@article{OmidbakhshfardProostFujikuraetal.2015, author = {Omidbakhshfard, Mohammad Amin and Proost, Sebastian and Fujikura, Ushio and M{\"u}ller-R{\"o}ber, Bernd}, title = {Growth-Regulating Factors (GRFs): A Small Transcription Factor Family with Important Functions in Plant Biology}, series = {Molecular plant}, volume = {8}, journal = {Molecular plant}, number = {7}, publisher = {Cell Press}, address = {Cambridge}, issn = {1674-2052}, doi = {10.1016/j.molp.2015.01.013}, pages = {998 -- 1010}, year = {2015}, abstract = {Growth-regulating factors (GRFs) are plant-specific transcription factors that were originally identified for their roles in stem and leaf development, but recent studies highlight them to be similarly important for other central developmental processes including flower and seed formation, root development, and the coordination of growth processes under adverse environmental conditions. The expression of several GRFs is controlled by microRNA miR396, and the GRF-miRNA396 regulatory module appears to be central to several of these processes. In addition, transcription factors upstream of GRFs and miR396 have been discovered, and gradually downstream target genes of GRFs are being unraveled. Here, we review the current knowledge of the biological functions performed by GRFs and survey available molecular data to illustrate how they exert their roles at the cellular level.}, language = {en} } @article{OmidbakhshfardFujikuraOlasetal.2018, author = {Omidbakhshfard, Mohammad Amin and Fujikura, Ushio and Olas, Justyna Jadwiga and Xue, Gang-Ping and Balazadeh, Salma and Mueller-Roeber, Bernd}, title = {GROWTH-REGULATING FACTOR 9 negatively regulates arabidopsis leaf growth by controlling ORG3 and restricting cell proliferation in leaf primordia}, series = {PLoS Genetics : a peer-reviewed, open-access journal}, volume = {14}, journal = {PLoS Genetics : a peer-reviewed, open-access journal}, number = {7}, publisher = {PLoS}, address = {San Fransisco}, issn = {1553-7404}, doi = {10.1371/journal.pgen.1007484}, pages = {31}, year = {2018}, abstract = {Leaf growth is a complex process that involves the action of diverse transcription factors (TFs) and their downstream gene regulatory networks. In this study, we focus on the functional characterization of the Arabidopsis thaliana TF GROWTH-REGULATING FACTOR9 (GRF9) and demonstrate that it exerts its negative effect on leaf growth by activating expression of the bZIP TF OBP3-RESPONSIVE GENE 3 (ORG3). While grf9 knockout mutants produce bigger incipient leaf primordia at the shoot apex, rosette leaves and petals than the wild type, the sizes of those organs are reduced in plants overexpressing GRF9 (GRF9ox). Cell measurements demonstrate that changes in leaf size result from alterations in cell numbers rather than cell sizes. Kinematic analysis and 5-ethynyl-2'-deoxyuridine (EdU) incorporation assay revealed that GRF9 restricts cell proliferation in the early developing leaf. Performing in vitro binding site selection, we identified the 6-base motif 5'-CTGACA-3' as the core binding site of GRF9. By global transcriptome profiling, electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) we identified ORG3 as a direct downstream, and positively regulated target of GRF9. Genetic analysis of grf9 org3 and GRF9ox org3 double mutants reveals that both transcription factors act in a regulatory cascade to control the final leaf dimensions by restricting cell number in the developing leaf.}, language = {en} } @article{KatagiriHasegawaFujikuraetal.2016, author = {Katagiri, Yohei and Hasegawa, Junko and Fujikura, Ushio and Hoshino, Rina and Matsunaga, Sachihiro and Tsukaya, Hirokazu}, title = {The coordination of ploidy and cell size differs between cell layers in leaves}, series = {Development : Company of Biologists}, volume = {143}, journal = {Development : Company of Biologists}, publisher = {Company of Biologists Limited}, address = {Cambridge}, issn = {0950-1991}, doi = {10.1242/dev.130021}, pages = {1120 -- 1125}, year = {2016}, abstract = {Growth and developmental processes are occasionally accompanied by multiple rounds of DNA replication, known as endoreduplication. Coordination between endoreduplication and cell size regulation often plays a crucial role in proper organogenesis and cell differentiation. Here, we report