Identification and functional characterization of a novel BEL1-LIKE homeobox transcription factor GmBLH4 in soybean

Abstract

The interaction between BEL1- and KNOTTED1-type homeobox transcription factors from TALE (Three-Amino-acid-Loop Extension) class plays key roles in plant growth and development. In our previous study, a soybean KNOTTED1-like gene GmSBH1, which played important roles in soybean growth and development as well as in response to high temperature and humidity (HTH) stress was identified. In the present study, 15 GmSBH1-interacting candidate proteins were identified by yeast two-hybrid system. From the 15 candidate proteins, a novel BEL1-LIKE homeodomain 4 protein, GmBLH4, was selected to isolate and characterize through sequence alignment, phylogenetic analysis and subcellular localization. GmBLH4 showed tissues specific expression and was involved in response to HTH stress in developing seeds. Overexpression of GmBLH4 in Arabidopsis altered leaf phenotype and silique length, and enhanced seed tolerance to HTH stress. Glutathione-S-transferase pull-down (GST) and bimolecular fluorescence complementation (BiFC) assays confirmed that GmBLH4 specifically interacted with GmSBH1 in vivo and in vitro. The conserved domains of GmSBH1 and GmBLH4 were sufficient for their interaction in yeast expression system. Our results indicated that GmBLH4 might heterodimerize with GmSBH1 to form functional complexes and function in modulating plant growth and development as well as in response to HTH stress in soybean.