The miR159 is a conserved microRNA (miRNA) among different plant species and
has various development functions in plants. In rice, studies on miR159 were
focused upon responses to nitrogen forms and abiotic stresses. The team of
Yafan Zhao and Huili Wen from Henan Agricultural University aim to study the
function of miR159 using Short Tandem Target Mimic (STTM), an effective tool
to block the activity of endogenous mature miRNA activity in plants.

The expression of miR159 was successfully suppressed by STTM, resulting in
the increased expressions of its two target genes, OsGAMYB and OsGAMYBL1.
The STTM159 plants exhibited short stature with smaller organ sizes as well
as decreases in stem diameter, length of flag leaf, main panicle, spikelet
hulls and grain size. Analysis showed a reduction in the number of small
vascular bundles (SVB), and less cell numbers in the outer parenchyma.

Meanwhile, analysis of differentially expressed genes between wild type
plants and STTM159 transgenic plants showed that genes involved in cell
division, auxin, cytokinin and brassinosteroids biosynthesis and signaling
are significantly downregulated in STTM159 plants.

These data suggest that miR159 positively regulates organ size via the
promotion of cell division.

[bmcplantbiol.biomedcentral.com]