Abstract:
Inclination of leaf and plant height are important agronomic traits that are closely related to grain yields. Proteins involved in regulating free auxin (IAA) levels have a central role in modulating rice leaf angle and plant height. In this study, a rice mutant (named
lc
4) was found to have enlarged leaf angles and exhibit dwarfism compared to wild-type (WT) plants. Flanking analysis revealed that the mutation was caused by a T-DNA insertion at 270 bp upstream of the oxalate oxidase 2 (
OsOxO2
) ATG start codon. The insertion significantly increased the transcript levels of indole-3-acetic acid glucosyltransferase (
OsIAAGLU
),
OsOxO1
,
OsOxO2
and
OsOxO3
and OxO activity in
lc
4. Mutation of
OsIAAGLU
in
lc
4 led to partial restoration of the WT leaf angle and plant height phenotypes in
iaaglu
/
lc
4 which, however, still exhibited OxO activity comparable with that in
lc
4. On the other hand, mutation of
OsOxO2
in
lc
4 also resulted in restoration of the WT leaf angle and plant height phenotypes, accompanied by reduced OxO activity and transcripts of
OsIAAGLU
,
OsOxO1
,
OsOxO2
and
OsOxO3
. Nevertheless, overexpression of
OsIAAGLU
, but not
OsOxO2
in the WT background, resulted in the transgenic plants showing leaf angle and plant height similar to
lc
4. Overexpression of
OsOxO2
had no effect on the transcripts of
OsIAAGLU
,
OsOxO1
and
OsOxO3
. These results suggest that activation of
OsOxO2
and
OsIAAGLU
together resulted in altered plant architecture of
lc
4, while
OsIAAGLU
played a more direct role,
OsOxO2
might be involved in regulating
OsIAAGLU
,
OsOxO1
and
OsOxO3
in a chromosome position-dependent manner.