title: Photosynthesis of root chloroplasts developed in Arabidopsis lines overexpressing GOLDEN2-LIKE transcription factors.
abstract: In plants, genes involved in photosynthesis are encoded separately in nuclei and plastids, and tight cooperation between these two genomes is therefore required for the development of functional chloroplasts. Golden2-like (GLK) transcription factors are involved in chloroplast development, directly targeting photosynthesis-associated nuclear genes for up-regulation. Although overexpression of GLKs leads to chloroplast development in non-photosynthetic organs, the mechanisms of coordination between the nuclear gene expression influenced by GLKs and the photosynthetic processes inside chloroplasts are largely unknown. To elucidate the impact of GLK-induced expression of photosynthesis-associated nuclear genes on the construction of photosynthetic systems, chloroplast morphology and photosynthetic characteristics in greenish roots of Arabidopsis thaliana lines overexpressing GLKs were compared with those in wild-type roots and leaves. Overexpression of GLKs caused up-regulation of not only their direct targets but also non-target nuclear and plastid genes, leading to global induction of chloroplast biogenesis in the root. Large antennae relative to reaction centers were observed in wild-type roots and were further enhanced by GLK overexpression due to the increased expression of target genes associated with peripheral light-harvesting antennae. Photochemical efficiency was lower in the root chloroplasts than in leaf chloroplasts, suggesting that the imbalance in the photosynthetic machinery decreases the efficiency of light utilization in root chloroplasts. Despite the low photochemical efficiency, root photosynthesis contributed to carbon assimilation in Arabidopsis. Moreover, GLK overexpression increased CO₂ fixation and promoted phototrophic performance of the root, showing the potential of root photosynthesis to improve effective carbon utilization in plants.
authors.affiliation: Graduate School of Arts and Sciences, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Daichi
authors.initials: D
authors.lastname: Sasaki
authors.forename: Ko
authors.initials: K
authors.lastname: Noguchi
authors.forename: Daiki
authors.initials: D
authors.lastname: Fujinuma
authors.forename: Hirohisa
authors.initials: H
authors.lastname: Komatsu
authors.forename: Masami
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Mayuko
authors.initials: M
authors.lastname: Sato
authors.forename: Kiminori
authors.initials: K
authors.lastname: Toyooka
authors.forename: Keiko
authors.initials: K
authors.lastname: Sugimoto
authors.forename: Krishna K
authors.initials: KK
authors.lastname: Niyogi
authors.forename: Hajime
authors.initials: H
authors.lastname: Wada
authors.forename: Tatsuru
authors.initials: T
authors.lastname: Masuda
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D008027:Light; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis / Q000502:physiology*; D010860:Pigments, Biological / Q000378:metabolism; D018515:Plant Leaves / Q000235:genetics / Q000502:physiology / Q000528:radiation effects / Q000648:ultrastructure; D018517:Plant Roots / Q000235:genetics / Q000502:physiology / Q000528:radiation effects / Q000648:ultrastructure; D036226:Seedlings / Q000235:genetics / Q000502:physiology / Q000528:radiation effects / Q000648:ultrastructure; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D029681:Arabidopsis Proteins; C468867:GLK1 protein, Arabidopsis; C468868:GLK2 protein, Arabidopsis; D010860:Pigments, Biological; D014157:Transcription Factors; D002245:Carbon Dioxide; D010100:Oxygen
keywords: Arabidopsis root; Chloroplast development; Construction of photosynthetic systems; GLK; Photosynthesis