Manipulation of the transcription factor SlNAC1 for improved tolerance to abiotic stress in tomato.

The tomato transcription factor SlNAC1 plays an important role in abiotic stress response and is fine-tuned at both transcriptional and posttranslational levels. The SlNAC1 gene is strongly induced by multiple abiotic stresses and the SlNAC1 protein is subjected to ubiquitin proteasome-mediated degradation. We found here that SlNAC1 possesses two distinct transactivation domains (TADs), TAD1 and TAD2. Significantly, the instability of SlNAC1 was attributed to the acidic amino acid-rich TAD1, in which the instability and transcriptional potential of TAD1 functionally overlapped; whereas the glutamine-rich TAD2 was stable and accounted for the abiotic stress signalling mediated by SlNAC1. Towards the goal of enhanced tolerance to abiotic stress in tomatoes, we manipulated SlNAC1 at both gene and protein levels: we generated a stable and functional SlNAC1 mutant SlNAC1∆191-270 by removing TAD1 and further engineered it to be stress-controllable by fusing the corresponding cDNA with the abiotic stress-inducible promoter ProStNAC1 . Transgenic tomato plants expressing the ProStNAC1 ::SlNAC1∆191-270 transgene did not display any undesired traits and exhibited enhanced tolerance to cold, drought and salt stresses. Taken together, our manipulation of the stress-related transcription factor via conditional expression of its derived stable and functional mutant provides a successful example for developing crops dynamically adapted to abiotic stress.

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.