Rice LecRK5 phosphorylates a UGPase to regulate callose biosynthesis during pollen development

Area of Science:

• Plant Biology
• Molecular Plant Science
• Reproductive Biology

Background:

• Callose deposition is crucial for male gametophyte development in flowering plants.
• Aberrant callose biosynthesis can cause microspore abortion and male sterility.
• The precise molecular mechanisms regulating callose synthesis pathways remain largely unelucidated.

Purpose of the Study:

• To investigate the role of OsLecRK5 in rice male gametophyte development and callose deposition.
• To elucidate the molecular function of OsLecRK5 in regulating callose biosynthesis.

Main Methods:

• Characterization of a rice male-sterile mutant (oslecrk5) with defective callose deposition.
• Analysis of OsLecRK5 protein localization and dimerization.
• In vitro phosphorylation assays to determine OsLecRK5's substrate and activity.

Main Results:

• The oslecrk5 mutant exhibited abnormal callose deposition during meiosis, leading to male sterility.
• OsLecRK5, a plasma membrane-localized receptor-like kinase, requires K-phosphorylation for function.
• OsLecRK5 directly phosphorylates and enhances the activity of the callose synthesis enzyme UGP1.

Conclusions:

• Plasma membrane-localized OsLecRK5 positively regulates callose biosynthesis by phosphorylating UGP1 in rice.
• This study provides the first evidence of a receptor-like kinase positively controlling callose biosynthesis.
• OsLecRK5 plays a critical role in ensuring normal anther and male gametophyte development through UGP1-mediated callose production.