Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 42 (12), 858-868

Chromatin Interacting Factor OsVIL2 Is Required for Outgrowth of Axillary Buds in Rice

Affiliations

Chromatin Interacting Factor OsVIL2 Is Required for Outgrowth of Axillary Buds in Rice

Jinmi Yoon et al. Mol Cells.

Abstract

Shoot branching is an essential agronomic trait that impacts on plant architecture and yield. Shoot branching is determined by two independent steps: axillary meristem formation and axillary bud outgrowth. Although several genes and regulatory mechanism have been studied with respect to shoot branching, the roles of chromatin-remodeling factors in the developmental process have not been reported in rice. We previously identified a chromatin-remodeling factor OsVIL2 that controls the trimethylation of histone H3 lysine 27 (H3K27me3) at target genes. In this study, we report that loss-of-function mutants in OsVIL2 showed a phenotype of reduced tiller number in rice. The reduction was due to a defect in axillary bud (tiller) outgrowth rather than axillary meristem initiation. Analysis of the expression patterns of the tiller-related genes revealed that expression of OsTB1, which is a negative regulator of bud outgrowth, was increased in osvil2 mutants. Chromatin immunoprecipitation assays showed that OsVIL2 binds to the promoter region of OsTB1 chromatin in wild-type rice, but the binding was not observed in osvil2 mutants. Tiller number of double mutant osvil2 ostb1 was similar to that of ostb1, suggesting that osvil2 is epistatic to ostb1. These observations indicate that OsVIL2 suppresses OsTB1 expression by chromatin modification, thereby inducing bud outgrowth.

Keywords: bud outgrowth; chromatin modification; rice.

Conflict of interest statement

Disclosure

The authors have no potential conflicts of interest to disclose.

