers in Press, October 20, 2000, DOI 10.1074/jbc.M007447200
2 In the UGT nomenclature system, a gene name includes (a) UGT, defining a putative UDP-dependent glycosyltransferase; (b) an Arabic number from 71 to 100, which designates a UGT family of plant origin, the same number being used for sequences with >45% sequence identity; (c) a letter, representing a subfamily whose members share >60% identity; and (d) a number, corresponding to the individual gene. The letter "P" after the gene number is used to denote a pseudogene. For clarity, the prefix UGT is omitted throughout this paper.
![]() |
ABBREVIATIONS |
---|
The abbreviations used are: UGT, UDP-glycosyltransferase; ORF, open reading frame; PCR, polymerase chain reaction.
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
1. | Campbell, J. A., Davies, G. J., Bulone, V., and Henrissat, B. (1997) Biochem. J. 326, 929-942[Medline] [Order article via Infotrieve] |
2. | Mackenzie, P. I., Owens, I. S., Burchell, B., Bock, K. W., Bairoch, A., Belanger, A., Fournel-Gigleux, S., Green, M., Hum, D. W., Iyanagi, T., Lancet, D., Louisot, P., Magdalou, J., Chowdhury, J. R., Ritter, J. K., Schachter, H., Tephly, T. R., Tipton, K. F., and Nebert, D. W. (1997) Pharmacogenetics 7, 255-269[Medline] [Order article via Infotrieve] |
3. | de Wildt, S. N., Kearns, G. L., Leeder, J. S., and van den Anker, J. N. (1999) Clin. Pharmacokinet. 36, 439-452[Medline] [Order article via Infotrieve] |
4. | Nebert, D. W. (1994) Biochem. Pharmacol. 47, 25-37[CrossRef][Medline] [Order article via Infotrieve] |
5. | Mock, H., and Strack, D. (1993) Phytochemistry 32, 575-579[CrossRef] |
6. | Sembdner, G., Atzorn, R., and Schneider, G. (1994) Plant Mol. Biol. 26, 1459-1481[Medline] [Order article via Infotrieve] |
7. | Kleckowski, K., and Schell, J. (1995) Crit. Rev. Plant Sci. 14, 283-298 |
8. | Hostel, W. (1981) The Biochemistry of Plants , Vol. 7 , pp. 725-753, Academic Press, Inc., New York |
9. | Szerszen, J. B., Szczyglowski, K., and Bandurski, R. S. (1994) Science 265, 1699-1701[Medline] [Order article via Infotrieve] |
10. | Tanaka, Y., Yonekura, K., Fukuchi-Mizutani, M., Fukui, Y., Fujiwara, H., Ashikari, T., and Kusumi, T. (1996) Plant Cell Physiol. 37, 711-716[Medline] [Order article via Infotrieve] |
11. | Moehs, C. P., Allen, P. V., Friedman, M., and Belknap, W. R. (1997) Plant J. 11, 227-236[CrossRef][Medline] [Order article via Infotrieve] |
12. |
Ford, C. M.,
Boss, P. K.,
and Høj, P. B.
(1998)
J. Biol. Chem.
273,
9224-9233 |
13. | Fraissinet-Tachet, L., Baltz, R., Chong, J., Kauuffmann, S., Fritig, B., and Saindrenan, P. (1998) FEBS Lett. 437, 319-323[CrossRef][Medline] [Order article via Infotrieve] |
14. | Vogt, T., Grimm, R., and Strack, D. (1999) Plant J. 19, 509-519[CrossRef][Medline] [Order article via Infotrieve] |
15. |
Yamazaki, M.,
Gong, Z.,
Fukuchi-Mizutani, M.,
Fukui, Y.,
Tanaka, Y.,
Kusumi, T.,
and Saito, K.
(1999)
J. Biol. Chem.
274,
7405-7411 |
16. |
Miller, K. D.,
Guyon, V.,
Evans, J. N. S.,
Shuttleworth, W. A.,
and Taylor, L. P.
(1999)
J. Biol. Chem.
274,
34011-34019 |
17. |
Jones, P. R.,
Møller, B. L.,
and Høj, P. B.
(1999)
J. Biol. Chem.
274,
35483-35491 |
18. |
Lee, H.,
and Raskin, I.
(1999)
J. Biol. Chem.
274,
36637-36642 |
19. |
Martin, R. C.,
Mok, M. C.,
and Mok, D. W. S.
(1999)
Proc. Natl. Acad. Sci. U. S. A.
96,
284-289 |
20. |
Martin, R. C.,
Mok, M. C.,
and Mok, D. W. S.
(1999)
Plant Physiol.
120,
553-557 |
21. |
Lim, E.-K.,
Li, Y.,
Parr, A.,
Jackson, R.,
Ashford, D. A.,
and Bowles, D. J.
(2001)
J. Biol. Chem.
276,
4344-4349 |
22. |
Jackson, R. G.,
Lim, E.-K.,
Li, Y.,
Kowalczyk, M.,
Sandberg, G.,
Hoggett, J.,
Ashford, D. A.,
and Bowles, D. J.
