TIP2-UDT1-OsUPEX1/2 module regulates tapetum development and function in rice.

Area of Science:

• Plant reproductive biology
• Molecular genetics
• Agricultural science

Background:

• The tapetum, a vital anther wall layer, is crucial for plant fertility and pollen development.
• Tapetal development is orchestrated by transcription factors and signaling pathways, with UDT1, TIP2, TDR, and EAT1 forming a known cascade in rice.

Purpose of the Study:

• To elucidate the largely unknown UDT1- and TIP2-dependent regulatory networks in early rice anther development.
• To identify downstream targets of TIP2 and UDT1 essential for tapetum function and male fertility.

Main Methods:

• Functional analysis using knockout mutants.
• Spatial-temporal expression analysis of key genes.
• Investigation of protein-protein interactions (heterodimerization).

Main Results:

• TIP2 and UDT1 exhibit overlapping expression in the middle layer and tapetum, with TIP2 acting epistatically to UDT1.
• TIP2 and UDT1 heterodimerize to activate downstream genes, including OsUPEX1 and OsUPEX2, which encode galactosyltransferases.
• OsUPEX1 and OsUPEX2 are functionally redundant and critical for tapetum development, function, and secretion.

Conclusions:

• TIP2 and UDT1 play essential roles in early rice anther development through heterodimerization and activation of downstream targets.
• OsUPEX1 and OsUPEX2 are identified as key downstream effectors of the TIP2-UDT1 pathway, vital for tapetum function and rice male fertility.