How do I realize a second y-axis in a heatmap in R
===

I'm trying to add a second y-axis to a heatmap.2 plot in R. So far I tried to use axis() but it didn't work. The obtained error message was:

Fehler in match.arg(dendrogram) : 
  'arg' muss NULL sein oder ein Charakter-Vektor.

In englisch:

Error in match.arg(dendogram):
'arg' hast to be zero or a vector of characters



Since i only want to separate two infos (gene name and a symbol explaining the gene function) the use of a tabulator with a function like paste(gene name, "\t", gene symbol) would also work for me. The problem with the latter attempt is that \t is not suitable for labeling in heatmap.2. 

Code:

    heatmap.2(Trans_matrix, distfun = dist,
    
    #Dendogram-Kontrolle
    hclustfun = hclust, 				
    Colv = FALSE,
    Rowv = TRUE,
    
    # Row/Column Labeling
    cexRow = 1.5,
    font = 9,
    labCol = NULL,
    
    #Beschriftung des Plots
    main = "",
    
    #Block-Trennung
    colsep=c(1,2),
    rowsep=c(Rows),
    sepcolor = "white",
    sepwidth = c(0.005 , 0.005),
    
    #Farbskala - bei welchem Foldchange, welche Farbe
    breaks=c(seq(min(range(Trans_heat))-1, min(range(Trans_heat))/2,length=seqlength), seq(min(range(Trans_heat))/2,-1, length=seqlength),seq(-1,1, length=seqlength), seq(1,max(range(Trans_heat))/2,length=seqlength), seq(max(range(Trans_heat))/2,max(range(Trans_heat))+1,length=seqlength)),
    
    #Generelles Farbschema
    col=Farbschema,
    
    # Farbe von Counterspur
    tracecol="black", 
    
    # Platz, den die Grafik zum unteren und rechten Rand haben soll. Spalten (unten) / Reihen (rechts)
    margins = c(5, 20), 
    )

 
I really appreciate any kind of solution or advice.
René