OsMPH1 regulates plant height and improves grain yield in rice

Abstract

Plant height is a major trait affecting yield potential in rice. Using a large-scale hybrid transcription factor approach, we identified the novel MYB-like transcription factor OsMPH1 (MYB-like gene of Plant Height 1), which is involved in the regulation of plant height in rice. Overexpression of OsMPH1 leads to increases of plant height and grain yield in rice, while knockdown of OsMPH1 leads to the opposite phenotypes. Microscopy of longitudinal stem sections indicated that a change in internode cell length resulted in the change in plant height. RNA sequencing (RNA-seq) analysis of transgenic rice lines showed that multiple genes related to cell elongation and cell wall synthesis, which are associated with plant height and yield phenotypes, exhibited an altered expression profile. These results imply that OsMPH1 might be involved in specific recognition and signal transduction processes related to plant height and yield formation, providing further insights into the mechanisms underlying the regulation of plant height and providing a candidate gene for the efficient improvement of rice yield.

Fig 1. Phenotypic analysis of OsMPH1V- and OsMPH1E-overexpressing plants.

A Gross morphology of WT, OsMPH1V and OsMPH1E. Bars = 20 cm. B Comparison of plant height between WT, OsMPH1V and OsMPH1E transgenic rice. Data are shown as the means ± s.d. (Student’s t tests, **P < 0.01, n = 60). C Internode morphology of WT, OsMPH1V and OsMPH1E. Bars = 5 cm. D Schematic representation and comparison of the various elongation patterns of internodes in WT, OsMPH1V and OsMPH1E transgenic rice. Data are shown as mean as the means ± s.d. (Student’s t tests, **P < 0.01, n = 10).

Fig 2. Phenotypic analysis of OsMPH1-overexpressing plants.

A Gross morphology of WT and OsMPH1-OX. Bars = 20 cm.B Comparison of plant height between WT and OsMPH1 transgenic rice. Data are shown as the means ± s.d. (Student’s t tests, **P < 0.01, n = 60). C Internode morphology of WT and OsMPH1-OX. Bars = 5 cm. D Schematic representation and comparison of the various elongation patterns of internodes in WT and OsMPH1-OX transgenic rice. Data are shown as the means ± s.d. (Student’s t tests, **P < 0.01, n = 10).

Fig 3. Histological observations of OsMPH1V and OsMPH1E internodes.

A Longitudinal section of the first internode from OsMPH1V and OsMPH1E in the heading stage. Bars = 100 μm. B Statistical analysis of internode cell length in OsMPH1V and OsMPH1E. Data are shown as the means ± s.d. (Student’s t tests, **P < 0.01, n = 10).

Fig 4. Analysis of plant height and heading dates in OsMPH1V, OsMPH1E and OsMPH1-OX plants.

A,B Panicle morphology of WT, OsMPH1V, OsMPH1E and OsMPH1-OX transgenic rice C,D Comparison of panicle length between WT, OsMPH1V, OsMPH1E and OsMPH1-OX transgenic rice. Data are shown as the means ± s.d. (Student’s t tests, **P < 0.01, n = 60). E,F Morphology of WT, OsMPH1V, OsMPH1E and OsMPH1-OX transgenic rice on the heading date G,H Comparison of heading dates between WT, OsMPH1V, OsMPH1E and OsMPH1-OX transgenic rice. Data are shown as the means ± s.d. (Student’s t tests, **P < 0.01, n = 60).

Fig 5. Analysis of yield traits in OsMPH1V and OsMPH1E plants.

A-G Comparison of the number of primary branches per panicle, grains per primary branch, secondary branches per panicle, grains per secondary branch, grains per plant, tillers per plant, grain weight per plot and plant height between WT, OsMPH1V and OsMPH1E transgenic rice. Data are shown as the means ± s.d. (Student’s t tests, *P < 0.05, **P < 0.01, n = 60).

Fig 6. OsMPH1 encodes a MYB family protein.

A Phylogenetic tree analysis of the OsMPH1 protein and its rice and Arabidopsis homologues. B Amino acid alignment of the OsMPH1 protein and its Arabidopsis and rice homologues. Conserved amino acids are highlighted in black. C Subcellular localization of OsMPH1. The OsMPH1-YFP fusion proteins were located at the plasma membrane and in the nucleus. YFP was used as a control. The AHL-RFP fusion protein was used as a nuclear marker. Bars = 10 μm.

Fig 7. Analysis of the OsMPH1 expression pattern in rice.

A-H OsMPH1 expression revealed by GUS staining in OsMPH1 promoter-GUS transgenic plants. A Germinated seed (2 day); B leaf, C root; D sheath; E shoot; F stem node; G pulvinus; H spike. I Expression pattern analysis of OsMPH1 in various vegetative organs via quantitative RT-PCR. Data are shown as the means ± s.d. (n = 3).

Fig 8. Transcription activation analysis of OsMPH1 in the yeast GAL4 system.

Each transformed yeast strain was dropped onto SD/-W and SD/-W-H-Ade plates and allowed to grow for 48 hours before taking photographs. β-galactosidase activity was quantified through a liquid culture assay using CPRG as the substrate. Data are shown as the means ± s.d. (Student’s t tests, **P < 0.01, n = 3).

Fig 9. Identification of OsMPH1-regulated genes through RNA-seq analysis.

A Type one Venn diagram showing the overlapping profile of up-regulated genes in the OsMPH1V transgenic line and down-regulated genes in the OsMPH1E line in comparison with the WT, as determined via RNA-seq; Type two Venn diagram showing the overlapping profile of down-regulated genes in the OsMPH1V transgenic line and up-regulated genes in the OsMPH1E line in comparison with the WT, as determined via RNA-seq. B, Type one and Type two gene function categories.