qHD5 encodes an AP2 factor that suppresses rice heading by down-regulating Ehd2 expression.

Area of Science:

• Plant genetics
• Molecular biology
• Crop science

Background:

• Heading date is critical for rice reproduction and cultivation range.
• Previous work identified LOC_Os05g03040 as a candidate gene for qHD5, a major heading date QTL.
• Understanding heading date regulation is key for crop improvement.

Purpose of the Study:

• To functionally verify LOC_Os05g03040 as the causal gene for qHD5.
• To elucidate the molecular mechanism by which qHD5 affects heading date.
• To investigate the evolutionary role of qHD5 in rice domestication.

Main Methods:

• Genetic complementation using near-isogenic lines (NILs).
• CRISPR/Cas9 gene editing to create knockout mutants.
• Subcellular localization and transactivation assays.
• Quantitative real-time PCR (qRT-PCR) to analyze gene expression.

Main Results:

• LOC_Os05g03040 (qHD5) was confirmed to repress heading date in rice.
• Both qHD5^XLJ and qHD5^BG1 alleles are functional and semi-dominant.
• Knockout mutants exhibited earlier heading under various photoperiod conditions.
• qHD5 protein functions as a transcription factor in the nucleus, repressing Ehd2 expression.

Conclusions:

• qHD5 acts as a negative regulator of rice heading date.
• The C-terminus of qHD5 is crucial for its self-activation.
• qHD5 likely played a role in indica rice domestication and adaptation.