1. Abstract Auxin Evo-Devo: Genetic and Genomic Approaches to Understanding the Role of Auxin in Shoot Development Auxin regulates nearly every aspect of plant growth and development. A better understanding of auxin’s function is therefore fundamentally important to basic plant biology and crop improvement. Previous research has demonstrated both conservation and diversification of auxin’s role in maize and Arabidopsis. This project will further our understanding of how auxin regulates shoot development, emphasizing maize shoot organogenesis. To identify additional genes functioning in auxin-mediated organogenesis, we are characterizing 147 maize mutants with distinctive vegetative and reproductive developmental defects. Together with previously characterized mutants, we have mapped 71 mutants to 40 locations in the maize genome. Eight of these loci had been cloned previously, and an additional six genes have been cloned on this project. Many of these genes encode proteins required for auxin biosynthesis, transport, and response. Preliminary phylogenetic analyses of 15 gene families have illustrated complex relationships amongst monocot and eudicot clades. Reverse genetic efforts guided by these phylogenetic relationships have confirmed 18 insertions in 12 genes. Further phylogenetic, functional and comparative expression analyses will test the conservation and diversification of auxin action mechanisms in all flowering plants. ArabidopsisMaizeProteinFunction taa1vanishing tassel 2 (vt2) Tryptophan amino- transferase Auxin biosynthesis yucca (yuc) sparse inflorescence1 (spi1) Flavin mono-oxygenaseAuxin biosynthesis pinformed1 (pin1)ZmPIN1a,b,cAuxin efflux carrierAuxin Transport pinoid (pid)barren inflorescence2 (bif2) Serine threonine protein kinase Auxin Transport naked pins in yucca (npy) ZmNPYBTB-POZ-NPH3Auxin signaling? monopteros (mp)Zmmp2/10Auxin Response FactorAuxin signal transduction Aux/IAAZmAux/IAA Aux/IAA transcription factor Auxin signal transduction topless (tpl)ramosa enhancer2 (rel2) Transcriptional co- repressor Auxin signal transduction Rox1barren stalk1 (ba1) bHLH transcription factor Auxin response ?barren stalk2 (ba2) Protein interaction domain Auxin response nip5;1tassel-less1 (tls1)Major intrinsic proteinMembrane transport bor1rotten ear1 (rte1)Efflux transporterMembrane transport thi1tassel-less3 (tls3)Thiazole biosynthesisThiamine biosynthesis Mutants with a pin phenotype in Arabidopsis and a barren phenotype in maize ArabidopsisMaize Acknowledgements We thank Gerry Neuffer and the Maize Inflorescence Project for generating the mutants, the Maize Coop for providing the seed, Lu Gao, Mitzi Wilkening and Pat Schnable at Iowa State University for Sequenom analysis. This research was supported by the National Science Foundation grant number IOS 0820729/1114484. Auxin is essential for shoot development Jacob R. Withee 1, Paula C. McSteen 1, Simon T. Malcomber 2, Andrea Gallavotti 3, Yunde Zhao 4, Naomi Altman 5, Reka Albert 6 1 Division of Biological Sciences, University of Missouri. Columbia, MO 65211. 2 Department of Biological Sciences, California State University. Long Beach, CA, 90840. 3 The Waksman Institute of Microbiology, Rutgers University. Piscataway, NJ 08854. 4 Section of Cell and Developmental Biology, University of California, San Diego. La Jolla, CA 92093. 5 Department of Statistics, The Pennsylvania State University. University Park, PA 16802. 6 Department of Physics, The Pennsylvania State University. University Park, PA 16802. Reverse genetics: Confirmed Mu insertions Relative, qualitative gene expression for maize vt2 gene family determined from in silico analysis The vt2 and TAA1 clades are broadly expressed Duplicate genes are expressed at a lower level ZmTAR1/OsTAR1 clade is endosperm and seed specific TAR1 TAA1 TAR2 TAR3 vt2 ZmTAR1 ZmTAR1 dup vt2 dup TAR4 OsTAR1 ZmTAR3 ZmTAR4 Functional genomics of maize barren mutants Genetic analysis of 147 EMS-induced barren mutants (in progress) Mapped mutants using Sequenom MassArray SNP detection (71 completed, 22 in progress) Allelism test and sequence (in progress, 15 confirmed or cloned) Map-based cloning of 10-15 mutants (6 cloned, 12 in progress) Map location of 40 barren* mutants in maize (blue have been cloned, dark blue cloned on this project) ba2 Ba-ub* blast 1 2345678910 rte1 kn1 Bif3 ba2 lg2 Baub* Dvd1 Bif1 baf1 rel2 ba1 tls1 bif2 spi1 tls3 br-ub bif* Bif4 br* tls2 bl* te1 bif* tls6 tls4 bl* dw* vt* smp* ub* bl* smp* bif* tls5 tls3 bif* br-ub* Mutants being cloned vanishing tassel 2 (vt2) phylogeny and gene expression patterns OsTAR2 OsTAR3 OsTAR4 Coleoptile or Hypocotyl Root Seedling SAM/Veg. Meristem Internode/ Stem Immature Leaves Mature Leaves Inflorescence Meristem Panicle/ Inflorescence Flowers Tassel Anthers or Floral Organs Ear Silks/Stigma Husk Leaf Fruit Seed Endosperm Embryo Highly expressed Not expressed bif* an1 tls7 bl* ba* vt2 spi1bif2PIN ARF1 AUX/ IAA NPY Auxin BiosynthesisAuxin Transport Auxin Signal Transduction