Functional characterization of cold-responsive Zinc Finger Homeodomain () gene in abscisic acid and osmotic stress tolerance.

Background: We have previously performed an analysis of the cold-responsive transcriptome in the mature leaves of tiger lily () by gene co-expression network identification. The results has revealed that a gene, notated as encoding zinc finger homeodomain protein, may play an essential regulating role in tiger lily response to cold stress.

Methods: A further investigation of the gene (termed as ) responding to osmotic stresses, including cold, salt, water stresses, and abscisic acid (ABA) was performed in this study. Based on the transcriptome sequences, the coding region and 5' promoter region of were cloned from mature tiger lily leaves. Stress response analysis was performed under continuous 4 °C, NaCl, PEG, and ABA treatments. Functional characterization of was conducted in transgenic , tobacco, and yeast.

Results: encodes a nuclear-localized protein consisting of 180 amino acids. The N-terminal region of LlZFHD4 has transcriptional activation activity in yeast. The 4 °C, NaCl, PEG, and ABA treatments induced the expression of . Several stress- or hormone-responsive cis-acting regulatory elements (T-Box, I. and ARF) and binding sites of transcription factors (MYC, DRE and W-box) were found in the core promoter region (789 bp) of . Also, the gene driven by promoter was up-regulated by cold, NaCl, water stresses, and ABA in . Overexpression of improved cold and drought tolerance in transgenic ; higher survival rate and better osmotic adjustment capacity were observed in transgenic plants compared to wild type (WT) plants under 4 °C and PEG conditions. However, transgenic plants were less tolerant to salinity and more hypersensitive to ABA compared to WT plants. The transcript levels of stress- and ABA-responsive genes were much more up-regulated in transgenic than WT. These results indicate is involved in ABA signaling pathway and plays a crucial role in regulating the response of tiger lily to cold, salt and water stresses.