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The Roles of miR156 and miR172 in Phase Change Regulation

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MicroRNAs in Plant Development and Stress Responses

Part of the book series: Signaling and Communication in Plants ((SIGCOMM,volume 15))

Abstract

Growth and development in plants is organized as a series of developmental stages, most importantly embryogenesis, vegetative, and reproductive growth. The timing of transitions between those stages is highly regulated to allow the successful completion of a life cycle by producing maximum numbers of progeny. Targets of both miR156 and miR172 have been implicated in the timely control of several phase transitions in various plant species. This chapter describes the role of both miRNAs’ targets as well as the regulatory information provided by miRNA-mediated repression of their accumulation.

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References

  • Abdurakhmonov IY, Devor EJ, Buriev ZT, Huang L, Makamov A, Shermatov SE, Bozorov T, Kushanov FN, Mavlonov GT, Abdukarimov A (2008) Small RNA regulation of ovule development in the cotton plant, G. hirsutum L. BMC Plant Biol 8:93

    Article  PubMed  Google Scholar 

  • Abelenda JA, Navarro C, Prat S (2011) From the model to the crop: genes controlling tuber formation in potato. Curr Opin Biotechnol 22:287–292

    Article  PubMed  CAS  Google Scholar 

  • Allen MD, Yamasaki K, Ohme-Takagi M, Tateno M, Suzuki M (1998) A novel mode of DNA recognition by a beta-sheet revealed by the solution structure of the GCC-box binding domain in complex with DNA. EMBO J 17:5484–5496

    Article  PubMed  CAS  Google Scholar 

  • Amasino R (2010) Seasonal and developmental timing of flowering. Plant J 61:1001–1013

    Article  PubMed  CAS  Google Scholar 

  • An FM, Hsiao SR, Chan MT (2011) Sequencing-based approaches reveal low ambient temperature-responsive and tissue-specific microRNAs in phalaenopsis orchid. PLoS One 6:e18937

    Article  PubMed  CAS  Google Scholar 

  • Arazi T, Talmor-Neiman M, Stav R, Riese M, Huijser P, Baulcombe DC (2005) Cloning and characterization of micro-RNAs from moss. Plant J 43:837–848

    Article  PubMed  CAS  Google Scholar 

  • Aukerman MJ, Sakai H (2003) Regulation of flowering time and floral organ identity by a MicroRNA and its APETALA2-like target genes. Plant Cell 15:2730–2741

    Article  PubMed  CAS  Google Scholar 

  • Axtell MJ, Bartel DP (2005) Antiquity of microRNAs and their targets in land plants. Plant Cell 17:1658–1673

    Article  PubMed  CAS  Google Scholar 

  • Axtell MJ, Snyder JA, Bartel DP (2007) Common functions for diverse small RNAs of land plants. Plant Cell 19:1750–1769

    Article  PubMed  CAS  Google Scholar 

  • Birkenbihl RP, Jach G, Saedler H, Huijser P (2005) Functional dissection of the plant-specific SBP-domain: overlap of the DNA-binding and nuclear localization domains. J Mol Biol 352:585–596

    Article  PubMed  CAS  Google Scholar 

  • Bowman JL, Smyth DR, Meyerowitz EM (1989) Genes directing flower development in Arabidopsis. Plant Cell 1:37–52

    PubMed  CAS  Google Scholar 

  • Buhtz A, Springer F, Chappell L, Baulcombe DC, Kehr J (2008) Identification and characterization of small RNAs from the phloem of Brassica napus. Plant J 53:739–749

    Article  PubMed  CAS  Google Scholar 

  • Cardon G, Hohmann S, Klein J, Nettesheim K, Saedler H, Huijser P (1999) Molecular characterisation of the Arabidopsis SBP-box genes. Gene 237:91–104

    Article  PubMed  CAS  Google Scholar 

  • Chen X (2004) A microRNA as a translational repressor of APETALA2 in Arabidopsis flower development. Science 303:2022–2025

    Article  PubMed  CAS  Google Scholar 

  • Chuck G, Cigan AM, Saeteurn K, Hake S (2007a) The heterochronic maize mutant Corngrass1 results from overexpression of a tandem microRNA. Nat Genet 39:544–549

