Abstract
Morphological and biochemical changes accompanying embryogenesis and seed development are crucial for plant survival and crop productivity. Here, we identified a novel
y
ellowish-pericarp
e
mbryo
l
ethal
(
yel
) mutant of the
japonica
rice cultivar Sindongjin (
Oryza sativa
L.), namely,
yel
-
sdj
. Seeds of the
yel
-
sdj
mutant showed a yellowish pericarp and black embryo, and were embryonic lethal. Compared with wild-type seeds, the
yel
-
sdj
mutant seeds exhibited significantly reduced grain size, grain weight, and embryo weight, and a remarkably lower rate of embryo retention in kernels subjected to milling. However, the volume of air space between embryo and endosperm, density of embryo, and total phenolic content (TPC) and antioxidant activity of mature grains were significantly higher in the
yel
-
sdj
mutant than in the wild type. Genetic analysis and mapping revealed that the
yel
-
sdj
mutant was non-allelic to the
oscop1
null mutants
yel
-
hc
,
yel
-
cc
, and
yel
-
sk
, and its phenotype was controlled by a single recessive gene,
LOC
_
Os01g01484
, an ortholog of
Arabidopsis thaliana DE-ETIOLATED 1
(
DET1
). The
yel
-
sdj
mutant carried a 7 bp deletion in the second exon of
OsDET1
. Seeds of the
osdet1
knockout mutant, generated
via
CRISPR/Cas9-based gene editing, displayed the
yel
mutant phenotype. Consistent with the fact that OsDET1 interacts with CONSTITUTIVE PHOTOMORPHOGENIC 10 (OsCOP10) and UV-DAMAGED DNA BINDING PROTEIN 1 (OsDDB1) to form the COP10-DET1-DDB1 (CDD), seeds of
oscop10
and
osddb1
knockout mutants also showed the
yel
phenotype. These findings will enhance our understanding of the functional roles of
OsDET1
and the CDD complex in embryogenesis and flavonoid biosynthesis in rice seeds.