Over-expression of GsZFP1, an ABA-responsive C2H2-type zinc finger protein lacking a QALGGH motif, reduces ABA sensitivity and decreases stomata size

A cDNA of the gene GsZFP1 was cloned from Glycine soja. GsZFP1 encodes a protein with one C2H2-type zinc finger motif. The QALGGH motif, which exists in most plant C2H2-type zinc finger proteins (ZFPs), does not exist in GsZFP1. Real-time RT-PCR revealed that GsZFP1 expression was significantly up-regulated by exogenous ABA, both in leaves and roots. Over-expression of this gene, in Arabidopsis thaliana, resulted in a reduced sensitivity to ABA during seed germination and seedling growth. Transcript levels of some stress and ABA marker genes, including RD29A, RD22, NCED3, COR47, COR15A and KIN1 were increased, in the GsZFP1 over-expression lines, when plants were treated with exogenous ABA. We further studied the effects of GsZFP1 over-expression on the regulation of genes involved in ABA signaling. Negative ABA signaling regulators, such as ABI1 and ABI2, were up-regulated in over-expression lines, while positive ABA signaling regulators, such as ABF4, ABI5, GTG1, GTG2, PYR1/RCAR11, PYL2/RCAR13, SnRK2.2 and SnRK2.3, were down-regulated, in comparison to wild type plants. GsZFP1 over-expression lines also exhibited small stomata, impairment of ABA-induced stomata closure. The data presented, herein, suggests that GsZFP1 plays a crucial role in ABA signaling in A. thaliana, GsZFP1 may be a promising gene for negative regulating ABA signaling. Our findings broaden our understanding of this C2H2 ZFP subtype's function, and add to the body of evidence that has been developed in earlier studies.