    Article  PubMed  CAS  Google Scholar 

  • Chuck G, Meeley R, Irish E, Sakai H, Hake S (2007b) The maize tasselseed4 microRNA controls sex determination and meristem cell fate by targeting Tasselseed6/indeterminate spikelet1. Nat Genet 39:1517–1521

    Article  PubMed  CAS  Google Scholar 

  • Chuck G, Whipple C, Jackson D, Hake S (2010) The maize SBP-box transcription factor encoded by tasselsheath4 regulates bract development and the establishment of meristem boundaries. Development 137:1243–1250

    Article  PubMed  CAS  Google Scholar 

  • De Smet I, Lau S, Mayer U, Jurgens G (2010) Embryogenesis – the humble beginnings of plant life. Plant J 61:959–970

    Article  PubMed  Google Scholar 

  • Elliott RC, Betzner AS, Huttner E, Oakes MP, Tucker WQ, Gerentes D, Perez P, Smyth DR (1996) AINTEGUMENTA, an APETALA2-like gene of Arabidopsis with pleiotropic roles in ovule development and floral organ growth. Plant Cell 8:155–168

    PubMed  CAS  Google Scholar 

  • Franco-Zorrilla JM, Valli A, Todesco M, Mateos I, Puga MI, Rubio-Somoza I, Leyva A, Weigel D, Garcia JA, Paz-Ares J (2007) Target mimicry provides a new mechanism for regulation of microRNA activity. Nat Genet 39:1033–1037

    Article  PubMed  CAS  Google Scholar 

  • Gandikota M, Birkenbihl RP, Hohmann S, Cardon GH, Saedler H, Huijser P (2007) The miRNA156/157 recognition element in the 3′ UTR of the Arabidopsis SBP box gene SPL3 prevents early flowering by translational inhibition in seedlings. Plant J 49:683–693

    Article  PubMed  CAS  Google Scholar 

  • Giakountis A, Coupland G (2008) Phloem transport of flowering signals. Curr Opin Plant Biol 11:687–694

    Article  PubMed  CAS  Google Scholar 

  • Giraldez AJ, Mishima Y, Rihel J, Grocock RJ, Van Dongen S, Inoue K, Enright AJ, Schier AF (2006) Zebrafish MiR-430 promotes deadenylation and clearance of maternal mRNAs. Science 312:75–79

    Article  PubMed  CAS  Google Scholar 

  • Gou JY, Felippes FF, Liu CJ, Weigel D, Wang JW (2011) Negative regulation of anthocyanin biosynthesis in Arabidopsis by a miR156-targeted SPL transcription factor. Plant Cell 23:1512–1522

    Article  PubMed  CAS  Google Scholar 

  • Griffiths-Jones S (2004) The microRNA registry. Nucleic Acids Res 32:D109–111

    Article  PubMed  CAS  Google Scholar 

  • Gu M, Xu K, Chen A, Zhu Y, Tang G, Xu G (2010) Expression analysis suggests potential roles of microRNAs for phosphate and arbuscular mycorrhizal signaling in Solanum lycopersicum. Physiol Plant 138:226–237

    Article  PubMed  CAS  Google Scholar 

  • Hsieh LC, Lin SI, Shih AC, Chen JW, Lin WY, Tseng CY, Li WH, Chiou TJ (2009) Uncovering small RNA-mediated responses to phosphate deficiency in Arabidopsis by deep sequencing. Plant Physiol 151:2120–2132

    Article  PubMed  Google Scholar 

  • Hultquist JF, Dorweiler JE (2008) Feminized tassels of maize mop1 and ts1 mutants exhibit altered levels of miR156 and specific SBP-box genes. Planta 229:99–113

    Article  PubMed  CAS  Google Scholar 

  • Jung JH, Seo YH, Seo PJ, Reyes JL, Yun J, Chua NH, Park CM (2007) The GIGANTEA-regulated microRNA172 mediates photoperiodic flowering independent of CONSTANS in Arabidopsis. Plant Cell 19:2736–2748

