Hd3a promotes lateral branching in rice.

Area of Science:

• Plant Biology
• Molecular Plant Physiology
• Developmental Biology

Background:

• FLOWERING LOCUS T (FT) protein, known as florigen, is a mobile floral signal.
• Rice Heading date 3a (Hd3a), an FT homolog, interacts with 14-3-3 proteins and OsFD1 to form a florigen activation complex (FAC).
• Florigen's roles in plant development beyond flowering are not fully understood, including its transport to organs outside the shoot apex and FAC requirement.

Purpose of the Study:

• To investigate the role of Hd3a protein in plant development beyond flowering.
• To determine if FT proteins are transported to organs outside the shoot apex.
• To ascertain if FAC formation is essential for processes other than flowering.

Main Methods:

• Analysis of transgenic plants expressing Hd3a.
• Investigating Hd3a protein accumulation in axillary meristems.
• Studying the requirement of FAC formation and transport for Hd3a function.

Main Results:

• Hd3a protein accumulates in axillary meristems, promoting branching through lateral bud outgrowth.
• Hd3a transport from the phloem to the axillary meristem is essential for branching.
• Mutant Hd3a proteins defective in FAC formation but transport-competent did not promote branching.
• Hd3a promotes branching independently of strigolactone and the FC1 transcription factor.

Conclusions:

• Hd3a functions as a mobile signal for promoting branching in rice.
• FAC formation is required for Hd3a-mediated branching.
• This study reveals a novel role for Hd3a in regulating plant architecture.