The zinc-finger transcription factor ZFP8 negatively regulates the drought stress response in Arabidopsis thaliana by inhibiting the transcriptional activity of ABF2.

Drought stress limits plant growth and development. To cope with drought stress, abscisic acid (ABA) accumulates in plants. Although ABA-dependent drought tolerance pathways have been widely investigated, the feedback mechanisms and the negative regulatory roles within these pathways remain largely unknown. Here we characterize the roles of a C2H2 transcription factor, ZFP8, whose expression is repressed by ABA in the tolerance of drought stress. ZFP8-overexpressing plants were hyposensitive to ABA and exhibited less dehydration tolerance while ABA or drought-induced marker genes were more highly expressed in zfp8, suggesting that ZFP8 functions as a negative regulator in the ABA-mediated drought response. A transcriptome assay showed that ZFP8 positively regulates gene expression for cellular function and negatively regulates hormone and stress response gene expression. Moreover, we found that ZFP8 can interact with ABF2, one of the basic leucine zipper (bZIP) family transcription factor members, to inhibit its transcription activity. In conclusion, our results demonstrate a novel negative regulation pathway of ZFP8, which contributes to plants' ability to fine-tune their drought responses.

LEAFY and APETALA1 down-regulate ZINC FINGER PROTEIN 1 and 8 to release their repression on class B and C floral homeotic genes.

Organ initiation from the shoot apical meristem first gives rise to leaves during vegetative development and then flowers during reproductive development. LEAFY (LFY) is activated after floral induction and together with other factors promotes the floral program. LFY functions redundantly with APETALA1 (AP1) to activate the class B genes APETALA3 (AP3) and PISTILLATA (PI), the class C gene AGAMOUS (AG), and the class E gene SEPALLATA3, which leads to the specification of stamens and carpels, the reproductive organs of flowers. Molecular and genetic networks that control the activation of AP3, PI, and AG in flowers have been well studied; however, much less is known about how these genes are repressed in leaves and how their repression is lifted in flowers. Here, we showed that two genes encoding Arabidopsis C2H2 ZINC FINGER PROTEIN (ZFP) transcription factors, ZP1 and ZFP8, act redundantly to directly repress AP3, PI, and AG in leaves. After LFY and AP1 are activated in floral meristems, they down-regulate ZP1 and ZFP8 directly to lift the repression on AP3, PI, and AG. Our results reveal a mechanism for how floral homeotic genes are repressed and derepressed before and after floral induction.