Biology Reference
In-Depth Information
Phylogenetic analyses indicate that
SBP
/
SPL
genes with miR156 target
sites can be grouped into five clades (
Guo et al., 2008; Salinas et al., 2012
).
The phenotypes of plants transformed with miR156-resistant forms of
these genes, as well as their loss-of-function phenotypes, suggest that they
regulate many different aspects of plant development. These include glume
architecture (
Wang et al., 2005
), inflorescence branching/bract develop-
ment (
Chuck, Whipple, Jackson, & Hake, 2010
), and ligule differentiation
(
Moreno, Harper, Krueger, Dellaporta, & Freeling, 1997
) in maize; panicle
(
Jiao et al., 2010; Miura et al., 2010
) and grain morphology (
Wang et al.,
2012
) in rice; fruit ripening in tomato (
Manning et al., 2006
); and leaf
initiation (
Martin et al., 2010; Wang et al., 2008
), embryo development
(
Nodine & Bartel, 2010
), pollen development (
Xing, Salinas, Hohmann,
Berndtgen, & Huijser, 2010
), and trichome (
Gan, Xia, Chen, & Wang,
2011
) and anthocyanin patterning (
Gou, Felippes, Liu, Weigel, & Wang,
2011
) in the inflorescence in
Arabidopsis
. Thus, SBP/SPL genes regulate a
variety of processes
in addition to those associated with vegetative
phase change.
The divergent functions of SPL genes are apparent from the phenotypes
of plants overexpressing these genes (
Cardon et al., 1997; Martin et al., 2010;
Usami et al., 2009; Wang et al., 2008; Wu et al., 2009; Wu & Poethig,
2006
). However, their normal functions have been difficult to establish
because of the high degree of functional redundancy within this family.
SPL8
(
Unte et al., 2003; Zhang, Schwarz, Saedler, & Huijser, 2007
),
SPL14
(
Stone, Liang, Nekl, & Stiers, 2005
), and
SPL9
are the only members
of this family in
Arabidopsis
that have a loss-of-function phenotype on their
own, and of these only
SPL9
is regulated by miR156.
SPL9
and
SPL15
are
members of the same clade.
spl9
mutations produce a slight increase in the
rate of leaf initiation and a very weak juvenilized phenotype, and
spl15
mutations are nearly wild type in appearance. However, plants mutant for
both genes have a prolonged juvenile phase, are late flowering, have an
increased number of branches, and an increased rate of leaf initiation
(
Schwarz, Grande, Bujdoso, Saedler, & Huijser, 2008; Wang et al.,
2008
).
spl9
and
spl15
also enhance the male sterility phenotype of
spl8
, dem-
onstrating that they act redundantly with this gene to promote pollen devel-
opment (
Xing et al., 2010
).
SPL2
,
SPL10
, and
SPL11
are also members of a
single clade in
Arabidopsis
.
spl2
mutations have no apparent loss-of-function
phenotype, but slightly enhance the delayed phase change phenotype of the
spl9 spl15
double mutant (
Schwarz et al., 2008
) and the male sterile pheno-
type of the
spl9 spl15 spl8
triple mutant (
Xing et al., 2010
).
SPL10
and
