Genome-Wide Analysis of the GRF-GIF Module in Coffea arabica L.: Insights into the Starlet-Flower Phenomenon

The Growth-Regulating Factor (GRF) family and their co-activators, GRF-Interacting Factors (GIFs), are key players in the trade-off between plant development and stress adaptation, functioning as canonical targets of the highly conserved miR396 family, which mediates responses to environmental stressors including high temperatures and water deficits. The "starlet" phenomenon in the allotetraploid Coffea arabica L. is a developmental disorder that results in malformed flowers, frequently associated with environmental stress and floral sterility. Since their underlying molecular mechanisms remain uncharacterized, we performed a genome-wide identification of the CaGRF and CaGIF families and quantified their transcriptional profiles in shoot apical meristems (SAMs) and across multiple stages of floral bud development. Our findings reveal significant differential expression of the GRF-GIF module between typical and starlet tissues throughout development, including the SAM. Intriguingly, these results do not correlate with the levels of a representative member of the miR396 family, indicating that the GRF-GIF expression shifts in starlet-flowers may be uncoupled from miR396 levels. This work provides the first molecular insights into the enigmatic starlet phenomenon in Coffea arabica L., addressing an understudied aspect of coffee reproductive development and its implications for the reproductive stability (and productivity) of this important tropical crop species.