The Rice E3 Ubiquitin Ligase Gene OsPUB77 Regulates Head Milled Rice Rate by Affecting Grain Starch Accumulation

Area of Science:

• Plant genetics
• Molecular biology
• Agricultural science

Background:

• Head milled rice rate (HMRR) is crucial for rice yield and economic value.
• The genetic underpinnings of HMRR are not well understood, limiting breeding efforts.

Purpose of the Study:

• To identify the genetic factors controlling HMRR in rice.
• To elucidate the molecular mechanism regulating starch accumulation and grain quality.

Main Methods:

• Genome-wide association study (GWAS) across multiple environments.
• Gene knockout and overexpression in transgenic rice lines.
• Promoter binding assays and transcriptomic analysis.

Main Results:

• A major quantitative trait locus (QTL), qHMRR4-2, was identified, pinpointing OsPUB77 (a U-box E3 ubiquitin ligase) as the causal gene.
• Both OsPUB77 knockout and overexpression significantly reduced HMRR by disrupting starch synthesis and increasing grain chalkiness.
• OsMADS29 was found to directly bind and repress the OsPUB77 promoter, indicating a regulatory role.

Conclusions:

• The OsMADS29-OsPUB77 regulatory module is critical for controlling HMRR and grain quality in rice.
• OsPUB77 plays a vital role in maintaining metabolic homeostasis for starch biosynthesis during grain filling.
• This study provides a valuable genetic resource and target for improving rice milling quality via precision breeding.