title: Hahb-4, a sunflower homeobox-leucine zipper gene, is a developmental regulator and confers drought tolerance to Arabidopsis thaliana plants.
abstract: Homeodomain-leucine zipper proteins constitute a family of transcription factors found only in plants. Hahb-4 is a member of Helianthus annuus (sunflower) subfamily I. It is regulated at the transcriptional level by water availability and abscisic acid. In order to establish if this gene plays a functional role in drought responses, transgenic Arabidopsis thaliana plants that overexpress Hahb-4 under the control of the 35S Cauliflower Mosaic Virus promoter were obtained. Transformed plants show a specific phenotype: they develop shorter stems and internodes, rounder leaves and more compact inflorescences than their non-transformed counterparts. Shorter stems and internodes are due to a lower rate in cell elongation rather than to a stop in cell division. Transgenic plants were more tolerant to water stress conditions, showing improved development, a healthier appearance and higher survival rates than wild-type plants. Indeed, either under normal or drought conditions, they produce approximately the same seed weight per plant as wild-type plants under normal growth conditions. Plants transformed with a construct that bears the Hahb-4 promoter fused to gusA show reporter gene expression in defined cell-types and developmental stages and are induced by drought and abscisic acid. Since Hahb-4 is a transcription factor, we propose that it may participate in the regulation of the expression of genes involved in developmental responses of plants to desiccation.
authors.affiliation: Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Santa Fe, Argentina.
authors.forename: Carlos Alberto
authors.initials: CA
authors.lastname: Dezar
authors.forename: Gabriela Marisa
authors.initials: GM
authors.lastname: Gago
authors.forename: Daniel Héctor
authors.initials: DH
authors.lastname: Gonzalez
authors.forename: Raquel Lía
authors.initials: RL
authors.lastname: Chan
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D018556:Crops, Agricultural / Q000235:genetics / Q000502:physiology; D018744:DNA, Plant / Q000302:isolation & purification; D004190:Disasters; D018506:Gene Expression Regulation, Plant; D005801:Genes, Homeobox / Q000502:physiology*; D017343:Genes, Plant; D006368:Helianthus / Q000235:genetics; D018398:Homeodomain Proteins; D016350:Leucine Zippers / Q000235:genetics*; D010641:Phenotype; D010937:Plant Growth Regulators / Q000235:genetics*; D030821:Plants, Genetically Modified / Q000235:genetics; D011401:Promoter Regions, Genetic; D018749:RNA, Plant / Q000302:isolation & purification / Q000378:metabolism; D014157:Transcription Factors
chemical_list: D029681:Arabidopsis Proteins; D018744:DNA, Plant; D018398:Homeodomain Proteins; D010937:Plant Growth Regulators; D018749:RNA, Plant; D014157:Transcription Factors