Genome-Wide Analysis of Flax ( Linum usitatissimum L.) Growth-Regulating Factor (GRF) Transcription Factors

Flax is an important cash crop globally with a variety of commercial uses. It has been widely used for fiber, oil, nutrition, feed and in composite materials. Growth regulatory factor (GRF) is a transcription factor family unique to plants, and is involved in regulating many processes of growth and development. Bioinformatics analysis of the GRF family in flax predicted 17 genes, which all contained the characteristic QLQ and WRC domains. Equally, 15 of 17 (88%) are predicted to be regulated by lus-miR396 miRNA. Phylogenetic analysis of GRFs from flax and several other well-characterized species defined five clades; genes were found in four clades. Most gene promoters contained cis-regulatory elements known to be responsive to hormones and stress. The chromosomal locations and collinearity of genes were also analyzed. The three-dimensional structure of proteins was predicted using homology modeling. The transcript expression data indicated that most family members were highly expressed in flax fruit and embryos, whereas , and were enriched in response to salt stress. Real-time quantitative fluorescent PCR (qRT-PCR) showed that both and were up-regulated under ABA and MeJA stimuli, indicating that these genes were involved in defense. was demonstrated to be localized to the nucleus as expected for a transcription factor. These results provide a basis for further exploration of the molecular mechanism of gene function and obtaining improved flax breeding lines.