Biology Reference
In-Depth Information
as well as woody plants, makes it possible to study the underlying molecular
mechanism of vegetative phase change across the plant kingdom.
4. miR156 AND miR157: MASTER REGULATORS
OF VEGETATIVE PHASE CHANGE
miR156 was initially discovered as a regulator of vegetative phase
change in
Arabidopsis
(
Wu & Poethig, 2006
) and maize (
Chuck, Cigan,
Saeteurn, & Hake, 2007
), and has since been shown to regulate this process
in a number of other herbaceous (
Fu et al., 2012; Salinas, Xing, Hohmann,
Berndtgen, &Huijser, 2012; Shikata, Yamaguchi, Sasaki, &Ohtsubo, 2012;
Xie et al., 2012; Xie, Wu, & Xiong, 2006; Zhang et al., 2011
) and woody
(
Wang et al., 2011
) species. miR156 is present in all land plants including
moss (
Axtell & Bowman, 2008
), where it has been implicated in the tran-
sition from the protonemal to the leafy gametophore stage of development
(
Cho, Coruh, & Axtell, 2012
). miR157 differs by three nucleotides
from miR156, but is frequently misannotated as miR156; it is therefore
difficult to determine its taxonomic distribution from the literature.
Sequence searches of various databases demonstrate that it is not present
in the moss
Physcomitrella patens
, but is present as a single nucleotide variant
in the lycopod
Selaginella moellendorffii
. It is also present in the gymnosperm
Taxus chinensis
(
Qiu et al., 2009
), in some monocots, and in most if not
all
eudicots (
www.mirbase.org
)
. The overexpression phenotype of miR157
is quite similar to that of miR156 (
Shikata, Koyama, Mitsuda, &
Ohme-Takagi, 2009; Shikata et al., 2012
), but its expression pattern and
function have not been as well characterized.
Evidence for the involvement of miR156 in vegetative phase change has
come primarily from the phenotype of plants overexpressing this miRNA.
Plants expressing miR156 under the regulation of a strong constitutive pro-
moter have a common phenotype consisting of a prolonged juvenile phase,
increased branching, accelerated leaf production, and delayed flowering.
This phenotype has been observed in
Arabidopsis
(
Schwab et al., 2005;
Shikata et al., 2009; Wang, Czech, & Weigel, 2009; Wang, Schwab,
Czech, Mica, &Weigel, 2008; Wu et al., 2009; Wu & Poethig, 2006
), maize
(
Chuck et al., 2007
), rice (
Xie et al., 2006
), switchgrass (
Chuck et al., 2011;
Fu et al., 2012
), poplar (
Wang et al., 2011
), tomato (
Zhang et al., 2011
), and
Torenia fournieri
(
Shikata et al., 2012
). In
Arabidopsis
, inactivation of miR156
with a target site mimic (
35S::MIM156
)(
Franco-Zorrilla et al., 2007;
Todesco, Rubio-Somoza, Paz-Ares, & Weigel, 2010; Wu et al., 2009
),
