title: Application of HB17, an Arabidopsis class II homeodomain-leucine zipper transcription factor, to regulate chloroplast number and photosynthetic capacity.
abstract: Transcription factors are proposed as suitable targets for the control of traits such as yield or food quality in plants. This study reports the results of a functional genomics research effort that identified ATHB17, a transcription factor from the homeodomain-leucine zipper class II family, as a novel target for the enhancement of photosynthetic capacity. It was shown that ATHB17 is expressed natively in the root quiescent centre (QC) from Arabidopsis embryos and seedlings. Analysis of the functional composition of genes differentially expressed in the QC from a knockout mutant (athb17-1) compared with its wild-type sibling revealed the over-representation of genes involved in auxin stimulus, embryo development, axis polarity specification, and plastid-related processes. While no other phenotypes were observed in athb17-1 plants, overexpression of ATHB17 produced a number of phenotypes in Arabidopsis including enhanced chlorophyll content. Image analysis of isolated mesophyll cells of 35S::ATHB17 lines revealed an increase in the number of chloroplasts per unit cell size, which is probably due to an increase in the number of proplastids per meristematic cell. Leaf physiological measurements provided evidence of improved photosynthetic capacity in 35S::ATHB17 lines on a per unit leaf area basis. Estimates of the capacity for ribulose-1,5-bisphosphate-saturated and -limited photosynthesis were significantly higher in 35S::ATHB17 lines.
authors.affiliation: Mendel Biotechnology, 3935 Point Eden Way, Hayward, CA 94545, USA.
authors.forename: Graham J
authors.initials: GJ
authors.lastname: Hymus
authors.forename: Suqin
authors.initials: S
authors.lastname: Cai
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Kohl
authors.forename: Hans E
authors.initials: HE
authors.lastname: Holtan
authors.forename: Colleen M
authors.initials: CM
authors.lastname: Marion
authors.forename: Shiv
authors.initials: S
authors.lastname: Tiwari
authors.forename: Don R
authors.initials: DR
authors.lastname: Maszle
authors.forename: Marjorie R
authors.initials: MR
authors.lastname: Lundgren
authors.forename: Melissa C
authors.initials: MC
authors.lastname: Hong
authors.forename: Namitha
authors.initials: N
authors.lastname: Channa
authors.forename: Paul
authors.initials: P
authors.lastname: Loida
authors.forename: Rebecca
authors.initials: R
authors.lastname: Thompson
authors.forename: J Philip
authors.initials: JP
authors.lastname: Taylor
authors.forename: Elena
authors.initials: E
authors.lastname: Rice
authors.forename: Peter P
authors.initials: PP
authors.lastname: Repetti
authors.forename: Oliver J
authors.initials: OJ
authors.lastname: Ratcliffe
authors.forename: T Lynne
authors.initials: TL
authors.lastname: Reuber
authors.forename: Robert A
authors.initials: RA
authors.lastname: Creelman
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism* / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D017343:Genes, Plant / Q000235:genetics; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D017403:In Situ Hybridization; D016350:Leucine Zippers; D008027:Light; D058503:Mesophyll Cells / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D017440:Photoperiod; D010788:Photosynthesis / Q000528:radiation effects; D018517:Plant Roots / Q000378:metabolism; D030821:Plants, Genetically Modified; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C000588571:HB17 protein, Arabidopsis; D018398:Homeodomain Proteins; D012333:RNA, Messenger; D014157:Transcription Factors
keywords: Chloroplast number; chloroplast size; homeodomain-leucine zipper; leaf development; photosynthetic capacity; transcription factor.