TRANSCRIPTOME-WIDE IDENTIFICATION AND FUNCTIONAL CHARACTERIZATION OF BBX TRANSCRIPTION FACTOR FAMILY IN TOONA SINENSIS

The B-box proteins (BBXs) are a class of transcription factors that play important regulation roles in plant growth and development, and in the response to biotic and abiotic stresses as well. Currently there are few studies reporting Toona sinensis BBX transcription factors (TsBBX). In order to characterize the function of the TsBBX family, we used an array of bioinformatic tools to assess their types, nuclear localization, domains, phylogeny and advanced structures. Results showed that a total of 20 TsBBX protein sequences were identified from the Toona sinensis transcriptome database, with the number of amino acids ranging from 99 to 296 and the relative molecular mass ranging from 11293.3 to 31839.46 kD. Four TsBBX family members were identified to be stable proteins and 16 were unstable proteins; 15 family members were hydrophobic proteins and the remaining 5 family members were hydrophilic proteins. Most of the secondary structural elements of the proteins were irregular coils, followed by alpha helices and beta sheets. Subcellular localization analysis showed that 16 TsBBX proteins were predominantly distributed in the nucleus and 4 were distributed in the extracellular matrix. Phylogenetic analysis showed that 20 TsBBX proteins were classified into type IV transcription factors, indicating that they may have similar functions. The results provide clues for further functional studies of TsBBX proteins as well as genetic resources for agronomic trait improvement by molecular genetic breeding in Toona sinensis and other crops.