Genome-wide analysis of small RNA and novel microRNA discovery during fiber and seed initial development in Gossypium hirsutum. L.

Cotton is the source of the most important, renewable natural textile fiber and oil in the world. MicroRNAs (miRNAs) are endogenous, non-coding, approximately 18-24 nucleotides long RNAs and function in the negative regulation of their target genes. Two mostly overlapping libraries of small RNA molecules were constructed and sequenced, and served as repetition sets of data to identify miRNAs involved in fiber initiation and seed development. The D genome sequence of Gossypium raimondii was used in conjunction with EST sequences to predict miRNA precursors. Overall, 93 new miRNA precursors were identified, of which 28 belonged to 10 known families and the other 65 were considered to be novel miRNAs. Seven hundred EST sequences were proposed to be candidate target genes which involved in the regulation of a diverse group of genes with diverse functions and transcription factors. Some of the novel miRNAs and candidate target genes were validated by the Northern blot and rapid amplification of 5' cDNA ends (5' RACE).