title: The different growth responses of the Arabidopsis thaliana leaf blade and the petiole during shade avoidance are regulated by photoreceptors and sugar.
abstract: During the shade-avoidance response, leaf blade expansion is inhibited and petiole elongation is enhanced. In this study, we examined the roles of photoreceptors and sugar on the differential growth of the leaf blade and petiole in shade conditions. Under the conditions examined, cell expansion, not cell division, played a major role in the differential leaf growth. The enhanced cell expansion in the leaf blade is associated with an increase in the ploidy level, whereas cell elongation was stimulated in the petiole in dark conditions without an increase in the ploidy level. Analysis of phytochrome, cryptochrome and phototropin mutants revealed that phytochromes and cryptochromes specifically regulate the contrasting growth patterns of the leaf blade and petiole in shade. Examination of the effects of photo-assimilated sucrose on the growth of the leaf blade and petiole revealed growth-promotional effects of sucrose that are highly dependent on the light conditions. The leaf blades of abscisic acid-deficient and sugar-insensitive mutants did not expand in blue light, but expanded normally in red light. These results suggest that both the regulation of light signals and the modulation of responses to sugar are important in the control of the differential photomorphogenesis of the leaf blade and petiole.
authors.affiliation: Department of Biosystems Science, School of Advanced Science, The Graduate University for Advanced Studies, Hayama, Kanagawa, 240-0193 Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Kozuka
authors.forename: Gorou
authors.initials: G
authors.lastname: Horiguchi
authors.forename: Gyung-Tae
authors.initials: GT
authors.lastname: Kim
authors.forename: Maki
authors.initials: M
authors.lastname: Ohgishi
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Sakai
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Tsukaya
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism / Q000528:radiation effects; D029681:Arabidopsis Proteins; D050260:Carbohydrate Metabolism; D002241:Carbohydrates / Q000494:pharmacology; D002455:Cell Division / Q000528:radiation effects; D048429:Cell Size / Q000528:radiation effects; D056931:Cryptochromes; D005420:Flavoproteins / Q000235:genetics / Q000378:metabolism; D017343:Genes, Plant; D008027:Light; D009154:Mutation; D018462:Photobiology; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism / Q000528:radiation effects; D010834:Phytochrome / Q000235:genetics / Q000378:metabolism; D018515:Plant Leaves / Q000166:cytology / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D011003:Ploidies
chemical_list: D029681:Arabidopsis Proteins; C538962:CRY1 protein, Arabidopsis; D002241:Carbohydrates; D056931:Cryptochromes; D005420:Flavoproteins; D045322:Photosynthetic Reaction Center Complex Proteins; D010834:Phytochrome