that the level of correlation between ploidy and cell volume is different in the outer and inner cell layers of leaves of Arabidopsis thaliana using a novel imaging technique. Although there is a well-known, strong correlation between ploidy and cell volume in pavement cells of the epidermis, this correlation was extremely weak in palisade mesophyll cells. Induction of epidermis cell identity based on the expression of the homeobox gene ATML1 in mesophyll cells enhanced the level of correlation between ploidy and cell volume to near that of wild-type epidermal cells. We therefore propose that the correlation between ploidy and cell volume is regulated by cell identity.}, language = {en} } @article{FujikuraJingHanadaetal.2018, author = {Fujikura, Ushio and Jing, Runchun and Hanada, Atsushi and Takebayashi, Yumiko and Sakakibara, Hitoshi and Yamaguchi, Shinjiro and Kappel, Christian and Lenhard, Michael}, title = {Variation in splicing efficiency underlies morphological evolution in capsella}, series = {Developmental cell}, volume = {44}, journal = {Developmental cell}, number = {2}, publisher = {Cell Press}, address = {Cambridge}, issn = {1534-5807}, doi = {10.1016/j.devcel.2017.11.022}, pages = {192 -- 203}, year = {2018}, abstract = {Understanding the molecular basis of morphological change remains a central challenge in evolutionary-developmental biology. The transition from outbreeding to selfing is often associated with a dramatic reduction in reproductive structures and functions, such as the loss of attractive pheromones in hermaphroditic Caenorhabditis elegans and a reduced flower size in plants. Here, we demonstrate that variation in the level of the brassinosteroid-biosynthesis enzyme CYP724A1 contributes to the reduced flower size of selfing Capsella rubella compared with its outbreeding ancestor Capsella grandiflora. The primary transcript of the C. rubella allele is spliced more efficiently than that of C. grandiflora, resulting in higher brassinosteroid levels. These restrict organ growth by limiting cell proliferation. More efficient splicing of the C. rubella allele results from two de novo mutations in the selfing lineage. Thus, our results highlight the potentially widespread importance of differential splicing efficiency and higher-than-optimal hormone levels in generating phenotypic variation.}, language = {en} } @article{FujikuraElsaesserBreuningeretal.2014, author = {Fujikura, Ushio and Elsaesser, Lore and Breuninger, Holger and Sanchez-Rodriguez, Clara and Ivakov, Alexander and Laux, Thomas and Findlay, Kim and Persson, Staffan and Lenhard, Michael}, title = {Atkinesin-13A modulates cell-wall synthesis and cell expansion in arabidopsis thaliana via the THESEUS1 pathway}, series = {PLoS Genetics : a peer-reviewed, open-access journal}, volume = {10}, journal = {PLoS Genetics : a peer-reviewed, open-access journal}, number = {9}, publisher = {PLoS}, address = {San Fransisco}, issn = {1553-7390}, doi = {10.1371/journal.pgen.1004627}, pages = {15}, year = {2014}, abstract = {Growth of plant organs relies on cell proliferation and expansion. While an increasingly detailed picture about the control of cell proliferation is emerging, our knowledge about the control of cell expansion remains more limited. We demonstrate the internal-motor kinesin AtKINESIN-13A (AtKIN13A) limits cell expansion and cell size in Arabidopsis thaliana, ion atkinl3a mutants forming larger petals with larger cells. The homolog, AtKINESIN-13B, also affects cell expansion and double mutants display growth, gametophytic and early embryonic defects, indicating a redundant role of he two genes. AtKIN13A is known to depolymerize microtubules and influence Golgi motility and distribution. Consistent his function, AtKIN13A interacts genetically with ANGUSTIFOLIA, encoding a regulator of Golgi dynamics. Reduced AtIGN13A activity alters cell wall structure as assessed by Fourier-transformed infrared-spectroscopy and triggers signalling he THESEUS1-dependent cell-wall integrity pathway, which in turn promotes the excess cell expansion in the atkinl3a mutant. Thus, our results indicate that the intracellular activity of AtKIN13A regulates cell expansion and wall architecture via THESEUS1, providing a compelling case of interplay between cell wall integrity sensing and expansion.}, language = {en} }