title: Epidermal cell differentiation in cotton mediated by the homeodomain leucine zipper gene, GhHD-1.
abstract: Gossypium hirsutum L. (cotton) fibres are specialized trichomes a few centimetres in length that grow from the seed coat. Few genes directly involved in the differentiation of these epidermal cells have been identified. These include GhMYB25-like and GhMYB25, two related MYB transcription factors that regulate fibre cell initiation and expansion. We have also identified a putative homeodomain leucine zipper (HD-ZIP) transcription factor, GhHD-1, expressed in trichomes and early fibres that might play a role in cotton fibre initiation. Here, we characterize GhHD-1 homoeologues from tetraploid G. hirsutum and show, using reporter constructs and quantitative real-time PCR (qRT-PCR), that they are expressed predominantly in epidermal tissues during early fibre development, and in other tissues bearing epidermal trichomes. Silencing of GhHD-1 reduced trichome formation and delayed the timing of fibre initiation. Constitutive overexpression of GhHD-1 increased the number of fibres initiating on the seed, but did not affect leaf trichomes. Expression of GhHD-1 in cotton silenced for different fibre MYBs suggest that in ovules it acts downstream of GhMYB25-like, but is unaffected in GhMYB25- or GhMYB109-silenced plants. Microarray analysis of silencing and overexpression lines of GhHD-1 indicated that it potentially regulates the levels of ethylene and reactive oxidation species (ROS) through a WRKY transcription factor and calcium-signalling pathway genes to activate downstream genes necessary for cell expansion and elongation.
authors.affiliation: CSIRO Plant Industry, Canberra ACT 2601, Australia.
authors.forename: Sally-Ann
authors.initials: SA
authors.lastname: Walford
authors.forename: Yingru
authors.initials: Y
authors.lastname: Wu
authors.forename: Danny J
authors.initials: DJ
authors.lastname: Llewellyn
authors.forename: Elizabeth S
authors.initials: ES
authors.lastname: Dennis
mesh_terms: D000595:Amino Acid Sequence; D020013:Calcium Signaling / Q000502:physiology; D002454:Cell Differentiation / Q000235:genetics* / Q000502:physiology; D049108:Cell Enlargement; D032561:Cotton Fiber; D005030:Ethylenes / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D005801:Genes, Homeobox; D003368:Gossypium / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D016350:Leucine Zippers / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D035261:Plant Components, Aerial / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D019441:Plant Epidermis / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D012639:Seeds / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D016415:Sequence Alignment; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D005030:Ethylenes; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D014157:Transcription Factors; C036216:ethylene