Modulation of Rice Leaf Angle and Grain Size by Expressing OsBCL1 and OsBCL2 under the Control of OsBUL1 Promoter

Area of Science:

• Plant Biology
• Genetics
• Agronomy

Background:

• Leaf angle and grain size are crucial agronomic traits influencing rice productivity and crop architecture.
• OsBC1, a bHLH transcription factor, interacts with LO9-177 and OsBUL1 to regulate these traits.

Purpose of the Study:

• To functionally characterize two OsBC1 homologues, OsBCL1 and OsBCL2, in rice.
• To investigate their role in regulating cell elongation, leaf angle, and grain size.

Main Methods:

• Expression of OsBCL1 and OsBCL2 under the OsBUL1 promoter in rice.
• Analysis of phenotypic changes in transgenic rice, including leaf angle, grain size, and cell morphology.
• Measurement of gibberellin A3 (GA3) levels.
• Gene expression analysis to infer the mechanism of cell elongation.
• Functional validation in the dicot species Arabidopsis.

Main Results:

• Transgenic rice overexpressing OsBCL1 and OsBCL2 exhibited increased leaf angle and grain length.
• Elongated cells were observed in the lamina joint and grain hull of transgenic plants.
• GA3 levels were significantly higher in transgenic rice compared to wild type (WT).
• Evidence suggests cell elongation occurs via cell expansion rather than cell division.
• OsBCL1 and OsBCL2 demonstrated conserved function in Arabidopsis, promoting cell elongation.

Conclusions:

• OsBCL1 and OsBCL2 act as positive regulators of cell elongation in rice.
• Their function is at least partially mediated by increasing gibberellin biosynthesis.
• These genes contribute to modulating leaf inclination and grain size, offering potential targets for crop improvement.