Characterization of grape C-repeat-binding factor 2 and B-box-type zinc finger protein in transgenic Arabidopsis plants under stress conditions.

Simultaneous induction of multiple stress tolerance by single-gene transfer is a powerful strategy to engineer crop plants to improve tolerance to environmental stress under field condition. The possibility of enhancement of multiple stress tolerance by four grape transcription factors that enhance low-temperature tolerance (VvCBF2, VvCBF4, VvCBFL, and VvZFPL) were analyzed using the Arabidopsis plants overexpressing these factors. Consequently, two of the four proteins, VvCBF2 and VvZFPL, were found to confer tolerance to cold, drought, and salinity stresses in Arabidopsis plants, but not to heat stress. Photosynthesis-related genes were down-regulated in both CBF2- and ZFPL-overexpressing plants, resulting in plant growth retardation. On the other hand, the overexpression of VvCBF2 activated the transcription of CBL-interacting protein kinase 7, a serine/threonine kinase involved in cold response, in Arabidopsis plants. Our study provides that one of grape CBF family, VvCBF2, and one of B-box ZFP family, VvZFPL, confer multiple stress tolerance to plants.

ER stress-induced protein, VIGG, disturbs plant cation homeostasis, which is correlated with growth retardation and robustness to ER stress.

VIGG is a putative endoplasmic reticulum (ER) resident protein induced by virus infection and ER stress, and is correlated with fruit quality in grapevine. The present study was undertaken to determine the biological function of VIGG in grapevine. Experiments using fluorescent protein-VIGG fusion protein demonstrated that VIGG is localized in ER and the ER targeting sequence is in the N-terminus. The overexpression of VIGG in Arabidopsis plant led to growth retardation. The rosette leaves of VIGG-overexpressing plants were smaller than those of the control plants and rolled at 42days after seeding. VIGG-overexpressing plants revealed robustness to ER stress as well as the low expression of ER stress marker proteins, such as the luminal binding proteins. These characteristics of VIGG-overexpressing plants were supported by a microarray experiment that demonstrated the disruption of genes related to ER stress response and flowering, as well as cation mobility, in the plants. Finally, cation homeostasis in the plants was disturbed by the overexpression of VIGG. Taken together, these results suggest that VIGG may disturb cation homeostasis in plant, which is correlated with the robustness to ER stress and growth retardation.

Low-temperature-induced transcription factors in grapevine enhance cold tolerance in transgenic Arabidopsis plants.

We report the characterization of low-temperature-induced transcription factors in grapevine (Vitis vinifera). Four transcription factors were identified in low-temperature-treated grapevine. The expression of V. vinifera C-repeat-binding factors, VvCBF2, VvCBF4, and VvCBFL, and V. vinifera B-box-type zinc finger protein, VvZFPL, was immediately induced and upregulated in leaves by the low-temperature treatment. Similar induction of the gene expression was observed in low-temperature-treated stems and flowers, although VvZFPL was constitutively expressed in flowers. Tendrils expressed all the four genes constitutively. In berry skin, VvCBF2 and VvCBFL were induced by the low-temperature treatment before the onset of véraison, while only VvCBF2 was induced under the low-temperature condition after the onset of véraison. The overexpression of VvCBF2 and VvZFPL in Arabidopsis plants led to longer hypocotyls than the control plants. The rosette leaves of these plants were smaller and had lower chlorophyll contents than those of the control plants, resulting in a pale green color. Finally, the VvCBF2- and VvZFPL-overexpressing plants revealed growth retardation. These results suggest that VvCBF2 and VvZFPL may affect photomorphogenesis and growth in grapevine. Meanwhile, no morphological changes were detected in the VvCBF4- and VvCBFL-overexpressing plants. The cold tolerance test demonstrated that all of the overexpressing plants remained viable and noticeably healthy compared with the control plants even after exposure to severe cold treatment, suggesting that VvCBF2, VvCBF4, VvCBFL, or VvZFPL may enhance cold tolerance in grapevine.