Figures

Fig. 1
Fig. 1. Flowering time and tiller phenotypes of WT and osvil2 mutants
(A) Days to heading in WT, osvil2-1 and osvil2-2 mutants under long-day condition (14-h light/10-h dark). The date at which the first panicles emerged were scored as the number of DAG to heading date. Error bars are SD (n = 6). (B) Number of tiller at different developmental stages. Error bars are SD (n = 6). (C–F) Tiller production by the WT and the osvil2 mutant was monitored at 14 DAG (C), 21 DAG (D), 42 DAG (E), and 77 DAG (F). Arrowhead indicates a tiller. Scale bars = 1 cm (C and D) or 10 cm (E and F). Error bars are SD (n = 10). Statistical significance is indicated by *P < 0.05 and ***P < 0.001.
Fig. 2
Fig. 2. Axillary bud development in the WT and the vil2 mutant
(A and B) Longitudinal sections of the basal parts of rice seedlings in the WT (A) and the osvil2-1 mutant (B) at 14 DAG. (C and D) Longitudinal sections of the basal parts of rice seedlings in the WT (C) and the osvil2-1 mutant (D) at 28 DAG. Scale bars = 500 μm. Red arrows indicate axillary bud AM. Black arrow indicates SAM.
Fig. 3
Fig. 3. Expression patterns of OsVIL2 in the basal parts at seedling stages
(A) Expression patterns of OsVIL2 promoter-GUS transgenic plants in the basal region of rice seedlings at 24 DAG. Arrowheads indicate axillary buds. Scale bars = 0.5 cm. (B and C) In situ RNA hybridization of OsVIL2 in the basal parts of WT seedlings at 20 DAG. Scale bars = 500 μm. (D) Control experiment with a sense probe of OsVIL2. Scale bars = 500 μm. (E and F) Enlarged images of shoot apical region (E) and axillary bud region (F). Scale bars = 100 μm. Black arrows indicate SAM and red arrows indicate axillary buds.
Fig. 4
Fig. 4. Expression levels of genes that control tiller development at 28 DAG
(A) Transcript levels of OsVIL2 in WT and osvil2-1 mutant plants. (B–F) Transcript levels of axillary bud formation genes: OSH1 (B), LAX1 (C), MOC1 (D), CUC1 (E), and RFL (F). (G–R) Transcript levels of axillary bud outgrowth genes: IAA7 (G), IAA20 (H), OsPIN1 (I), OsPIN3 (J), OsCKX2 (K), D10 (L), D27 (M), HTD1 (N), D3 (O), D14 (P), OsMADS57 (Q), and OsTB1 (R). Error bars are SD (n = 4). Statistical significance is indicated by *P < 0.05 and ***P < 0.001.
Fig. 5
Fig. 5. Temporal expression patterns of OsVIL2 and OsTB1
Expression levels of OsVIL2 (A) and OsTB1 (B) in the basal regions of WT and osvil2 rice seedlings between 12 and 32 DAG. Error bars are SD (n = 4). Statistical significance is indicated by *P < 0.05.
Fig. 6
Fig. 6. Chromatin immunoprecipitation assay
(A) Genome structure of OsTB1. (B) Genome structure of OsTB1. (C) Analysis of H3K27me3 level on OsTB1 chromatin in WT (white) and osvil2-1 mutant (gray). (D) Analysis of H3K27me3 level on Hd3a chromatin in WT (white) and osvil2-1 mutant (gray) using antibodies against H3K27me3. (E) Analysis of H3K27me3 level on OsTB1 chromatin in WT (white) and osvil2-2 mutant (gray). (F) Analysis of H3K27me3 level on Hd3a chromatin in WT (white) and osvil2-2 mutant (gray) using antibodies against H3K27me3. (G) ChIP analysis of OsVIL2 enrichment on OsTB1 chromatin. OsVIL2-Myc epitope-tagged transgenic lines were used to detect the enrichment. As a control, we used transgenic plants expressing Myc alone. (H) ChIP analysis of OsVIL2 enrichment on Hd3a chromatin. Plants were sampled at 28 DAG for the ChIP assay. For normalization, we used the fold enrichment method. Error bars are SD (n = 2). Statistical significance is indicated by *P < 0.05.
Fig. 7
Fig. 7. Analysis of vil2 tb1 double mutant
(A) Schematic diagrams of OsTB1 (left) and OsVIL2 (right) genes. The positions of mutation target sites are indicated with arrows. (B) Schematic diagram of the polycistronic tRNA-gRNA (PTG)/Cas9 vector for targeting multiple sites. The synthetic PTG consists of tandemly arrayed tRNA-gRNA units. (C) Mutated sites in OsTB1. Target sequences are indicated in red. Deleted sequences are indicated by =. (D) Mutated sites in OsVIL2. Target sequences are indicated in red. Deleted sequences are indicated by =. (E) Tiller phenotypes of osvil2-1, ostb1, and osvil2 ostb1 double mutants. As a control, we generated transgenic plants with pRGEB32 empty vector. Phenotypes were observed immediately before heading stages. Scale bars = 10 cm. (F) Number of tiller in control, osvil2-1, ostb1, and osvil2 ostb1 double mutant. Error bars are SD (n = 6).

Similar articles

See all similar articles

References

    1. Arite T., Iwata H., Ohshima K., Maekawa M., Nakajima M., Kojima M., Sakakibara H., Kyozuka J. DWARF10, an RMS1/MAX4/DAD1 ortholog, controls lateral bud outgrowth in rice. Plant J. 2007;51:1019–1029. doi: 10.1111/j.1365-313X.2007.03210.x. - DOI - PubMed
    1. Bemer M., Grossniklaus U. Dynamic regulation of Polycomb groub activity during plant development. Curr Opin Plant Biol. 2012;15:523–529. doi: 10.1016/j.pbi.2012.09.006. - DOI - PubMed
    1. Chen Y., Fan X., Song W., Zhang Y., Xu G. Over-expression of OsPIN2 leads to increased tiller numbers, angle and shorter plant height through suppression of OsLAZY1. Plant Biotechnol J. 2012;10:139–149. doi: 10.1111/j.1467-7652.2011.00637.x. - DOI - PubMed
    1. Cho L.H., Pasriga R., Yoon J., Jeon J.S., An G. Roles of sugars in controlling flowering time. J Plant Biol. 2018a;61:121–113. doi: 10.1007/s12374-018-0081-z. - DOI
    1. Cho L.H., Yoon J., Pasriga R., An G. Homodimerization of Ehd1 is required to induce flowering in rice. Plant Physiol. 2016;170:2159–2171. doi: 10.1104/pp.15.01723. - DOI - PMC - PubMed
Feedback