Table II. Ratio of 21-nt sRNAs to 24-nt sRNAs for selected gene classes in poplar.

The ratio was calculated for those annotation classes containing five or more genes among those 500 with the highest sRNA counts.

Annotation	No. of Genes	Ratio	Total Reads
NBS-LRR resistance protein	512	15.8	183,882
Unknown function	472	1.9	74,508
Reverse transcriptase	64	0.2	15,173
Polyprotein	21	0.5	10,647
ORF V protein	5	0.4	7,429
Retroelement	14	0.4	6,796
GRAS family transcription factor	22	16.6	2,987
Retrotransposon	11	0.3	1,590
Xylem Ser proteinase1	5	12.9	1,006