    Article  PubMed  CAS  Google Scholar 

  • Kasschau KD, Xie Z, Allen E, Llave C, Chapman EJ, Krizan KA, Carrington JC (2003) P1/HC-Pro, a viral suppressor of RNA silencing, interferes with Arabidopsis development and miRNA unction. Dev Cell 4:205–217

    Article  PubMed  CAS  Google Scholar 

  • Kidner CA, Martienssen RA (2004) Spatially restricted microRNA directs leaf polarity through ARGONAUTE1. Nature 428:81–84

    Article  PubMed  CAS  Google Scholar 

  • Kim S, Soltis PS, Wall K, Soltis DE (2006) Phylogeny and domain evolution in the APETALA2-like gene family. Mol Biol Evol 23:107–120

    Article  PubMed  CAS  Google Scholar 

  • Klein J, Saedler H, Huijser P (1996) A new family of DNA binding proteins includes putative transcriptional regulators of the Antirrhinum majus floral meristem identity gene SQUAMOSA. Mol Gen Genet 250:7–16

    PubMed  CAS  Google Scholar 

  • Klucher KM, Chow H, Reiser L, Fischer RL (1996) The AINTEGUMENTA gene of Arabidopsis required for ovule and female gametophyte development is related to the floral homeotic gene APETALA2. Plant Cell 8:137–153

    PubMed  CAS  Google Scholar 

  • Kropat J, Tottey S, Birkenbihl RP, Depege N, Huijser P, Merchant S (2005) A regulator of nutritional copper signaling in Chlamydomonas is an SBP domain protein that recognizes the GTAC core of copper response element. Proc Natl Acad Sci USA 102:18730–18735

    Article  PubMed  CAS  Google Scholar 

  • Lauter N, Kampani A, Carlson S, Goebel M, Moose SP (2005) microRNA172 down-regulates glossy15 to promote vegetative phase change in maize. Proc Natl Acad Sci USA 102:9412–9417

    Article  PubMed  CAS  Google Scholar 

  • Lee H, Yoo SJ, Lee JH, Kim W, Yoo SK, Fitzgerald H, Carrington JC, Ahn JH (2010) Genetic framework for flowering-time regulation by ambient temperature-responsive miRNAs in Arabidopsis. Nucleic Acids Res 38:3081–3093

    Article  PubMed  CAS  Google Scholar 

  • Liu B, Li P, Li X, Liu C, Cao S, Chu C, Cao X (2005) Loss of function of OsDCL1 affects microRNA accumulation and causes developmental defects in rice. Plant Physiol 139:296–305

    Article  PubMed  CAS  Google Scholar 

  • Luo YC, Zhou H, Li Y, Chen JY, Yang JH, Chen YQ, Qu LH (2006) Rice embryogenic calli express a unique set of microRNAs, suggesting regulatory roles of microRNAs in plant post-embryogenic development. FEBS Lett 580:5111–5116

    Article  PubMed  CAS  Google Scholar 

  • Magnani E, Sjolander K, Hake S (2004) From endonucleases to transcription factors: evolution of the AP2 DNA binding domain in plants. Plant Cell 16:2265–2277

    Article  PubMed  CAS  Google Scholar 

  • Maher C, Stein L, Ware D (2006) Evolution of Arabidopsis microRNA families through duplication events. Genome Res 16:510–519

    Article  PubMed  CAS  Google Scholar 

  • Martin RC, Asahina M, Liu PP, Kristof JR, Coppersmith JL, Pluskota WE, Bassel GW, Goloviznina NA, Nguyen TT, Martinez-Andujar C, Kumar AMB, Pupel P, Nonogaki H (2010) The microRNA156 and microRNA172 gene regulation cascades at post-germinative stages in Arabidopsis. Seed Sci Res 20:79–87

    Article  CAS  Google Scholar 

  • Mathieu J, Yant LJ, Murdter F, Kuttner F, Schmid M (2009) Repression of flowering by the miR172 target SMZ. PLoS Biol 7:e1000148

