Genome-wide identification and characterization of growth-regulating factors in mulberry (Morus spp.)

Abstract

Mulberry GRFs (MnGRFs) were identified from draft genome sequence of Morus notabilis by genome-wide analysis. The expression analysis of MnGRFs was studied in a contrasting set of genotypes for growth. Growth-regulating factors (GRFs) are multigene family of plants which encode putative transcription factors and play vital role in regulating growth and development. GRF genes of Arabidopsis, rice, maize, Chinese cabbage, etc., have been well characterized but, in mulberry they have not been so far explored. Mulberry growth is the key determinant in leaf yield and is the only source of nutrition for silk-producing insect—Bombyx mori L. In this study, we report ten mulberry-specific GRFs (MnGRFs) identified from the draft genome sequence of Morus notabilis by genome-wide analysis. The MnGRFs contained GRF-specific domains, i.e., QLQ (Glu, Leu, Glu) and WRC (Trp, Arg, Cys) in their N-terminal and Pro, Gln, His, Ala/Gly, Ser/Thr, acidic amino acid residues in C-terminal region. The phylogenetic and motif structure analysis showed that MnGRFs have higher similarity to Arabidopsis and Chinese cabbage (dicots) than rice (monocot). Expression analysis of MnGRFs was undertaken in young leaves of ten contrasting genotypes for growth and observed a significant difference in the transcript levels of MnGRF 1, MnGRF 7 and MnGRF 8 with higher expression in high growth than the low growth genotypes. It is inferred that MnGRFs have an important role in growth and development of immature and young leaves of mulberry contributing to the leaf yield. Furthermore, the study provides a basis for investigation into the function of MnGRF proteins in leaf development and molecular basis for crop improvement.