conference schedule and program with abstracts - Horticulture ...

O-30
Annette Nassuth
Function of Vitis CBF transcription factors in stress tolerance
Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
Corresponding author: anassuth@uoguelph.ca
The CBF pathway functions in the acquisition of freezing tolerance in plants. Eight CBF genes
are present in the wild grape Vitis riparia (Vr). It is likely that these genes have different
functions because they are present on different chromosomes and place on different clades in a
dendogram produced with all CBF protein sequences known to date. This hypothesis is
supported by our qualitative and quantitative analysis of Arabidopsis lines overexpressing
VrCBF1 or VrCBF4. Whole plant, electrolyte leakage and chlorophyll imaging experiments
showed that while both CBF1 and CBF4 transgenic lines had increased freezing and drought
tolerance, CBF4 affected freezing tolerance and CBF1 affected drought tolerance to a larger
degree. Microscopy revealed that this was correlated with features that could explain the increase
in stress tolerance, such as smaller and thicker leaves with larger palisade mesophyll cells, a
higher number spongy mesophyll cells with fewer airspaces, and a higher number of trichomes.
Further phenotypic changes with a less obvious connection to stress tolerance included dwarfing,
and an extension of the vegetative phase prior to flowering. Differential activation of several
genes in VrCBF1- versus VrCBF4-expressing Arabidopsis plants suggests that this is because
these transcription factors have different regulons. This presentation will discuss how these
findings affect strategies to breed or genetically engineer wine grapes with increased freezing
tolerance but without any undesirable traits.
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