Rate of meristem initiation driven by the MADS-WUS axis contributes to floral survival and inflorescence evolution in grasses

The rate at which floral initiation, maturation, and survival occur within floral inflorescences has been significantly altered through crop domestication, yet the underlying mechanisms remain elusive. By integrating morphometry, modeling, and molecular genetic studies, researchers have uncovered that the rate of floral production in barley's indeterminate inflorescences follows an "initiate fast, die young" strategy. This is primarily driven by a key MADS-box gene called SPIKELET INITIATION AND FERTILITY (SIF).

SIF plays a dual role in orchestrating this strategy. It simultaneously terminates the inflorescence meristem through WUSCHEL and activates the floral meristem via APETALA1 (Vrn-H1). Consequently, the ancestral SIF "slow" allele fosters a timely commitment to floral maturation, while the derived "fast" allele allows for more frequent floral initiations.

The selection of SIF alleles post-domestication enabled the diversification of reproductive strategies in barley populations, ultimately enhancing yield traits in real-world conditions.

Furthermore, the study reveals that a lineage-specific SIF duplication played a crucial role in meristem fate transition and inflorescence evolution during Triticeae cold adaptation. These findings establish developmental rate as a pivotal factor in architectural innovation and reproductive success within grasses.