(2001)
J. Biol. Chem.
276,
4350-4356 |
23. | Truesdale, M. R., Doherty, H. M., Loake, G. J., McPherson, M. J., Roberts, M. R., and Bowles, D. J. (1996) Plant Physiol. 112, 446 |
24. | Sambrook, J., Fritsch, E. F., and Maniatis, T. (1989) Molecular Cloning: A Laboratory Manual , 2nd Ed. , Cold Spring Harbor Laboratory, Cold Spring Harbor, NY |
25. | Thompson, J. D., Higgins, D. G., and Gibson, T. J. (1994) Nucleic Acids Res. 22, 4673-4680[Abstract] |
26. | Mackenzie, P. I. (1990) Frontiers in Biotransformation , Vol. 2 , pp. 211-243, Akademie-Verlag, Berlin |
27. | Hughes, J., and Hughes, M. A. (1994) DNA Sequence 5, 41-49[Medline] [Order article via Infotrieve] |
28. | O'Donnel, P. J., Truesdale, M. R., Calvert, C. M., Dorans, A., Roberts, M. R., and Bowles, D. J. (1998) Plant J. 14, 137-142[CrossRef] |
29. | Radominska-Pandya, A., Czernik, P. J., Little, J. M., Battaglia, E., and Mackenzie, P. I. (1999) Drug Metab. Rev. 31, 817-899[CrossRef][Medline] [Order article via Infotrieve] |
30. | Nilsson, T., Jackson, M., and Peterson, P. A. (1989) Cell 58, 707-718[Medline] [Order article via Infotrieve] |
31. | Jackson, M. R., Nilsson, T., and Peterson, P. A. (1990) EMBO J. 9, 3153-3162[Abstract] |
32. | Shin, J., Dunbrack, R. L., Lee, S., and Strominger, J. L. (1991) Proc. Natl. Acad. Sci. U. S. A. 88, 1918-1922[Abstract] |
33. | Yokota, H., Yuasa, A., and Sato, R. (1992) J. Biochem. (Tokyo) 112, 192-196[Abstract] |
34. | Meech, R., Yogalingam, G., and Mackenzie, P. I. (1996) DNA Cell Biol. 15, 489-494[Medline] [Order article via Infotrieve] |
35. | Mackenzie, P. I., and Owens, I. S. (1984) Biochem. Cell Biol. Commun. 122, 1441-1449 |
36. | Baldauf, S. L., and Parmer, J. D. (1993) Proc. Natl. Acad. Sci. U. S. A. 90, 11558-11562[Abstract] |
37. | Kranz, H. D., Denekamp, M., Greco, R., Jin, H., Leyva, A., Meissner, R. C., Petroni, K., Urzainqui, A., Bevan, M., Martin, C., Smeekens, S., Tonelli, C., Paz-Ares, J., and Weisshaar, B. (1999) Plant J. 16, 263-276[CrossRef] |
38. | Edwards, R., Dixon, D. P., and Walbot, V. (2000) Trends Plant Sci. 5, 193-198[CrossRef][Medline] [Order article via Infotrieve] |
39. | Rogers, J. H. (1990) FEBS Lett. 268, 339-343[CrossRef][Medline] [Order article via Infotrieve] |
40. | Cavalier-Smith, T. (1991) Trends Genet. 7, 145-148[Medline] [Order article via Infotrieve] |
41. | Patthy, L. (1991) Bioessays 13, 187-192[Medline] [Order article via Infotrieve] |
42. | Palmer, J. D., and Logsdon, J. M. (1991) Curr. Opin. Genet. Dev. 1, 470-477[Medline] [Order article via Infotrieve] |
43. | van Audenhove, K., Marillia, E., Peferoen, M., Grootwassink, J. W., Reed, D. W., Hemmingsen, S. M., Kolenovsky, A. D., MacPherson, J. M., and Underhill, E. W. (May 9, 1997) Patent WO 9716559-A 34, Plant Genetic Systems NV(BE) |
44. | Fedoroff, N., Furtek, B., and Nelson, O. E. (1984) Proc. Natl. Acad. Sci. U. S. A. 81, 3825-3829[Abstract] |
45. | Furtek, B., Schiefelbein, J. W., Johnston, F., and Nelson, O. E. (1988) Plant Mol. Biol. 11, 473-481 |
46. | Kroon, J., Souer, E., de Graaff, A., Xue, Y., Mol, J., and Koes, R. (1994) Plant J. 5, 69-80[CrossRef][Medline] [Order article via Infotrieve] |
47. | Brugliera, F., Holton, T. A., Stevenson, T. W., Farcy, E., Lu, C., and Cornish, E. C. (1994) Plant J. 5, 81-92[CrossRef][Medline] [Order article via Infotrieve] |
48. | Bak, S., Nielsen, H. L., and Halkier, B. A. (1998) Plant Mol. Biol. 38, 725-734[CrossRef][Medline] [Order article via Infotrieve] |
49. | Halkier, B. A. (1999) Naturally Occurring Glycosides , pp. 193-223, John Wiley & Sons, Chichester, UK |