The Arabidopsis AtDi19 gene family encodes a novel type of Cys2/His2 zinc-finger protein implicated in ABA-independent dehydration, high-salinity stress and light signaling pathways

The AtDi19 (drought-induced) gene family encodes seven hydrophilic proteins that contain two atypical
Cys2/His2 (C2H2) zinc finger-like domains that are evolutionarily well-conserved within angiosperms
suggesting a conserved and important function. Five of the seven Arabidopsis AtDi19-related:DsRed2
fusion proteins exhibited speckled patterns of localization within the nucleus as shown by transient
expression analysis in Arabidopsis protoplasts. In contrast, AtDi19-2:DsRed2 was present in the nucleus
and cytoplasm, whereas AtDi19-4:DsRed2 was localized to the nuclear periphery. mRNA expression
studies showed that AtDi19 genes are ubiquitously expressed in Arabidopsis tissues, although some
differences were observed. In seedlings, RT-PCR analyses showed that AtDi19-1 and AtDi19-3 steadystate
transcript amounts were rapidly induced by dehydration, whereas transcript amounts for AtDi19-2
and AtDi19-4 increased in response to high-salt stress. In addition, the mRNA abundance of all the
AtDi19-related gene family members was not regulated by ABA. These data, taken together, suggest
that several AtDi19-related gene family members may function in ABA-independent, dehydration and
salinity stress signaling pathways. However, they may also be regulated by other abiotic stimuli.
AtDi19-7, for example, has been implicated in regulating light signaling and responses. Finally, we
show that most AtDi19-related proteins are phosphorylated in vitro by calcium-dependent protein
kinases suggesting that this post-translational modification may be important for regulating the function
of this novel protein family