title: Compensated Cell Enlargement in fugu5 is Specifically Triggered by Lowered Sucrose Production from Seed Storage Lipids.
abstract: To reveal the logic of size regulation in multicellular organisms, we have used Arabidopsis thaliana as a model organism and its leaves as a model organ. We discovered the existence of a compensatory system, whereby a decrease in leaf cell number often triggers unusual cell enlargement. However, despite the large number of compensation-exhibiting mutants analyzed to date, we have only a limited understanding of the detailed molecular mechanisms triggering the decrease in cell number and subsequent compensated cell enlargement (CCE). CCE in fugu5, the vacuolar type H+-pyrophosphatase loss-of-function mutant, is specific to cotyledons and completely suppressed when sucrose (Suc) is supplied or cytosolic pyrophosphate (PPi) is specifically removed. In addition, several lines of evidence suggest that excess cytosolic PPi in fugu5 impairs gluconeogenesis from triacylglycerol (TAG) to Suc. Here, detailed cellular phenotyping revealed that the loss-of-function mutants icl-2, mls-2 and pck1-2 triggered CCE in cotyledons. All double mutant combinations between fugu5-1 and the above three mutants exhibited compensation, but did not display a further increase in cell size. Importantly, similar phenotypes were observed in icl-2 mls-2, icl-2 pck1-2 and mls-2 pck1-2. Quantification of TAG breakdown and Suc contents further supported our findings. Taken together, we demonstrate that de novo Suc synthesis from TAG is fundamentally important for proper resumption of post-germinative cotyledon development. Moreover, provided that icl-2, mls-2 and pck1-2 are only compromised in Suc biosynthesis de novo from TAG, our findings clearly indicate that lowered Suc production in fugu5, rather than excess cytosolic PPi, is the direct trigger of CCE.
authors.affiliation: Department of Biology, Tokyo Gakugei University, Koganei-shi, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Takahashi
authors.affiliation: Department of Biology, Tokyo Gakugei University, Koganei-shi, Japan.
authors.forename: Ryousuke
authors.initials: R
authors.lastname: Morimoto
authors.affiliation: Department of Biology, Tokyo Gakugei University, Koganei-shi, Japan.
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Tabeta
authors.affiliation: Department of Biology, Tokyo Gakugei University, Koganei-shi, Japan.|Laboratory of Cell Dynamics, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Asaoka
authors.affiliation: Department of Biology, Tokyo Gakugei University, Koganei-shi, Japan.|Hatoyama High School, Saitama, Hiki-gun, Hatoyama-machi, Japan.
authors.forename: Masanori
authors.initials: M
authors.lastname: Ishida
authors.affiliation: Laboratory of Cell Dynamics, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Maeshima
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan.|Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Okazaki, Japan.
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Tsukaya
authors.affiliation: Department of Biology, Tokyo Gakugei University, Koganei-shi, Japan.
authors.forename: Ali
authors.initials: A
authors.lastname: Ferjani
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D049108:Cell Enlargement; D005943:Gluconeogenesis / Q000235:genetics; D006038:Glyoxylates / Q000378:metabolism; D018546:Hypocotyl / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D050356:Lipid Metabolism / Q000235:genetics; D009154:Mutation; D059828:Plant Cells / Q000378:metabolism*; D018515:Plant Leaves / Q000166:cytology* / Q000378:metabolism; D012639:Seeds / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism*; D014280:Triglycerides / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D006038:Glyoxylates; D014280:Triglycerides; D013395:Sucrose; C031150:glyoxylic acid
keywords: Compensation; Leaf size; Pyprophosphate; Seed storage lipids; Sucrose; fugu5 mutant