sunflower HD-Zip transcription factor HAHB4 is up-regulated in darkness, reducing the transcription of photosynthesis-related genes

• Published in: Journal of experimental botany Vol. 59; no. 11; pp. 3143 - 3155
• Main Authors: Manavella, Pablo A, Dezar, Carlos A, Ariel, Federico D, Drincovich, María F, Chan, Raquel L
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01-08-2008; Oxford Publishing Limited (England)
• Subjects: Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis thaliana; beta-glucuronidase; Biological and medical sciences; Carbon Dioxide - metabolism; chlorophyll; Chlorophyll - metabolism; Chlorophylls; Chloroplasts; complementary DNA; dark regulation; Dark-inducible promoter; Darkness; drought tolerance; electrophoresis; Fundamental and applied biological sciences. Psychology; gene expression; Gene expression regulation; Gene Expression Regulation, Plant; Genes; HAHB4; HD-Zip; Helianthus - genetics; Helianthus - metabolism; Helianthus annuus; Homeodomain Proteins - metabolism; Leaves; light; messenger RNA; Metabolism; Mutation; Photosynthesis; Photosynthesis, respiration. Anabolism, catabolism; pigments; Plant growth regulators; Plant physiology and development; Plant Proteins - metabolism; Plants; Plants, Genetically Modified - metabolism; promoter analysis; promoter regions; Promoter Regions, Genetic; proteins; reporter genes; Research Papers; response elements; RNA; senescence; Sequence Homology, Nucleic Acid; sunflower; Sunflowers; transcription (genetics); transcription factor; transcription factors; Transcription, Genetic; Transgenic plants; Up-Regulation; HD-Zip; transcription factor; dark regulation; promoter analysis; Dark-inducible promoter; sunflower; Gene; Transcription; HAHB4; Transcription factor; Photosynthesis
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/ern170

HAHB4 belongs to the sunflower subfamily I of HD-Zip proteins and is involved in drought-tolerance response and ethylene-mediated senescence. Cross-talk between these two processes through this transcription factor was recently described. In this study it is shown that the expression of HAHB4 is induced in darkness and quickly disappears when plants are exposed to light. This regulation of HAHB4 was confirmed at the transcriptional level through the use of transgenic Arabidopsis plants bearing constructs in which different segments of the HAHB4 promoter were fused with the reporter gene GUS. Together with electrophoretic mobility shift assays performed with sunflower nuclear proteins, these experiments allowed a cis-acting element involved in this response to be located. Transient overexpression of the HAHB4 cDNA in sunflower leaf discs and HAHB4 knockdown by iRNA were performed, demonstrating the participation of this transcription factor in the transcriptional down-regulation of a large group of photosynthesis-related genes. In accordance with the reduction in the transcripts encoding chlorophyll a/b-binding proteins, the content of these pigments is diminished in Arabidopsis HAHB4-expressing transgenic plants. Thus, it appears that HAHB4 may participate with other factors in the intricate regulation mechanism of the photosynthetic machinery in darkness.