    Article  PubMed  Google Scholar 

  • Mi S, Cai T, Hu Y, Chen Y, Hodges E, Ni F, Wu L, Li S, Zhou H, Long C, Chen S, Hannon GJ, Qi Y (2008) Sorting of small RNAs into Arabidopsis argonaute complexes is directed by the 5′ terminal nucleotide. Cell 133:116–127

    Article  PubMed  CAS  Google Scholar 

  • Molnar A, Schwach F, Studholme DJ, Thuenemann EC, Baulcombe DC (2007) miRNAs control gene expression in the single-cell alga Chlamydomonas reinhardtii. Nature 447:1126–1129

    Article  PubMed  CAS  Google Scholar 

  • Montgomery TA, Howell MD, Cuperus JT, Li D, Hansen JE, Alexander AL, Chapman EJ, Fahlgren N, Allen E, Carrington JC (2008) Specificity of ARGONAUTE7-miR390 interaction and dual functionality in TAS3 trans-acting siRNA formation. Cell 133:128–141

    Article  PubMed  CAS  Google Scholar 

  • Moose SP, Sisco PH (1996) Glossy15, an APETALA2-like gene from maize that regulates leaf epidermal cell identity. Genes Dev 10:3018–3027

    Article  PubMed  CAS  Google Scholar 

  • Naya L, Khan GA, Sorin C, Hartmann C, Crespi M, Lelandais-Briere C (2010) Cleavage of a non-conserved target by a specific miR156 isoform in root apexes of Medicago truncatula. Plant Signal Behav 5:328–331

    Article  PubMed  CAS  Google Scholar 

  • Nodine MD, Bartel DP (2010) MicroRNAs prevent precocious gene expression and enable pattern formation during plant embryogenesis. Genes Dev 24:2678–2692

    Article  PubMed  CAS  Google Scholar 

  • Park W, Li J, Song R, Messing J, Chen X (2002) CARPEL FACTORY, a Dicer homolog, and HEN1, a novel protein, act in microRNA metabolism in Arabidopsis thaliana. Curr Biol 12:1484–1495

    Article  PubMed  CAS  Google Scholar 

  • Park MY, Wu G, Gonzalez-Sulser A, Vaucheret H, Poethig RS (2005) Nuclear processing and export of microRNAs in Arabidopsis. Proc Natl Acad Sci USA 102:3691–3696

    Article  PubMed  CAS  Google Scholar 

  • Preston JC, Hileman LC (2010) SQUAMOSA-PROMOTER BINDING PROTEIN 1 initiates flowering in Antirrhinum majus through the activation of meristem identity genes. Plant J 62:704–712

    Article  PubMed  CAS  Google Scholar 

  • Reddy VR, Reddy KR, Acock B (1994) Carbon dioxide and temperature effects on cotton leaf initiation and development. Biotronics 23:59–74

    Google Scholar 

  • Reinhart BJ, Weinstein EG, Rhoades MW, Bartel B, Bartel DP (2002) MicroRNAs in plants. Genes Dev 16:1616–1626

    Article  PubMed  CAS  Google Scholar 

  • Rhoades MW, Reinhart BJ, Lim LP, Burge CB, Bartel B, Bartel DP (2002) Prediction of plant microRNA targets. Cell 110:513–520

    Article  PubMed  CAS  Google Scholar 

  • Riechmann JL, Heard J, Martin G, Reuber L, Jiang C, Keddie J, Adam L, Pineda O, Ratcliffe OJ, Samaha RR, Creelman R, Pilgrim M, Broun P, Zhang JZ, Ghandehari D, Sherman BK, Yu G (2000) Arabidopsis transcription factors: genome-wide comparative analysis among eukaryotes. Science 290:2105–2110

    Article  PubMed  CAS  Google Scholar 

  • Riese M, Hohmann S, Saedler H, Munster T, Huijser P (2007) Comparative analysis of the SBP-box gene families in P. patens and seed plants. Gene 401:28–37

    Article  PubMed  CAS  Google Scholar 

  • Schmid M, Uhlenhaut NH, Godard F, Demar M, Bressan R, Weigel D, Lohmann JU (2003) Dissection of floral induction pathways using global expression analysis. Development 130:6001–6012

