Can anybody help me to find the dataset for s. pombe on BioMart? And also some help on how to use `makeTranscriptDbFromBiomart` to create TranscriptDB?

cheers,
Looks like you figured out another way of getting what you needed, but, for the record, here is the answer to your question:

S pombe is at http://fungi.ensembl.org/index.html

The biomart is here: http://fungi.ensembl.org/biomart/martview/248a3d2deec76fa7be1e94e32b3972df

Access it using BioConductor's GenomicFeatures as follows. Note the warnings....

    library(GenomicFeatures)
    library(biomaRt)
    
    txdb<-makeTranscriptDbFromBiomart(
                ,biomart ="fungi_mart_22"
                ,dataset = "spombe_eg_gene"
                ,host="fungi.ensembl.org"
                )
    
     Download and preprocess the 'transcripts' data frame ... OK
     Download and preprocess the 'splicings' data frame ... OK
     Download and preprocess the 'genes' data frame ... OK
     Prepare the 'metadata' data frame ... OK
     Make the TranscriptDb object ... OK
     Warning messages:
     1: In .normargSplicings(splicings, transcripts_tx_id) :
       no CDS information for this TranscriptDb object
     2: In .normargChrominfo(chrominfo, transcripts$tx_chrom, splicings$exon_chrom) :
       chromosome lengths and circularity flags are not available for this TranscriptDb object
    
    > transcriptsBy(txdb)
     GRangesList of length 7017:
     $SPAC1002.01
     GRanges with 1 range and 2 metadata columns:
           seqnames             ranges strand |     tx_id       tx_name
              <Rle>          <IRanges>  <Rle> | <integer>   <character>
       [1]        I [1798347, 1799015]      + |       510 SPAC1002.01.1
    
     $SPAC1002.02
     GRanges with 1 range and 2 metadata columns:
           seqnames             ranges strand | tx_id       tx_name
       [1]        I [1799061, 1800053]      + |   511 SPAC1002.02.1
    
     $SPAC1002.03c
     GRanges with 1 range and 2 metadata columns:
           seqnames             ranges strand | tx_id        tx_name
       [1]        I [1799915, 1803141]      - |  2075 SPAC1002.03c.1
    
     ...
     <7014 more elements>
     ---
     seqlengths:
             I       II      III       MT      MTR AB325691
            NA       NA       NA       NA       NA       NA