A rice seed-specific glycine-rich protein OsDOR1 interacts with GID1 to repress GA signaling and regulates seed dormancy.

Seed dormancy is an important agronomic trait under the control of complex genetic and environmental interactions, which have not been yet comprehensively understood. From the field screening of rice mutant library generated by a Ds transposable element, we identified a pre-harvest sprouting (PHS) mutant dor1. This mutant has a single insertion of Ds element at the second exon of OsDOR1 (LOC_Os03g20770), which encodes a novel seed-specific glycine-rich protein. This gene successfully complemented the PHS phenotype of dor1 mutant and its ectopic expression enhanced seed dormancy. Here, we demonstrated that OsDOR1 protein binds to the GA receptor protein, OsGID1 in rice protoplasts, and interrupts with the formation OsGID1-OsSLR1 complex in yeast cells. Co-expression of OsDOR1 with OsGID1 in rice protoplasts attenuated the GA-dependent degradation of OsSLR1, the key repressor of GA signaling. We showed the endogenous OsSLR1 protein level in the dor1 mutant seeds is significantly lower than that of wild type. The dor1 mutant featured a hypersensitive GA-response of α-amylase gene expression during seed germination. Based on these findings, we suggest that OsDOR1 is a novel negative player of GA signaling operated in the maintenance of seed dormancy. Our findings provide a novel source of PHS resistance.

QTL Mapping of Tiller Number in Korean Japonica Rice Varieties.

Tiller number is an important trait associated with yield in rice. Tiller number in Korean japonica rice was analyzed under greenhouse conditions in 160 recombinant inbred lines (RILs) derived from a cross between the temperate japonica varieties Odae and Unbong40 to identify quantitative trait loci (QTLs). A genetic map comprising 239 kompetitive allele-specific PCR (KASP) and 57 cleaved amplified polymorphic sequence markers was constructed. qTN3, a major QTL for tiller number, was identified at 132.4 cm on chromosome 3. This QTL was also detected under field conditions in a backcross population; thus, qTN3 was stable across generations and environments. qTN3 co-located with QTLs associated with panicle number per plant and culm diameter, indicating it had pleiotropic effects. The qTN3 regions of Odae and Unbong40 differed in a known functional variant (4 bp TGTG insertion/deletion) in the 5' UTR of OsTB1, a gene underlying variation in tiller number and culm strength. Investigation of variation in genotype and tiller number revealed that varieties with the insertion genotype had lower tiller numbers than those with the reference genotype. A high-resolution melting marker was developed to enable efficient marker-assisted selection. The QTL qTN3 will therefore be useful in breeding programs developing japonica varieties with optimal tiller numbers for increased yield.

Low SP1 expression differentially affects intestinal-type compared with diffuse-type gastric adenocarcinoma.

Specificity protein 1 (SP1) is an essential transcription factor that regulates multiple cancer-related genes. Because aberrant expression of SP1 is related to cancer development and progression, we focused on SP1 expression in gastric carcinoma and its correlation with disease outcomes. Although patient survival decreased as SP1 expression increased (P<0.05) in diffuse-type gastric cancer, the lack of SP1 expression in intestinal-type gastric cancer was significantly correlated with poor survival (P<0.05). The knockdown of SP1 in a high SP1-expressing intestinal-type gastric cell line, MKN28, increased migration and invasion but decreased proliferation. Microarray data in SP1 siRNA-transfected MKN28 revealed that the genes inhibiting migration were downregulated, whereas the genes negatively facilitating proliferation were increased. However, both migration and invasion were decreased by forced SP1 expression in a low SP1-expressing intestinal-type gastric cell line, AGS. Unlike the intestinal-type, in a high SP1-expressing diffuse-type gastric cell line, SNU484, migration and invasion were decreased by SP1 siRNA. In contrast to previous studies that did not identify differences between the 2 histological types, our results reveal that low expression of SP1 is involved in cancer progression and metastasis and differentially affects intestinal-type compared with diffuse-type gastric adenocarcinoma.