    Article  PubMed  CAS  Google Scholar 

  • Schwab R, Palatnik JF, Riester M, Schommer C, Schmid M, Weigel D (2005) Specific effects of microRNAs on the plant transcriptome. Dev Cell 8:517–527

    Article  PubMed  CAS  Google Scholar 

  • Schwarz S, Grande AV, Bujdoso N, Saedler H, Huijser P (2008) The microRNA regulated SBP-box genes SPL9 and SPL15 control shoot maturation in Arabidopsis. Plant Mol Biol 67:183–195

    Article  PubMed  CAS  Google Scholar 

  • Shigyo M, Hasebe M, Ito M (2006) Molecular evolution of the AP2 subfamily. Gene 366:256–265

    Article  PubMed  CAS  Google Scholar 

  • Shikata M, Koyama T, Mitsuda N, Ohme-Takagi M (2009) Arabidopsis SBP-box genes SPL10, SPL11 and SPL2 control morphological change in association with shoot maturation in the reproductive phase. Plant Cell Physiol 50:2133–2145

    Article  PubMed  CAS  Google Scholar 

  • Smith MR, Willmann MR, Wu G, Berardini TZ, Moller B, Weijers D, Poethig RS (2009) Cyclophilin 40 is required for microRNA activity in Arabidopsis. Proc Natl Acad Sci USA 106:5424–5429

    Article  PubMed  CAS  Google Scholar 

  • Solano R, Stepanova A, Chao Q, Ecker JR (1998) Nuclear events in ethylene signaling: a transcriptional cascade mediated by ETHYLENE-INSENSITIVE3 and ETHYLENE-RESPONSE-FACTOR1. Genes Dev 12:3703–3714

    Article  PubMed  CAS  Google Scholar 

  • Sunkar R, Jagadeeswaran G (2008) In silico identification of conserved microRNAs in large number of diverse plant species. BMC Plant Biol 8:37

    Article  PubMed  Google Scholar 

  • Tang M, Li G, Chen M (2007) The phylogeny and expression pattern of APETALA2-like genes in rice. J Genet Genomics 34:930–938

    Article  PubMed  CAS  Google Scholar 

  • Telfer A, Bollman KM, Poethig RS (1997) Phase change and the regulation of trichome distribution in Arabidopsis thaliana. Development 124:645–654

    PubMed  CAS  Google Scholar 

  • Usami T, Horiguchi G, Yano S, Tsukaya H (2009) The more and smaller cells mutants of Arabidopsis thaliana identify novel roles for SQUAMOSA PROMOTER BINDING PROTEIN-LIKE genes in the control of heteroblasty. Development 136:955–964

    Article  PubMed  CAS  Google Scholar 

  • Wang S, Zhu QH, Guo X, Gui Y, Bao J, Helliwell C, Fan L (2007) Molecular evolution and selection of a gene encoding two tandem microRNAs in rice. FEBS Lett 581:4789–4793

    Article  PubMed  CAS  Google Scholar 

  • Wang JW, Schwab R, Czech B, Mica E, Weigel D (2008) Dual effects of miR156-targeted SPL genes and CYP78A5/KLUH on plastochron length and organ size in Arabidopsis thaliana. Plant Cell 20:1231–1243

    Article  PubMed  CAS  Google Scholar 

  • Wang JW, Czech B, Weigel D (2009) miR156-regulated SPL transcription factors define an endogenous flowering pathway in Arabidopsis thaliana. Cell 138:738–749

    Article  PubMed  CAS  Google Scholar 

  • Wang JW, Park MY, Wang LJ, Koo Y, Chen XY, Weigel D, Poethig RS (2011) miRNA control of vegetative phase change in trees. PLoS Genet 7:e1002012

    Article  PubMed  CAS  Google Scholar 

  • Wu G, Poethig RS (2006) Temporal regulation of shoot development in Arabidopsis thaliana by miR156 and its target SPL3. Development 133:3539–3547

