The evening complex promotes maize flowering and adaptation to temperate regions

Area of Science:

• Plant Biology
• Genetics
• Circadian Rhythms

Background:

• Maize (Zea mays) adaptation to temperate climates requires reduced photoperiod sensitivity.
• Understanding the genetic basis of flowering time is crucial for crop improvement.

Purpose of the Study:

• To clone a quantitative trait locus (QTL) for flowering time in maize.
• To elucidate the role of ZmELF3.1 in the maize circadian clock and photoperiodic flowering.

Main Methods:

• Cloning of the ZmELF3.1 gene.
• Protein interaction studies to identify evening complex (EC) components.
• Analysis of loss-of-function mutants under different photoperiods.
• Gene expression analysis of flowering time regulators.

Main Results:

• ZmELF3.1, the ortholog of Arabidopsis thaliana EARLY FLOWERING3, was identified as the causal gene for a flowering time QTL.
• ZmELF3.1 and ZmELF3.2 interact with ZmELF4 and ZmLUX1/2 to form ECs in the maize circadian clock.
• Loss-of-function mutants showed delayed flowering under both long-day and short-day conditions.
• ECs were shown to directly repress flowering suppressor genes (ZmCCT9, ZmCCT10, ZmCONSTANS-LIKE 3, ZmPRR37a, ZmPRR73).
• Two retrotransposons in the ZmELF3.1 promoter were identified, potentially selected during maize's spread to temperate regions.

Conclusions:

• ZmELF3.1 plays a critical role in the maize circadian clock, regulating photoperiodic flowering.
• The evening complex directly represses flowering suppressors, facilitating timely flowering.
• Retrotransposons in the ZmELF3.1 promoter may have driven adaptation to new environments.
• These findings offer targets for genetic improvement in maize breeding programs.