Overexpression of the Epidermis-Specific Homeodomain-Leucine Zipper IV Transcription Factor OUTER CELL LAYER1 in Maize Identifies Target Genes Involved in Lipid Metabolism and Cuticle Biosynthesis

• Published in: Plant physiology (Bethesda) 2010-09, Vol.154 (1), p.273-286
• Main Authors: Javelle, Marie, Vernoud, Vanessa, Depège-Fargeix, Nathalie, Arnould, Christine, Oursel, Delphine, Domergue, Frédéric, Sarda, Xavier, Rogowsky, Peter M
• Format: Article
• Language: English
• Subjects: alcohols; Animal cuticle; Biological and medical sciences; biosynthesis; Corn; cutin; Epicuticular wax; Epidermal cells; Fundamental and applied biological sciences. Psychology; gene expression; Gene Expression Regulation, Plant; Gene Knockout Techniques; gene targeting; Genes; Genes, Plant - genetics; Genetics; Homeodomain Proteins - genetics; Homeodomain Proteins - metabolism; leucine zipper; Leucine Zippers - genetics; Life Sciences; lipid metabolism; Lipid Metabolism - genetics; Lipids; mutation; Oligonucleotide Array Sequence Analysis; Organ Specificity - genetics; Plant cuticle; Plant Epidermis - genetics; Plant Leaves - cytology; Plant Leaves - genetics; Plant physiology and development; Plant Proteins - genetics; Plant Proteins - metabolism; Plants; Plants genetics; proteins; Reproducibility of Results; seeds; SYSTEMS BIOLOGY, MOLECULAR BIOLOGY, AND GENE REGULATION; Transcription factors; Transcription Factors - genetics; Transcription Factors - metabolism; transcriptional activation; Transcriptional Activation - genetics; Transformation, Genetic; transgenic plants; Waxes; Waxes - metabolism; Zea mays; Zea mays - genetics; Zea mays - immunology
• ISSN: 0032-0889; 1532-2548; 1532-2548
• DOI: 10.1104/pp.109.150540

Transcription factors of the homeodomain-leucine zipper IV (HD-ZIP IV) family play crucial roles in epidermis-related processes. To gain further insight into the molecular function of OUTER CELL LAYER1 (OCL1), 14 target genes up- or down-regulated in transgenic maize (Zea mays) plants overexpressing OCL1 were identified. The 14 genes all showed partial coexpression with OCL1 in maize organs, and several of them shared preferential expression in the epidermis with OCL1. They encoded proteins involved in lipid metabolism, defense, envelope-related functions, or cuticle biosynthesis and include ZmWBC11a (for white brown complex 11a), an ortholog of AtWBC11 involved in the transport of wax and cutin molecules. In support of the annotations, OCL1-overexpressing plants showed quantitative and qualitative changes of cuticular wax compounds in comparison with wild-type plants. An increase in C24 to C28 alcohols was correlated with the transcriptional up-regulation of ZmFAR1, coding for a fatty acyl-coenzyme A reductase. Transcriptional activation of ZmWBC11a by OCL1 was likely direct, since transactivation in transiently transformed maize kernels was abolished by a deletion of the activation domain in OCL1 or mutations in the L1 box, a cis-element bound by HD-ZIP IV transcription factors. Our data demonstrate that, in addition to AP2/EREBP and MYB-type transcription factors, members of the HD-ZIP IV family contribute to the transcriptional regulation of genes involved in cuticle biosynthesis.