Drought and Heat Stresses Have Distinct Impacts in Sub-Genomic Regulation Patterns of a Mannitol Biosynthesis Gene in Allotetraploid Coffea arabica

Coffea arabica is an allotetraploid originating from a natural hybridization between C. canephora and C. eugenioides, and it accounts for 75% of the world’s coffee production. For allotetrapolyploids, it is expected that most genes are present in two homoeologous forms, highly similar but non-identical.  Abiotic stresses, such as drought and extreme temperatures limit commercial coffee production. The accumulation of solutes, such as mannitol, is known to be involved in abiotic stress tolerance in plants. The key-enzyme involved in mannitol biosynthesis in plants is mannose-6-phosphate reductase (M6PR). Here, we report an inference of M6PR copies in C. arabica genome and the M6PR transcriptional profile under drought and heat stress. Based in allelespecific PCR and BAC library (~5X genome coverage) screening, we could infer that two homoeologous CaM6PR loci should exist in the tetraploid coffee genome. These observations are supported by analysis in sequenced diploid plant genomes, where M6PR is a single-copy gene. Using qPCR primers with specific amplification to C. canephora subgenome present in C. arabica, we could also evaluate transcriptional responses of “total” CaM6PR expression and “canephora-specific” pattern under water deficit and heat stress (37^oC). Both total and subgenomic M6PR transcripts, as well as mannitol concentration, are up-regulated upon drought in C. arabica leaves. Under high temperatures, we observed the opposite response: mannitol and M6PR transcripts are downregulated.  Our results highlights that stress responses may trigger opposite molecular responses in plants, and guarantee further analysis in Coffea arabica homoelogous M6PR genes, in order to depict its response under abiotic stresses.

Finnancial support: FINEP, CNPq and Consórcio Pesquisa Café.