A novel BSD domain-containing transcription factor controls vegetative growth, leaf senescence, and fruit quality in tomato.

BSD (mammalian BTF2-like transcription factors, synapse-associated proteins, and DOS2-like proteins) is a conserved domain that exists in a variety of organisms, but its function has not been well studied. Here, we identified a novel BSD domain-containing protein (SlBSD1) in tomato (Solanum lycopersicum). Biochemical and microscopy assays indicated that SlBSD1 is a functional transcription factor that is predominantly localized in the nucleus. Loss-of-function and overexpression analyses suggested that SlBSD1 is a novel regulator of vegetative growth and leaf senescence in tomato. SlBSD1-knockdown (-KD) plants exhibited retarded vegetative growth and precocious leaf senescence, whereas SlBSD1-overexpression (-OX) plants displayed the opposite phenotypes. The negative role of SlBSD1 in leaf senescence was also supported by RNA-seq analysis comparing leaf tissues from SlBSD1-KD and wild-type plants. In addition, contents of soluble solids were altered in fruits in the SlBSD1-KD and SlBSD1-OX plants. Taken together, our data suggest that the novel transcription factor SlBSD1 plays important roles in controlling fruit quality and other physiological processes in tomato, including vegetative growth and leaf senescence.