    Article  PubMed  CAS  Google Scholar 

  • Wu G, Park MY, Conway SR, Wang JW, Weigel D, Poethig RS (2009) The sequential action of miR156 and miR172 regulates developmental timing in Arabidopsis. Cell 138:750–759

    Article  PubMed  CAS  Google Scholar 

  • Wu XM, Liu MY, Ge XX, Xu Q, Guo WW (2011) Stage and tissue-specific modulation of ten conserved miRNAs and their targets during somatic embryogenesis of Valencia sweet orange. Planta 233:495–505

    Article  PubMed  CAS  Google Scholar 

  • Xie K, Wu C, Xiong L (2006) Genomic organization, differential expression, and interaction of SQUAMOSA promoter-binding-like transcription factors and microRNA156 in rice. Plant Physiol 142:280–293

    Article  PubMed  CAS  Google Scholar 

  • Yamaguchi A, Wu MF, Yang L, Wu G, Poethig RS, Wagner D (2009) The microRNA-regulated SBP-Box transcription factor SPL3 is a direct upstream activator of LEAFY, FRUITFULL, and APETALA1. Dev Cell 17:268–278

    Article  PubMed  CAS  Google Scholar 

  • Yamasaki K, Kigawa T, Inoue M, Tateno M, Yamasaki T, Yabuki T, Aoki M, Seki E, Matsuda T, Nunokawa E, Ishizuka Y, Terada T, Shirouzu M, Osanai T, Tanaka A, Seki M, Shinozaki K, Yokoyama S (2004) A novel zinc-binding motif revealed by solution structures of DNA-binding domains of Arabidopsis SBP-family transcription factors. J Mol Biol 337:49–63

    Article  PubMed  CAS  Google Scholar 

  • Yang Z, Wang X, Gu S, Hu Z, Xu H, Xu C (2008) Comparative study of SBP-box gene family in Arabidopsis and rice. Gene 407:1–11

    Article  PubMed  CAS  Google Scholar 

  • Yang L, Conway SR, Poethig RS (2011) Vegetative phase change is mediated by a leaf-derived signal that represses the transcription of miR156. Development 138:245–249

    Article  PubMed  CAS  Google Scholar 

  • Yant L, Mathieu J, Dinh TT, Ott F, Lanz C, Wollmann H, Chen X, Schmid M (2010) Orchestration of the floral transition and floral development in Arabidopsis by the bifunctional transcription factor APETALA2. Plant Cell 22:2156–2170

    Article  PubMed  CAS  Google Scholar 

  • Yin ZJ, Shen FF (2010) Identification and characterization of conserved microRNAs and their target genes in wheat (Triticum aestivum). Genet Mol Res 9:1186–1196

    Article  PubMed  CAS  Google Scholar 

  • Yu N, Cai WJ, Wang S, Shan CM, Wang LJ, Chen XY (2010) Temporal control of trichome distribution by microRNA156-targeted SPL genes in Arabidopsis thaliana. Plant Cell 22:2322–2335

    Article  PubMed  CAS  Google Scholar 

  • Zhang L, Chia JM, Kumari S, Stein JC, Liu Z, Narechania A, Maher CA, Guill K, McMullen MD, Ware D (2009) A genome-wide characterization of microRNA genes in maize. PLoS Genet 5:e1000716

    Article  PubMed  Google Scholar 

  • Zhao T, Li G, Mi S, Li S, Hannon GJ, Wang XJ, Qi Y (2007) A complex system of small RNAs in the unicellular green alga Chlamydomonas reinhardtii. Genes Dev 21:1190–1203

    Article  PubMed  CAS  Google Scholar 

  • Zhou X, Wang G, Zhang W (2007) UV-B responsive microRNA genes in Arabidopsis thaliana. Mol Syst Biol 3:103

    Article  PubMed  Google Scholar 

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Acknowledgments

RS is supported by an HFSP postdoctoral fellowship.

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Correspondence to Rebecca Schwab .

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Schwab, R. (2012). The Roles of miR156 and miR172 in Phase Change Regulation. In: Sunkar, R. (eds) MicroRNAs in Plant Development and Stress Responses. Signaling and Communication in Plants, vol 15. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-27384-1_3

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