The floral development of the allotetraploidCoffea arabicaL. correlates with a small RNA dynamic reprogramming

Summary Non-coding and coding RNAs are key regulators of plant growth, development, and stress responses. To investigate the types of transcripts accumulated during the vegetative to reproductive transition and floral development in the Coffea arabica L., we sequenced small RNA libraries from eight developmental stages, up to anthesis. We combined this data with messenger RNA and PARE sequencing of two important development stages that marks the transition of an apparent latent to a rapid growth stage. In addition, we took advantage of multiple in silico tools to characterize genomic loci producing small RNAs such as phasiRNAs, miRNAs and tRFs. Our differential and co-expression analysis showed that some types of small RNAs such as tRNAs, snoRNAs, snRNAs and phasiRNAs preferentially accumulate in a stage- specific manner. Members of the miR482/miR2118 superfamily and their 21-nucleotide phasiRNAs originating from resistance genes show a robust co-expression pattern that is maintained across all the evaluated developmental stages. Finally, the majority of miRNAs accumulate in a family-stage specific manner, related to modulated hormonal responses and transcription factors expression. Societal Impact Statement This research holds potential to benefit millions of coffee-producing families in over 60 countries. We uncovered molecular regulatory mechanisms governing flower development, one of the causes for the Coffea arabica ’s uneven ripening. The absence of uniformity in coffee production, spanning from floral induction to branch senescence, has a detrimental impact on the final product’s quality. These insights will inform strategies for controlled coffee maturation, leading to improved, uniform harvests.