I maintain a CRAN package and a user has submitted a new function that calls a function from a bioconductor package. I know how to specify Imports and Suggests for other CRAN packages but was wondering what the recommended mechanism is for linking to a bioconductor package::function().

Many thanks!

AFAIK, same as for CRAN packages (my WGCNA package also lives on CRAN but imports functions from a few Bioconductor packages). CRAN includes Bioconductor packages on its package check machines. The only issue is that users cannot simply type install.packages("your package") to install it, they will need to install BiocManager and use BiocManager::install.