TAC1, a major quantitative trait locus controlling tiller angle in rice

Area of Science:

• Plant Genetics
• Crop Science
• Molecular Biology

Background:

• Dense planting in rice (Oryza sativa) cultivation requires efficient plant architecture.
• Tiller angle significantly impacts leaf shading and photosynthesis efficiency.
• The genetic basis for tiller angle control in rice was previously unknown.

Purpose of the Study:

• To identify the molecular basis controlling tiller angle in rice.
• To understand the genetic factors influencing plant architecture for dense planting.

Main Methods:

• Quantitative trait locus (QTL) mapping using an F(2) population from indica (IR24) and japonica (IL55) rice crosses.
• Genetic complementation to identify the TAC1 gene.
• Sequence verification of the TAC1 gene and its regulatory regions in various rice accessions.

Main Results:

• A major quantitative trait locus, Tiller Angle Control 1 (TAC1), was mapped to chromosome 9.
• A mutation in the 3'-splicing site of a 1.5-kb intron in TAC1 ('AGGA' to 'GGGA') results in decreased tac1 levels.
• This mutation leads to a compact plant architecture with a near-zero tiller angle, observed in japonica rice varieties.

Conclusions:

• Tiller Angle Control 1 (TAC1) is a key gene regulating tiller angle in rice.
• A specific intronic mutation in TAC1 is responsible for the compact plant architecture in japonica rice.
• This mutation has been widely selected in japonica rice for cultivation in dense planting environments.